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| 个人信息 |
| 姓 名： |
张译员 [编号]:1278 |
性 别： |
女 |
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| 擅长专业： |
水处理 |
出生年月： |
1983/7/1 |
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| 民 族： |
汉族 |
所在地区： |
山东 青岛 |
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| 文化程度： |
本科 |
所学专业： |
计算机科学与技术 |
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| 毕业时间： |
38898 |
毕业学校： |
曲阜师范大学 |
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| 第一外语： |
英语 |
等级水平： |
CET6 |
|
|
| 口译等级： |
中级 |
工作经历： |
3 年 |
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| 翻译库信息 |
| 可翻译语种： |
英语 |
|
|
| 目前所在地： |
山东 青岛 |
| 可提供服务类型： |
笔译、家教 |
| 每周可提供服务时间： |
每日18：00至次日8：00；
每周六、周日；
国家法定节假日。 |
| 证书信息 |
| 证书名称： |
CET6 |
|
| 获证时间： |
2004/12/1 |
|
| 获得分数： |
79 |
|
|
| 工作经历 |
| 工作时期： |
2006/8/1--2009/8/1 |
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| 公司名称： |
青岛阿迪埃脱盐中心 |
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| 公司性质： |
其它 |
| 所属行业： |
咨询/顾问 |
| 所在部门： |
市场宣传 |
|
| 职位： |
文职 |
| 自我评价： |
专业基础扎实，思维活跃，知识面较宽；
良好的文学修养，文字编辑能力，良好的语言表达能力；
具备一定的创新能力和团队意识；
工作踏实，为人真诚，富于责任心和使命感。
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| 笔译案例信息 |
| 案例标题： |
可持续性和突破性的膜技术 |
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| 原文： |
ABSTRACT
Incremental improvements in reverse osmosis
(RO) technology in the last 20+ years have
dramatically reduced energy usage, improved
water quality and lowered overall treatment
costs nearly threefold making RO the preferred
technology. As the technology improves,
energy inputs and associated CO2 emissions
will continue to decline. However, desalination
is still an energy intensive process when
compared to conventional treatment of fresh
water resources.
The development of disruptive desalination
technology will significantly reduce the energy
required to produce desalinated water. By
definition a disruptive technology, due to its
significant benefits, will progressively displace
current widely ultilised desalination technology.
As disruptive technology compatible with
current technology may be available during the
next decade or so, the design of new
desalination facilities should consider the
potential lower pressure requirements and/or
increased production capacity from
incorporation of the new technology.
INTRODUCTION
Desalination and water reuse are the only
avenues to increase water availability beyond
the natural hydrogeological cycle (water
vapour, surface water and groundwater). Given
that these technologies are currently energy-
intensive water purification processes, added
use will likely worsen the cycle of greenhouse
gas emissions and associated climate change
(Tal 2006).
Studies, testing and development of promising
desalination related technologies are ongoing
in a number of countries around the world. In
Australia, the Advanced Membrane
Technologies for Water Treatment Research
Cluster has been formed between CSIRO and
nine Australian universities for collaborative
efforts to evaluate and improve properties of
thin film composite (TFC) membranes and the
related CSIRO research into advanced
membrane and carbon nanotube technologies.
(CISRO undated)
Incremental improvements of sustaining
technology will continue to reduce RO
treatment costs about 4% a year. Prospects for
further incremental improvements are high,
based on improved understanding of existing
processes, improved simulation techniques and
market forces.
Conventional thermal processes are very
mature processes and a breakthrough would be
very unlikely. However further improvements are
anticipated in RO and present R&D
opportunities exist – in operations, materials
and modelling of hybrid processes
The prospects for a major breakthrough for
disruptive technology are less evident. A
number of technologies have been investigated
and tested over the years with the potential to
become disruptive but have not lived up to the
promise due to unforseen technical, energy use
or cost issues or lack of financial backing for
development and commercialisation of the
technology.
Because the water industry is generally
conservative and risk averse, construction and
successful operation of demonstration scale
plants for several years will likely be necessary
before new technology will be adopted at the
municipal level.
POTENTIAL NEW SUSTAINING
TECHNOLOGY
Nanoparticle Disinfection
Photocatalytic treatment of water is being
evaluated as a potential effective method for
degradation of pollutants and the destruction of
micro-organisms. Currently there are more than
5000 publications on photocatalytic organic
degradation.
A laboratory scale reactor that uses
electrochemically assisted photocatalysis (EAP),
to break down organic molecules in water has
been developed. Work is ongoing to determine
the salient parameters for water which affect the
rate of photocatalytic disinfection under UVA
illumination and to design an optimal reactor
for solar water disinfection, taking into account
the synergistic effects of UV, heat and UV-
photocatalysis (Rickersby et al 2007).
Another method that has been developed
deposits homogeneous polycrystalline boron
doped diamond (BDD) film on a silicon
2
substrate of up to 0.5m . Bipolar electrodes are
coated with diamond on both sides, between
monopolar electrodes and self-polarized. The
BDD/Si electrodes allow a very high anodic
potential producing very efficient oxidants for
water treatment and disinfection. Disinfection is
achieved without the use of chlorine,
independent of water turbidity, and with a low
by-product potential.
Small scale DiaCell(R)-Systems have been
developed and installed for water disinfection
and conservation, e.g. in spas and swimming
pools as well as for electro-oxidation of
industrial wastewater and hazardous effluents.
Future objectives are:
? find an alternative cathode material to
BDD to lower cost;
? reduce energy use;
? reduce COD, N-organics and NH4
content and
? optimise the efficiency.
A method for Sol-gel synthesis of nanosized
TiO2 particles on polypropylene fibres is being
developed for use for photocatalytic
degradation of organic pollutants. In another
development, modification of TiO2 particles
with noble metals has shown significant
promise in increasing the activity of titania for a
variety of catalytic processes. Even so, relatively
few studies have been carried out on Au-
modified TiO2 where metal particle sizes <5
nm give rise to unique physical and chemical
properties(Rickersby et al. 2007).
Investigation is also needed regarding the
potential risks of using nanoparticles for water
purification, including the long-term fate of
nanoparticles in the environment, detection of
nanoparticles in various environmental media,
and safe disposal.
Chlorine tolerant RO membranes
Chlorine is added to feedwater to disinfect it
and prevent the formation of a biofilm that
decreases the efficiency of the treatment
process. However, chlorine damages polymide
based RO membranes, so the filtered water has
to be de-chlorinated prior to the RO membrane.
Chlorine is added again after the RO process to
provide disinfection for the product water.
Professors at University of Texas – Austin and
Virginia Polytechnic Institute, have developed
a new membrane from polysulfone, a sulfur-
containing thermoplastic that is highly resistant
to chlorine. Therefore, the chlorine treatment
can remain effective throughout the
desalination process and improve membrane
bio-fouling resistance.
Two hydrophilic, charged sulfonic acid groups
were added together during the polymerization
process to synthesize a durable and
reproducible polymer. The polymer
composition is being further treated to find a
more selective and chlorine-resistant
membrane.
For water quality comparable to seawater, the
membrane is currently slightly less permeable
than commercial SWRO membranes. Talks
have been held with a leading manufacturer of
membranes, with the goal of bringing the new
membrane to market (Heimbuch 2008).
The chlorine tolerant membranes would
incrementally decrease the cost of desalination
by simplifing the treatment process, reducing
the biological fouling of the RO membranes
and reducing the use of chemicals.
DNA-based Contaminant Detectors
DNA-based sensors are being investigated and
developed for trace contaminant detection and
quantification.
The liquid MicroChemLab is a hand-portable
instrument which under development at Sandia
National Laboratories designed to detect a
broad range of chemical and biological agents
in less than five minutes. The detector uses
capillary electrophoresis with three analysis
trains: 1) DNA analysis to identify bacteria and
viruses, 2) immunoassays to identify bacteria,
viruses, toxins, and 3) protein signatures to
identify toxins. However the device requires
additional development to detect VOCs.
Repeatability of results and drift present
significant issues needing to be resolved (Ho et
al. 2005).
A catalytic DNA sensor for simple, low-cost field
tests has been developed by Yi Lu of the
WaterCAMPWS and colleagues. The sensor
uses DNAzymes with fluorophores as a sensitive
and selective fluorescent sensor for lead. The
lead field test has been brought to the market
by a start-up company, DzymeTech, Inc. (Illman
2006)
The performance of two new arsenic field-
testing kits using biosensors, the Hach EZ and
the Quick Arsenic kits (Industrial Test Systems,
Inc.), have been independently evaluated. In
the study, both kits which are in the market were
able to properly identify all water samples that
had arsenic concentrations >15 μg/L (WHO
guideline value 10 μg/L) (Steinmaus et al.
2006).
POTENTIAL DISRUPTIVE TECHNOLOGIES
Thin Film NanoComposite (TFN) Membranes
One of the efforts to develop a TFNC
membrane is being lead by UCLA Assistant
Professor Hoek's team using a unique
nanocomposite material comprised of a cross-
linked matrix of polymers and engineered
nanoparticles that draw in water ions and repel
nearly all contaminants. Dr. Hoek stated "The
water-loving nanoparticles embedded in our
membrane also repel organics and bacteria,
which tend to clog up conventional membranes
over time."
The team claims that the process is just as
effective as the current RO process but more
energy efficient and potentially much less
expensive. Initial tests suggest the new
membranes have up to twice the productivity or
consume 50 percent less energy reducing the
total cost of desalinated water by as much as 25
percent.
Dr. Hoek has filed patents and is working with
NanoH2O, LLP, an early-stage partnership, to
develop the fouling-resistant nanocomposite
membrane technology. The goal is to have a
commercial product within 2 years (UCLA
2006). Initial production will likely be directed
toward use in high value markets such as the
food industry.
The CSIRO team are pursuing development of
new inorganic-organic nanocomposite
membranes for desalination using a
electrodialysis membrane process. The
nanocomposite membranes are formed by
incorporating oxide nanoparticles into ion-
conducting polymers. This results in a
membrane with significantly increased stability,
ion-exchange ability and durability. During the
project, the relationship between structure,
composition and ion-exchange properties, and
the desalination performance will be
systematically investigated.
Carbon Nanotube (CNT) membranes
CNT membranes under development at
Lawrence Livermore National Laboratory show
promise of improved desalination with flow
velocities 4 to 5 orders of magnitude greater
than predicted from conventional fluid flow
theory, providing significant potential energy
savings.
The CISRO study seeks to establish a
technology platform for CNT based membranes
and a benchmark that relates the performance
of CSIRO-made CNT membranes to
conventional membranes (CSIRO undated).
A major issue with the Carbon Nanotube (CNT)
membrane is that if it is driven at the very high
fluxes it is capable of, fouling would likely be
severe unless effective means of fouling control
are developed. CNT has to date only been
produced in small samples and there are no
reports of CNT films with salt rejections
acceptable for use in desalination.
Membrane Distillation (MD)
MD has been the subject of worldwide
academic studies. There are various
configurations of MD under study such as direct
contact membrane distillation, air gap
membrane distillation, sweeping gas
membrane distillation and vacuum membrane
distillation (El-Bourawi 2006). MD utilises low
grade waste steam/heat from power plants,
refuse incineration plants and other heat
sources to produce near distilled water quality
from seawater through vaporisation and
condensation processes using membranes.
CSIRO'sAdvanced Membrane Technology for
Water Treatment research team has been
exploring the potential benefits of Membrane
Distillation in desalination, demonstrating its
possible application over a wide range of
salinity, from brackish to high salt content water
up to the saturation point (CISRO undated).
MD is by definition a thermal process but also
involves features of membrane technology,
including issues with concentrate polarization
and membrane fouling. MD involves the
transport of water vapor from a saline solution
through the pores of a hydrophobic membrane.
It differs from other membrane technologies in
that the driving force for desalination is the
difference in vapour pressure of water across the
membrane, rather than total pressure.
Theoretically, a high water recovery is possible
for sea water desalination in the order of 80 per
cent.
A major problem is that large air flows are
required to achieve significant water yields and
the costs associated with transporting this air are
high. Other challenges include MD membrane
and module design, membrane pore wetting,
low permeate flow rate and flux decay as well
as uncertain energetic and economic costs (El-
Bourawi et al. 2006, McGinnis et al. 2008).
The patented Memstill(R) process, which has a
multiple effect design (heat recovery) using
waste heat, is being tested at two pilot plants,
one at the Senoko power plant in Singapore
and the other in Maasvlakte, Netherlands, each
of them delivering 2 m3/hour (Keppel Seghers
2007).
Another group, the Fraunhofer Institute for
Solar Energy (ISE), has developed a spiral-
wound membrane distillation module that also
has integrated heat recovery. The ISE is
developing systems driven by solar thermal
3
energy with capacities of 0.2 to 20 m /day.
These units are stated as being tested in the
Middle East.
Biomimetic membranes
Hybrid protein-polymer biomimetic membranes
have the potential to be approximately 100
times more permeable than current RO
membranes with near perfect solute rejection.
CISRO is conducting a biomimetic membrane
investigation to develop a greater
understanding of the pore structure and
membrane processes of diatoms and other
biological structural membrane filters. As part of
the program a systematic investigation of the
role of the pore structure in separation and
filtration will be conducted. CISRO hopes to
develop methods to mimic the diatom pore
structure in manufactured membranes (CISRO
undated).
There is interest in aquaporins that are very
selective to water transport. Aquaporins have
been inserted into polymer membranes by
researchers at the University of Illinois.
Macroscopic fabrication and testing have yet to
be demonstrated.
Another approach is to develop synthetic
analogues for biological membranes that pump
salt ions rather than water molecules. This
would be more favourable energy wise than
pumping water molecules because the number
of salt molecules is much lower than the water
molecules.
Large scale fabrication and testing have yet to
be demonstrated and may prove challenging,
including proof of concept at high salt
concentration levels, long-term stability, scale-
up, module design, and the need for fouling
control. Biomimetic membranes are likely to be
developed first for the medical and food
industry fields.
Capacitive deionization (CDI)
CDI has attracted the interest of the community
investigating water treatment technologies
since the mid-1960s. The technology is based
on the recognition that high-surface-area
electrodes, when electrically charged, can
quantitatively adsorb ionic components from
water, thereby resulting in desalination (Oren
2008). During the purification cycle, the salt
solution flows between the electrodes. When
the ion capture capacity of the electrodes is
reached, flow is stopped and the capacitor is
discharged, rejecting the ions back into a now
concentrated solution. The CDI approach to
desalination was sidelined for over a decade
due to problems with the use of carbon
electrodes. However, the CDI concept was
revived when carbon aerogel electrodes were
developed by the Lawrence Livermore National
Laboratory. One cubic centimeter of the
aerogel could have a surface area as large as a
football field.
Laboratory-scale CDI units built by various
entities use rectangular stacks of thin titanium
plates, which on both sides are attached thin
layers of aerogel. The water to be treated is
passed between the closely-spaced pairs of
carbon aerogel electrodes, whereupon ions
such as sodium and chloride are removed from
the stream of water and held in an electric field
on the surface of the material. The aerogel’s
pores trap huge numbers of ions before they
were saturated, but they were also prone to
clogging up with bacteria, which feed on
organic particles in the water.
Campbell Applied Physics, which is managing
an Australian project, has developed a
proprietary ozone technology that kills the
bacteria before they can fill the aerogel’s pores.
According to a news release, Northeastern
Australia will be the first location where a CDI
system will be used to provide desalinated
brackish water to nearby communities from
coal-bed gas mines, where pressurized
underground water is used to release the
trapped gas (Adee 2008).
Sandia National laboratories has been
investigating the energy recovery and net use,
yield, selectivity for specific ions, and material
cost for laboratory-scale CDI units.
Another study is investigation using carbon
nanotube technology in CDI as a flow-through
capacitor for desalination.
Clathrate Hydrate Desalination
Clathrate hydrates are crystalline inclusion
compounds in which cavities within the
hydrogen bonded water molecule (major
specie) lattice trap the hydrate-forming guest
molecule. Clathrate hydrates form
spontaneously at temperatures near but above
the freezing point of water. The clathrate
structure excludes dissolved solutes such as
sodium chloride and thereby offers a potential
means to produce potable water, primarily from
seawater (Bradshaw et al. 2006).
The desalination process is typically based on
the manufacture of a clathrate hydrate 'slurry'
(loosely aggregated or suspended in solution)
by mixing a clathrate hydrate forming gas and
water at low temperature and high pressure.
A number of processes have been investigated
that take advantage of near freezing water
found at ocean depth to provide the latent heat
required for hydrate formation. These processes
also take advantage of the natural buoyancy of
gas clathrate hydrates to produce a bubble lift
effect to assist in pumping the clathrate hydrate
slurry ashore. Many of these continuous
production methods result in complex processes
that also require large pump and piping
systems for movement and storage of the
hydrate product (Solid Gas Technologies LLC
2007).
Despite the comparatively large amount of
publicized literature and small- scale field tests,
there appear to have been no successful large
scale applications of gas hydrate desalination
to date. A significant problem appears to be the
separation of the slurry from the concentrated
seawater.
In addition, problems of controlling hydrate
formation, hydrate size and morphology,
agglomeration, amount of entrapped salt, and
the efficient recovery of hydrates must be
understood and solved (Bradshaw et al. 2006).
A number of researchers, institutions and
companies are focused on trying to improve the
gas clathrate formation process by speeding
formation, lowering required pressure, and
increasing the required temperature for hydrate
formation.
Recent published and/or patented art has
identified and described potential mechanisms
by which formation of natural gas clathrates can
be made significantly more efficient. These
include the use of certain formation catalysts
which increase the efficiency of clathrate
hydrate formation as well as various approaches
to increase the rate of thermal transfer (Solid
Gas Technologies LLC 2007).
Forward Osmosis (FO)
In osmotically driven or sometimes referred to
as engineered osmosis, the osmotic driver for
membrane transport is the difference in
concentration across the membrane, and
hydraulic pressure, when used, is an intentional
resistive force used to do mechanical work.
The FO desalination process can use low
temperature heat with a temperature difference
of 20 °C available between the heat input and
output streams. The FO process is more
efficient than conventional evaporative
desalination processes, as it is the solute which
is removed from solution by a change of phase,
rather than the water itself. Furthermore, the FO
process does not require the multiple stages,
large heat transfer areas, and large pumping
volumes required by MSF and MED. Claims
have been made that FO uses approximately
an order of magnitude less electrical energy
than RO (McGinnis et al. 2008).
The basis of FO, as well as of the majority of
other technically and economically feasible
engineered osmosis processes, is in the ability
to create a solution of high osmotic pressure,
which contains solutes that are well-rejected by
semipermeable membranes and may be at any
time readily, efficiently, and completely
removed. This high-osmotic-pressure solution is
referred to as a “draw solution”.
A major challenge for FO is finding the right
the Draw Solute, which must have a high
osmotic pressure but also be able to release its
water at a modest energy cost (
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| 译文： |
摘要
在过去20多年里，反渗透（反渗透）技术的逐步改善已大幅度减少了能源的使用量，改善了水质，总体处理成本降低了接近四分之三，使反渗透成为淡化的首选技术。并且，随着技术的改进，能源的投入与相关的二氧化碳排放量将继续下降。不过，与淡水资源的常规处理方法相比，海水淡化仍然是一个能源密集型的过程。
突破性的海水淡化技术的发展将大幅度降低淡化水生产所需的能量。根据定义，突破性的技术具有巨大的优势，将逐步取代目前广泛使用的海水淡化技术。
由于与目前技术兼容的突破性淡化技术将在未来十年左右的时间内实现，因此，设计新的海水淡化设施应考虑到将来与新技术结合，应降低压力要求，增加生产量。
引言
除了水的天然循环（水蒸汽，地表水和地下水）供应之外，海水淡化和水回用是增加水供应的唯一途径。由于目前这些技术都是能量密集型的技术，因此其使用量的增加可能会进一步恶化温室气体的排放及相关的气候变化（Tal，2006年）。
世界各地的一些国家正在研究、测试和开发有前途的海水淡化相关技术。在澳大利亚，联邦科学与工业研究（CSIRO）已和9所大学之间组成了水处理研究联合体，致力于开发先进的膜分离技术，联合开发评价和改进薄膜复合膜（TFC）的性能，以及CSIRO的先进膜与纳米管技术的相关研究（CISRO，未标日期）。
可持续技术的逐渐改善将使反渗透的处理成本以约4％每年的速度继续减少。在更好地理解现有过程、改进模拟技术和市场推动力的作用下，进一步改善的前景很大。
常规热法淡化过程是非常成熟的过程，进一步的突破将很难。但在反渗透的操作、材料以及耦合过程的模拟方面，存在进一步的改进和研究开发的机会。在过去几年中已研究和测试了几种技术，这几种技术有可能成为突破性的技术，但由于不可预见的技术、能源使用或费用问题，或缺乏技术开发和商业化动作的金融支持等原因，目前还没有实现。
由于水行业普遍保守和回避风险，因此，在新技术应用于市政工程之前，有必要建设示范工程装置，并成功运行几年。
可能的新型支撑技术
纳米颗粒消毒
光催化水处理作为一种降解污染物和破坏微生物的潜在的有效方法，正在接受评估。目前已有超过5000篇关于光催化降解有机物的论文发表。
已经开发了利用电化学辅助光催化（EAP）分解水中有机分子的实验室规模的反应器。正在进行的工作是确定影响紫外线照射下光催化消毒速度的主要盐水溶液参数，并考虑紫外线，热和紫外光催化的协同效应，设计一个最佳太阳能水消毒反应器（Rickersby等2007）。
已经开发的另一种方法是在硅基材料上沉积均质多晶硼掺杂金刚石（BDD）薄膜，面积约0.5平方米。双极电极的两侧均覆盖有金刚石。BDD/硅电极具有非常高的阳极电势，可产生非常有效的氧化剂，用于水处理和消毒。可实现无氯消毒，并且与水的浊度无关，且副产物量很小。已开发和安装了一台小型的DiaCell®-系统用于水消毒和保护，例如在温泉和游泳池，以及工业废水和有害排放物的电氧化。
今后的目标是：
•寻找可替代BDD的正极材料，以降低成本；
•降低能耗；
•减少化学需氧量，有机氮和NH4的含量；
•优化效率。
正在开发一种利用溶胶凝胶法在聚丙烯纤维上合成纳米TiO2颗粒，用于光催化降解有机污染物的方法。另一项开发是用贵重金属修饰二氧化钛粒子，在各种催化过程中提高了二氧化钛的活性，显示出了巨大的前景。但在金修饰二氧化钛这种金属颗粒粒径<5纳米时引起独特的物理和化学特性（Rickersby等，2007年）方面的研究很少。
还需要研究考虑使用纳米粒子净化水的潜在风险，包括纳米粒子在环境中的使用期限，纳米粒子在各种环境介质中的检测，以及安全处置。
耐氯反渗透膜
加氯消毒可防止降低处理过程效率的生物膜的形成。但是，氯会破坏聚酰亚胺反渗透膜，因此过滤水在进入反渗透膜之前必须去除氯。在反渗透过程之后再补充加氯，提供消毒的产品水。
美国德克萨斯大学-奥斯汀和弗吉尼亚理工学院的教授们已经开发出一种新的聚砜膜，聚砜是一种含硫的热塑性材料，具有很高的耐氯性。因此，加氯处理可在整个淡化过程期间保持有效，并提高膜的耐生物污染性能。
在合成持久和可重复性聚合物的聚合过程中，增加了两个亲水、荷电的磺酸基团。正在进一步处理聚合物组成，以便找到一种更有选择性和耐氯性的膜。
对于与海水差不多的水质，这种膜的渗透性略低于商用SWRO膜。正在与一家领先膜制造商协商，其目标是把新膜推向市场（Heimbuch，2008年）。
耐氯膜通过简化处理过程、降低反渗透膜的生物污染、减少化学品的使用量等方式将逐渐降低海水淡化的成本。
基于DNA的污染物检测器
用于微量污染物检测与定量的DNA传感器正在研发中。液相微观化学实验室（MicroChem Lab）是正在桑迪亚国家实验室开发的一种手持式便携式仪器，其设计目的是在5分钟内检测范围广泛的化学品和生物制剂。该检测器采用毛细管电泳，有三套分析方法：1）DNA分析，以确定细菌和病毒；2）免疫测定，以确定细菌，病毒，毒素；3）蛋白质印迹，以确定有毒物质。但是该设备需要进一步的开发，以检测挥发性有机物。目前需要解决的重要问题是结果的可重复性和漂移（Ho等，2005年）。
WaterCAMPWS公司的Yi Lu及其同事开发了一种用于现场检测的低成本的催化DNA传感器。该传感器使用脱氧核酶与氟磷酸盐作为一个敏感的选择性荧光传感器，用于铅的分析。铅现场分析仪已由DzymeTech公司推向市场（Illman，2006）。
已独立地评价了两个使用生物传感器的新的砷现场测试仪：Hach EZ和快速砷测试仪（工业性试验系统公司）。在这项研究中，这两个已上市的测试仪能够正确识别砷浓度>15微克/升的所有水样（卫生组织准则值10微克/升）（Steinmaus等，2006年）。
潜在的突破性技术
薄膜纳米复合（TFNC）膜
加州大学洛杉矶分校霍克助理教授的研究小组的一项研究是开发一种薄膜纳米复合TFNC膜，使用独特的纳米复合材料组成的基体聚合物的交联和工程纳米粒子，可以吸引水中的离子，并排斥几乎所有的污染物。霍克博士指出，“亲水的纳米粒子嵌入到膜中，可以排除有机物和细菌，它们往往一直阻塞常规膜。”
该小组称，这一进程与目前的反渗透过程同样有效，但更节能，有可能更便宜。初步测试表明，这种新开发的膜具有高达两倍的生产率或消耗不到一半的能源，使淡化水总成本的降幅可达百分之二十五。
霍克博士提出了专利，并正在与其早期阶段伙伴关系NanoH2O LPP公司开发耐污染纳米复合膜技术。其目标是在二年内开发出一个商业产品（UCLC，2006年）。初期生产将有可能针对高端市场，如食品行业。
联邦科学与工业研究小组正在开发新的无机有机纳米复合膜，用于电渗析海水淡化过程。纳米复合膜是把氧化性的纳米颗粒结合到离子导电聚合物上形成的，使膜的稳定性、离子交换能力和耐用性显着增加。在项目研究期间，将系统研究膜的结构、组成和离子交换性能，以及淡化性能之间的关系。
碳纳米管（CNT）膜
正在Lawrence Livermore国家实验室开发的碳纳米管膜的淡化流速比由常规流体流动理论预测的流速高4到5个数量级，在节能方面呈现出了巨大的发展潜力。
CISRO的研究旨在建立一个基于碳纳米管膜的技术平台，以及与CISRO制备的碳纳米管膜和常规膜的性能相关的基准（CSIRO，未标日期）。
使用碳纳米管（CNT）膜的一个主要问题是，如果以非常高的通量驱动，则它会污染严重，除非有控制污染的发展的有效手段。碳纳米管膜迄今只生产了小样本，也没有CNT薄膜在淡化方面可接受的脱盐率报导。
膜蒸馏（MD）
膜蒸馏已成为世界各地学术研究的目标。研究了各种不同结构的膜蒸馏，如直接接触式膜蒸馏，气隙式膜蒸馏，气体清扫式膜蒸馏和减压膜蒸馏（El-Bourawi，2006年）。膜蒸馏可利用蒸汽/热电厂、垃圾焚烧发电厂和其他热源的低品位废热，使用膜通过汽化和冷凝过程从海水中生产蒸馏水质量。
CSIRO的水处理研究小组的高级膜技术研究一直在探索膜蒸馏在淡化方面的潜在优势，表明它可能适用范围广泛的盐度，从苦咸水到盐含量高达饱和点的盐水（CISRO，未标日期）。
MD的定义是热过程，但也涉及膜技术的特征，包括浓差极化和膜污染问题。MD涉及水蒸汽从盐溶液通过疏水膜的毛细孔的运输过程。MD与其它膜技术的不同在于其淡化的驱动力是在蒸汽穿过膜的压力，而不是总压力。从理论上讲，海水淡化的水回收是有可能达到百分之八十。一个主要问题是，需要大量的空气流量，才能得到较高的水产量，因此，与空气输送相关的费用很高。其它挑战包括MD膜和模块设计、膜孔的润湿、低渗透流率和通量衰减以及能耗和经济成本的不确定性（El-Bourawi等，2006年；McGinnis等，2008年）。
专利的Memstill®过程是一种利用余热的多效设计（热回收），正在两个试验装置上测试，一个在新加坡的圣诺哥发电厂，另一个是在荷兰的马斯弗拉克特，每个装置提供2立方米产水/小时（Keppel Seghers，2007年）。另一研究团队是Fraunhofer太阳能研究所（ISE），开发了一种卷式膜蒸馏模块，也有集成的热回收。ISE正在开发一种太阳能驱动的系统，产水能力为0.2至20m3/day。据报导这些装置正在中东试验。
仿生膜
耦合的蛋白高分子仿生膜具有可能比目前的反渗透膜高大约100倍的渗透率和近乎完美的溶质截留。
CISRO正在研究仿生膜，以便更深入地了解膜孔结构和硅藻的膜过程和其他生物结构的膜过滤器。作为计划的一部分，将系统地研究孔隙结构在分离和过滤过程中的作用。CISRO希望开发出一种在制膜过程中模拟硅藻孔结构的方法（CISRO，未标日期）。
对水的传递具有非常高选择性的水溶性蛋白质正引起人们的兴趣。伊利诺伊大学的研究人员已将水通道蛋白嵌入到聚合物膜中。还需要得到宏观制造和测试的证明。
另一种办法是合成类似生物膜的结构，这种结构输送的是盐离子，而不是水分子。这将更节能，因为盐分子的数目远低于水分子数。
大规模制造和测试还需要得到证明，而且可能非常具有挑战性，包括证明在高盐浓度下的应用、长期稳定性、放大效应、模块设计，并且需要控制污染。仿生膜很可能最先开发用于医疗和食品工业等领域。
电容去离子过程（CDI）
自20世纪60年代中期，电容去离子过程已引起水处理技术领域研究人员的兴趣。这种技术是基于这样的认识：具有高表面积的电极，当其带电时，可以从水中定量地吸附离子组分，从而实现水的淡化（Oren，2008年）。在净化周期内，盐溶液在电极之间流动。当电极达到离子捕捉能力的极限后，流动停止，电容器放电，将离子排放到浓溶液中。由于以前一直使用碳电极，因此十多年来CDI淡化方法一直没有得到发展。然而，随着劳伦斯利弗莫尔国家实验室的碳气凝胶电极的开发，才又重提CDI的概念。1立方厘米的气凝胶的表面积可能相当于一个足球场大。
不同研究部门建立的实验室规模的CDI装置均使用长方形的薄钛板，在钛板的两侧都涂上了薄层气凝胶。待处理的水穿过紧密排列的碳气凝胶电极对的间隔，钠和氯离子等被材料表面的电场捕获，从水流中去除。气凝胶的孔隙在饱和前可捕获大量离子，但他们也容易被细菌堵塞，这些细菌以水中的有机颗粒为食。
Campbell应用物理研究所正在管理一个澳大利亚项目，已开发出一种专利技术，在细菌堵塞气凝胶孔隙之前，进行臭氧杀菌。据报道，澳大利亚东北部将是第一个把CDI系统将用于从煤层气矿废水中提供脱盐苦咸水给附近社区的地方，其高压地下水用于释放煤层（Adee，2008）。桑迪亚国家实验室一直在研究能源回收和净使用，收益，特定离子的选择性，以及实验室规模装置的原材料成本。调查的另一项研究是利用碳纳米管技术在CDI中作为一种流通的电容器用于淡化。
笼形水合物海水淡化技术
笼形水合物是一种晶体包合物分子，在其氢键水分子（主要种）晶格腔内捕获水合客体分子。笼形水合物在温度稍高于水的冰点附近自发形成。笼形结构可排斥溶解的溶质如氯化钠，从而提供了一个可能的生产饮用水，主要是从海水生产饮用水的方法（Bradshaw等，2006年）。该淡化过程的基础是低温和高压下，将形成笼形水合物的天然气和水混合，制造笼形水合物'泥浆'（松散的絮体或悬浮在溶液）。
已经研究了一些过程，可充分利用在大洋深处冰点附近水的优点，提供形成水合物所需的潜热。这些过程还利用天然气水合物包合物的自然浮力产生泡沫升力效应，以协助把笼形水合物浆抽输送到岸上。许多这些持续的生产方式过程复杂，还需要大量的泵和管道系统的输送与储存水合物产品（固体燃气技术公司，LCC 2007年）。
尽管关于天然气水合物淡化已有大量的文献发表，并有小规模的现场测试，但至今还没有成功应用天然气水合物淡化的大型装置。一个重大的问题似乎是如何从浓缩海水中分离这些泥浆。此外，也必须理解和解决控制水合物形成、水合物的大小和形态、集聚、捕获盐的量，高效率地回收水合物等方面的问题（Bradshaw等，2006年）。
一些研究人员，机构和公司正从加速水合物的形成、降低所需的压力、增加水合物形成所需的温度等方面，致力于改善气体包合物形成过程。
最近发表的文献及出版的专利已确定和描述了可以更有效地形成天然气水合物的潜在机制。这些措施包括使用特定形式的催化剂，提高笼形水合物形成的效率，以及采取各种办法增加热传递的速度（固体燃气技术公司LLC 2007年）。
正向渗透（FO）
在渗透驱动（有时也被称为工程渗透）中，其膜传递的渗透驱动力是膜两侧的浓度差，而水力学压力是一种做机械功的阻力。
正向渗透脱盐过程可以使用低温差，输入和输出流的温差20℃即可。正向渗透过程的效率比传统蒸发海水淡化过程更高，因为它是溶质是从溶液中因为发生相变去除，而不是水本身。此外，FO过程并不需要象MSF和MED那样的多级（段）操作，大的传热面积和大的水量。据称，FO过程的电能消耗比反渗透过程大约低一个数量级（McGinnis等，2008年）。FO以及大多数其他技术上和经济上可行的工程渗透过程的基础，是需要有能力制造出一种高渗透压的溶液，其中所含的溶质可被半渗透膜很好地截留，可在任何时间很容易、高效地完全去除。这种高渗透压的溶液称为“提取液”。
对于FO过程，面临的一个重大挑战的是找到正确的提取溶质，它必须具有很高的渗透压，而且还能够在温和的能源成本（低于反渗透）下将所提取的水释放出来。一个成功的提取液是采用浓的铵水溶液（将氯溶解于水）和二氧化碳（CO2） 。这种溶液是热不稳定的，当加热时，盐会分解形成氨和二氧化碳气体。这些气体，当再次在较低的温度下引入到溶液中，很容易重新形成所需的提取溶质。这一过程比蒸发水有其固有的效率，因为水的蒸发焓远远超过这些溶解盐的汽化焓。
对于海水，因为水流过膜时，无论是海水盐还是提取溶质都被膜截留，海水进料被浓缩，提取液则被稀释。稀释后的提取液然后进入一个简单蒸馏塔，在负压条件下，使用低温热源，将氨和二氧化碳气体从提取液中回收再利用，生产的淡水中含有百万分之一的氨氮。然而，一个可行的正渗透过程有几个关键的障碍。常规反渗透膜并不适合。只有一个供应商供应商品化的正渗透膜，这些正渗透膜更有效，但远没有达到最优。不同的研究人员得到的渗透通量不一致，甚至会差一个数量级，还需要更好的实验工作。正渗透的有效和高效地使用基本上限于水电联产或其它废水或低成本的热量可用的场合（McGinnis等，2008年）。
在工程渗透方面，现代水利公司收到了第一份使用渗透技术（MOT）的海水淡化装置的合同。这个100m3/day的淡化装置将设在直布罗陀的现有海水淡化厂，并将使用同样的给水。
这个MOT是萨里大学开发的一个两级的海水淡化过程，使正渗透与反渗透相结合，旨在减少能源消耗。
两级纳滤过程
Long Beach水利部门（LBWD）已开发并申请了专利两级纳滤（NF）的过程，称为NF/NF或称为常见纳米-纳米技术，以淡化海水达到饮用水标准。已建立了一个1135m3/day的双级纳滤技术的海水淡化装置，并正在测试（Cheng等，2007年）。
预处理后，海水在525psi的压力下通过纳滤膜，去除大部分的二价离子和少量的一价离子，留下约12％的原始盐浓度。第一级纳滤的产水在较低的压力250pso下，通过了第二级纳滤膜，去除足量的剩余盐，以满足饮用水标准。一个关键组成部分是第二级浓缩液循环回用，稀释了第一级的给水。
比较“疏松”的NF膜需要的操作压力较低，因此可比一级反渗透系统节省约20％的能量。一个关键目标是建立全面系统总资本支出和运营成本的准确资料。
一体化的技术创新
西门子公司正在开发一种使用电场去除海水中盐的创新技术。西门子水技术团队正在研究将电渗析，离子交换软化，然后连续电驱动集成用于盐分离（Siemens，2008）。
发展先进的海水淡化技术已获得新加坡环境与水工业发展理事会（EWI）400万新元的研究基金。西门子将利用这笔研究基金，在该公司设在新加坡的全球研发中心开发这一技术。EWI的挑战要求证明能源消耗为1.5千瓦小时每立方米，约为已证实的现有的最佳技术的一半。
结论
基于更好地理解现有的过程、改进模拟技术和市场驱动力，可持续海水淡化技术继续逐步改善的前景很高。
突破性的技术一大突破的前景不那么明显。在过去几年中研究和测试的一些技术可能成为突破性的技术，但由于不可预见的技术，能源利用，成本问题或无法获得技术开发和商业化的资金，还没有实现。
目前还不清楚，上述技术或其变化形式有可能会成为一种革命性的技术。表1提供所描述技术的名单，技术介绍，总结了优势和现存的障碍，并粗略估计该技术可能商品化的时间。
TFC膜可能是进入市场的第一个具有潜在突破性的技术，但很可能开始时数量相对较小。这可能再需要3至5年的时间，才能实现大量生产TFC膜的能力。NF/NF技术利用现有的元件和系统，如果它显出了重大的生命周期成本优势，则可以相对迅速地适应淡化市场。
一些技术障碍可能需要几年时间才能解决，其它技术的进步可能不会超过实验室或中试装置的阶段。
新技术的采用可能是缓慢的，因为水工业往往很保守并且回避风险。在新的技术应用于市政工程之前，需要建设示范工程并成功地运行几年。
由于突破性技术可能在未来十年左右的时间里出现，因此设计新的海水淡化设施时，应考虑将会与新技术相结合，从而可能降低压力需求，和/或增加生产量。这可能涉及诸如设计电机安装预制，以便于安装低功率电动机，并选择叶轮可以改变的高压泵，以提高效率和降低操作压力。在反渗透系统安装较大的给水管和产品水管径，将允许使用增强流动性能的串联膜元件。
致谢
前面讨论的各种技术基于文献检索，当然，有些是作者个人了解的。不可能包括所有的技术、结构等。增量技术改进和破坏性的技术，更容易克服显著的技术、能源和市场的挑战，以实现商业上的成功说明。应指出的是，文献检索并不总是揭示了目前技术的发展状态。
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海水淡化成本概述 |
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1.4 The cost of desalination |
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1.4 海水淡化费用
同其它供水方法相比，经过几十年的发展，海水淡化的费用已有了大幅的降低。尤其是反渗透海水淡化从90年代初的$1.50/m3降到了现在的$0.50/m3以下，近来在新加坡建造的Tuas淡化厂的运行费用就是这样（见图4.1）
虽然在新加坡由Singspring建造的Tuas海水淡化厂是第一个吨产水费用低于50美分的淡化厂，但并不是所有的反渗透淡化厂都能达到的。例如在阿布扎比的Taweelah反渗透淡化厂产水费用为$0.64/m3，由于海湾地区的水质较差，在该地区的反渗透产水费用都大致如此。在加利福尼亚，计划中的海水淡化项目的产水费用预计在$0.65/m3~$0.89/m3间，这是由于当地的高地价、高劳动成本及管理费用，以及水输送到管网线的费用。
在过去十几年中，由于提高了淡化效率，能源的消耗也降低了，膜性能及海水的预处理水平得到提高，详情见第二章。
虽然淡化厂公布的数据不多，热法海水淡化的费用也有所降低，大多数的淡化厂位于中东地区，费用的降低在主要的操作计划中可以看到（这些数据是公开的），因为这些主要的数据占到整个费用的近60%。表1.4.2由Zhou Yuan1制作。
在2005年，淡化厂的产水费用通常在$0.65/m3~$0.90/m3之间，阿布扎比的Taweelah A1和Taweelah A2淡化厂建于2003年，产水费用为$0.70/m3，Shuweihat建于2004年，产水费用为$0.73/m3，多极闪蒸（MSF）技术的使用提高了淡化厂的效率，增加了规模经济效益，详情见第二章。
在脱盐领域内，成本的降低是脱盐市场发展的一个至关重要的因素，所以经常出现成本降低的情况。很多水务公司在寻找可以成指数增长的新水资源的成本，任何成本的降低都会引起脱盐设施的指数增长。但是，海水淡化仍然是水务公司企图增加淡水供应量的选择之一。
图表1.4.2 MSF海水淡化成本
1.5 海水淡化的其他选择
面临水的需求增长和水的边缘成本提高这样的情况，水务公司有几种不同的选择。这些选择大致分为三类：
需求管理
提高效益
开发新水源
需求管理或许是最合算的缓解水资源压力的方式。提高效益需要投资，但是对于许多水务公司来讲是比增加供应量更具成本效益的方式。开发新水源可能是最耗钱的解决方法，但是这是一种政治需要，也是一种财政可能性。
需求管理
有三种主要的需求管理工具：税率，配额，水的经销权。可以通过改变消费习惯影响因素来减少需求。上面Namwater的例子说明了这些因素是如何高效地起作用的。除了引入成本和资本回收定价，公用事业公司可以利用刑事税率处理那些用水量超过基本配额的水用户。
减少水需求的一个最大的环节是农业中对不适当的土地用水进行补贴的部分。 在历史上加利福尼亚州帝王谷曾是一个沙漠，后来变成美国物产最丰富的农业区，代价是科罗拉多河的萎缩。帝王谷的农民拥有该河流38亿立方米（310万英尺）的配额，他们需为每立方米水支付0.013美元的运费。这个配额是圣地亚哥年供应水量的五倍还要多。圣地亚哥县水务局，城市的供水区域和帝王谷的灌溉区域于2003年10月签订了协议，减少帝王谷农民用水7％的配额，使得圣地亚哥每年可以多从科罗拉多河汲取2.47亿立方米水——相当于圣地亚哥年供水量的三分之一。为此，帝王谷的农民可获得每立方米水0.26美元的补偿金。67.7万立方米/日的原水供应明显比从科罗拉多河汲取的原水昂贵，但是相比远程调水和海水淡化还是要便宜。
加里福尼亚水需求的增长在理论上说，可以利用自发的水经销权和水运送的方式得到解决。实际操作中，有很多减少从农业环节再分配水的政策上的变化。农业部门是农村地区最大的雇主，失去水就意味着失去工作岗位。帝王谷协议尽管在农业方面的反应相对中庸（46万英亩中的2.7万英亩将退耕），仍然花费了几年的时间协商，还差点没有取得所有政党的必要支持。
加里福尼亚州的农业只是经济中很小的一部分。在地中海地区，如西班牙南部和以色列，农业在经济中所起的作用就相当重要了。
以色列曾经用一个由国家水委员会操纵的分配系统来管理水需求。这个系统曾经一度有助于遏制水需求。以色列农业环节里每单位水的生产效率在50年里提高了5倍，水利用的有效率为95％。农业用水仍然滞后，维持津贴的政治压力很大，这意味着水在整个国民经济中没有得到有效分配。
家庭用水节约空间不及农业用水的节约空间大。节水厕所和节水型家庭用品，合适的园林植物，节制用水量多的活动，这些都是可以通过罚款性的水价和法律做到的。工业领域内水的价格问题不是那么敏感，但是可以通过限额和罚款性的水价鼓励工业领域有效地利用水资源。工业环节引入水重复利用的概念是减少需求的最有效的方式。
1.5.2 提高效率
除了使客户提高水利用的效率，水务公司还可以提高自身供水的效率。很多涉足脱盐领域的水务公司运输网络中存在着惊人的水量流失（UFW）——他们供给用户的水量和向用收取费用的水量之间的差。例如，阿尔及利亚花费了大约2.5亿美元的代价建造了一个日产量水为10万吨的脱盐工厂，其中超过一半的水浪费在了运输网络中。这样的效率将城市的淡化水成本增加了一倍。
UFW的产生是由几个原因造成的：
免费的计量消耗
免费的非计量消耗
未经授权的偷窃用水
测量误差
主要线路渗漏
储存过程中的渗漏和溢出
服务连接和客户计量处的渗漏
世界平均UFW被认为是35％，运营最好的水务公司的UFW目标是在10％到20％之间。这个指标使得降低UFW的边缘成本变得不经济。由于造成每个水务公司的UFW的原因不同，所以很难给减少水量流失的花费定一个指标。
在一个定量的世界，所有的水务公司都面临以他们的能力只能保证对客户的不足量供应的情况，只有当这种情况威胁到其成本的有效性，才能把降低水量流失放在优先考虑的位置上。在现实社会中，很多水务公司发现很难在减少水量流失问题上有所行动。
原因常常会涉及到这样一个现实情况：在很多国家，水供应通常不会被认为是一种商业活动。而是期望市政当局把水以低于成本价的亏损价供给当地的市民，水供应成为一项吸收了大量资金却没有动力去投资的商业活动。而在一些国家（如阿尔及利亚），投资的缺少导致水供应能力的不足达到了一种平衡。家庭主妇们不得不学着在一种免费但间歇行供水的情况下生活。拿阿尔及利亚的斯基克达来说，当地水务公司在2002的夏季只能保证每星期3小时的供水。在暴动发生后，作为回应，政府许诺在司机达克建造一座日产100,000立方的水的设施。花费120亿美元建一个新的海水淡化工厂和保证修复地下管网的泄漏比起来，能够更有效的让暴动的人群从大街上撤离。地下的设施永远不会象地面上的设施那样为众人所见。
沙特阿拉伯的UFW也很高：官方数字是20％，但是据内部人员说，大城市的UFW的实际数字接近50％。尽管有可用的投资资金，但是在政策上的关注和管理技术上尚存在欠缺。当局需要负责太多的活动，水问题仅仅能在水务部门那里被优先考虑，而运作的规模却不足以吸引到最好的管理。这种无效性和举足轻重的国家供水的运作形成了强烈的对比，有私营部分参与到其中淡化公司保证了国际标准的有效性。
对于降低水量流失，政治态度是不理智的。一方面，他们轻率的认为水是应该免费的，如果政治家们不认可供水的成本，那他们对浪费行为的绅士般大方的态度就可以理解了。也许为一个大型淡化公司筹集大量资金的经历将会成为矫正他们水应该是免费的这个信念的最好方法。
1.5.3开发新的水源
不得已取用传统水源，提取一定水量的地下水和地表水的水务公司,在开发新水源方面有以下四种方式:
从其它地区进口地下水
废水再利用
致力于低品质的未净化水
海水淡化
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百沃特公司资料 |
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2. The Perfect Water Company
Pure Water
Perfect, pure water could be considered as ‘captured’ rain from the sky, delivered unadulterated to customers at a rate and pressure to suit their every need.
This would be possible if sterile reservoirs, as large as seas and in upland locations, could be created. However, even this utopia would be inadequate in the very arid regions of the world.
Problems occur as soon as rain falls; it becomes contaminated immediately. Where it falls determines the degree of contamination and this, in turn, determines the treatment process necessary.
Technology exists to remove all contaminants from water and to supply customers with a product as pure as the day it fell from the sky. Unfortunately, however, the cost of providing such quality water is enormous. Indeed, far too high for use as just drinking water. In reality, criteria for the Perfect Water Treatment Plant is much simpler than one might expect.
Desalination
Where rain water is insufficient to meet demand, Biwater has supplied water treatment plants that extract water from the sea and purify it to a stage where it surpasses that of ‘rain’ water. Ironically, this is too pure for most people’s taste and requires re-mineralisation to make the water wholesome.
Salt from sea water is removed using a process known as reverse osmosis. (Three other processes also exist, namely ‘freeze desalination’, ‘distillation’ and ‘vapour recompression’). Before the salt is removed from the water, all suspended solids have to be filtered out to prevent the membrane used in the reverse osmosis process from clogging. Pre-treatment by a conventional filtration plant is carried out in order to condition the water so that it can pass through the membrane. The reverse osmosis process requires a great deal of energy to be effective. The whole process therefore represents the optimum for water treatment plants in terms of technology input and cost.
Biwater has provided some of the largest plants of this kind in the world, thereby producing cost-effective drinking water from salt water.
Picture title: Reverse osmosis plant for the city of Oxnard, USA, built by Biwater AEWT
Surface Raw Water
Where rain is plentiful and contamination is light, there is usually no need for a complex treatment plant. If the source of water is an impounding reservoir or river, the raw water normally has suspended solids, bacteria, algae, colour (humic acids), etc. Occasionally it may contain viruses (through pollution) and/or agricultural by-products such as pesticides and fertilisers. It may also contain the naturally occurring soluble metals iron and manganese that, although not poisonous at normal raw water concentrations, will affect taste and lead to staining of water fitments unless removed. In these instances, conventional water treatment plants offer the most cost effective solution.
This method would generally consist of coagulation/flocculation and clarification, colloidal solids, colour and algae removal, which would be followed by sand filtration stages for removal of suspended solids and, if necessary, dissolved iron and manganese. Disinfection is also required to ensure that pathogens do not reach the consumer.
Agricultural Contamination
If agricultural by-products, such as pesticides or other potentially harmful compounds are considered a problem then a Granular Activated Carbon (GAC) absorption stage, sometimes preceded by ozone treatment, may be necessary before disinfection. GAC can also be used for taste and odour removal.
Another agricultural by-product, nitrate, can become a health problem if the concentration in drinking water exceeds a specific level. It is often possible to reduce the concentration by blending with an uncontaminated source, but otherwise processes such as ion exchange or reverse osmosis are needed to reduce the nitrate concentration.
In order to remove the contaminants a wide range of chemicals are added to the water. To achieve effective clarification, further treatment may be necessary by adding chemicals for disinfection or precipitation of soluble iron and/or manganese before removal by filtration. Acid or alkalis may be added to adjust pH; orthophosphate dosing to control dissolution of lead from the inside of old pipes and finally coagulants and a polyelectrolyte to aid flocculation.
Waterworks Sludge Treatment and Disposal
Processes such as clarification and filtration generate sludge that can be up to 10% of the raw water extraction rate if untreated. It is often considered more efficient and environmentally friendly to concentrate the solids in the sludge to reduce its volume for disposal whilst returning the ‘trapped’ water to the head of the works. Process units such as filter washwater clarifiers, sludge thickeners and sludge filter presses are commonly used for this purpose. Sludge thickeners and filter presses in particular require polyelectrolyte dosing chemicals to achieve the best results.
The broad principle of plant design is well understood, but the most cost effective solutions are invariably determined by the design skills of the technologists.
The Process Scientist
The process scientist selects the optimum process types and sizes as well as working out the quantity of chemicals in order to remove contaminants and to minimise running costs.
Running Costs
The running costs will be dramatically reduced if gravity is used to pass the water through the treatment works and, where possible, through the distribution network to the customer. The initial capital cost will be reduced by achieving a flow with as small a hydraulic gradient, and as an efficient a layout, as possible.
Underground Raw Water
Water from an underground source has normally percolated through the strata and is held in underground aquifer. Nature does its own ‘clean up’ by slowly filtering the water through the layers of soil and rock removing biological life and suspended solids. Aquifers can be tapped by boreholes or wells. The water in some aquifers will be fit to drink but in others it will have dissolved minerals such as iron and manganese, or even possibly ammonia. In the latter cases, water is brought to the surface where aeration, followed by simple chemical treatment and filtration, is all that is normally required. This represents the simplest of water treatment plant.
Remote Communities
For people living great distances from urban areas the supply of wholesome water is often a problem as they live beyond the service range of large urban water treatment plants. Alternative sources of water in these circumstances vary greatly.
The cost and difficulties in running a conventional treatment plant for a small community are considerable. It is here that the ‘membrane’ process can come into its own. The membrane process does not need to filter to the level of salt removal, as with desalination, as coarser membranes can be used. This means that the energy required to push water through the process is much lower and the pre-treatment stage is much simpler. The raw water entering the plant usually has an adequate physical barrier to assure a drinkable result.
Picture title: Asset Survey Team, UK
Is Perfect Water Treatment Unnecessary?
Whilst the ‘Perfect Water Treatment Plant’ may not yet be available, or indeed necessary, one that can deliver near perfect ‘drinking’ or ‘potable’ water is. If we can accept water that is less than perfect but is still wholesome (i.e. to standards that are set out by the World Health Organisation and the European Economic Community directives) then the costs of treatment are considerably reduced.
The ‘Perfect Water Treatment Plant’ is one that can meet the accepted standards in the most cost effective way – taking into account the source of raw water, the location of the plant and the ingenuity of those who design the treatment processes.
Picture title: Analysis of Downloaded Information, UK:
Water Network Management
To manage a Perfect Water Company, we have to prepare a water distribution management strategy, which may also be called an Integrated Network Management Strategy (INMS) or Water Asset Management (WAM) plan. The Perfect Water Company would have a perfect Integrated Network Management Strategy. If they do not have the perfect Integrated Network Management Strategy it is essential for investors to realise that, whilst it is necessary to have a treatment works of suitable capacity, if the network cannot distribute the water efficiently, the investment is devalued. Increasingly, investors are making network management strategies a condition of the grant or loan. Whilst it is easy to develop a distribution network management strategy, it is harder to develop one that works.
The work involves a wide range of hydraulic studies to solve water, sewage and environmental infrastructure problems. Biwater’s engineers benefit from being part of a large diverse Group with support services and a wide resource base. The techniques developed have been applied to many Biwater projects throughout the world.
A well balanced network management strategy is as much about managing information as it is about managing water. Good investment decisions rely on accurate information. It is too easy to rush into large scale pipe laying, rehabilitation or customer metering projects without considering the full implications on investment strategy. Biwater has extensive experience of developing these strategies with its clients.
Historically, a significant number of network investment strategies were driven by banks or investors with experience of construction. Large capital schemes are easier to identify and quantify but network repair and maintenance is often being taken as operational expenditure and lost in day to day operational budgets. It is also common for client organisations to want large scale engineering works because that is what they have been used to in the past and politically can be seen by their customers to be taking immediate action.
However, whilst large construction schemes may be the answer, the need for large scale capital investment projects can often be deferred or reduced by less capital through suitable investment in the distribution network.
In general the development of a network management strategy can be divided into five key phases.
• Identification of the key issues
• Creation of the management tools
• Collection of key network information
• Derivation and delivery of the network management strategy
• Review of strategy goals
These phases may last several weeks or several years depending on the needs and size of the utility operator. Network management strategies are an iterative process and may have to go through several cycles to meet the desired outcome. Each of these stages is discussed in more detail below.
Identification of the Key Issues
At the start of any network management project it is essential to identify the main drivers of the strategy. These may include poor level of service, lack of raw water reserve, insufficient water into supply, ageing infrastructure, lack of storage, poor water quality, future expansion, poor revenue recovery or regulatory pressure. These drivers are often obvious and can normally be ascertained in a few days with water company personnel.
However care should be taken in identifying the root cause of the problem. For example what is initially described as a poor supply pressure problem may be actually be due to high leakage levels or incorrect zoning.
Additionally, stakeholders may have their own schemes or ideas and will try to steer the strategy towards getting funding for these. It is important that these schemes are assessed fairly as part of the overall strategy goals. This may necessitate the development of a scoring system to prioritise the issues to be addressed as part of the strategy.
Once the issues are understood it is important to set clear objectives for the strategy, enabling all stakeholders to understand the project and its direction. It may not be possible at this stage to set numerical targets.
Creation of the Management Tools
Once the overarching objectives of the strategy are known, the first stage of implementation is the assessment and collection of existing information. In order to do this a number of information storage and manipulation tools need to be developed or modified.
One of the key tools is a GIS system. This is a geographically linked database of network assets that is invaluable in managing a distribution network. Another valuable tool is a hydraulic network model. Models can normally be classified as strategic or all mains. However, all mains models can be expensive and time consuming to develop and therefore their use needs to be carefully considered. Other network management tools might include telemetry systems, flow and DMA meter analysis packages, billing systems, work order systems, customer contact systems, procedures and policies.
Underlying all the management tools is a data model. It need not be a totally software based system and can include other information types. It is a defined storage system for all the information required for the effective management of the network. The data model is defined by the requirements of the business and the proposed goals. It will define what needs to be collected and when, where it is stored, how it is used and what information is used by the business and in what form it is required.
A data model is not fixed and will evolve as the distribution management strategy is developed. However, it is important to get as much of the fundamental structure in place at the start of the process as possible to ensure that as little work is revisited as is practicable.
Collection of key network information
Once the storage and manipulation tools have been established, the next stage is to collect the required base data. This is largely dependant on the targeted goals of the network management strategy. Typical data might include:
• Mapping;
• Pipe location, diameter, material, age, condition;
• Water volume into supply;
• Flow and pressure data;
• Billing data;
• Customer contact history;
• Pipe failure repair;
• Cost data;
• Per capita demand profiles;
• Population and industrial growth.
Once data collection is complete it should then be possible to set some realistic numerical targets by which to measure achievement of the set objectives.
Derivation and Delivery of Management Strategy
Once the business need goals are confirmed the major component of the work is undertaken on the distribution network. This is discussed in more detail in later sections.
Review of Strategy Goals
At the end of the development of the network management strategy the goals of the project need to be reviewed before implementing the next stage. It is important to reassess the overall goals after each stage of the project implementation as the objectives may change as information and control of the network improves.
The network management strategy should be reviewed at least annually to ensure that the key business issues continue to be met. However, major changes in direction should be undertaken with caution as most network management strategies will take more than one cycle to deliver real benefits.
The Fundamentals
The main tenet of a network management project is to gain control of the network. It has long been an adage of management text books, “If you can’t measure it, you can’t manage it”. In a distribution network the key variables are flow, pressure and cost. It is essential to measure where water is going, at what pressure and how much does it cost to deliver it. This is achieved by setting up a “Hydraulic Structure”.
Picture title: Downloading Datalogger Information, UK
Picture title: Asset Management, UK
Non-revenue water
To develop a water distribution management strategy, one of the areas of confusion is the difference between Non-revenue water (NRW) and leakage. Many assume that they are the same – they are not.
Leakage is normally defined as water lost from the network though structural defects in the pipes, tanks and other network apparatus. Leakage is only one component of Non-revenue water, which includes water taken unbilled, water used for operational purposes, bad debts (water billed but revenue not recovered), governmental use etc. In the UK the NRW level for most companies is between 20% and 30% of distribution input.
For this type of investigation, a calculation model based on local regulatory requirements will normally have to be used. Where no requirements exist, the International Water Association IWA methodology can be used. This is one of the most widely accepted water use models in the world.
Reducing non-revenue water involves improving revenue collection, reducing leakage and improving operational efficiency by, for example, improving meter accuracy, reducing operational water usage and incident response time.
The Hydraulic Structure
The hydraulic structure is defined by the pipe network and can be set up in many ways. However one of the most effective uses the principle of Water Operational Areas, Water Supply Zones and District Meter Areas.
The District Meter Area (DMA) is the building block结构单元 for a modern distribution network.
A DMA is an hydraulically isolated area with all bulk inflows and outflows monitored by water meters. Typically containing 1,500 to 2,500 properties, a DMA is the primary tool for managing a water distribution network and assessing non-revenue water. The size and shape of DMAs are defined by topography, the nature of the distribution network, the customer type and distribution and the operational needs of the network.
A Water Supply Zone (WSZ) (usually referred to as a “zone”) is a hydraulically isolated area normally fed from a single reservoir or pumping station. It can consist of one or more District Meter Areas. A zone is often used as the cost reporting level for the network.
A Water Operational Area (WOA) (usually known as an “operational area”) is normally taken as the area fed by a single or group of water treatment works. It is a high level grouping that consists of one or more WSZ. It is normally a notional structure, its boundary following that of its constituent Water Supply Zones and is used as a management reporting tool. Many distribution systems are made up of a single WOA. Where a large urban area is fed from multiple mixed sources of water it may be desirable to define WOAs as a subsection of the network for management reporting purposes.
Using the Hydraulic Structure
The hydraulic structure is used to assign information to every asset in the network. This could be flows, asset register information and costs. By assigning costs to suitable levels in the hydraulic structure a more robust asset maintenance cost model can be derived and then fed through to Economic Level of Leakage (ELL), asset replacement and rehabilitation cost benefit calculations.
Information Collection
In order to both manage the network effectively and optimise the design of any new sections of network a large amount of information is required. Therefore, the first phase of a typical project will be to collect and distil the information, creating a storage system to allow easy access to the data.
It is important that all data is assessed for accuracy and given a confidence grade. The confidence grade takes account of the source, age and reliability of the data and assigns a code to the information. High quality as-surveyed information would have a much higher “confidence” than information interpolated from old records. Investment decisions can then be weighted to take account of the confidence level in the data.
Establishment of a Distribution Management Centre
One of the key aims of the strategy is to provide better information on and control of the distribution network. In order to ensure that this can continue once the strategy is in place a distribution management computer centre within a suitable utility company property is desirable. This centre will act as the reception point for all the information from the DMA meters, surveying etc.
Geographic Information System
One of the most powerful tools for managing network distribution data is a Geographical Information System (GIS). This is a computer system that uses electronic maps and a number of databases, displaying the information overlaid on maps.
Creation of a GIS system will greatly speed up the subsequent distribution management activities and is much easier to utilise and maintain than a paper based mapping archive. It also allows for customers, pipe failures, complaints etc to be analysed spatially which gives a much clearer picture of the issues.
In most developed countries the utility will have an existing GIS. In this case the issue is ensuring the system is capable of undertaking the required processes and verifying the data is reasonably complete and accurate. If the utility does not currently have any computer mapping of their network then the issue becomes more complex. A system will need to be procured, configured and populated with all the information.
In most cases it is possible to obtain some form of background mapping. This is normally divided into two types, raster and vector. Raster mapping is a single layer electronic scan of a paper type map. It is a picture that contains little or no in built intelligence. Vector mapping is normally a multilayer data structure where individual mapping objects are made up of points, lines and region items. This allows individual items to be selected and displayed giving much greater intelligence to the system. In general, vector mapping, is preferred to raster mapping.
One of the main sources of information is network plans available on paper. The accuracy and level of completeness of the records will need to be assessed and the asset information extended to include the required data. It is therefore sometimes necessary to check the information on site using survey techniques.
One of the common aims of the project is to integrate the customer billing and contact information into the GIS. A full review of the billing data will need to be made, ensuring that the dataset is accurate prior to merging with the GIS system. Additional information may be required to allow the link to be established. It is also important to use the billing information to identify the location of all large, key or sensitive customers and display these on the GIS.
Picture title: Asset Management, UK
Asset surveying
In order to fully populate the GIS system it is normal to have to undertake some asset survey work. The type and extent of the survey work will depend on the goals of the strategy, the criticality of the asset and the timescale available. Asset survey may be as simple as using a pipe locator and marking the location of the pipe on a map. More complex methodologies could involve trial holes, ground radar and Global Positioning Systems (GPS).
As part of the asset survey process the opportunity should be taken to collect as much asset register information as possible. This includes pump characteristics, plant serial numbers, monitoring equipment makes, serial numbers, estimated replacement dates, service schedules etc.
Picture title: Biwater staff using a global information system
Network Modelling
Once a GIS model of the distribution system has been developed and the key elevation data has been obtained from the survey process, a computerised hydraulic model of the distribution system can be developed. The model will allow the distribution engineer to assess and optimise the current network, analyse changes in demand, optimise the design of the proposed network extensions and ensure that the system can cope with rezoning and expansion.
Models fall into two broad types, strategic and all-mains. Strategic models normally only contain larger diameter mains, for example those connecting the service reservoirs and DMAs to the treatment works. They are used for large scale planning purposes such as new reservoirs or transmission mains. It is normal to create a strategic model at the start of a strategy to assess large capital projects.
An all-mains model normally contains all pipes in the network over 75mm. Demand is allocated on a pipe by pipe basis. This type of model is time consuming and costly to build, but is invaluable in undertaking ‘what if’ scenarios when designing a change or expansion to the network.
Design and installation of a hydraulic structure for the existing network
The normal method of designing the hydraulic structure for a network is to define the Water Supply Zones (WSZ) before sub dividing to create the DMAs.
From the surveys undertaken, key monitoring points can be identified. Should there be a shortfall in metering points then temporary monitoring equipment can be installed prior to design of in-situ metering arrangements. From this, flow balancing throughout the system can be established, allowing the reservoirs to be balanced, identifying any overflows.
Once the WSZ flows have been established, cost information can be allocated to each zone and the investment priority can be established. Each zone will have a metered inflow. All customers would be assigned to the DMA from which they draw their water. In this way a true picture of the revenue, consumption, leakage, illegal consumption and wastage can be derived.
Once established, the distribution manager can look at the monthly or weekly flows into each area and spot trends that will allow him to target the investigation and repair resources more efficiently. In order to achieve this, a DMA monitoring system will need to be established, which will take the information from the data loggers on the meters via telemetry and undertake trend analysis.
District Meter Area (DMA) establishment
The process of setting up a DMA is reasonably straight forward if a good quality GIS and model have been developed. The design is proposed using GIS information such as elevation and pipe layout. The design is then tested on the model to ascertain the effect on the rest of the distribution network and that sufficient flow and pressure can be maintained.
Once the design has been proved, meters and boundary valves are installed on the network. The valves are then shut and the integrity of the DMA checked with a Pressure Zero Test (PZT). The confirmed boundaries of the DMA and the customers within it can then be added to the GIS system.
Closure of boundary valves will affect the flow and pressure characteristics of the network. To ensure that the required levels of service can be maintained, pressure monitoring equipment is installed at key locations in the network and the boundaries established in stages. At the inlet to the DMA it is normal to install a meter with a permanent data logger or telemetry link to monitor night flows and pressures.
Designated boundary valves are normally included in the GIS system and held in a linked register. It is often desirable to create a small number of trial DMAs. From these trial areas the issues associated with a wider DMA programme can be identified and the cost of the whole scheme quantified in much greater detail. This will allow a smoother roll out of the wider project. In addition the information from the trial DMAs is required to improve the strategic network model utilised for the detailed design of the network. The trial DMAs also act as training models for the utility company staff.
Trial DMAs should be designed to give information on the typical characteristics of the distribution. From these DMAs, information will be extrapolated to give a greater understanding of the behaviour of customers for the whole network. Therefore these DMAs must be carefully chosen to be representative of the customer base.
During the DMA establishment programme, careful consideration must be given to the availability of water and any programme of treatment works capacity, service reservoir or distribution enhancement. Initially it may be necessary to work in areas that already have an established distribution system. Once the new treatment plant is commissioned, the new system can be closed in to produce the water supply zones.
Boundary valve management
Boundary valve management is essential in maintaining the integrity of the hydraulic structure. If a boundary valve is opened it destroys the integrity of both of the zones or DMAs it separates. Therefore it is in the interests of the utility to return the valve to its correct status as soon as possible.
Boundary valve status is normally recorded in a system linked to the GIS. When a valve changes status (for example for operational reasons) it should be recorded. Then once the valve is returned to its normal status the system is updated. Therefore the DMAs out of action due to breached boundaries can be monitored and the leakage figures discounted from the analysis. In order to prevent accidental operation of a designated boundary valve it is normal to fill the valve chamber with polyurethane foam, tag them or mark them with a plate.
Property classification and allocation
As part of the GIS modelling and DMA setup process it will be necessary to classify and allocate all properties to the relevant DMA or WSZ. This will allow the potential demand to be estimated and attributed to the correct part of the distribution network. This will also help to calculate customer take up statistics and locate potential illegal connections.
It will also be necessary to classify industrial and commercial users by type and consumption pattern. This can often be undertaken by Standard Industrial Classification (SIC) codes. Classification and allocation will normally take place in the GIS system and be undertaken during the data verification period in phase 3.
Customer categorisation and per capita consumption studies
Customers are normally either billed on a metered basis or charged by some other method. It is therefore essential that a small number of control customers are set up at the start of the project to ensure that the current estimates of water consumption are valid. Once supply is more reliably available within the distribution system, the consumption pattern of the customers may change. It is important for future water infrastructure investment strategies that this change in behaviour can be quantified.
It is therefore normal to undertake a per capita consumption study to look at how the customers actually use water. A small number of ‘typical’ customers from each economic group or area are monitored daily for a month to establish their true consumption pattern. This can be supplemented by a visit with a questionnaire to get the number of people in the property and their perceived water consumption pattern etc.
Identification of investment priorities
Investment plans are normally drawn up at a Water Supply Zone level. Once the zones are defined and the costs allocated, data to support the investment priorities can be identified. This can include customer contact frequency, level of service failure, burst history, energy use, residual asset life, future demand expansion and operational efficiency savings.
Each proposal can then be priced in outline and prioritised on a cost/benefit or Return on Investment (ROI) basis. The assessments may include scoring items for non-financial benefit. Once developed the prioritised investment schemes are documented in Zone Asset Plans and may be implemented by the client after the project is completed.
Design, installation and commissioning of distribution enhancements
Utilising the models and GIS developed for the existing distribution network simplifies the process of designing system reinforcements and extensions into the proposed areas. Once the mains are designed in outline using the model, a detailed design can be undertaken and a construction programme created.
Commissioning of mains must be closely controlled to ensure that the existing network is not adversely affected. In some cases it may be preferable to use the network model to simulate the commissioning process to confirm that unforeseen effects do not occur. For any areas where pipework is not installed prior to the end of the project, distribution plans can be developed and retained by the client for subsequent implementation.
Picture title: Biwater staff undertaking leakage detection, Panama
Leakage control
Leakage control is most effective when targeted by output from the DMA meters. Once data is received from a DMA meter the imbalance between the known consumption and the inflow can be assessed and the leakage level calculated. This is normally achieved by analysing the flow during the early hours of the morning and making suitable allowances for legitimate usage.
It is normal to set an Economic Level of Leakage (ELL) that is allowed in a DMA. This is the point at which it is no longer economic to try to locate and repair leaks in an area.
It will not be possible to provide an accurate estimate of ELL prior to establishment of the trial DMAs. The ELL is dependent on many cost factors, including the cost of water, the institutional cost of running the water utility, the accuracy and effectiveness of the revenue collection system, leakage detection costs, repair costs, reinstatement costs etc. It is not possible to assess this figure with any degree of certainty until the required data has been collected. In addition the ELL will change as the project progresses. As the unit detection and repair costs change as the network is brought under control and the increased revenue generated by the savings in the network is taken into account the ELL will reduce.
There are a range of different leakage detection techniques including listening sticks, ground microphones, leak noise correlators, leak noise loggers, pressure loggers, flow loggers, step testing etc. Leakage detection exercises often locate illegal connections to the network as they behave in a similar manner to a leak. Acoustic techniques can then be applied to locate and disconnect them or make them legal.
Pressure management
Pressure management is one of the most cost effective methods of reducing leakage and wastage from running taps. However, if the terrain is flat or there is a high density demand pattern it is unlikely that such measures will be appropriate.
Pressure management is often required on DMAs fed directly from transmission mains running between the treatment plant and the storage sites. From the network model it is possible to look at the pressure regime on a DMA basis and reduce the pressure to an acceptable level by using passive measures such as throttled valves or orifice plates, or to use active methods such as Pressure Reducing Valves (PRVs). Similarly if areas of low pressure are identified then alternative supply routes, system reinforcements or booster pumps can be employed to provide adequate pressure.
Customer education
The fact is that a significant amount of water is wasted or lost from the distribution system due to the actions of the customers. In order to reduce this, a programme of education and information has been found to be effective. The key is to get local people to acknowledge the scope of the project, the costs involved in producing the water and how they can help to maintain the supply. One way that has been found to be effective is to visit schools and explain to the children about water supply and water conservation. They then pass this information to their parents and family.
This can be backed up with information meetings to explain to customers what is happening in their area, encouraging community programmes, other educational information, ways and places to pay the tariff etc.
It is also essential to develop a culture of water conservation within other government and local authority organisations. By reducing the consumption of these departments more water will be available for domestic purposes. It has been found that such programmes can reduce water wastage by up to 5% in some areas. These types of programmes are found to work best when fronted by local representatives of the water utility in conjunction with a non-governmental organisation. Such programmes have been applied with great success all over the world by Biwater.
Training
The key to the long term viability of this type of approach is the transfer of skills to local personnel of the water company. It is suggested that a small number of personnel be seconded to the project team from the water company. This has three main advantages:
• Ensures that maximum transfer of knowledge from the project team to the client organisation by working alongside experienced staff to deliver the project
• Improves the project team efficiency by providing local knowledge and experience
• Reduces overall project cost to the client
Where possible it is good for one or two engineers to join the project team from the start. A training programme should be agreed at the outset to ensure that staff receive training in all the appropriate areas. It is important that the seconded personnel are themselves capable of helping to train other client staff later in the project, prior to handover. To aid in this process, Biwater will normally help develop a training scheme for the client to use in-house.
Picture title: Pipeline rehabilitation, Panama
Pipeline Rehabilitation
In the ‘Perfect Water Company’ all assets would be in ‘Perfect Condition’. In reality, most pipeline systems are subject to both internal and external corrosion, pressure, stress or strain and are subject to ever increasing demand. Over time, systems decay or become inadequate for the demand, and replacement or reinforcement becomes necessary. There is however an alternative to total replacement of the asset through system refurbishment.
Prioritisation
If the Perfect Water Company assumed all its pipe networks had a 100 year life, to maintain the network in a serviceable condition, it would require the replacement or refurbishment of 1% of its pipe network every year. Unfortunately, most water companies did not historically budget for this situation, and in addition, some pipe materials in some locations do not achieve the 100 year life predicted – more like 60 years – which has indicated that 2% or more of the network should be replaced or refurbished each year, to effectively catch up.
However, in the Perfect Water Company, working on a limited budget, we must prioritise which pipes are to be replaced or refurbished on an evidential condition basis. This will reduce the risk of any significant water supply/ distribution pipe failures to occur on pipes in severely poor condition, before they are identified for replacement or refurbishment.
As the GIS records of the location of all network pipes, their size, material, age and coatings can now be considered as accurate and reliable, they can be accessed to be used for further analysis. Within the GIS software packages, it allows each pipe segment to be separately tagged to identify every pipe attribute recorded, to be annotated on the GIS system. Some information, which is kept in separate electronic or paperwork systems, can be linked into the GIS system with information such as pipe failures (including full consequence details), water quality samples, and pressure and flow logger and metering data. This information has to be analysed and tabulated to create a scoring matrix, incorporating the following information:
Likelihood
Burst Score (Range 1-3) – from bursts per km
Condition Score (Range 1-3) – from Condition Grade 1-5
Pressure Score (Range 1-3) – from reservoir top water level – Minimum ground level in Bars <4 to >9
Pipe size (Range 1-3) – from <300mm to >900mm diameter
Proximity analysis (Range 1-3) – from urban (close to buildings) to rural areas
Consequence
Number of properties connected (Range 2-6) – from <1,000 to >10,000
Reservoir Storage Score (Range 1-4) – from Volume of Storage / No of properties x
30 litres/prop/hour for <6 hours to >24 hours
Attendance Score (Range 1-3) – from burst repair times from <6 hours to >24 hours
Proximity analysis (Range 1-3) – risk of road, railway, watercourse damage from No crossing of pipeline to >2 crossings
Score for each Likelihood Category is added – maximum of 15 points
Score for each Consequence Category is added – maximum of 16 points
Risk (of Pipe Failure Analysis) Score = Likelihood x Consequence
This will give a score range of between 25 to 240
This analysis gives a scoring mechanism to identify those pipes which are most in need of replacement or refurbishment. The scoring can be used for distribution mains and trunk mains, from small sections to total pipe length depending on the criteria used. Scores can be colour coded to display across the GIS map of the area to indicate areas with the highest priority, hence set proportional budgets for detailed design of replacement mains. From this prioritisation, site investigations will be necessary for route economics, and network analysis for hydraulic assessment of pipe replacement sizes, where required.
Rehabilitation Economics
From the prioritisation exercise, which must be updated and reassessed at regular or annual periods, including the latest data available, the detailed preparation of the pipe replacement or refurbishment project must be carried out.
Various rehabilitation techniques are available to be considered. However, the prime consideration is whether Trenchless Technologies (or NoDig) can be utilised, as rehabilitation options have been calculated by funding agencies to cost as little as 30% of the cost of mains replacement. NoDig rehabilitation techniques also minimise the social and environmental disruption caused when undertaking an upgrading programme of buried pipeline systems.
Maximising the efficiency and life of a water company’s distribution network, using pipeline rehabilitation must therefore be a key objective for the following reasons:
• Maximising the hydraulic efficiency of the asset
• Improving water quality
• Reducing leakages
• Increasing asset life for minimum cost
• Increasing asset value for minimum investment
• Reducing social and environmental impact
Rehabilitation Planning
All of the above factors are considered in selecting the most appropriate rehabilitation technique, which fall into two categories:
• Non structural
• Structural
Non Structural Pipeline Rehabilitation
This technique is applied where the structural integrity of the pipeline is good, but the pipe internal diameter has become restricted due to tuberculation (narrowing of pipe internal diameter over time creating a loss in hydraulic capacity), corrosion or deposits. The process involves the internal cleaning of the pipeline and the application of a new non structural lining to the internal wall.
Picture title: Pipeline cleaning, Panama
Cleaning
There are various cleaning processes, the purpose of which is to remove all internal tuberculation, corrosion and deposits and to leave the pipeline internal surface in a suitable condition to receive a new lining.
The most common cleaning techniques are power boring (pushing a system of rotating scraping flails up the pipeline on extending rods) or drag scraping (pulling a similar system of flails into a pipeline – which can be bi-directional).
The aggressiveness of these techniques is such that bare metal internal surfaces are generated, which start to ‘bleed’ (re-oxidise) after a period of time, and therefore a new lining is required to be applied.
Less aggressive techniques involve jetting, swabbing and flushing which can remove soft deposits, but not hard tuberculation.
Cleaning Techniques
Power boring - diameter range 75 - 150mm
to remove debris and encrustations from the pipe.
1. Boring Machine
2. Steel Rods
3. Water/Debris
4. Boring Cutters
Drag scraping - diameter range 150 - 600mm
to remove debris and encrustations from the pipe.
Plunging - diameters 75mm and above
to remove residual corrosion and water from the pipe.
1. Rubber plungers
2. Debris
The Biwater Pressure Scraping technique utilises water pressure to drive a scraper ‘pig’ through several kilometers of uniform diameter water main in one operation, generally where this is 600mm or greater.
1. Mixer
2. Hopper
3. Pump
4. Control Unit
5. Winch Hose Reel
6. Lining Machine
7. Drag Trowel
For mains up to 600mm diameter, a pump located adjacent to the access point delivers the cement mortar mix to a mobile carriage. The integral carriage unit is complete with a drag trowel mechanism and is winched through each individual section.
In-situ Epoxy Resin Lining Process
Key
1. Power pack & pumps
2. Monitor unit
3. Powered hose reel
4. Pipe end roller
5. In-line mixer unit
6. Lining machine
Lining
The lining processes employed for the majority of pipeline rehabilitation applications in the field, have developed over the years from techniques for respraying with a bitumen lining (similar to factory lining processes), through the application of a cement mortar lining (which created high pH alkaline conditions on curing) to epoxy resin (a two part mix which is now computer controlled at the point of application). New nylon based materials are also now in use. In all instances, the method of application is similar as the lining materials are applied centrifugally in a one pass application.
The selection criteria for linings depend upon, pipe diameter, water quality and cost of application. Cement mortar was predominantly used for large diameter applications, where the 2-4 mm thickness was less of a flow restriction, but not where extremes of pH were likely. There are now issues with constituents and water quality issues, although cement mortar costs tended to be less. Epoxy resin has a better performance in all pH conditions and provides a better finish for improved flow characteristics over cement mortar, although its cost was higher.
Structural Pipe Lining Rehabilitation
Structural rehabilitation techniques are employed when the condition of the pipework will not permit non structural lining, due to excessive external corrosion or where the pipe diameter is incapable of meeting demand. In the circumstances the pipe must be completely replaced. The ‘NoDig’ rehabilitation techniques available as an alternative to the most expensive open cut and lay, are:
• Slip lining
• Pipe bursting
• Soft insertion lining
• Pipe moling for service connections
• Directional drilling
The most common and cost effective techniques offering complete pipeline replacement are Slip Lining and Pipe Bursting. These are described as follows:
Slip Lining
In this technique access to the existing pipeline is gained at a convenient location. The pipeline is cleaned using the cleaning methods used for non structural techniques. A pre-welded length of Medium Density Polyethylene (MDPE) pipe is then drawn through the main.
The major limitation associated with this rehabilitation technique is that system hydraulic capacity is reduced. However this should be offset by an improved hydraulic performance. To insert a slip lining the existing mains must also be reasonably straight and all bends and fittings excavated and removed.
Pipe Bursting
In this technique pre-cleaning of the existing pipeline is not required as the pipeline is destroyed and replaced during the operation.
Access to the pipeline is gained at a convenient point and a hydraulic or pneumatic percussion head is driven through the main thereby breaking the existing pipe and compressing the fragments into the surrounding ground. A UPVC or MDPE sleeve is drawn behind the percussion head for later installation of the replacement pipe. The advantage of this process is the ability to increase the size of the pipe diameter in a single operation.
Metering
Picture title: Meter reading outside of a customers property in the UK
Picture title: Residential meter reading, UK
Metering
Any water company has to have a means of charging its customer for the water they received and therefore the service provided. Perhaps the most obvious method of deciding the charges is by metering the volume supplied and basing the charge on this volume so that the more customers use the more they pay.
Alternatives – Flat rate charge
There are however other possibilities available to the water supplier. Charges can be based on the size or value of a property or the number of people living there. The simplest but perhaps most flawed method of deciding charges would be to charge all residential customers the same using a flat rate charge. A company will wish to consider the overall cost of any charging system, the degree of fairness which it brings to charging different customers and the effect the method has on overall water use and therefore investment in infrastructure.
The ‘Perfect Water Company’ should perhaps have all customers metered so that they pay for what they use which is totally non-discriminatory. This is probably the fairest way to charge and is normally essential for industrial customers using water in processes. Customers will be less inclined to waste water and it is possible to devise tariffs which penalise high seasonal usage. If all supplies are metered the water company will have much better information regarding different patterns of use in different parts of the distribution system and more importantly will be better able to establish how much water is unaccounted for (i.e. lost through leakage, meter inaccuracy, bad debts, theft or illicit usage etc).
Is it ‘perfect’ for you?
The inherent deterrent value of payment by visible metered use assumes that widespread metering will have an impact on overall demand by encouraging some degree of prudence in water use. The reduction will obviously bring savings to the water company in the areas of investment in resources, treatment and distribution systems. It will be necessary to attempt to evaluate those savings as an offset against the cost of installing, reading, maintaining and replacing meters. The relative cost of labour means that the economic balance will vary in different countries.
Drawbacks
There are some drawbacks to universal metering. The installation and running costs of meters are high with an ongoing requirement for a programme of replacement. The meters have to be read and the customers billed based on their consumption and this requires a relatively sophisticated billing system and large numbers of staff to read them and administer the accounts. It is essential to find a low cost, but sufficiently accurate meter and an efficient method of reading it. Currently technology with ‘outreaders’ allows one person to read 400 meters a day. New technology, however, is enabling automatic reading from mobile vans of thousands of meters a day.
With metering, customers are more likely to query their account and any system based on volumetric charge may lead to a fraud either as a result of illegal by-passing of meters or as a result of corruption amongst meter reading staff.
Metering provides uncertainty of income
One further concern regarding charging universally by meter is that the company has some uncertainty about income. Volumes of water used and therefore income may be affected by the weather or economic conditions over which the water supplier has no control.
Benefits of flat rate charges
At the opposite end of the scale from metering would be to charge all household customers on a flat rate basis such that they all pay the same. Such a system is very easy to administer, simply needing a register of customers and a means of billing them a pre-determined amount. In addition, a means of defining a household would be necessary so that industrial users could be billed by a metered account. The advantages are low cost and simplicity but a flat rate system can be criticised because of its possible unfairness and inability to make any differentiation between lower and higher users. Any system that does not relate to volume is less likely to encourage careful use of water and will therefore result in increased investment in water infrastructure; however revenue collection systems already out of control must start with such a ‘flat rate’ basis.
The intermediate option where charges for household customers are linked to a graded tariff for water use possibly represents a compromise solution. If information is available as to either the size of house or number of residents – perhaps from taxation or rating authorities – a scheme could be derived linking water charge to likely usage. Once the information is obtained, such a system is relatively easy to administer and of course there are none of the costs associated with meter installation or reading. The system is fairer than a flat rate system but ultimately flawed compared with metering. The company would know its income but there is little incentive for the customer to be prudent in the use of water.
Local influences decide
Clearly a fully metered system provides the fairest charging method, and a visible incentive for conserving water and therefore helps to minimise the cost of providing and distributing supplies. It may be that scarcity of water resources will influence the situation and become a significant factor in the decision making process. The costs of operating a system with widespread metering are high and the company must decide on the best way forward taking into account the costs, benefits and any statutory obligations, so that it may optimise the return on investment made.
Current developments of combining meter reading with gas and electricity are reducing costs dramatically, especially when utilising one combined bill.
Billing System
Picture title: Modern billing system
Billing Systems
Whatever method is chosen for charging for the use of water, it is absolutely essential that an efficient Billing System is used in order to accurately bill all customers on time; to collect all monies due as speedily as possible; to take adequate recovery action for non payment where necessary, and to achieve all at the lowest possible cost.
Interface
It is important that a Billing System is developed within the whole framework of the business and its relationship with its customer. To this end the Billing System must not be viewed in isolation from the other operations of the company and suitable interfaces with other uses must be established. Having said that, however, the Billing System will be the core and the focal point to all other systems, as these will use the billing database as a means of providing information in, for example, operation log management systems, water quality information and other more recent innovations such as Geographical Information Systems.
Database
We have already mentioned that the first essential aspect of a good Billing System is to have an accurate customer database which links in with a property database. In this way historical information can be generated relating to not only a property and its past use but also for customers who may have a history of bed debts. This database will be used for all customer enquiries as a possible ‘one stop shop’ for convenience.
Software
Equally important as the database is the software itself which enables the billing function to be efficient. Bills should be sent out on time and reminders, final notices and court action or any other recovery action can be automatically generated within the billing timetable. Adequate payment facilities will be offered and the Billing System must be able to cater for all variables on offer. The billing cycle will start with meter reading which may be manual through hand held computers which are subsequently downloaded each day onto a main property database. Recent trends are towards more sophisticated means of data capture through reading by touchpad or outreader to remote reading by telephone lines or radio signal. The media in which the information is communicated must interface with the main billing property database.
Payment
Payment options will vary but the emphasis must be towards more automation. Direct debits are generally accepted as the cheapest and most convenient form of payment method and once set up, maintenance of the information can be controlled relatively easily. Payment by this method is automated through modern link through a bank clearing system and posting to customer records is automatic by means of a suitable disc or tape. Other payment methods such as cash, cheque, bank giro and post office giro are generally more costly to administer, but again transfer of information by tape, disk or web based technology helps speed up the operation and keeps costs to a minimum.
Management information system
An efficient Billing System copes with all the billing requirements of customers from different payment arrangements to different payment facilities such as by instalments. In order to control and manage this operation an effective management information system must be the final part in a smooth running billing operation. The management information system determines statistics such as key performance indicators from the data generated by the three primary functions of customer service, billing and recovery. It will access the customer and property databases to generate reports on a daily, weekly or monthly basis depending on specific requirements.
Flexibility
To summarise therefore, whilst a good Billing System is a means to an end, it should be flexible in order to meet changing needs. Computers play an important role and must be considered within the overall strategy of the company’s requirements. Flexibility is the key with the potential in today’s market to enable “add on services” such as billing for other utilities (electricity, solid waste collection etc), to be carried out with minimum cost implications. Today’s Billing System must be not only functional, aimed at low cost and efficient billing, but must also have regard to other users, such as other departments within the company. In doing so it will provide an overall effective management tool not just a simple Billing System.
Picture title: Handheld billing system used by Cascal’s concession, Subic Water in the Philippines
Picture title: Leak detection training, Bournemouth, UK
Picture title: Staff training centre, Nelspruit, South Africa
Staff Training
Staff Training and Development
Training Culture
An essential component in successful staff training and development is to create the appropriate culture. This invariably necessitates the acquisition of new skills by the staff involved and development of existing ones. Staff Training and Development is therefore a cornerstone of Biwater’s own strategy in undertaking the operations of its own water companies.
Over many years we have developed a structured modular approach to Staff Training and Development which can be tailored to meet the needs of any individual or group of employees. We have been applying such programmes with great success all over the world. For example, in Ofwat, the UK regulators 2006/07 report, Bournemouth and West Hampshire Water was rated as second best for overall performance out of 22 companies in England and Wales. Its leakage rate is low, its customer service levels amongst the best and its charges to customers are well below the average. The Company has the National Standard for Staff Training and Development (Investors in People) and ISO 9001 quality assurance accreditation. The Company has been awarded ‘centre of excellence’ status by the Confederation of British Industry. These achievements are entirely attributable to providing the staff with the tools and skills to do the job of meeting the Company’s strategic objectives through training.
We transfer our skills and expertise through our training and development programmes. These programmes are designed to meet the specific needs of any particular operation. Training can be provided locally or in the UK and can encompass both theory and practical work on site. Modules have been developed to cover both technical and commercial disciplines. Examples are:
• Top quality management
• Abstraction and supply
• Water treatment
• Engineering strategy and project management
• Distribution
• Sewerage and sewage treatment
• Scientific services
• Environmental protection
• Customer services
• Billing and revenue collection
Investment in Staff Training and Development can in most cases be just as important as investment in plant and machinery in ensuring the success of a perfect water company in terms of meeting its agreed objectives.
3. The Perfect Sewerage System
Pure Effluent
The ‘Perfect Sewerage System’ could collect every drop of wastewater in its catchment area and transfer it without leakage or infiltration to the perfect sewage treatment plant. The plant would remove all impurities from the wastewater and covert it back to the pure water which formed in clouds from which it fell! This is all possible but the cost would far outweigh the benefits. Sewage collection and treatment, like so many other activities, are subject to the laws of diminishing returns.
Low Flow/Flood Capacity
Sewerage systems are designed for normal flows (normal flows include some ‘normal’ rain etc.) arising from a catchment area, and to handle flows from storms (which are many times greater than normal flows). Above this ‘maximum value’, storm overflows direct any excess to a receiving water course. The choice of the ‘maximum value’ is, as ever, a question of striking the right balance. Higher capacity means higher costs and the facility will only be needed on very rare occasions and this varies from country to country. In some cases it may be appropriate to install ‘holding’ tanks which can receive flows under flood conditions which can be released later in a controlled manner, either to the treatment works or the watercourse. Some treatment is usually provided for storm flows, normally screening to prevent the discharge of unsightly materials which could accumulate in and alongside the watercourse. To manage a Perfect Sewerage Company, we would have to examine the adequacy of the sewerage network by preparing a wastewater network management strategy, in a similar way to how we would operate the clean water network. Investors need to realise that, whilst it is necessary to have a sewage treatment works with the capacity to treat the volumes of effluent received into it (and to achieve the required quality of treated effluent to be discharged from it), if the wastewater network cannot adequately deal with the flows to prevent flooding, siltation or blockages, the investment is devalued if not wasted.
Increasingly investors and lenders realise the need to make wastewater network management strategies a condition of a grant or loan, to meet key environmental standards. However, whilst the development of a wastewater management strategy is a key requirement, its full implementation is difficult to achieve due to lack of detailed local network knowledge. These issues can be addressed through asset management and GIS analysis which is used as a precursor to network and treatment plant designs.
Wastewater network investigations cover a similar scope to that described in full in the cleanwater network management section, but the wastewater strategy uses the following terms to describe its range of activities:
Drainage Area Planning is the term used to describe the study of the complete sewerage system within a drainage catchment. The area plans are used to examine and assess the asset data for The Perfect Sewerage System, including information on hydraulic and structural conditions, records of the pollution of water courses and any future development within the catchment area. As the flow due to rainwater increases, the concentration of pollutants decreases, therefore the environmental impact of the discharge reduces. Careful design and sizing of a practical collection system is vital if the right balance is to be struck between value for money and environmental protection.
The Perfect Sewage Works
Having achieved the right balance between environmental protection and economic viability for excess flows, the same is required to decide on the right degree of treatment. The ‘Perfect Sewage Works’ could be expected to treat every drop of waste and storm water a catchment area received. It would also be infinitely large and costly. Most works have storage facilities which feed the storm water to the treatment process at times of low flow. This allows the treatment plant to be smaller and cheaper. Process skills are required to determine the correct balance between storage and treatment capacity. Some World Health Organisation environmental and health standards can be met by just primary sedimentation of sewage. Further cost in the form of secondary treatment will allow compliance with more stringent quality requirements.
Most developed countries have legislation and directives in place governing the degree of treatment required based on the quality and quantity of the receiving waters. The measure of treatment is usually expressed in terms of amounts of organic pollutants Biochemical Oxygen Demand (BOD) or Chemical Oxygen Demand (COD) and suspended solids (SS) removed. Newer more stringent standards require Ammonia. Phosphorus, Nitrogen and even Total Nitrogen to be removed. Biwater has not only installed many plants to achieve such standards but has specially developed proprietary processes to meet such stringent requirements.
In today’s environment, where so much emphasis is placed on conservation and water reuse, energy conservation is vital. Plants with tertiary treatment have been designed to produce effluents suitable for irrigation or groundwater recharging. It is technically possible to remove almost all organic, inorganic and bacteriological pollutants through further advanced treatment processes so that drinking water standards are achieved. Through its demineralisation, reverse osmosis and ultra-violet disinfection processes Biwater has built many plants to meet ultrapure standards. It must however be remembered that each progressive treatment stage involves increased capital and operational costs. Biwater is committed to providing appropriate technology and through its almost unparalleled experience in treatment processes, can advise on the most appropriate solutions. In many cases where effluent is discharged through a long sea outfall, preliminary treatment will suffice e.g. the North Coast Wastewater Treatment Scheme (serving coastal communities in Northern Ireland). In many other cases where removal of nutrients (nitrogen and phosphorus) is deemed necessary, a biological nutrient plant may be required (e.g. Tai Po Sewage Treatment Works, Hong Kong).
In order to gradually introduce sewage treatment to places where none exists, most World Aid Agencies would prefer to see pollution control implemented in stages. For smaller rural sites this may begin with installation of septic tanks or cesspools. A decision to treat wastewater centrally would require some sort of piped collection system followed perhaps by only preliminary or primary sewage treatment. At a later stage secondary or even tertiary treatment would be introduced. Cost and levels of pollution dictate whether more than one stage should be implemented at a time. To increase the treatment to higher levels than those mentioned, the technology changes from the more traditional sewage processes to those more commonly used in water treatment. These processes can produce water which is almost drinking water standard but may have too many dissolved salts.
At present the World Bank and International Finance Corporation (IFC) are stressing that effluents should receive the appropriate treatment, i.e. the effect the effluent has on the receiving water course must be taken into account. If a very small quantity of effluent (say 0.1 m3/ sec) is discharged into a river of, say, 100 m3/sec, the effect is minimal, but, if only 1 m3/sec, the effect could be major. Many aspects, therefore, have to be considered when designing the most practical, cost effective solutions.
Demineralisation of sewage effluent by, for example, reverse osmosis can remove dissolved salts and produce water of a higher standard than most drinking water. A plant such as this has been provided by Biwater for the City of Jeddah in Saudi Arabia with a capacity of 30,000 m3/day. The water is used for irrigation purposes.
The ‘Perfect Sewage Works’ would be modular in construction so that it can be extended easily to cope with the increasing flows. The operators of this plant would be able to predict precisely when such extensions would be required so that they can plan their capital expenditure to suit. Unfortunately these perfect situations are few and far between as most sewage treatment plants experience hydraulic or organic overloading at some stage. Special skills are required for rehabilitation or refurbishment of treatment plants often involving process redefinition/design, control and automation expertise. Biwater has been involved extensively in refurbishing sewage works as most of the treatment plants built in the UK in the second half of the last century had at least some Biwater involvement!
In summary, sewage treatment plants require careful planning and implementation at every stage. From the start, where consent standards have to be determined, to operation and maintenance of the constructed facility, special skills are required to choose the correct solution for optimum benefit at the right cost.
Picture title: Sha Tin Sewage Treatment Plant, Hong Kong
Picture title: Cape Flats Sewage Treatment Plant, South Africa
Perfect Sewage Pumping
The most efficient movement of fluids is by gravity. However, populations are rarely located so that gravity driven water supply, effluent discharge and treatment processes are possible or indeed economically viable. Pumps provide the energy needed to move fluids where gravity systems are inadequate, impractical or impossible.
Pumps have been used over centuries and some of the early designs, such as the Archimedean screw, are still used in sewage treatment plants. Today, there are a large numbers of different pump designs to satisfy a wide range of operational requirements. The ‘skill’ is to select the most appropriate pump, bearing in mind the:
• Nature of the fluid to be pumped
• Suction and discharge conditions
• Efficiency
• Volume and pressure
• Required degree of control
• Reliability and maintenance requirements
Nature of the Fluid
The fluid, gas or liquid, greatly influences the type of pump as well as its material of construction. Liquids such as raw sewage require a non-clog design made with conventional abrasion resistant materials, whereas, a seawater reverse osmosis feed water pump will be built to fine tolerances using exotic corrosion resistant materials.
Suction and Discharge Conditions
Each pump model has specific suction conditions to prevent cavitation and maximise efficiency. Equally, discharge conditions need to be carefully evaluated to create the system curve and any actions necessary to minimise surge.
Efficiency
Perfect pumps would be 100% efficient. Unfortunately, this is impossible, although the most efficient pumps can transfer over 90% of the input energy to the pumped fluid. The best designed pumping systems match peak pump efficiency to the ‘duty’ point. Systems designed to be ‘economic’ so that the whole life cost of a pumping system is minimised, might have high running costs, whereas an initially more expensive system might cost less to operate. Biwater can compare the available alternatives for you using present value comparisons of capital, operating and maintenance costs.
Picture title: Design and Build Contract, Eastbourne Wastewater Treatment Plant, UK
(built under the beach)
Volume and Pressure
These parameters dictate the pump range, which, together with the system curve, identifies the operating point. In general terms, very low head duties could be met using propeller or mixed flow pumps, whereas very high head duties are usually catered for by using turbine pumps (often multi stage) or even positive displacement pumps.
Reliability and Maintenance Requirements
Pumping systems should only be designed with the long term reliability of the whole installation in mind. In this respect, careful attention to various aspects will ensure that maintenance does not unduly affect the system’s operational capability. Such aspects include the layout of pumping stations for easy access to critical machinery and the design of pumping mains to ensure components, such as air release valves, can be maintained without having to isolate the mains.
When considering reliability it may be necessary to consider the degree of standby plant required to provide security against breakdowns. Here again careful attention to the overall design can minimise the likelihood of failures. Biwater has techniques available to allow quantitative assessment of the risk of failure which can be used to minimise investment by avoiding an unnecessary ‘belt and braces’ approach to design. This enables the designer to ‘design out’ often overlooked hazards which could give rise to failures.
Odour Free
Sewage treatment works, which were originally positioned well outside towns, have become surrounded by housing and industry as a result of growth. Such close proximity has led to many complaints of bad odours.
Coastal towns that have for many years pumped untreated sewage into the sea through long outfalls are increasingly being required to provide treatment. Large pumping stations would be necessary along the sea front to pump the sewage inland for treatment. Alternatively, compact sewage treatment plants can be built on the sea shore. In either case, these plants need to be completely free of odour nuisance due to their location.
Biwater’s ‘state-of-the-art’ treatment plant in Eastbourne in the UK is an excellent example of an odour free design and is built under the sea shore as shown on the previous page.
Where space is available, a low rate biological process, operated correctly, creates no odour nuisance. Areas from where odours emanate are the screenings, grit removal and the sludge treatment processes. It is perfectly possible to extract these odours by feeding the emanations through a biological system where they are absorbed. This is without doubt one of the most cost-effective means of odour control.
Where space does not permit the use of a low rate process or where the treatment plant has no secondary stage then an odour control plant can be constructed. This is achieved by housing all the treatment elements in one building or covering individual stages and then ducting the air through odour treatment equipment.
Most odours arise from the formation of hydrogen sulphide (H2S) and other malodorous compounds. A selection of the systems available for treating odours includes:
• Chemical scrubbing
• Biofiltration (peat, fibre, heather etc)
• Biological scrubbing
• Molecular absorption
The objective of an odour control scheme is to reduce the nuisance to zero. There is little point in setting extremely stringent standards if these are not essential; which in most cases they are not. Modelling of potential odour risks can be carried out before a treatment plant is built to predict the affect on the surrounding environment. Generally good management by professional operations will be sufficient to minimise odour nuisance.
Picture title: Concept drawing of Managua Wastewater Treatment Plant, Nicaragua
Sludge Treatment and Disposal
The “Perfect Sewage Works” would purify wastewater without producing any by-products. In reality all treatment plans rely on solid-liquid separation processes (screening, grit removal, sedimentation, clarification etc.) and produce solid by-products. The main by-product is sludge produced as a result of primary sedimentation (primary sludge) and removal of excess biological organisms (secondary or humus sludge).
In developed countries sludge disposal has become increasingly difficult as environmental regulations and directives governing their disposal have been introduced. In Europe for example, the traditional option of dumping at sea has been completely banned and new tougher laws introduced for the landfill option. Indeed safe disposal of sludge can be as complex and costly as treatment of sewage itself. This is because sludge has to be handled, transferred, thickened and sometimes dewatered before it can be treated and stabilised. In addition to high concentrations of polluting matter, sewage sludge contains valuable substances such as nitrogen, phosphorous and potassium and can be good sources of energy if processed in the right way. The most fashionable name for sludge is ‘biosolids’, signifying their usefulness rather than treating them as a ‘nuisance’ byproduct. Biwater is in the forefront of biosolids treatment technology.
Before embarking on sludge treatment, a sludge disposal strategy must be discussed with the relevant authorities and the ultimate disposal route agreed, which could be any one of the following:
• Sea disposal (where permitted)
• Landfill (after dewatering, drying or incineration)
• Reuse and recycling (agricultural use, composting, energy source, building material etc)
Clearly reuse or recycling, where economically feasible, should be the preferred option. Anaerobic sludge digestion not only produces stabilised sludge but also produces biogas which can be used to produce valuable heat and electricity. Biwater has built many sludge digestion plants using both anaerobic and aerobic processes. Sludge drying and composting is another area where Biwater is involved in pioneering techniques for converting waste sludge into valuable soil supplements.
In summary, there are many options available for treating sludge but the choice depends to a large extent on the ultimate disposal route, type of sludge involved and the particular circumstances such as land availability and economic constraints all of which tend to be unique to each plant.
4. The Regulatory Role
The Regulatory Role
Private sector involvement in water supply, with its capital intensity, makes it a local monopoly business and therefore requires a degree of regulation. This is as much a political and social issue as it is an economic and environmental one. On the political and social side, customers will need to be reassured that their interests are being safeguarded by the Government, and will continue to be protected into the future. On the economic and environmental side, private sector investors must be able to earn a fair rate of return whilst providing benefits to customers in line with the agreed quantity and quality standards laid down for the protection of public health and the environment.
Economic regulation and environmental regulation go hand in hand as the tariff must reflect the quality, environmental and service standards which the Authorities and the water customer expect to be delivered as part of the private finance contract.
Controls
Economic regulation can take many forms but all require the provision of information from the water supplier to the regulator. There can be controls on tariffs, dividends, rates of return on capital or sales. Each has been applied with varying degrees of success both singly and in combination across the world. It is important that economic regulation is transparent and consistently and fairly applied. Measures which are the subject of regulatory control should be clearly specified and adequately defined and the regulator should report openly and in an unbiased manner.
Fair Return for Investors
The private sector investor is seeking at least medium term stability, reasonable predictability of income and a return on existing and new capital. In addition, the regulatory framework should provide incentives for the private sector participant to maximise efficiency (for example through reducing leakage or costs of operation) and to retain part of the benefit from such improvements, as should customers in due course. Fixed rates of return or dividend controls do not provide such incentives but price cap regulation does and has been used with great success since the privatisation of water in England and Wales in 1989. England and Wales also has the benefit of having a number of private water operators, each covering a discrete and separate geographic area and this enables their performance to be compared.
Quality
Quality and environmental regulation varies considerably from market to market according to perceived priorities, needs and budgets. The drinking water quality and environmental protection regime in the UK is one of the most sophisticated and thorough in the World. Again, we have vast experience in such areas and are able to apply this to match the needs of our clients in a cost effective and efficient way.
Regulation
Regulation should not be adversarial or intrusive. The Regulation should be consultative and work in partnership with the private sector part to achieve common objectives as defined by parties to the private finance initiative. However, the Regulators must be seen to be independent and objective and must have sanctions available to them for non-performance against the agreed targets and objectives within the control of the water supplier. Sanctions used in the event of poor performance should be proportionate.
Tailor made
We have extensive experience of economic regulation all over the world and are able to advise and assist in development of a regulatory framework and structure which will fulfil the objectives of the private sector financing initiative.
Our global experience in private finance initiatives is extensive and regulatory frameworks from the simplest to the most complex have been developed which will meet the needs and aspirations of all parties in such arrangements to ensure success.
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2.完美的水处理公司
纯净水
理想的纯净水应该象从空中降下的雨水一样纯净，以合适的水压和适中的速度输送给客户，并满足他们各方面的需求。
如通能创造出像海洋和高地这样的大容量的无菌储存水库，这似乎还有可能。可是，在世界上一些极其干旱的地区，连这样理想化的想法都是不合实际的。
只要一下雨问题就又出现了——雨水很快被污染了。降雨的地区决定了雨水的污染度，也决定了水处理过程的必要性。
消除所有杂质，为客户提供如空中降雨一样纯净的纯净水的技术出现了。不过，这种技术耗费惊人。到目前为止，这种技术用于应用水成本还太高。现实中，水处理厂的标准比一般预期的要简单。
海水淡化
在雨水供应不充足的地区，百沃特公司建立了水处理工厂，将汲取的海水净化处理为比雨水还要纯净的水。讽刺的是，对于大多数来说，这种水的纯净程度超出了大部分人的口味，还需要重新矿化处理，成为更有益健康的水。
从海水中除掉盐采用了一种被称之为反渗透处理的过程。（还有其他的处理方式，称之为冷冻法脱盐， 蒸馏法脱盐，蒸汽压缩脱盐）。在海水脱盐之前，必须过滤掉海水中所有的悬浮杂质，以防止堵塞反渗透过程中使用的膜。一般采用传统过滤装置进行预处理，以保证处理得到的水能够通过膜。反渗透过程需要大量的能量。整个过程从技术投入和成本上来讲，代表了水处理的最优方式。
百沃特已经在世界上建立了几个此类的大型海水淡化厂。从海水中生产出具有成本效益的饮用水。
图片标题：由百沃特AEWT兴建的美国Oxnard市的反渗透海水淡化厂
地表原水
在雨量充足，污染轻微的地方，通常没有必要兴建复杂的处理厂。如果水源是一个蓄水库或河流，原水中通常含有悬浮固体、细菌、藻类、有机污染物（腐殖酸）等。偶尔还可能含有病毒（污染所致），或其他农业副产物，比如农药和化肥。可能也含有自然可溶解性金属铁和锰，这些物质在正常的原水浓度中虽然没有毒性，但是如果不消除会影响水的口味， 并导致水设备染色。在这些情况下，传统的水处理厂可以提供最具成本效益的解决方案。
这种方法通常包括混凝/絮凝和澄清，胶体颗粒、有机污染物和藻类的去除，接下来还要进行砂滤阶段，去除悬浮固体，如果有必要，除去溶解的铁和锰。此外，还需要消毒，确保病原体不会到达消费者。
农业污染
农业副产品，例如农药或其他可能有害的化合物，也是一个问题。因此，还需要经过一个吸收颗粒活性炭的阶段，有时消毒前通过臭氧处理也是必要的。颗粒活性炭也会用于去除异味和气味。
另一个农业副产物硝酸盐，如果在饮用水中的浓度超过特定的范围，就会危害健康。一般可以通过与其他未受污染的水源混合的方式来降低它的浓度。否则的话，则需要用离子交换或反渗透过程来降低硝酸盐的浓度。
为了去除污染物，需要向水中加入很多化学品。为了有效地澄清，处理过程中可能需要加入化学品，用于消毒或可溶解性铁和锰沉淀，再通过过滤方式去除。也可能需要加入酸或碱用以调节PH值，加入磷酸盐药剂控制铅从陈旧的供水管内壁溶解，最后还加入混凝剂和聚合电解质以帮助絮凝。
水处理工程中的污泥处理和处置
澄清和过滤等处理过程中产生的污泥，如果不加处理的话，可占原水提取率的10%。为了使处理过程更加有效和环境友好，通常要浓缩污泥中的固体以减少待处理污泥的体积，并将截留的污水送还工程初期。通常会用过滤冲洗澄清池、污泥增稠剂、污泥压滤机实现这个目的。加药聚电解质的化学品和污泥增稠剂和压滤机，能取得最佳效果。
工厂设计的大原则是很容易理解的，但是最具成本效益的解决方案则往往取决于技术人员的设计技巧。
The Process Scientist
工艺科学家
工艺科学家选取最佳工艺类型、工厂规模、计算出用于去除污染物的化学品的数量，并最大程度地降低运营成本。
运营成本
如果在水处理工程中运用重力，在可能的地区通过分销网络输送给客户，则运营成本将会大大降低。如果能实现尽可能小的水力梯度水流，和一个尽量有效的布局，就可以减少最初的资本。
地下原水
地下水资源一般通过地层渗出，并存储于地下含水层。自然界有其自己的清洁方式，通过土壤层和岩石层过滤掉生命物质和悬浮固体。含水层可通过钻空或水井触及。在一些含水层，水是可以饮用的，但是在另一些含水层，水中会含有溶解矿物，如铁和锰，甚至可能含有氨。像后面这种情况中，地下原水需要先经过曝气，其次是简单的化学处理和过滤，通常经过这些处理之后才可以饮用。这是最简单的滤水厂所做的工作。
偏远地区
对于生活在远离都市地区的人们来讲，由于居住在都市水处理厂的供应范围之外，有益健康的饮用水供应往往是个问题。在这些情况下，可替代性水资源往往差异很大。
在一个小型社区运营常规水处理厂的成本和困难都是相当大的。膜在这里可以为他们所用。膜过程不需要像海水淡化过程一样达到去除盐的水平，用粗膜就可以。这意味着过程中需要的驱动能源要少得多，预处理过程也简单得多。进入工厂的原水通常有足够的物理屏障，保证可以被饮用。
图片名称：英国资产调查队
完美的水处理没有必要吗？
虽然完美的水处理厂可能还不能为我们所用，或确有必要，但是确可提供近乎完美的饮用水。如果我们可以接受非完美但是有益健康的水（例如符合世界卫生组织和欧洲共同体制定标准的水），那么水处理的成本就会大大降低。
完美的水处理厂，是指这样一种水处理厂：能以最具成本效益的方式获得符合可接受标准的水。其中成本需要考虑原水的水源、水处理厂的位置、水处理过程设计者的创造力。
图片标题：分析下载的资料 英国，水网管理
水网管理
管理完美的水处理公司，需要具备水管理策略，也称作综合网络管理策略（INMS）或水资产管理（WAM）计划。完美的水公司需要有一个完善的综合网络管理策略。如果不具备完善的综合网络管理战略，则投资者需要认识到，尽管水处理能力是必要的，如果配水网络不能有效地输送水，这种投资就是贬值的。投资者越来越将网络管理策略作为投资和贷款的必要条件。制定一个配水网络管理策略是件简单的事情，不过制定一个有效的配水网络管理策略就困难多了。
工作涉及面很广，从液压研究到解决水、废水和环保基础设施等。百沃特的工程师们置身于一个各异的团体，不仅有支持服务，还拥有广泛的资源基础。百沃特的技术已经应用到了世界各地的很多项目中。
在一个均衡的网络管理策略中，管理信息和管理水同样重要。良好的投资决策需要依赖准确的信息。如果不考虑对投资策略的影响，很容易误入铺设大型管道、修复、客户计量工程的盲目中。百沃特在与客户制定这些策略方面具有丰富的经验。
从历史上看，相当数量的网络投资策略，都是由银行或有建设经验的投资者推动的。大资本项目便于识别和量化，但是网络的维修和保养常常被视为运作开支，耗费在日常运作预算中。客户组织期望大型工程，就像他们过去习惯的，也能从客户要采取的立即行动中看出政策来。
不过，虽然大型工程可能是解决方案，不过大规模投资工程常常被推迟，或适当分配一些资金到分销网络中以减少资本。
通常的网络管理策略可分为五个主要阶段：
•分清关键问题
•建立管理工具
•收集关键网络信息
•推导和交付网络管理信息
•审视战略目标
这些阶段可能会持续数周甚至数年，主要取决于需要和经营者的规模。网络管理战略是一个迭代的过程，可能要经过几个周期，才能得到预期的结果。每个阶段都需要做详细的讨论。
分清关键问题
在任何网络管理工程的起初阶段，都必须要明确这个战略的主要驱动因素。其中会包括服务水平不高、原水储备缺乏、水供应不足、基础设计老化、缺少存储空间、水质不佳、未来扩充、低水平的税收收入和法律压力等。这些驱动因素往往显而易见，可以在几天内与自来水公司的人员确定。
但是，要谨慎确定问题的根源。例如，被形容为低供应的压力，其实可能是由于渗漏率太高或不正确的分区所造成的。
此外，利益相关者可能有自己的计划或想法，试图引导策略利用资金实现自己的目的。这些项目评估将作为总体战略目标的一部分。需要发展计分制，优先考虑将这些待解决的问题作为战略的一部分。
一旦这些问题明了了，就需要制定明确的战略目标，使所有股东都了解这项工程及目标。这个阶段可能还无法设定具体的数字目标。
建立管理工具
总体战略目标一旦推出，第一阶段要做的就是评估及征集现有的信息。为了做到这一点，需要制定或修改一些信息存储和操作的工具。
地理信息系统就是其中的一个重要工具。地理信息系统是一个地域上相关的数据库，对于管理配水网络是非常宝贵的资源。液压网络模型也是一个重要工具。这种模型通常可分为战略的或所有主管道的。主管道的模型价格昂贵，建模费时，所以使用时需要仔细考虑。其他管理工具可能包括遥测系统、流量和区域测量区仪表分析包、计费系统、工作秩序系统、客户联系制度、程序和政策。
所有的管理工具是一个数据模型。它不必是一个完全基于软件的系统，可以包含其他信息类型。被定义为一个存储系统，存储所有有效管理网络所需的数据。该数据模型需要根据商业需要和预期目标来定义。定义需要收集的信息、存储的时间位置、应用方式、业务需要的信息及所需信息的形式。
数据模型并非固定不变的，会随着分配管理策略的改变而变化。不过，在开始时要尽可能多的获知基本结构，以确保重做的工作尽量少，和更切实可行。.
收集关键网络信息
一旦存储和操作工具确定，接下来的步骤就是搜集所需要的基础数据。这在很大程度上取决于网络管理策略的特定目标。典型的数据可能包括如下部分：
•映射
•管道的位置、直径、材料、年限、状况
•供应水量
•流量和压力数据
•账单数据
•客户接触史
•管道失修史
•成本数据
•人均需求概况
•人口和工业的增长
数据收集完毕之后，就可以设定一些具体的数值目来标衡量既定目标的完成程度。
管理策略的推导和交付
一旦商业需要的目标确定下来，接下来要做的主要工作由分配网络来做。关于这部分的详细内容我们将在稍后讨论。
审视战略目标
在网络管理策略制定的末期，在执行下一阶段的工作之前需要对工程目标进行审视。在每个阶段完成后要对总体的目标进行重新评估，因为随着信息的改变和网络的改进，目标可能会随之发生变化。
网络管理策略至少要每年审视一次，以确保关键业务部分能达到要求。主要的改动则需要谨慎，因为大部分的网络管理策略需要在数周之后才能带来实实在在的利益。
基础
网络管理项目的主要宗旨是控制网络。一直以来，管理学课本中都有这句谚语：如果你无法衡量它，那么你就无法管理它。在一个分配网络中关键的变量是流量、压力和成本。水流向哪里，水压多大，以及需要的成本，这些都是必须要测量的。这个目标是通过建立“水工结构”实现的。
图片标题 下载数据存储器的信息 英国
图片标题：资产管理，英国
产销差水
为了制定配水管理策略，地区间容易混淆的是产销差水和渗漏。很多地区假定产销差水和渗漏水是相同的，事实上他们是不同的。
渗漏一般定义为因为管道、容器或输送系统中因为设备的结构缺陷而流失的水。渗漏水仅仅是产销差水的一个组成部分，产销差水还包括未开票水，操作过程水，坏账（虽开票但是费用没收回的水），政府用水等。在英国，大部分公司的产销差率都在20%到30%之间。
针对此类的调查，通常会使用一个符合当地监管要求的计算模型。在没有要求的地方，可以采用国际水协IWA的方法。这是世界上最为广泛接受的水利用模式。
减少产销差水，可以通过以下几个方式：提高税收征管、减少渗漏、通过改进测量准确性、减少操作用水、减少事件响应时间来提高操作效率。
水工结构
水工结构被定义为管网，可以通过多种方法设定。但是其中最有效的方法需要利用水操作区、水供应区和区域测量区。
区域测量区（DMA）是现代配水系统的结构单元。
DMA是一个液压孤立区域，利用水表监管所有流入和流出的流量。通常载有1500-2500个道具。DMA是管理配水网络和评估产销差水的基本工具。区域测量区的大小和形状是由地形、配水网络的性质、客户类型和分布及其网络运行需要等因素决定的。
供水区（WSZ）（通常被称为“区”）是一个液压孤立的区域，通常从单个的水库或抽水站补给。它可以由一个或多个区域测量区组成。供水区通常作为网络的成本申报水平。
水调度区WOA（通常称作调度区）通常由一个或多个水处理工程供水。是一个高水平的组，由一个或多个供水区组成。它通常是个名义上的结构，边界即为组成它的供水区的边界，用来作为管理报告的工具。许多分配系统都是由一个水调度区组成的。从多种渠道取得供水的大都市，可能希望利用水调度区作为网络的一小部分，用于管理报告。
利用水工结构
水工结构被用来给网络内的装置分配信息。可能是流量信息、资产登记信息和费用信息。通过在水工结构中分配合适的费用，能够构造出更强大的资产维修成本模型，通过经济渗漏程度，资产置换和更新成本效益计算。
信息收集
为了有效地管理网络并优化网络设计的每一个新增部分，需要大量的信息。因此，项目的第一阶段就是收集和提炼信息，建立一个容易访问的存储系统。
给所有的数据进行准确性评估，并给数据建立信用级别，这是非常重要的。信用级别的裁定需要考虑数据的来源、时间和数据的可靠性，并给信息指定一个代码。高品质的统计调查数据会比从原有记录中拷贝的数据拥有更高级的信用级别。投资决策便可以通过考察数据的信用等级水平来进行权衡了。
建立一个分配管理中心
管理战略的一个重要目标是更好地提供分配网络的信息和管理分配网络的信息。一旦策略恰当，为了确保能够继续，需要有一个分配管理计算机中心。这个中心将作为接收点，接收来自区域测量区仪表的信息和调查信息等。
地理信息系统
管理网络分布数据的其中一个最强大的工具是地理信息系统。地理信息系统是一个采用电子地图和大量数据库的计算机系统，显示地图上的信息。
建立地理信息系统将会大大加快随后的分配管理活动，而且，相对于利用纸本存档，地理信息系统更容易利用和保存。因为它能提供更为清晰的图片，所以更利于顾客、水管故障和投诉等问题的分析。
在大多数发达国家，公用事业局都有现成的地理信息系统可以利用。在这种情况下，需要确保该系统能够实现需要的过程，和核实数据是合理完整和准确的。如果公用事业局目前还没有他们网络的计算机绘图，那问题就复杂多了。就需要建立一个系统，配置所有的信息。
多数情况下可以获得一些形式的底图。通常有两种类型：栅格图和矢量图。栅格地图是一个对纸质地图的单层电子扫描。这是一种智能成分很少或没有智能的地图。矢量地图通常是一个多层数据结构，每个地图对象由点、线和地区等项目组成。通过这种地图可以选择和显示单个的项目，使得系统的智能程度大大提高。总之，矢量地图要优于格栅地图。
信息的一个主要来源是论文中的网络计划。记录的完整度和准确度必须加以评估，并把信息扩展到包含所有信息。所以，有时现场利用调查技术检测资料是必要的。
工程的一个共同目标是将客户的账单和联系信息整合到地理信息系统中。需要对账单进行全面核对，确保数据在并入地理信息系统之前是准确的。为了将账单和地理信息系统合并，可能还需要一些其他的信息。利用账单信息确认所有大型重点客户或敏感客户，并在地理信息系统中标出，这一点也尤为重要。
图片标题：资产管理，英国
资产调查
为了充分填充地理信息系统，通常需要进行一些资产调查工作。资产调查的类型和广度取决于战略目标、资产的关键性和时间表。资产调查可能会象在地图上使用管道定位并在地图上标出管道位置那么简单。复杂些的方法则可能需要涉及试孔、地面雷达和全球定位系统。
资产调查过程中，应该借机尽量多地收集资产登记资料。包括泵的特点、序列号、估计更换日期和服务调度等。
图片标题：百沃特的员工利用全球信息系统
网络建模
一旦分配系统的地理信息系统模型建立，主要海拔数据也从调查过程中取得，就可以建立电脑化的分配系统的水工结构模型了。利用这个模型，分配工程师可以评估和优化现有网络、分析需求变化、优化拟建网络扩展设计，并确保该系统能够应付改化和扩大。
分配系统的水工结构模型分为两大类：战略型和主要管道。战略型模型一般只包含大直径的水管，例如那些连接配水库和区域测量区到处理厂的管道。这种管道主要用于大规模的规划用途，例如新水库或传输管道。一般在战略的开始阶段，会创建一个战略型模型，来评估大型资本项目。
一个主要管道模型中通常包括网络中所有超过75毫米的管道。需求分配原则是管道接管道。这种模型的建立很耗时，很耗资金，但是在设计网络更改和扩大这种“如果”情况时它的作用是无法估计的。
为现有的网络设计和建立水工结构
为一个网络建立水工结构的一般方法是在划分创建区域测量区之前界定供水区。
一旦调查开始，关键监测点就可以确定。计量点处应该有一个缺口，并在设计原位测量安排之前先安装临时检测装置。这样，就能够建立整个系统的流量平衡，使蓄水池平衡，并能找出任何溢出。
一旦水供应区建立，费用信息就可以分配给每个区，投资优先权也可以设立了。每个区都有一个计量的流入。所有的客户都将被分配给区域测量区，取得他们的用水。这样，关于真实收入、消费、渗漏、非法消费和浪费的图都可以得到了。
建立后，分配经理可以查看每月或每周流入每个地区的流量和趋势，这能让他更有效地勘察目标和修复资源。为了实现这个目的，需要建立一个区域测量区检测系统，通过遥测和进行趋势分析从仪表的数据记录器上取得信息。
建立区域测量区（DMA）
如果一个高质量的地理信息系统建好了，顺理成章地，就要进入到建立区域测量区的环节。区域测量区的设计需要利用地理信息系统的信息，例如海拔和管道布局等信息。设计结构接着会在模型上进行测试，以确定对其余分配网络的影响，确定能承受足够的流量和压力。
一旦设计被证实通过，仪表和边界阀门就会被安装到网络中。然后，关闭阀门，对整个区域测量区进行零测试（PTZ）。接下来，通过验证的区域测量区的界限和范围内的客户信息将被加入到地理信息系统。
关闭边界阀门将会影响网络的流量和压力。为了保证所需的服务水平，需在网络的关键位置和设立的边界安装压力检测装置。通常在区域测量区的入口安装一个带有永久数据存储器或遥测网络的仪表，以检测夜间的流量和压力。
指定的边界阀门也会包括在地理信息系统中，保存在连接的注册表中。通常需要创建少量试验区域测量区。从这些试验区，一系列广泛的与区域测量区相关的项目就可以确定，整个项目的花费也就更为详细了。这将使得广泛项目的推出更加顺利。而且，改进战略网络模型，细化网络设计，还需要试验区域测量区的信息。试验区域测量区还能给公用事业公司的员工充当培训模型。
试验区域测量区的设计应当使得分配的典型特点有所体现。从这些区域测量区中推断出的信息，应能够更好的帮助理解网络中客户们的行为。因此，这些区域测量区应该谨慎选取，选取客户层的典型。
在区域测量区建立的过程中，必须谨慎考虑水的可利用性和水处理厂处理能力的项目，配水库或分配改进。最初可能需要在已经建立分配系统的地区试运行。一旦新的处理厂启用，新的系统就可以用于在供水区生产水。
边界阀门管理
边界阀门的管理对于维持水工结构的完整是非常必要的。一旦一个边界阀门被打开，就会毁掉它所分离出的整个区域或区域测量区。为了公用事业局的利益，他们必须尽快将这阀调回正常状态。
边界阀门的状态通常都会记录在一个连接到地理信息系统的系统。当某个阀门状态改变（例如因为操作上的原因），应予以记录。当修复到正常状态的时候再把系统记录更新。因此，由于边界缺口出现故障的区域测量区能够被检测出来，渗漏数据也将被从分析中扣除。为了防止边界阀门的非正常运作，一般会用聚氨酯泡沫塑料填充阀室，并做标记。
资产的分类和分配
在地理信息系统建模和DMA建立过程中，需要将所有资产进行分配，分配给区域测量区和供水区。这有利于估计潜在需求，也有助于纠正部分分配网络。也有助于计算客户占有的统计资料和找到潜在的非法连接。
根据类型和消费模式对商业用户进行分类也是必要的。这些通常是根据标准产业分类代码进行分类。地理信息系统中通常会在第三阶段的数据核查阶段进行分类和分配。
客户分级制度和人均消费研究
顾客通常根据水表或其他方式付账。因此，在工程起初建立起一小部分控制客户，确保目前估计的用水量有效，是非常必要的。一旦分配系统内的供应更可靠了，客户的消费类型可能就会发生改变。对未来水利基础设计的投资是很重要的，以便量化消费行为的变化。
因此，需要对人均消费量进行研究，得出客户实际在如何用水。在每个经济群体或地区中选取一小部分典型代表，持续一月每日检测他们的用水情况，建立他们的实际消费模型。还可以以问卷的形式调查用水单位的人口数量和他们以前的用水消费模式，作为补充。
确定投资的优先顺序
通常在水供应区的水平上起草投资计划。一旦水供应区确立，成本分配完毕，帮助裁定投资优先权的数据就得到了。包括客户联系频率、服务失败率、破裂史、能源消耗、剩余资产生活、未来需求增长和运用效率节省成本。
每种建议在成本/收益或投资回报率的基础上定价和确定优先权。这个评估可能包括得分项目的非经济利益。一旦投资优先权建立，这个计划将被写入到区域资产计划，而且可能在项目完成后交给客户执行。
设计、安装和启用分配改进
在现有的分配网络中利用模型和地理信息系统简化了将系统扩展到计划地区的设计过程。一旦利用模型设计出来管道大纲，就能进行更详细地设计和创建建设方案了。
主管道的使用必须严密控制，确保不会对现有的网络产生不利影响。在一些情况下，最好利用网络模型模拟调试过程，来确认不会出现不可预见的影响。在一些管道没有在工程结束之前安装的地区，分配计划可能会受客户端随后行动的影响。
图片题目：百沃特员工在进行渗漏测试，巴拿马
渗漏控制
当测试到渗漏来自区域测量区时候，渗漏控制是最有效的方式。从区域测量区仪表接收到数据之后，就能够评估出已知的消费和流入的不平衡，渗漏程度也就能够计算出来了。通常通过分析清晨的流量和给合法使用做适当津贴之后得出。
通常情况下会在区域测量区中设定一个经济漏控水平（ELL）。从这个经济漏控水平点开始，寻找并设法修复渗漏区域不再经济可行。
在试验区域测量区建立之前是不能准确估计经济漏控水平（ELL）的。ELL取决于很多成本因素，包括水成本、运营水设施的体制成本、税收征集系统的准确性和有效性、渗漏检测费用、维修费用、恢复费用等。在需要的数据收集完毕之前是不可能准确评估ELL的。而且，随着工程的进展ELL也会发生变化。由于网络被纳入控制，导致部件检测和修理的费用发生变化，网络中节约导致的税收增加，都会使ELL减小。
渗漏检测技术有很多，包括听杆、地面麦克风、相关渗漏噪音、渗漏噪音记录仪、压力记录仪、流量记录仪和步骤测试等。渗漏检测活动往往能找到网络中行为类似于渗漏的非法连接。可以利用声学技术找到它们并断开或使她们合法化。
压力管理
压力管理是减少水管的渗漏和流失的一个最具成本效益的方法。不过，如果地形平坦或有一个高密度的需求模式，这种方法可能就不太合适了。
直接从水处理厂和存储点之间的传输水管取得供给的区域测量区往往需要压力管理。从网络模型中，从网络模型中可以从区域测量区查看压力体制，并用被动方法如调节阀门或孔板，或主动方法如减压阀，将水压减小到可以接受的水平。
客户教育
在实际中，由于客户的行为，大量的水被浪费或遗失在配水系统中。教育和信息方案对于减少损失比较有效。关键是工程范围、生产过程的费用和如何维持供应这些得到当地人民的认可。目前发现的一个有效的方式是造访学校，向孩子们讲述如何供水和节约。然后，由孩子将这些信息转达给他们的父母及家人。
包括下列信息：如何向客户解释发生在他们所在区域的情况、鼓励社区方案、其他培训信息、支付水费的方式和支付地点等。
在其他政府和地方当地的组织中发展节水文化也是至关重要的。通过减少这些部门的用水量，将节省更多的水可以用于家庭用途。据发现，在很多地区，通过这种节约活动可以减少5%的水流失率。这种类型的活动在当地水公用事业机构连同非政府组织中的代表中开展得比较好。百沃特将这种活动在全球范围内都推广得非常成功。
培训
这种做法长期可行的关键是将方法传授给当地水公司的人员。建议从水务公司借调少数人员到项目小组。这样做三个主要优点：
•移交工程的有经验的工作人员尽可能地将知识传授给并肩工作的客户组织，确保了传授知识的最大化
•通过提供当地的知识和经验，提高了项目组的效率
•降低了给客户的整体项目成本
如果可能的话，最好是从一开始就有一到两名工程师加入项目组。开始应签订一个培训协议，保证员工在所有合适的地区都能接受培训。有一点非常重要，即借调人员本身应能够在项目的后期和移交工程之前帮助训练其他客户端的工作人员。为了配合这个过程，百沃特通常会协助客户制定一个可以让客户在内部使用的培训计划。
图片标题：管道修复，巴拿马
管道修复
完美的水处理公司的所有资产也应该是状况完美。事实上，大部分管道系统都会受到来自内部和外部的腐蚀、压力、重压张力。天长日久，系统变得衰退或不能满足需求，必须要进行更换和加固。通过系统整修替代资产更换。
优先顺序
假定完美水处理公司的所有管道网络的寿命都是100年，为了维持管道网络的可用状态，就需要每年更新或更换其1%的管道网络。很遗憾，大多数水处理公司都没有为这种情况做过预算，而且大部分管道材料在有些地区的服务寿命达不到预期的100年，很可能只有60年，这就意味着每年需要更新或更换2%的管道网络才能够有效地工作。
在完美水处理公司，在预算有限的情况下，我们必须根据情况考虑哪些管道需要优先更新或更换。这样可以避免状况较差的管道在被更换或更新之前发生供水/配水失败的问题。
由于可以将地理信息系统记录的管道网络的位置、管道尺寸、材料、年龄和涂层信息视为是准确和可靠的，所以这些信息可以用于进一步的分析。在地理信息系统软件数据包内，可以对每个管段分别标记以便查找每个管段在地理信息系统中的属性记录。分别以电子文档系统和纸质系统保存的一些信息，可以应用相关信息连接到地理信息系统中，例如管道故障（包括所有重要细节）、水质样本、水压、流量记录仪和测量数据。这些信息将被分析和汇总，并利用下列信息创建一个分析矩阵。
可能性
爆裂分（范围1-3）—每公里爆裂
状况分（范围1-3）— 状况分1-5
水压分（范围1-3）—蓄水库最高水位度——地面最低压强小于4个大气压或大于9个大气压
管道尺寸（范围1-3）—直径小于300毫米或大于900毫米的管道
临近分析（范围1-3）—从城市（临近建筑物）到农村地区
后果
连接道具的数目（范围2-6）小于1000或大于10000
水库储水评分（范围1-4）储水量/ 道具数目X
30公升/PROP/小时 小于6小时或大于24小时
表现分（范围1-3）爆管抢修时间 小于6小时或大于24小时
临近分析（范围1-3）没有管道穿越的或穿越管道数目大于2的公路、铁路、水道的破坏风险
每个可能性分类的评分—最高15分
每个后果类评分—最高16分
风险分（管道失效分析）—可能性分数乘以后果分数
这样能够得到一个25-240分范围内的得分。
这种分析能够利用分数机制找出那些最需要更新或更换的管道。这种分数机制可以用于配水管和主水管，从一小段到整段管道，取决于采用的标准。可以在该地区的地理信息系统地图上采用彩色编码标记具有最高优先权的地区，拨相应的预算用于管道的细节设计。从这个优先顺序中，实地考察实现路径经济化是必要的，有的还需要对管道更换尺寸的液压评估进行网络分析。
修复经济学
需要定期或每年更新和重新评估的优先顺序，将包含最新的数据、必须要执行的管道更换或更新工程的详细准备情况。
有多种修复技术可供考虑。选择修复技术要考虑的首要因素是是否可以利用非开挖技术，因为投资机构计算出的修复方案允许花费30%的更换成本。非开挖修复技术也会在进行管道系统升级方案的过程中尽量减少对社会和环境的干扰。
水务公司为了最有效的利用分配网络和延长网络寿命，管道修复是一个关键，原因如下：
资产的液压效率最大化
改善水质
减少渗漏
以最低的成本增加资产寿命
以最低的成本增加资产价值
减少对社会和环境的影响
修复计划
在选择最适当的修复技术的过程中要考虑上述所有因素，一般修复技术可分为两类：
非结构性
结构性
非结构性管道修复
这类修复技术主要用于那些结构完整性较好的管道的修复，由于水管积垢（管道内部直径的减小造成液压损失）管道内部直径变小、腐蚀或结垢。过程包括管道内部清洗及在内壁应用一种新的结构性内层。
图片标题：管道清洗，巴拿马
清洗
清洗过程有很多种。清洗过程的目的是消除内壁的积垢、腐蚀和结垢，改善内壁以便涂新内衬。
最常见的清洗技术是power boring (pushing a system of rotating scraping flails up the pipeline on extending rods) 和拖擦(拖动一个类似的追踪系统进入一个双向管道)。
这些技术具有很强的攻击性，能生成裸露的内壁表面，经过一段时间之后开始流血（重新氧化），所以需要一个新的内层。
攻击性不是很强的技术包括喷射、擦拭和冲洗，这些技术可以去除软积垢，但是硬结垢是去除不掉的。
清洗技术
Power boring——管道直径在75-150毫米
清除掉管道的碎片和硬壳
1.镗床
2.钢条
3.水/碎片
4.镗刀
拖擦——管径范围为150-600毫米
从管道中除掉碎片和硬壳
Plunging——管径大于75毫米
消除管道中残余的腐蚀和水
1.橡胶活塞
2.碎片
百沃特的压力刮板技术利用水的压力驱动”pig”刮板通过数公里的管道直径，一般情况下这样一个运作是600毫米或更大。
搅拌器
贮水槽
泵
控制元件
Winch Hose Reel
贴合机
拖拉铲
对于直径达到600毫米的管道来说，位于临近接入点的泵将水泥砂浆混合物传送到一个移动拖板。拖板部件是由拖拉铲，依次通过每个部分。
原位环氧树脂衬砌工艺
关键
1. 电力装置/泵
2. 检测装置
3. 电动软管卷筒
4. 管端滚筒
5. 原位搅拌装置
6. 衬砌机
衬砌
当一个地区绝大部分管道需要修复的时候采用衬砌过程。衬砌技术已经发展了多年，从用沥青衬砌（类似工厂衬砌过程）重新喷涂技术，到应用水泥砂浆（在固化过程中会产生高PH值的碱性环境）衬砌技术，在到利用环氧树脂（两部分的混合物，现在都会在应用点用电脑控制）。新的尼龙材料在现代也有所应用。在所有情况下，应用方式类似于衬砌材料一次离心应用。
衬砌的选择标准取决于以下因素：管径、水质和应用成本。水泥砂浆主要用于大直径的管道，2-4毫米的厚度对流速限制不大，但是对PH极值区域影响较大。还与组分和水质有关系，虽然水泥砂浆的成本较低。环氧树脂在所有PH值的环境中都有良好表现，也能比水泥砂浆更好地改善流动特性，但是成本较高。
结构性管道衬砌修复
结构性修复技术使用于这种情况：管道状况由于过度的外部腐蚀或管径不能满足需要，不允许非结构性衬砌。这种情况下，需要对管道进行完全更换。“非开挖”修复技术能作为最昂贵的明挖铺设技术的代替技术。有以下几种：
内衬管滑（拉）入衬
爆(碎)管衬装
软插入衬砌
服务连接的管设置（Pipe moling for service connections）
定向钻
最常见最具成本效益的全管更换技术是内衬管滑（拉）入衬和爆(碎)管衬装。描述如下：
内衬管滑（拉）入衬
在方便的位置接近现有管道。使用用于非结构性技术的清洗技术清洗管道。将预先焊接好长度的中等密度聚乙烯（MDPE）管拉入主管道。
这种修复技术最大的限制是系统过水能力减小。不过，这可以通过改进水压性能予以抵销。为了插入内衬管滑（拉）入衬，现有的管道必须在一定程度上是直的，需要挖除和拆除所有弯头和配件。
爆(碎)管衬装
应用这种技术是不需要预先清理现有管道的，因为管道将会在操作中被摧毁和更换。
在方便的地点接近管道，液压或气动碎管头沿着管道前行，破碎了旧管道，将碎片压入了周围的地面。后面拖动着一根UPVC或MDPE用来安装作为替换管。这个过程的优势是通过一次操作增加了管径的尺寸。
测量
图片标题：在英国一个客户的住宅抄表
图片标题：住宅区抄表，英国
测量
任何自来水公司都需要有一种向客户收取水费的方式，以便为客户提供服务。最显然的方式是测量供水量并据此收取水费，这样，客户用水越多缴费也越多。
另一种方式——划一收费
供水商也可以采用其他的方式收取水费。可以根据资产的大小或价值抑或居住人数收费。最简单的方法是采取划一收费方式，向所有用水单位收取一样的费用，但是这或许也是最有缺陷的收费方式。公司都会考虑所有收费系统的成本，各种收费系统对不同客户的公平度、对用水方式的影响和水务设施的投资。
完美的水处理公司应该计量所有客户的用水量，以便根据他们的用水量的向客户收取相应费用，完全公平地对待每个客户。这或许是最公平的收费方式了。对于工业用户的过程用水，这种计费方式是必要的。利用这种计费方式，还能减少客户的浪费水行为，也便于设计用水旺季罚款。如果能够测量所有供应，水务公司就能更好地掌握配水系统中不同地区的客户的消费类型，更重要的是，能够更好地得知有多少水没有计算在内（因为渗漏、测量误差、坏账单、盗窃和非法使用）。
对于你而言它完美吗？
根据有形的测量支付水费假定普遍测量会通过刺激客户审慎用水对整体需求产生影响。这种减少会给水务公司节省在资源领域和处理分配系统的投资。还需要估计这些节省能否抵消安装、抄表、维护和更换仪器的成本。相对劳动力成本即在各个国家经济平衡是不同的。
缺点
普遍的测量方式也有一些缺点。仪器的安装和操作费用很高，替代方案的需求也在增加。需要阅读仪器，客户依据自身的消费额缴费，这就需要一种相对复杂的计费系统，需要大量的人员去读取和管理账目。所以，必须找到一种成本低但是足够准确的测量方式和有效的读表方式。目前的技术利用‘抄表员（outreaders）’每人每天可以读取400个仪表。新技术每日能自动从移动增值网络上读取成千上万个仪表。
利用仪器，客户更容易查询自己的帐户。但是任何按消费体积计费的系统都可能会发生骗局，可能是由于非法测量或抄表人员不合法行为造成的。
测量导致了收入的不确定性
通过普遍测量计费的另一个问题是公司收入的不确定性。使用的水量，收入受到水供应商无法控制的经济或天气状况的影响。
划一收费的好处
与测量水量收费相对的，还有一种是向所有同座公寓的住户客户划一收费，收取一样的费用。这样的系统容易管理，只需要登记客户，和一种按照预先确定数额收费的方法。另外，定义住户的方式也是必要的，以便工业用户可以根据测量的数额计费。优点是成本低，操作简单。但是划一收费的方式也可能会收到批评，因为可能存在不公和无法区别用量较多和较少的用户。任何与用水体积无关的收费方式都不太可能促使用户谨慎用水，因此增加了在水利设施上的投资；但是，对于已经失控的收费系统，必须要从划一收费的基础上开始。
按照用水的分级税率对家庭用户收费的这种中间选择代表了一种折衷的解决方案。如果有这类或许能从税收机关或评级机构获得的信息，例如家庭居住人口数目，就能获得一种把水费和其可能用途联系起来的方案。一旦获得这些信息，这个系统就容易控制了，当然也就省去了测量仪器安装和读取的费用。这种系统比划一收费公平合理，但是与计量收费方式相比较还有瑕疵。水务公司能明了自己的收入了，但是对于激励客户审慎用水这方面作用甚小。
当地影响
显然，计量系统提供了一种最公平合理的收费方式，并调动了客户节水的积极性，从而实现了供水和配水的成本最小化。水资源不足将影响这种情况，也成为决策过程中的一个重要因素。一个广泛分布着测量仪表的系统的操作成本是很高的，公司在考虑最佳操作方式的过程中必须要考虑成本、收益和法定义务，以便优化投资回报率。
如今，发展出了将水、煤气和电抄表系统联合起来的方法，大大降低了成本，用综合账单尤为节省。
计费系统
图片标题：现代计费系统
计费系统
无论选用什么方式对用水收费，建立一个高效的结算系统是绝对必要的。这个结算系统需要按时对所有客户进行准确的计费；尽快收集所有款项；必要的时候采取适当的追讨行动，并尽可能以最低成本实现这些过程。
接口
在所有业务的框架和与客户的关系基础上建立计费系统是非常重要的。为了实现这个目的，计费系统不能与公司的其他业务分开来看，必须与其他用途建立接口。然而，计费系统将成为核心和其他系统的联络点，利用计费系统获取信息，例如，操作日志管理系统、水质信息、和其他近期更新的如地理信息系统一类的信息。
数据库
我们提到过，一个好的结算系统的第一要素是有一个连接到其他资产资料库的准确的客户资料库。通过这种方式可以生成有关的历史信息，例如资产的过去用途和有过历史债务的顾客。这个数据库可以方便地“一站式”查询所有客户。
软件
和数据库同样重要的是使计费功能起作用的软件本身。账单必须按时寄出，提醒、最后通知书及法律行动或其他追讨行动能按照计费时间表自动生成。采用合适的付款设施，计费系统应该能应付所有变化的情况。计费周期将从抄表开始，由人工通过手提电脑实现，随后下载到一个资产数据库中。最近的趋势是数据采用更复杂的方式，通过触摸屏或通过电话线或无线电信号读取外部远程数据。用来沟通的媒介必须与结算产权资料库有连通。
付款
付款有多种方式可供选择，但是重点是如何更自动化。直接转账被普遍认为是最容易接受和最方便的付款方式。一旦采用了直接转账，随后资料的维护就相对容易控制了。这种支付方式是通过连接到银行结算系统自动完成的，客户记录通过光盘和磁带自动记录。其他支付方式，如现金、支票、银行汇款和邮局汇款等，管理上通常都比较昂贵，但是通过磁带、磁盘或网络技术的帮助加快操作，也帮助将费用降到了最低。
管理信息系统
一个有效的计费系统要应对不同付款工具和付款安排的客户的账单要求，例如分期付款。为了控制和管理这个操作，一个有效的管理信息系统也是计费系统平稳运行的一部分。管理信息系统决定了统计数据，如由它的三大主要职能客户服务、计费和收取产生的关键绩效指标。管理系统能够读取客户和资产数据库，并根据具体需要产生每天、每周或每月的数据报告。
灵活性
总结来说，一个良好的计费系统作为实现目的的手段，应该灵活，以便满足不断变化的需求。计算机在此起了重要作用，应该在公司需求的整体策略上加以考虑。在当今的市场，添加潜在的服务，如为其他公用设施计费（电力、固体废物收集）灵活性很关键，还要以最低的成本实现这种变化。如今的计费系统不但要求功能，致力于低成本和高效率，而且要顾及到其他用户，例如公司的其他部门。做到这一切，计费系统就不仅仅是一个简单的计费系统，而是一个整体有效的管理工具了。
图片标题：菲律宾Subic Water 的Cascal’s concession的手持式计费系统
图片标题：英国伯恩茅斯的渗漏检测培训
图片标题：南非内尔斯普雷特的员工培训中心
员工培训
员工培训和发展
培训文化
建立适当的培训文化是成功的员工培训和发展不可或缺的部分。这往往包括需要员工获取的新技能和现有技能的发展。员工培训和发展是百沃特管理水务公司运作策略的基石。
多年来，我们制定了结构化的员工培训和发展模块化方法，可以为满足任何个人或团体员工的需求而制定。我们这种方案在世界各地都运用得非常成功。例如，在英国水务办公室，英国2006-2007年度的监管报告，Bournemouth and West Hampshire Water被评为英格兰和威斯尔地区22家水务公司中整体表现第二的水务公司。其不仅渗漏率低，客户服务水平佳，而且收费也低于平均水平。公司拥有国家级人员培训和发展标准，并有ISO9001质量认证。公司曾被英国工业联合会授予“卓越的培训中心”称号。这些成就的取得 完全归因于公司为满足公司战略目标需要给员工提供的技能和工具培训。
我们通过培训和拓展项目将我们的技能和专业知识进行传授。这些项目是为了满足每个操作的具体需要而设计的。培训可以在当地或英国进行，既有理论也有实际的现场工作。建立的模块涵盖了技术和市场两个学科。例如：
顶尖的质量管理
提取和供应
水处理
工程战略和项目管理
分配
污水和污水处理厂
科学服务
环境保护
客户服务
计费和费用征收
在确保水务公司完成其商定的目标方面，在员工培训和发展上的投资和在厂房和机器上的投资同样重要。
3.完美的污水处理系统
污水净化
完美的污水处理系统能够收集集水区的每一滴废水，并无渗漏的输送到完美污水处理厂。处理厂将除掉废水中的所有杂质，转化为其从云中落下时候的纯水状态。这个过程是完全可能的，但是耗费的成本远远高于收益。废水收集和处理，象其他很多活动一样，都会受到收益递减规律的制约。
低流量/防洪能力
污水系统是为收集区的正常流量和暴雨水流（大于正常流量好几倍的水流）设计的（正常流量包括某些正常雨水）。暴雨溢流直接通过各种途径进入集水水道。价值最大化的选择，与以往一样，是一个争取适当平衡的问题。大容量意味着高成本，仅在少数情况下才需要这种设施，而且因国家而异。在一些情况下，可能要安装容纳容器比较合适，可以在洪水状况下接收流量，随后以控制的方式流放到水处理厂或水道。有些通常用于处理暴雨流量，筛掉会聚集在水道里或水道旁的难看的物质。为了管理完美的污水处理公司，我们需要利用废水管网管理策略确保有足够的污水管网，也可以用相似的方式管理净水管网。投资者需要认识到，虽然需要有一个能处理接收到其内部的全部污水（并达到污水处理标准）的污水处理厂，如果废水网络不能妥善处理防洪、淤积或堵塞的水流，那么这项投资不是白费的就是贬值的。
为了满足主要环保标准，越来越多的投资者和放款者意识到必须把废水管网管理策略作为投资和放贷的一个条件。虽然发展废水管理策略是一个关键要求，但是由于缺乏详细的本地管网知识，废水管理策略的全面实施也很困难。这些问题可以通过管网和处理厂设计的前提——资产评估和地理信息系统分析得到。
废水管网调查涵盖了类似于净水管网管理部分中所描述的那样一个范围，但是废水管网管理策略用以下术语来描述其活动范围：
排水区规划是用来描述对一个排水集水区内的整个污水系统进行研究的术语。地区计划是用来检查和评估完美净化系统的资产数据的，包括水压和结构条件、水道污染记录和集水区未来的任何发展情况。由于水量随着雨水增加，导致污染物浓度下降，因此排放物对环境的影响也减小了。要想在现金价格和环境保护之间取得适当平衡，收集区的大小和细心设计是至关重要的。
完美的污水处理厂
环境保护和溢流的经济可行性的适当平衡后，还需要决定污水处理的适当的度。完美的污水处理厂最好是能够处理所有收集区收集到的废水和暴雨水。那这个污水处理厂需要无限大，费用也很昂贵。大部分工厂有储存设施，以低流速将暴雨水输送给处理过程，使得处理厂不必具备那么大的规模且费用也低了。需要具备处理技巧以维持储存容量和处理容量之间的适当平衡。一些世界卫生组织规定的环保和健康标准只需要将污水进行初级沉淀就能达到。经过二级处理的水将达到更严格的质量要求。
大部分发达国家都有立法和指令来管理根据集水的质量和数量要求的处理度。污水处理的尺度通常用一些术语来表达，如有机污染物生化需氧量（BOD）或化学需氧量（COD）和除掉的悬浮固体（SS）。更新的更严格的标准要求将氨、磷、氮甚至是总氮全部除掉。百沃特不仅建造了很多符合这些标准的污水处理厂，而且还特别研制了满足这种更严格的要求的专利过程。
在强调保护水资源和水回用的今天，节能是关键。水务公司设计出了带有三级处理系统的工厂，将污水适当处理后用来灌溉和补给地下水。通过进一步的处理工艺去掉所有有机和无机污染物及细菌，使出水符合饮用水标准，这在技术上是可行的。百沃特利用去矿化作用、反渗透和紫外线杀菌等过程建立了很多符合超纯标准的工厂。但是需要记住的是，每个处理步骤都会增加成本和运营开支。百沃特致力于为处理厂提供适当的技术，并根据其几乎无与伦比的处理经验找出最合适的方案。在许多污水被排放到长长的海水排污渠的情况下，污水只需要经过初步处理就可以了，例如北海岸废水处理项目（位于北爱尔兰沿海社区）。在另外一些去除营养盐（磷和氮）必要的情况下，就需要生物养分工厂了（例如香港大浦污水处理厂）。
为了逐步在尚无污水处理厂的地方引进污水处理厂，很多世界援助机构希望看到污染控制能够分阶段得到落实。在规模较小的农村网点，可以从建造化粪池或污水坑开始。集中处理污水需要某些形式的管道收集系统，接着可能还仅需要初级污水处理。在接下来的阶段可能需要引进二级甚至三级处理。成本和污染度决定了是否需要一个或多个阶段的处理。为了使处理度增加到新水平，所用的技术也要从传统的污水处理过程换成水处理中常用的那些过程。这些过程能生产出几乎符合饮用水标准的水，但是可能含有太多的溶解盐。
目前，世界银行和国际金融公司（IFC）都在强调污水应该得到适度的处理，即污水对接收水的污染必须要加以考虑。如果少量的污水（如0.1立方米/秒）排入100立方米/秒的河水中，影响很小，但是如果是排入1立方米/秒的河流中，那影响就很大了。因此，在设计最切合实际最符合成本效益的方案时要考虑很多方面。
反渗透污水去矿化作用能除去溶解盐，生产出比多数饮用水标准更高的水。百沃特已经在沙特阿拉伯的吉达建造了一个产量为30,000立方米/日的这种类型的海水淡化厂，用于农业灌溉。
完美的水处理厂将采用模块化建设方式，以便流量增加时的扩容。这种类型工厂的运营者能够准确预测出什么时候需要扩容，便于计划资本开支配合扩容。不过这种理想的情况并不多见，因为多数污水处理厂到一定阶段会遭遇水压或有机超载。需要特别的技巧去重建或翻新污水处理厂，包括重新定义/设计、控制和自动化方面的知识。百沃特广泛涉及了污水处理厂翻新工作，英国在上世纪后半期建造的多数污水处理厂的整修工作中都有百沃特参与。
总之，污水处理厂需要仔细地规划和在每个阶段的审慎实施。从一开始许可标准要确定的时候，到操作和维护兴建的设施，都需要特别的技巧来选择正确的方案，以适当的成本获取最佳的效益。
图片标题：香港沙田污水处理厂
图片标题：南非Cape Flats污水处理厂
完美的污水泵
液体运动的最有效方式是通过重力。不过，人口分布很少能使得水供应、污水排放和处理过程中能应用重力，或经济上可行。在重力系统不足或不切实际或不可能的情况下，水泵提供推动液体流动需要的能量。
水泵的应用已经有几百年的历史了。早期的一些设计，例如阿基米地螺旋泵在现在的污水处理厂仍在应用。今天，为了满足各方面的广泛操作需要，设计出了大量不同类型的泵。选取最恰当的泵，需要考虑：
要输送的液体性质
吸收和排放条件
效率
容量和压力
需要的控制程度
可靠性和维修方面的要求
液体的性质
要输送的液体、气体或流体极大地影响着泵的类型、材料和结构的选取。液体，如未经处理的污水需要采用非阻塞设计的传统耐磨材料的泵，反之，海水反渗透给水泵则需要采用耐腐蚀性材料的泵。
吸收和排放条件
每种泵模型都有具体的吸收条件，以防止汽蚀和实现效率最大化。同样的，排放条件也必须审慎评估，建立系统曲线和采取任何减缓流速的必要行动。
效率
完美的泵效率当是100%。不过，这种情况是不可能的。虽然最有效的水泵可以将90%以上的输入流体输送到泵浦。最优设计的泵系统可以将最大泵效率调整到工作点。设计到经济点的泵，泵系统的成本最低，可能操作成本较低。百沃特能够根据您的需要提供各种方式的资本、操作和维护成本数值比较。
图片标题：设计及建设合同，英国伊斯特本污水处理厂 (建于海岸线之下)
容量和压力
这些参数决定了泵的射程，又由射程和系统曲线一起确定了操作点。一般而言，螺旋桨或混流式水泵能满足低射程的用途。高射程的用途则通常要使用涡轮泵（通常是多级涡轮泵）或正排量泵实现。
可靠性和维修要求
泵系统的设计要谨记整个装置的长期可靠性。对各个方面的谨慎考虑能保证系统不过分影响运行能力。泵站的布局要方便获取关键机械装置，抽水水管的设计应确保放气阀门等组建可以保持而不需要隔离水管。
涉及到可靠性，可能需要考虑备用电厂，以便在出现故障的时候用。整体设计过程中仔细谨慎可将失败的可能性降至最低。百沃特拥有对失败的风险进行定量评估的技术，来尽量减少投资，避免不必要的“腰带和背带策略”的设计方法。让设计师发现可能会引起故障而往往被忽视的危险。
除味
经济的增长使得原本位于城镇外的污水处理厂四周被房屋建筑和工业包围了。这种近距离导致了很多关于不良味道的投诉。
百沃特在英国伊斯特本的最新式污水处理厂就是采用无气味设计的一个最好例子。如前页所示，该厂建在海岸线以下。
空间允许的话，如果正确利用低价的生物学过程，可以产生没有异味的效果。发出气味的是筛选，砂砾清除，污泥处理过程。利用生物系统在可以被吸收的地方投放放射物，可以完全清除异味。毫无疑问，这是最具成本效益的控制气味的方式。
如果空间无法允许使用低价生物过程，或处理厂没有二次沉淀过程，这时候就需要构造气味控制器了。将所有处理原件装在一个装置中，或放在各个处理阶段，让空气通过气味处理设备，实现除味过程。
大多数气味是在硫化氢（H2S）和恶臭化合物形成的过程中产生的。可用于处理气味的系统包括：
•化学洗涤
•生物过滤（泥炭、纤维、石南等）
•生物擦洗
•分子吸收
气味控制计划的目的是完全去除不良气味。如果不是必须的，在制定非常严格的标准时，这些是没有意义的，实际上在多数情况下不是必须的。在处理厂建造之前，需要用潜在气味风险模型来预测对周围环境的影响。一般而言，专业化的经营管理对于尽量减少异味就足够了。
图片标题：马那瓜污水处理厂的概念设计 尼加拉瓜
污泥处理和处置
完美的污水处理厂可以净化污水，并且不产生任何副产品。现实中，所有处理厂都应用固液分离过程（筛选，砂砾清除，沉淀，澄清等）分离出固体产物。主要副产物是污泥，是初次沉淀（初沉污泥）和去除过剩生物有机体（二沉淀污泥或腐殖质污泥）过程的产物。
在发达国家，随着环保法规和规范污泥处理的指令的相继出台，污泥处理变得日益困难。例如，在欧洲，将污泥倒入海洋的传统做法被彻底禁止，对于堆填区的做法也推出了更严格的法律。事实上，安全处置污泥已经变得和处理污水一样昂贵和复杂了。这是因为污泥必须要加以操作、运输、增厚，有时还需要脱水，然后才能加以处理和固化。污泥是高浓度的污染物，含有一些有价值的物质，包括氮、磷、钾。如果能正确地加以处理，这些物质会是很好的能量来源。污泥的另一个时尚的名称叫做“生物固体”，将污泥看做是有用物质，而非待处理的讨人厌的副产品。
在着手处理之前，必须与有关当局讨论污泥处置策略和最终抛弃路径。可能包括下面几种方式：
•海上处置（被允许的地方）
•堆填区（经过脱水干燥或焚烧后）
•循环利用（农业用途、堆肥、能量来源、建材等）
显然，如果经济上可行的话循环利用是最佳选择。污泥厌氧消化不仅能使污泥达到稳定状态，而且能产生用于发热和发电的沼气。百沃特已经利用厌氧和好氧过程建立了很多污泥处理厂。百沃特在污泥干化和堆肥方面也有涉及，尤其是在将污泥转化为宝贵的土壤补充剂方面，拥有领先的技术。
总之，污泥的处理有多种方案可供选择。但是选择的方式在很大程度上取决于最终抛弃路径、污泥的类型和具体情况，如可用土地，经济限制等，所有这些在每个污泥处理厂都是不同的。
4.监管的作用
监管的作用
由于供水具有资本密集的特点，如果有私人部门参与，使会得供水成为当地的垄断业务，因此需要一定程度的监管机制。这不仅仅是一个政治和社会问题，也是一个经济和坏境问题。从政治和社会的角度来讲，政府需要向客户保证维护客户的利益，并保证在以后继续维护客户的利益；从经济和环境角度讲，私人部门的投资者要向客户提供符合规定的数量和质量标准的保障公众健康和环境的用水，同时也要得到公平的回报率。
由于税率必须反应质量，环保和服务标准这些当局和水用户希望能够写入融资合同的因素。经济监管和环境监管是相辅相成的。
调控
经济调控可以采取许多种形式，但是都要求供水商提供给监管部门的信息。经济调控方式包括对税率、股息、资本或销售回报率的调控。在世界各地，无论是单独应用其中某个还是组合运用，都取得了不同程度的成功。透明、公平、一贯地应用经济调控是非常重要的。调控的措施应当有着清晰的界定，恰当的定义，并由监管者公平地以公开报告的形式公布。
给投资者的合理回报
私有部门投资者在寻求至少中期的稳定合理的可预测性收入和现有资本及新资本的回报。此外，规管体系应提供激励措施，激励私营部门参与者最大程度地提高效率（例如通过减少渗漏或减少经营成本），并从这种效率提高中保留部分利益，as should customers in due course 固定回报率或红利控制没有这种激励作用，但是价格上限管制却有激励作用。自从1989年英格兰和威尔斯的水务私有化以来，价格上限管制的激励方式取得了重大成功。英格兰和威尔斯还得益于若干私人水务经营者，这些水务经营者各自给离散和独立的地理区域供水，使得地区间供水比较成为可能。
质量
由于优先权、需求和预算的原因，各市场的质量和环保管制存在很大的不同。英国的饮用水质量和环境保护制度在世界上是最复杂和最彻底的。在这方面我们拥有丰富的经验，可以利用我们的经验以最具成本效益和最有效的方式满足我们客户的需要。
管制
不应该有对抗和侵扰。应该是协商的，和私有部门合作，完成各方在私人融资倡议中规定的共同目标。监管者必须是独立和客观的，对于无视协议目标和水供应商控制目标的行为具有制裁力。当供水商表现欠佳时采用制裁措施。
定制
我们熟知世界各地的调控政策，能够提供咨询和协助建立监管框架和结构，完成私营部门融资倡议里的目标。
我们在私营机构融资计划方面的全球经验非常广泛，从最简单的到最复杂的都已经开发出来了，能满足各方在这个计划中的需求和期望，并确保成功。
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