Water Supply

744 Pages·18.746 MB·English

by  Don D. Ratnayaka, Malcolm J. Brandt and K. Michael Johnson (Auth.)

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To the Memory of
Alan Charles Twort
Author of the First Five Editions of This Work

Who Left the World a Better Place
Foreword
Since the first edition of this book was published in 1963 the procurement and treatment of water for
public consumption has become increasingly difficult. There are real worries now that freshwater
supplies in many parts of the world are not sufficient to meet the demands of growing populations
and the need for increased food production. Water resources in some countries may even be entering
a period of decline due to global warming.
In the same period, the production of potable water from raw water supplies has become more
complicated with increasing awareness of the pollutants being discharged into the hydrological
environment and the harm they may be causing.
These adverse changes pose difficult problems for all water engineers and scientists. Means have
to be found of reducing wastage of water by consumers and losses from pipe distribution systems.
The former involves encouraging consumers to use only the water they need; the latter involves the
costly and difficult task of repairing or renewing many old water mains in densely populated urban
areas.
As a consequence of the need to cope with these diverse challenges the 6th Edition of this book
conveys the advice and experience of three authors plus thirty contributing specialists and advis-
ers, several of whom have high global standing in their specialisation. The authors and the majority
of specialists have experience of working for the consulting engineering firm of Binnie & Part-
ners—which practiced for over 100 years, for Paterson Candy Limited—which designed and built
water treatment plant worldwide and for Black & Veatch Corporation of Kansas City—who has
engineered water treatment and supply facilities across the USA since the early 20th century.
The importance of using the best specialist knowledge has to be emphasised because of the
ever increasing technical and social challenges as well as the relentless pressure to find the most
cost-effective and environmentally sustainable solutions. The in-depth knowledge of the expert,
when given time to study the task, can help meet these challenges and achieve the results needed in
tomorrow’s world.
Alan C. Twort
April 2008
xxv
Preface
The first edition of Water Supply provided the practicing water engineer with a practical treatise
on all aspects of the water supply in one book. Since then, the book’s readership has broadened to
include students of engineering and it is now used as a standard text in many universities. Recognis-
ing the contribution of Alan Twort, the lead author and editor of the first five editions, this edition
is titled Twort’s Water Supply. It benefits from the extensive experience of UK and US specialists
from across the water industry. The result is an extended and rebalanced coverage, with many new
references and illustrations, which brings the work up-to-date. Practice in the US, UK, Europe and
worldwide is included.
Chapters are arranged in order of: demand, statutory, financing and economic aspects of supply,
water sources and quality, treatment processes, hydraulics and system design, distribution, pipe-
lines, valves, pumps and other MEICA plant and treated water storage.
The institutional aspects covered now include international water rights, the EU Water Frame-
work Directive and experience with private sector participation. Text on hydrological yield has been
rewritten to reflect present methods and flood coverage is revised to reflect issues that have arisen
with the Flood Estimation Handbook.
The text gives up-dated standards for drinking water and describes in detail the significance of
the large number of chemicals and organisms, which now present, in raw waters, a potential hazard
to human health. Conventional and specialised treatment processes, waste treatment and disinfec-
tion are covered in five separate chapters. Treatment chemicals are described in detail. Developing
technologies such as membrane filtration and advanced treatment methods for micropollutants are
also dealt with. Desalination by reverse osmosis and thermal processes is covered.
Chapters on system hydraulic design and practice are rearranged to make access easier with cov-
erage of new methods. Pipe structural design and valves and meters are presented with new mate-
rial in separate chapters. The chapter on pumps is broadened to cover other electrical, control and
instrumentation aspects of water works and the chapter on service reservoirs is extended to embrace
treated water storage of most types likely to be encountered.
The authors are grateful to the many contributors and reviewers who have aided the production
of this sixth edition and to Black & Veatch for permitting use of their work.
Don D. Ratnayaka
Malcolm J. Brandt
K. Michael Johnson
xxvii
Abbreviations for organisations
ADB Asian Development Bank, Manila, Philippines
ASCE American Society of Civil Engineers, Reston, VA, USA
ASTM American Society for Testing Materials (now ASTM International), PA, USA
AWWA American Waterworks Association, Denver, USA
AwwaRF American Waterworks Association Research Foundation, Denver
BGS British Geological Survey, Nottingham, UK
BHRA British Hydromechanics Group, Cranfield, UK
BSI British Standards Institution, London
BW British Water, London
CIRIA Construction Industry Research & Information Association, London
CIWEM Chartered Institution of Water & Environmental Management, London
CRC Chemical Rubber Company, FL, USA
Defra Department for Environment, Food and Rural Affairs, London
DETR Department of Environment, Transport and Regions, London
DFID Department for International Development, London
DHSS Department of Health and Social Services, London
DoE Department of the Environment, London
DWI Drinking Water Inspectorate, London
EA The Environment Agency, Bristol, UK
EEA European Environment Agency, Copenhagen
FWR Foundation for Water Research, Marlow, UK
HMSO (OPSI) Her Majesty’s Stationery Office, London (Office of Public Sector Information)
HSE Health and Safety Executive, London
IAHS International Association of Hydrological Sciences, Wallingford, UK
IChemE Institution of Chemical Engineers, Rugby, UK
ICOLD International Committee of Large Dams, Paris
IET Institute of Engineering Technology, London
IMechE Institute of Mechanical Engineers, London
IoH (CEH) I nstitute of Hydrology, Wallingford, UK (now Centre for Ecology & Hydrology)
ISO International Organisation for Standardisation, Geneva
IUVA International Ultraviolet Association, Ontario
IWA / IWSA International Water Association, The Hague
IWEM / IWES Institution of Water Engineers (& Scientists), London
NERC Natural Environmental Research Council, Swindon, UK
NEWA New England Waterworks Association, Massachusetts, USA
NFPA National Fire Protection Agency, Massachusetts, US
NFPA National Fire Protection Association, Ascot, UK
Ofwat / WSRA Water Services Regulation Authority, Birmingham, UK (Term Ofwat still used)
PWC Portsmouth Water Company, Portsmouth, UK
STW Severn Trent Water, Coventry, UK
xxix
xxx Abbreviations for organisations
SWTE Society for Water Treatment and Examination, London
TWU Thames Water Utilities, Reading, UK
UKWIR UK Water Industry Research Ltd., London
UNESCO UN Educational, Scientific and Cultural Organisation, Paris
UNICEF UN Children’s Fund, New York
USACE US Army Corps of Engineers, Washington
US EPA US Environmental Protection Agency, USA
USGS United States Geological Survey, Washington, USA
WEDC Water Education Development Centre, Loughborough, UK
WHO World Health Organization, Geneva
WMO World Meteorological Organization, Geneva
WRc Water Research Centre, Medmenham, UK
WSA Water Services Association, London
WSRT - Aqua Water Supply: Research Technology – Aqua, IWA, The Hague
Contributing Authors, Reviewers and
Advisors
Contributing Authors
black & Veatch
Peter B. Clark MA, MSc, FICE Technical Director (Hydraulics)
Anthony N. Coe MA, FIMechE, FCIWEM Consultant Mechanical Engineer (Pumping
Plant)
Scott Freeman BS, BA Membrane Technology Leader (Membrane
processes)
Keith R. Gardner BSc, MSc, FIStrutE, MICE Consultant Structural Engineer (Service
Reservoir Structures)
John Hall BSc, MCIWEM Chief Hydrologist (Surface Supplies and
Floods)
Robert Hulsey BS, MS Director Water Technology (Ozone and
UV)
Mike J. Little MA, MICE, MCIWEM Technical Director (Pipelines)
John C. Maunder BSc, MIET Consultant, Control & Instrumentation
(Control and Automation Systems)
John L. Petrie BSc, MSc, FGS, CGeol. Chief Hydrogeologist (Groundwater
Supplies)
Alvin J. Smith BSc, MSc Consultant Biologist (Water Biology and
Storage)
others
Peter Mason BSc, MPhil, PhD, FICE Consultant (Dams)
Claire R. Stacey FRSC, MIWO Formerly Deputy Chief Inspector, DWI
(water Quality Issues and Standards)
reviewers and Advisors
John Ackers BSc, FICE Black & Veatch
Roger Brown BSc, MSc, DIC, FICE, FCIWEM Consultant
Nicholas Burns BS, MS Black & Veatch
Simon Cole BSc, Dphil, MCIWEM Wessex Water
Neville A. Cowton BSc, MSc, MICE, MCIWEM Black & Veatch
xxxi
xxxii Contributing Authors, Reviewers and Advisors
Sarah Dyer BA, MA Black & Veatch
Andrew Elphinston BSc, MIChemE, MCIWEM Black & Veatch
Terry Heard BSc, MRSC, MCIWEM Black & Veatch
Brian Hoyle MRSC Consultant
Heather Landis BS, MS Black & Veatch
Frank Law BSc, MICE, FCIWEM Institute of Hydrology
David E. MacDonald BSc, MSc, MCIWEM Black & Veatch
James Ostrowski BSc, MIChemE, MCIWEM Black & Veatch
Bill Querns BSc, FCIWEM, FCIM Consultant
Trevor Peploe B.Tech, MRSC Consultant
Bryan Townsend BS, MS Black & Veatch
H. Jane Walbancke BSc, MSc, PhD, FGS, MICE Black & Veatch
Paul A. Yiannouzis BSc, MIEE Consultant
Attribution of illustrations
The names of the organizations acknowledged in connection with illustrations are those current at
the time the illustrations were produced. Where an organization has since changed its name or has
been acquired by another, the new name is given below:
Sir Alexander Binnie, Son & Deacon Black & Veatch
Binnie & Partners Black & Veatch
Binnie Black & Veatch Black & Veatch
Paterson Candy Ltd Black & Veatch
CHAPTER
1
The Demand for Public Water
Supplies
1.1 Categories of Consumption
The demand for public water is made up of authorised consumption by domestic and non-domestic
consumers and water losses.
Domestic consumers use water within the household: for drinking, personal hygiene cooking
and cleaning, and outside the dwelling: for cleaning patios, irrigating gardens, filling ponds and
swimming pools and washing cars. Domestic consumers include households that are not connected
to the distribution mains but rely on collecting their supply from standpipes and public taps located
in the street.
In England and Wales in 2007 about 30% of domestic supplies were metered with individual
meter penetration ranging between 8% and 66% for the 22 water companies (Ofwat, 2007a). In
Scotland and Northern Ireland domestic consumers are not currently metered. Overseas metering
domestic supplies is widespread, although not universal. A survey by the ADB in 1996 (ADB,
1997) showed that, of 27 Asian cities serving over 1 million people, only 15 were fully metered
and six metered less than 7% of their connections (Calcutta 0%, Karachi 1%). UNESCO report
that in 2000 nearly a third of all urban dwellers worldwide, more than 900 million people, lived
in slums (UNESCO, 2006). Standpipes providing water to urban slums and rural communities are
not metered and the supplies are usually given free.
Non-domestic consumption comprises industrial, commercial, institutional and agricultural
demand legitimately drawn from the distribution mains. This category also includes legitimate public
use for irrigating public parks and green areas, street cleaning, flushing water mains and sewers and
for fire-fighting.
Commercial and industrial supplies are usually metered because they represent a major source
of income to a water utility. In the UK small shops and offices occupied only in the daytime used
not to be metered but now generally are, even though their consumption is small. In many countries
large quantities of water are used for watering public parks and green areas and supplying govern-
ment offices, military establishments and other institutional buildings. These supplies are often not
metered nor paid for if the government (state or city) supplies the water.
Twort’s Water Supply
1
Copyright information to come.
2 CHAPTER 1 The Demand for Public Water Supplies
Water losses comprise the leakage and wastage from the distribution network; these and other
components of non-legitimate use are categorised as:
Apparent losses: source and supply meter errors, unauthorised or unrecorded consumption, and
Real losses: leakage from transmission and distribution mains and service pipes upstream of
consumers’ meters, from valves, hydrants and washouts and leakage and overflows from the water
utility’s storage facilities.
1.2 LeveLs of totaL Consumption
The usual measure of total consumption is the amount supplied from sources per head of population.
However, in many cases the population served is not known accurately. In large cities there may be
thousands of commuters coming in daily from outside; in holiday areas the population may double
for part of the year. Other factors having a major influence on consumption figures are:
n whether the available supplies and pressure are sufficient to meet the demand, 24-hour or
intermittent;
n the population using standpipes;
n the extent to which waterborne sanitation is available;
n the utility’s efficiency in metering and billing and in controlling leakage and wastage;
n how much of the supply goes to relatively few large industrial consumers;
n the climate.
Many cities, more typically in Asia and Africa, either do not have a 24 hour supply, or the
supply pressure is so low that many consumers receive an intermittent supply. The ADB survey of
1996 (ADB, 1997) showed that 40% of 50 Asian cities surveyed did not have a 24-hour supply and
that about two-thirds had street standpipe supplies. Hence comparing average total consumption
between utilities is not informative. High consumption can be caused by large industrial demand
and low consumption by a shortage of resources. However, the general range of total supplies per
capita is:
n from 500 to 800 lcd (litres per capita per day) in the big industrial cities of USA;
n from 200 to 500 lcd for many major cities and urban areas throughout the world;
n from 90 to 150 lcd in areas where supplies are restricted, where there are many street stand-
pipes or where much of the population has private wells.
In 2006/07 in England and Wales the average total supply was 278 lcd (Ofwat, 2007a). In Scotland
it was about 494 lcd in 2003/04 (Scottish Water, 2005) and in Northern Ireland about 440 lcd.
1.3 DomestiC DemanD
Domestic consumption reported by various countries is not necessarily comparable mainly because
there is no assurance that the figures quoted are produced on the same basis. In the USA the typical
in-house consumption (excluding cooling) is 180–230 lcd but this can be expected to reduce
gradually with increased installation of low flush toilets and reduced rates of consumption by other
fittings. Average domestic plus small trade consumption reported by European countries for 2002
(IWA, 2004) centred about 150–160 lcd (range 100–330 lcd); France, Italy, Norway and Switzerland