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Twort’s Water Supply
Twort’s Water Supply
Seventh Edition
Malcolm J. Brandt
BSc, FICE, FCIWEM, MIWater
K. Michael Johnson
BSc, FICE, FCIWEM
Andrew J. Elphinston
BSc, MIChemE, MCIWEM
Don D. Ratnayaka
BSc, DIC, MSc, FIChemE, FCIWEM
AMSTERDAM • BOSTON • HEIDELBERG • LONDON
NEW YORK • OXFORD • PARIS • SAN DIEGO
SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO
Butterworth-Heinemann is an imprint of Elsevier
Butterworth-Heinemann is an imprint of Elsevier
The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, United Kingdom
50 Hampshire Street, 5th Floor, Cambridge, MA 02139, United States
Copyright r 2017 Malcolm J. Brandt, K. Michael Johnson, Andrew J. Elphinston, Don D. Ratnayaka. Published by Elsevier Ltd.
All rights reserved.
No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions.
This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein).
Notices
Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary.
Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility.
To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein.
British Library Cataloguing-in-Publication Data
A catalogue record for this book is available from the British Library
Library of Congress Cataloging-in-Publication Data
A catalog record for this book is available from the Library of Congress
ISBN: 978-0-08-100025-0
For Information on all Butterworth-Heinemann publications
visit our website at https://www.elsevier.com
Publisher: Joe Hayton
Acquisition Editor: Ken McCombs
Editorial Project Manager: Peter Jardim
Production Project Manager: Kiruthika Govindaraju
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Typeset by MPS Limited, Chennai, India
Cover images:
Black Esk Dam
Dumphries & Galloway, Scotland.
Raising of the Black Esk earthfill dam to increase storage by 40%, works designed by Black & Veatch. The work, completed in 2013, raises the overflow level by 2.5 m and involved the innovative application of precast concrete sections in “piano-key” form to raise the crest of the existing bellmouth spillway and to accommodate the peak design flood outflow of 183 m3/s, with a flood surcharge of 0.97 m.
Photographs by courtesy of Scottish Water.
Authors’ Biographic Details
The four authors, with combined experience of over 160 years, working for Binnie & Partners and then Black & Veatch, have written this text with the practicing water supply engineer in mind.
However, the book will also be essential reading for students of water engineering.
Malcolm J. Brandt
Global
Practice Technology Leader
Civil engineer specializing in water supply planning and distribution system management; responsibilities include research in the United Kingdom and overseas, as well as project execution in the United Kingdom, Europe, Asia, Middle East, and North and South America.
K. Michael Johnson
Technical Director
Civil engineer for design of large and small works, such as dams, spillways, intakes, pipelines, tunnels, pumping stations, conventional water treatment, reverse osmosis, and water storage in the United Kingdom, South and Central America, Middle East, and Far East.
Andrew J. Elphinston
Technical Director
Chemical engineer specializing in potable water treatment, including both conventional and advanced treatment processes, with experience in the United Kingdom, North and Southern Africa, and Far East.
Don D. Ratnayaka
Global Practice Technology Leader
Chemical engineer with extensive specialist knowledge of water treatment techniques; responsible for all aspects of water treatment process design for projects in the United Kingdom, Europe, Africa, Asian subcontinent, Middle East, Far East, and Australia.
Foreword
Twort’s Water Supply (and its predecessor—Water Supply) has been the first reference for many water engineers in the United Kingdom and internationally for over 50 years. In an age when a huge amount of information is accessible on the internet, some of unknown provenance, it is invaluable to the engineer engaged in water supply, and to students of the subject, to have a concise source of reliable guidance to hand. With the help of specialist contributors from the United Kingdom and the United States, the authors have managed to convey a large amount of information in a single volume. They have ensured, by means of extensive cross references, that the attention of the reader is drawn to all significant related matters, across all the disciplines involved in engineering new water supply facilities or in getting the most out of existing ones.
In the last decade the strains of rapid industrialization, rising population, and conflict are making themselves increasingly felt on basic infrastructure in many parts of the world, including water supplies and sanitation facilities. For huge numbers of people the provision and maintenance of even a basic supply of safe water seems to be an endless struggle. Meanwhile, the focus of attention globally, but particularly in post-industrialized nations, has moved to the quality of water in river basins, to more effective use of resources and assets, and to the treatment of the increasing number of pollutants of concern.
This Seventh Edition has been thoroughly updated to reflect current issues. It brings in two new chapters to allow extensive new material to be included on waste and energy efficiency and on water intakes, and for those needing further information, the references have been updated and increased in number. It is confidently expected that this new edition, like its predecessors, will prove to be an essential reference for those involved in the education and practice of water supply systems.
Nigel J.D. Graham MA (Cantab), MSc, PhD, ScD (Cantab), FICE, FIChemE, FCIWEM
Department of Civil and Environmental Engineering, Imperial College, London
October 2015
xxvii
Preface
Since the first edition of the book was published in 1963, Water Supply has provided the practicing water engineer with a practical treatise on all aspects of the water supply in one book. The readership of more recent editions has broadened to include students of engineering and it is now used as a standard text in many universities as well as a reference manual for water industry professionals worldwide.
The Sixth Edition recognized the valuable contribution of Alan Twort, the lead author and editor of the first five editions, by including his name in the title Twort’s Water Supply. We are pleased to continue to honor Alan’s valuable contribution to water engineering in the same way in this edition.
The Seventh Edition benefits from the extensive experience of nearly 30 UK and US specialists from across the water industry. The content has been expanded, revised, and updated to reflect the significant changes in the industry including international regulation, recognition of performance with respect to the customer, conservation, and the efficient use of resources and technology.
Practice in the United States, the United Kingdom, Europe, and worldwide is included. In addition, the index has been considerably enlarged to improve accessibility.
The book is structured to reflect the process of water supply from understanding demand for water, statutory, regulatory, water quality, financing, and economic aspects of the provision of wholesome water to the consumer, and then through the water cycle from abstraction through treatment to storage and distribution. The content addresses hydraulic and system design, pipelines, valves, pumps and other MEICA plant, dams, intakes and waste treatment, and energy demand reduction.
The text gives updated 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 specialized treatment processes, disinfection, and waste treatment are covered in five separate chapters. A new chapter brings together the storage and dosing of treatment chemicals and sampling. 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. A new chapter on intakes has allowed major expansion on this subject and coverage of pipelines has been increased.
The authors are grateful to the many contributors and reviewers who have aided the production of this Seventh Edition and to Black & Veatch for permitting use of their work.
Malcolm J. Brandt
K. Michael Johnson
Andrew J. Elphinston
Don D. Ratnayaka xxix
Abbreviations for Organizations
ADB
Asian Development Bank, Manila, Philippines
API
American Petroleum Institute, Washington, DC, USA
ASCE
American Society of Civil Engineers, Reston, VA, USA
ASME
American Society of Mechanical Engineers, New York, USA
AWWA
American Waterworks Association, Denver, USA
AwwaRF
American Waterworks Association Research Foundation, Denver, USA
BDS
British Dam Society, London, UK
BGS
British Geological Survey, Nottingham, UK
BHRA
British Hydromechanics Group, Cranfield, UK
BRE
Building Research Establishment, Watford, UK
BSI
British Standards Institution, London, UK
BW
British Water, London, UK
CIRIA
Construction Industry Research & Information Association, London, UK
CIWEM
Chartered Institution of Water & Environmental Management, London, UK
CRC
Chemical Rubber Company, FL, USA
CEH
Centre for Ecology & Hydrology (previously IoH), Wallingford, UK
CEU
Council of the European Union, Brussels, Belgium
Defra
Department for Environment, Food and Rural Affairs, London, UK
DETR
Department of Environment, Transport and Regions, London, UK
DFID
Department for International Development, London, UK
DHSS
Department of Health and Social Services, London, UK
DoE
Department of the Environment, London, UK
DWI
Drinking Water Inspectorate, London, UK
EA
The Environment Agency, Bristol, UK
EC
European Community (now European Union)
EEA
European Environment Agency, Copenhagen, Denmark
FAO
Food and Agriculture Organization, Rome, Italy
FWR
Foundation for Water Research, Marlow, UK
HMSO
Her Majesty’s Stationery Office (now TSO), London, UK
HSE
Health and Safety Executive, London, UK
IAHS
International Association of Hydrological Sciences, Wallingford, UK
IAM
Institute of Asset Management, Bristol, UK
IChemE
Institution of Chemical Engineers, Rugby, UK
ICOLD
International Committee of Large Dams, Paris, France
IEC
International Electrotechnical Commission, Geneva, Switzerland
IET
Institute of Engineering Technology, London, UK
IoH
Institute of Hydrology, Wallingford, UK
IMechE
Institute of Mechanical Engineers, London, UK
ISO
International Organisation for Standardisation, Geneva, Switzerland
IUVA
International Ultraviolet Association, Ontario, Canada
xxxi
xxxii Abbreviations for Organizations
IWA/IWSA
International Water Association, The Hague, Netherlands
IWEM/IWES
Institution of Water Engineers (& Scientists), London, UK
NEWA
New England Waterworks Association, Massachusetts, USA
NERC
Natural Environmental Research Council, Swindon, UK
NFPA
National Fire Protection Agency, Massachusetts, USA
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
SEPA
Scottish Environmental Protection Agency, Stirling, Scotland, UK
STW
Severn Trent Water, Coventry, UK
SWTE
Society for Water Treatment and Examination, London, UK
TSO
The Stationery Office (previously HMSO), London, UK
TWU
Thames Water Utilities, Reading, UK
UKWIR
UK Water Industry Research Ltd., London, UK
UN
United Nations, New York, USA
UNESCO
UN Educational, Scientific and Cultural Organisation, Paris, France
UNICEF
UN Children’s Fund, New York, USA
USACE
US Army Corps of Engineers, Washington, DC, USA
USBR
United States Bureau of Reclamation, Washington, DC, USA
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, Switzerland
WMO
World Meteorological Organization, Geneva, Switzerland
WRc
Water Research Centre, Medmenham, UK
WSA
Water Services Association, London, UK
WSRT Aqua
Water Supply: Research Technology—Aqua, IWA, The Hague, Netherlands
Contributing Authors, Reviewers and Advisors
CONTRIBUTING AUTHORS
Black & Veatch
Ian Barker BSc, FIET
Chief Engineer (Electrical)
Dipankar Basak BEng, MCIWEM, MICorr
Chief Pipeline Engineer, (now with MWH)
Nicholas Burns BS, MS
Ozone Technology Leader (Ozone)
Peter B. Clark MA, MSc, FICE
Consultant (Hydraulics)
Scott Freeman BS, BA
Membrane Technology Leader (Membrane processes)
John Hall BSc, MCIWEM
Consultant (Hydrology, Surface Supplies and Floods)
Tim A. Holmes BSc
Chief Instrumentation and Control Engineer
(I&C)
Robert Hulsey BS, MS
Global Practice Technology Leader - Water
(Advanced Oxidation Processes and UV)
Roger A. Middleton MPhil, FIMechE
Consultant (Sustainability and Renewable Energy)
John L. Petrie BSc, MSc, FGS
Consultant (Hydrogeologist, Groundwater
Supplies)
Hari R. Shah BSc, MICE, MASCE
Consultant (Water Intakes)
Bryan Townsend BS, MS
UV Technology Leader (Advanced Oxidation Processes and UV)
David J. Winzer BSc, MSc, MICE
Team Leader, Pipelines and Outfalls
Others
Simon Cole BSc, Dphil, MCIWEM, Microbiology & Public Health Manager
Wessex Water (Microbiology)
Sharon Evans MSc, MRSC, MBA
Head of Water Quality, Dwr Cymru Welsh
Water (Water Quality Issues and Standards)
Vikki Williams BSc, MCIWEM, MIAM
Principal Consultant
Energy and Utilities,
PA Consulting Group
xxxiii
xxxiv Contributing Authors, Reviewers and Advisors
REVIEWERS AND ADVISORS
John Ackers BSc, FICE
Black & Veatch
Michelle Ashford BEng, MCIWEM, MIWater
Bristol Water
Terry Heard BSc, MRSC, MCIWEM
Consultant
Stephen Murray BSc, Eng, MICE
Black & Veatch
James Ostrowski BSc, MIChemE, MCIWEM
Black & Veatch
Alvin J. Smith BSc, MSc
Consultant
Claire R. Stacey FRSC, MIWO
Consultant
Sarah Styan BA, MA
Black & Veatch
H. Jane Walbancke BSc, MSc, PhD, FGS, MICE
Black & Veatch
ATTRIBUTION OF ILLUSTRATIONS
The names of the organisations acknowledged in connection with illustrations are those current at the time the illustrations were produced. Where an organisation 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
The Demand for Potable Water
1.1 CATEGORIES OF CONSUMPTION
The demand for potable water is made up of authorized 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. Nondomestic consumption comprises industrial, commercial, institutional and agricultural demand legitimately drawn from potable water mains. This category also includes legitimate public use for irrigating public parks and green areas, street cleaning, flushing water mains and sewers and for firefighting.
Water is delivered to premises via service connections, the size of which depends on the demand from the premises. The majority of service connections feed single premises, but some supply a group of adjacent premises or a private development, such as an industrial estate, commercial complex or group of dwellings accessed from a private road.
Commercial and industrial supplies are generally fitted with an operational revenue meter
because they represent a major source of income to a water utility. Small shops and offices occupied only in the daytime are also generally metered even though their consumption is small.
In many countries where the national government, state or city owns the utility, large quantities of potable water used for watering public parks and green areas and within government offices, military establishments and other institutional buildings are often not metered nor accounted for as revenue.
Domestic revenue meters are widespread although not universal. For example in the USA,
mainland Europe and Australia meter penetration is effectively 100%; in England and Wales in 2012 nearly 40% of domestic supplies were metered with individual meter penetration ranging between 10% and 75% for the 22 water companies; while in Scotland and Northern Ireland domestic consumers are not currently metered. However, the underlying issue related to the effectiveness of domestic metering is one of operability not its coverage.
The world population is estimated to be in excess of 7 billion and international organizations estimate that over 1.4 billion people live in extreme poverty; nearly 900 million people live in Twort’s Water Supply. DOI: http://dx.doi.org/10.1016/B978-0-08-100025-0.000016 1
© 2017 Malcolm J. Brandt, K. Michael Johnson, Andrew J. Elphinston, Don D. Ratnayaka. Published by Elsevier Ltd. All rights reserved.
2 CHAPTER 1 The Demand for Potable Water
slum dwellings and over 700 million do not have access to an improved drinking water supply (WB, 2013; WHO, 2014; UNESCAP,
2013). Accordingly, not all consumers are supplied through a domestic service connection. In many cities, more typically in Asia and Africa, supplies are not 24-hour, do not reach 100% of the urban population or the pressure is so low that many consumers receive an intermittent supply. The Asian Development Bank (ADB) survey of 2005 (ADB, 2007a) showed that nine of 40 Asian water utilities surveyed did not have a 24-hour supply and that only eight of the utilities supplied 100% of the population in their service area, a connection being either in-house or a communal yard tap or standpipe.
A survey by the ADB published in 1997 (ADB, 1997) reported that of 27 cities in Asia with populations over 1 million, 15 were fully metered but six metered less than 7% of their service connections (Kolkata 0%, Karachi 1%). Further surveys by the ADB in 2005 and 2006 (ADB, 2007a, b) also highlighted that of 44 water utilities in Asia only 14 provided 100% individual service connections; in the remainder communal connections ranged between 2% and 70% of the population served.
Consumers who do not have direct access to a drinking water supply rely on collecting water from standpipes and public taps located in the street, on water tanker deliveries or on collecting water from an uncontrolled alternative source. Unmetered standpipe supplies to urban slums and rural communities are usually given free.
Water losses comprise the leakage and wastage from the distribution network.
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: I sufficiency of supplies and pressures to meet the demand, 24-hour or intermittent;
I population served by standpipes and tankers;
I population with waterborne sanitation;
I efficiency in metering and billing and in controlling leakage and wastage;
I proportion of supply going to relatively few large industrial consumers;
I the climate.
The supply situation described in Section 1.1 and the factors listed above mean that comparing average total consumption between utilities is not informative; e.g. high consumption could result from large industrial demand, whereas low consumption could be due to a shortage of resources.
However, the general range of total supplies per capita is:
I from 500 to 900 lcd (litres per capita per day) in the big industrial cities;
I from 200 to 500 lcd for many major cities and urban areas throughout the world;
I from 75 to 150 lcd in areas where supplies are restricted, where there are many street standpipes or where much of the population has private wells.
1.3 Domestic Demand 3
1.3 DOMESTIC DEMAND
As for total consumption data, domestic consumption figures reported by various countries are not necessarily comparable, mainly because there is no assurance that the figures quoted are produced on the same basis. However, data for 84 cities are presented in Table 1.1. Average domestic plus small trade consumption reported for 20 European countries for 2010 and 2012 (IWA, 2014) centred about 130160 lcd in a range of 61360 lcd, with Marseille in France having the highest reported consumption and three other listed cities recording over 200 lcd. For 12 countries in Asia consumption was generally between 200 and 250 lcd in a range of 40427 lcd, the highest consumption being in Darwin, Australia and the lowest in Hetauda, Nepal; 11 cities reported consumption over 250 lcd. In the USA the typical in-house consumption (excluding cooling water) is 180230 lcd, but the total household and small trade consumption can be significantly higher as the table suggests.
In-house domestic consumption is influenced by many factors including the class of dwelling, number of people in the household, changes in household income, ablution habits, culture, religion, differences in climate including seasonal variations, and the number and capacity of water fittings installed. The effect of such factors is illustrated in Table 1.2 by the range of metered and unmetered household consumptions for the water-only companies in England and Wales; the reported higher domestic consumption reflecting the fact that 77% of the population that they serve resides in the more affluent southeastern parts of England. The lower figures for metered consumption are not representative because metering is optional for most householders in the UK and those choosing to have a metered supply tend to be those expecting to pay less for their supply because of their low consumption, e.g. single occupants or elderly retired people. This is reflected in the household size, the ‘occupancy ratio’.
When estimating consumption for a whole area of a distribution system, it is the average
occupancy which is important. In England and Wales average occupancy according to census figures (Census, 2012) showed a decline from 2.70 in 1981 to 2.36 in 2011 and is expected to continue to fall slowly. The 2001 figures varied from 2.102.20 in retirement areas to 2.302.60
in the more dense populated urban areas. In the USA mean household occupancy reported by the US Census Bureau (US Census, 2012) declined from 2.63 people in 1990 to 2.34 in 2010. In many countries in Africa, the Indian sub-continent and in Southeast Asia, etc. the average occupancy is five or six people per household.
Table 1.3 shows the influence of occupancy ratio on household demand in selected parts of England; smaller households have proportionately larger per capita usage.
Water usage varies both in quantity and timing during the week, the pattern for working days being relatively consistent with morning and evening peaks coinciding with leaving for and returning from work and school. However, at weekends demand tends to increase with diurnal peaks often later than on working days and of greater magnitude. Cultural and religious characteristics of a supply area and religious days and public holidays can also influence weekly and seasonal demand patterns. For example during Ramadan, the Muslim holy month of fasting, domestic per capita demand increases and the diurnal pattern switches from day to night with peaks coinciding with sunrise and sunset.
Table 1.1 Domestic and small business per capita consumption for countries and cities with reference year (litres per capita per day; lcd)
Argentina, Buenos Aires, 20101
261 Gabon, 20101
New Zealand, Whangarei 20121
179 Australia, Darwin, 20101
425 Hungary, Budapest, 20121
150
Norway, Oslo, 20121
160 Australia, Perth, 20101
287 Hungary, Miskolc, 20121
80 Poland, Wroclaw, 20121
116 Australia, Sydney, 20101
200 India, Jamshedpur, 20073
302 Poland, Bialystok, 20121
Australia, Melbourne, 20101
148
India, Mumbai, 20073
191
Portugal, Lisbon, 20121
173
Austria, Vienna, 20121
143
India, Bhopal, 20073
72
Portugal, Porto, 20121
70
Bangladesh, Dhaka, 20072
140
Indonesia, Bandar Aceh, 20072
90
Romania, Suceava, 20121
125
Belgium, Antwerp, 20121
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ARTERITIS (THROMBOSIS, EMBOLISM) OF THE SPINAL CORD AND MEMBRANES.
Conditions of spinal circulation favorable to embolism and microbian invasion. Slow currents. Blood stasis. Free anastomosis a compensation. Symptoms. Treatment.
Facts are wanting with regard to these lesions in the domestic animals, but anatomical, physiological and pathological consideration are strongly suggestive of their occurrence. The vascular network of the spinal cord favors a tardy circulation, and this in turn is favorable to the arrest of solid bodies and the delay, proliferation and colonization of microbes. The median spinal artery receives a supply of blood by two trunks, right and left, entering by the intervertebral foramina at each intervertebral articulation. It has not, therefore, one continuous, equable, onward flow, but rather numerous independent currents corresponding to the entering vessels, and with intervening eddies or areas of comparative stagnation. The nervous material of the cord admits no large arteries but only capillary trunks which anastomose freely in its substance. This would seem to entail a sluggish flow, which would favor microbian arrest and colonization, even if the small size of the vessels serves to shut out clots of any material size. Finally the abundant venous plexus, and especially the two lateral venous sinuses, communicating freely with each other and, through each intervertebral foramen, with the extra spinal veins determine a similar tardy flow that should be favorable to morbid processes. If we pass back of these vessels, we find the posterior aorta to be at once the largest and the most direct channel for the entrance of emboli coming from the left heart or lungs. This danger is counteracted in greater part by the fact that the greater part of this blood passes into
the large vessels which supply the liver, spleen, kidneys, stomach, bowels, and hind limbs, and while embolism is well known in these parts it has not been demonstrated as yet in the spinal cord. The toxins produced in infectious diseases and circulated in the blood can often lead to destruction of the endothelium, and inflammation of the deeper structures. In this way any circulating microbes find a ready infection atrium. Hektoen seems to have demonstrated this in the case of tubercular meningitis. By pressure of the neoplasm on the vessel or by fibroid thickening and contraction of the walls of the vessel, the subsidiary cord is denied its full supply, and degeneration of the nervous substance is invited. In the human subject degeneration of the cord has been shown to follow the line of such diseased arteries. Thrombosis follows in every case in which the serous coat is involved, and embolism can easily occur from clots small enough to enter the capillary vessels. Lamy’s experiment of blocking the small arteries with inert powder, shows that this will give rise to foci of hemorrhagic softening, which commence in the gray substance. The blocking, however, must be multiple to produce any material effect, as the free anastomosis of the spinal capillaries otherwise secures an abundant blood supply to adjacent parts. In case of an infective embolism the disease will advance even if the obstruction is single.
The general symptoms of these conditions would depend on the exact seat of the lesion, and treatment would have to proceed on general principles, the object being to check the inflammatory conditions, and trust to the vis medecatrix naturæ in connection with rest and good hygienic conditions.
HEMORRHAGES INTO THE SPINAL MEMBRANES.
M S A . H .
H S C . S
A . H .
Definition. Causes: violent exertion, blows, falls, morbid blood, fractures, caries, tumors, tubercle, aneurisms. Lesions: Clot between or outside membranes in meningeal hæmorrhage, in gray matter and even in white in myelon bleeding. Cord bulges. If survives, nervous matter absorbed. Symptoms: Sudden stiffness or palsy of given areas; spasms more common in meningeal extravasation. Rapid muscular wasting. No fever at first. Treatment: cold to part; slings; atropia, ergot, lead acetate. Later as for myelitis. Large clot may warrant surgical interference.
In the first of these forms the bleeding takes place between the arachnoid and the two contiguous membranes—pia and dura, or outside the dura. In the second it takes place into the substance of the cord though it may encroach on the pia mater. Both conditions have been attributed to violent muscular efforts or contractions as in draught, racing, fighting, leaping, tetanic convulsions, also to blows on the back, or falls from a height. Morbid states of the blood in which there is a hemorrhagic tendency (scurvy, purpura, hæmophilia, anthrax) may be contributory causes. Spinal fractures, aneurisms, caries, tumors, and tubercle may be additional causes.
Lesions. In meningeal bleeding the clot is found outside the dura, or between the dura and arachnoid which may or may not be ruptured. A clot on the pia mater may press seriously on the cord or may cause rupture of the arachnoid. In hemorrhage of the cord, the effusion usually begins in the gray matter, though it may extend far into the white. It may be circumscribed to half an inch in diameter or
affect almost the entire length of the cord. The cord may be distinctly enlarged at the point of effusion, and in exceptional cases the blood may have broken through to the membranes. If the patient survives, absorption and degenerations of the cord are inevitable.
Symptoms. In both forms there is a sudden attack, with stiffness or paralysis of given muscles and without hyperthermia. Rigidity and spasms of the muscles are more characteristic of meningeal hemorrhage, and early paralysis of the spinal. An early hyperæsthesia is also most significant of an effusion in the cord. Rapid muscular atrophy is also characteristic of this. The two conditions resemble meningitis and myelitis but come on much more suddenly and are unattended by fever.
Treatment. Such cases are not hopeful. Cold to the affected part of the spine, keeping the patient in slings to solicit the good effect of gravitation, and giving ergot or lead acetate internally are among the first indications. Later, the treatment would be practically the same as for meningitis or myelitis. In case of complete paralysis from the sudden formation of a large clot, it has even been advised to cut down on the seat of the injury and evacuate the blood, using antiseptic precautions.