Water Pollution H. Fish, B.Sc., F.R.I.C., F.lnst.W.P.C., F.I.P.H.E. Chief Purification Officer, Thames Conservancy, London WC2 Historical aspects . . . . .. * . The present administrative position . . The present technical position . . . * The river authority role, 110 Wastewater purification and disposal, 1 13 Research and results, 114 Future requirements Bibliography 1 . . . .. .. .. .. . . .. In its simplest sense, water pollution can be taken to mean the fouling of water. There can be no doubt that when water is fouled it certainly is polluted, but if water is not fouled it does not follow that it is unpolluted. Another common mode of expression is to say that if water is polluted, it is no longer pure. But, to the chemist, absolute purity is unattainable, and purity is a matter of degree.In this context, pollution is also a matter of degree, and exactly what constitutes water pollution in some circumstances may not be considered as pollution in other circumstances. For example, a few bacteria of faecal origin present in 100 ml of a drinking water supply would constitute dangerous pollution, but the same state of affairs in a river or lake would not constitute significant pollution. In contrast, the presence of a fraction of a milligramme per litre of chlorine in a river or lake water would constitute harmful pollution, whereas the same situation in a cooling-water system would not constitute significant pollution. In this review, the pollution of water resources only will be considered.Water resources include the inland waters in streams, rivers, lakes and ponds, the groundwaters in permeable strata underground and the tidal waters of estuaries and creeks. In their natural state these waters, which have varying degrees of chemical purity, could be considered unpolluted because their quality has not been altered by man’s actions. Quality can be described in a variety of ways, but these can be expressed in terms of physical characteristics, in terms of chemistry, and in terms of macro- and microbiology. It is neces- sary to establish what degree of alteration of these quality terms transforms a water from the unpolluted to the polluted state. In short we must define generally when an alteration of quality matters to us.From the practical point of view, a change of water quality matters when the uses that we wish to make of water-for water supply, fishing or other sporting amenity, or our aesthetic enjoyment of it as part of the environment-are inhibited; or when environmental aspects of the public health are jeopardized by that change of water quality. .. 116 .. .. . . . . 117 Fish * . .. .. .. . . 106 .. . . 108 .. . . .. . . 110 . . . . 0 . 105 Qn this basis, a practical definition of water resources pollution can be given. Water resources are said to be polluted when, because of man’s actions in adding or causing the addition of matter to the water or in altering its temperature, the physical, chemical or biological characteristics of the water are changed to such an extent that its utility for any reasonable purpose, or its environmental value, is demonstrably depreciated.The practical aspects of water pollution and its control in the UK will be considered by reference to the position in England and Wales. Although somewhat different administrative arrangements exist for water pollution control in Scotland and Northern Ireland, the basic approach is the same as in England and Wales. HISTORICAL ASPECTS The British people have the distinction of being the first to have caused gross pollution of water. This occurred during the Industrial Revolution when mechanization permitted greatly increased manufacturing output and created a new intensive demand for labour, which led to the formation of the first industrial conurbations in the North, Midlands and South Wales.Discharges of sewage and trade effluent from these towns rendered the receiving rivers fishless and foul, and the water abstracted from them for public supply was contaminated with disease organisms. Following the massive cholera out- breaks in these towns in the early and middle nineteenth century, wholesome water supplies were sought and developed in the hill country and the disease outbreaks ended-but the river pollution continued. Yet for London no economic alternative to the River Thames as a source of water could be found, and the waterworks intakes were moved upstream of the Metropolis. This accident of geography explains why it has been essential to control effectively pollution of the River Thames (and the River Lee) over the last 100 years and why these rivers are still clean, even though the density of urban and industrial development on them is now nearly as great as anywhere else in the country. River pollution in the North continued and eventually became so bad that the first general pollution prevention legislation was enacted as the Rivers (Prevention of Pollution) Act 1876.This Act is the one on which the current law is modelled, and, in itself, it was a very sound measure. Its great fault was that it was to be applied by the Local Government Boards, who were also responsible for sewage discharges from towns. But in the catchment areas of the Rivers Thames and Lee, the conservancy boards operated their own private Acts of Parliament to control pollution.R.I.C. Reviews Over the next three-quarters of a century, government commissions and committees examined the problems of sewage purification and river pollution control, and apart from certain ineffective pollution control provisions made in the Salmon and Freshwater Fisheries Act 1923, no new general statutory provision was made until 1948, when the River Boards Act was passed. This Act set up 29 river boards, who were to be responsible for river flood control, pollution prevention and freshwater fisheries protection, over virtually all of England and Wales. New pollution prevention legislation was 106 10 5 0 10 30 II - - 0 7a 30 Mile Fig. I. The river authority areas of England and Wales.The Conservators of the River Thames are only responsible for underground water resources in the excluded area. given to the river boards in the Rivers (Prevention of Pollution) Act 1951, and stemming of the flood of river pollution began in earnest. In 1960 and 1961, supplementary legislation, in the form of the Clean Rivers (Estuaries and Tidal Waters) Act 1960 and the Rivers (Prevention of Pollution) Act 1961, was enacted. Finally in 1963, following water shortages in the severe drought of 1959, and the growing scarcity of and competition for new water supplies, Fish 107 the Water Resources Act was passed. This legislation provided for the 29 river boards to be transformed into 27 river authorities.These, and the two conservancy boards (hereafter referred to collectively as the river authorities) were given additional powers to include the quantitative aspects of conserva- tion of all water resources in their river management functions. The river authority areas are shown in Fig. I . At present, a committee of the Ministry of Housing and Local Govern- ment-the Central Advisory Water Committee-is in session considering what further changes will be necessary in water management to deal with future problems. THE PRESENT ADMINISTRATIVE POSITION The responsibility of central government for water pollution control rests with the Minister of Housing and Local Government. The Ministry supervises the work of the local sewerage authorities in sewerage, sewage purification and disposal, and controls their capital investment; but it has no power to take over any of their duties in default.It also supervises the pollution control work of the river authorities and has the power to take over their duties in default. The Water Resources Board, formed under the provisions of the Water Resources Act 1963 as a planning and advisory body to assist the Minister and river authorities on the quantitative aspects of water resources management, has no significant responsibilities for water pollution control. Figure 2 shows the responsibilities for water management in England and Wales. The Rivers (Prevention of Pollution) Acts 1951 and 1961, make two basic provisions. First it is an offence to cause or knowingly permit poisonous, noxious or polluting matter to enter a stream.Secondly, no discharge of sewage or trade efRuent to a watercourse (including a ditch which may dry out in summer) is legally made unless the consent of the appropriate river authority to that discharge has been obtained, or sought and not yet refused. In granting consent, which may not be unreasonably'withheld, a river authority lays down conditions as to the quantity and quality of the discharge. Provided a discharge conforms with the conditions of consent it is not to be considered as being poisonous, noxious or polluting, or as contravening Section 8 of the Salmon and Freshwater Fisheries Act 1923 which relates to the destruction of fish by pollution. The Clean Rivers (Estuaries and Tidal Waters) Act 1960 similarly provides that no new discharge of sewage or trade effluent to estuaries, and other defined arms of the sea, can be legally made without the consent of a river authority. The Water Resources Act 1963 makes two other provisions for water pollution control.First, no discharge of sewage or trade effluent or other polluting matter, made by means of a well, borehole or pipe into the ground, is legal unless the river authority has given its consent to such discharge. Again such consent may specify conditions as to the quantity and quality of the discharge. Secondly, a river authority may take emergency action to remove, or to mitigate the consequences of, pollution of a watercourse which has already occurred.These provisions are reasonably effective in the control of pollution arising R.I. C. Reviews 108 i .B Fish 109 from continuous discharges of used waters. But the decisions of river authori- ties as regards consents and conditions of consent may be questioned by any discharger of effluent by appeal to the Minister of Housing and Local Govern- ment, who will decide the matter and, if necessary, direct the river authority. In addition to dealing with domestic sewage produced in their areas, the local sewerage authorities are required, by the Public Health (Drainage of Trade Premises) Act 1937, to make provision for accepting trade effluents (including farm effluents) into public sewers for treatment and disposal at sewage purification works.These arrangements can be made by a consent procedure, or by agreement, and the sewage authority may levy charges on the industrialist or farmer concerned to cover the cost of conveyance, purifica- tion and disposal of the trade effluent. Sewerage authorities are not obliged to accept trade effluents if to do so would seriously interfere with the fabric of sewers or with sewage treatment processes or would overload sewers. The dischargers of trade effluent to sewers are expected to provide such pre-treat- ment plant as may be necessary to render the quality of the trade effluent with- in the conditions of consent or agreement laid down by the sewerage authority. Again, disputes may be settled by appeal to the Ministry of Housing and Local Government.The legal requirements of the river authorities may be enforced in Magistrates Courts or County Courts, and conviction will result in the offender receiving a maximum fine of 2200, or, in the case of repeated offences, a maximum period of imprisonment of six months. Conviction for un- authorized discharge of trade effluent to a sewer carries a maximum fine of 250. Nevertheless it is a practical fact that the control of water pollution arising from discharges of sewage and trade effluent must be essentially a co- operative exercise between river authorities, sewerage authorities, industria- lists and farmers. The subject is so technically complicated that widespread and rigid application of the law would be useless and self-defeating.The existence of the law is necessary to ensure that the required co-operation is forthcoming, and application of the law is generally reserved for those cases where lack of co-operation or negligence results, or is likely to result, in serious river pollution. THE PRESENT TECHNICAL POSITION The river authority role A river authority aims to maintain or restore the wholesomeness of inland waters-although there is no authoritative guidance on when inland waters are to be considered as ‘wholesome’. In general, a river authority, advised by its scientists and inspectorate staffs, seeks to prevent visual, smell or fly- swarm nuisance arising in rivers and streams, and to maintain satisfactory fish life in, or restore long-lost fish life to, rivers and streams. In so far as the maintenance or restoration of fish life in a river or stream does not produce water of adequate quality for public supply, an authority will also try to improve further the quality of discharges of effluent so that the water will be suitable for use as a source of public supply. In doing this, the following main effects1Y2 of pollution have to be controlled. 110 R .I.C. Reviews 1. The physical effects, such as deposits of solids in sludge banks, oil films, detergent foaming, gross turbidity or discoloration, and artificial rises in temperature derived from cooling water discharges. 2. The oxygen-demanding effects of biodegradable organic pollution. Sewage and. trade effluents, such as those from the food industries and farming, contain residual organic matter in suspension and solution which serves as food for the micro-organisms of decay.This biodegradation of organic matter is oxygen demanding and may take up all the oxygen dissolved in the stream water and redissolving from the air. If the stream water becomes devoid of dissolved oxygen, it will become putrid and offensive to sight and smell as a result of bioreduction of sulphate and devoid of fish and other oxygen-dependent fauna, and the rate of biodegradation of organic matter in the resulting anaerobic phase will be greatly reduced. The bio-oxidation of ammonia to nitrate is also oxygen consuming but is reversible to the bio- reduction of nitrate to nitrogen gas when the concentration of dissolved oxygen drops to less than 1 mg 1-l.At dissolved oxygen saturations of about 30 per cent ( 3 mg 1-1 dissolved oxygen at about 10 "C) most fish life will become asphyxiated within a short time. 3. The acutely toxic effects of cyanides, phenols, heavy metals, ammonia, pesticides etc. to fish and other aquatic fauna. These vary with water tempera- ture, dissolved oxygen saturation and the presence of mixtures of poisons. 4. The bioconcentration of non-degradable synthetic materials, such as organochlorine and other pesticides, through aquatic food-chains which debilitates fish and harms fish-eating animals. 5. The mineralizing effects of chloride and sulphate additions to the water, and the eutrophication characteristics of nitrate and phosphate derived from excreta and household synthetic detergents, and passed on to rivers and streams in sewage effluents.6. The taste and odour producing effects of very low concentrations of phenols, essential oils and certain mineral oils, in waters abstracted for treatment for public supply. 7. Residuals of potentially dangerous chemicals in waters abstracted for public supply, which may not be removed in conventional waterworks purification processes. 8. Rapid and large fluctuations of numbers of faecal bacteria, derived from sewer overflows in wet weather, in waters abstracted for public supply. Fish The required control is achieved by applying effluent quality conditions in the consent procedures. Where the clean water dilution in a stream receiving, or scheduled to receive, effluent is considerable, say not less than about 8 to 1, it is usual for a river authority to require the effluent to contain not more than 30 mg 1-1 suspended solids nor have a Biochemical Oxygen Demand in five days at 20 "C (BODS) exceeding 20 mg 1-1-the so-called Royal Commission standard. A similar standard would also be applied to an effluent afforded much less dilution than 8 to 1 if the receiving stream, by virtue of its turbu- lence of flow, had a high reaeration capacity.Where the dilution available and the reaeration characteristics of the receiving stream are unfavourable, it is usual for the river authority to require lower concentrations of suspended 111 solids and BOD in effluents-limits as low as 5 mg 1-1 for each characteristic have been applied.The objects of these prescriptions of quality are to prevent deposits of solids forming in watercourses below effluent outfalls, and to prevent marked loss of oxygen concentration in the stream water in consequence of the BOD of the effluent. Deposits of organic suspended solids on the bed of a stream cause local concentration of BOD which can exert a deoxygenating effect on the overlying water far in excess of the dissolved and colloidal BOD present in the stream flow. This benthal effect is largely brought about by the respiring and stirring-up effect of fauna specifically developing and proliferating in sludge deposits. In addition to these general prescriptions of quality, river authorities also limit the concentrations of specific toxic and other undesirable materials in effluents.Limitations on the concentration of ammonia in effluents, to control both the deoxygenating and toxic effects of this material on stream waters, are being increasingly applied. Sampling and laboratory examination of effluents and waters, and inspection of effluent purification plant to check the quality of effluents and the receiving waters, represents a large part of the work of the pollution control departments of river authorities. Because of increasing abstraction of stream flows for public supply, in- dustry and agriculture, and the resulting increasing discharge of these waters after use, the clean water dilution available in rivers and streams is steadily decreasing, requiring a compensating rise in the quality standards applied to effluents.On the freshwater lengths of the River Thames and its tributaries upstream of Teddington Weir, 250 million gallons per day (mgd) of sewage and trade effluent (excluding cooling waters) is discharged into a natural flow which can drop in dry weather to about 250 mgd. Of this total river flow of 500 mgd in a drought period, about 300 mgd are taken to supply two-thirds of London’s water supply. This very high level of river water utilization is maintained by requiring almost half of the total volume of effluent discharged to conform with standards of quality better or very much better than the 30 mg 1-1 suspended solids and 20 mg 1-1 BOD5 limits.In dealing with pollution control in the tidal waters of estuaries and other confined coastal waters, the river authority approach is similar to that applied to freshwaters, although the effects of tidal flow, in increasing the clean water dilution available to effluents or in increasing the time of retention of effluent- polluted water within the estuary, need to be taken into account. At the seaward end of estuaries the prescriptions of effluent quality can be con- siderably relaxed because of the immense reaeration capacity and dilution available in the nearby open sea. At the head of estuaries it may be necessary to prescribe standards as high as those specified for freshwaters. Control of the pollution of groundwaters by effluent discharges raises quite different considerations on effluent quality.The oxidative capacity of the surface soil is very considerable, and while this capacity diminishes with depth below the surface, the filtration and adsorptive capacity of the subsoil and lower strata is also very considerable. It is impossible to explain the technological approach of the river authority on this subject in a few words. The two basic factors involved are whether, having regard to the nature of R.I.C. Reviews 112 the subsoil and the depth of injection of an effluent, the effluent will physically reach any underground water of value or potential value as a water resource, and secondly, what will be the condition of the effluent at that point and its effect on the groundwater.Considerations of these factors do, of course, take account of the natural facts that waters after passing into the ground receive no further reaeration from the atmosphere, and that groundwaters, other than deep primordial ones, do in effect flow as rainfall percolates into aquifers and emanates in springs, in pumped abstractions, or as discharges from the sea-bed. Groundwaters generally are clean, but in a few localities these have been grossly and almost irreversibly fouled. Although effluent discharges are the main sources of water pollution, some or all of the main causes and effects of pollution can and often do arise from sources other than continuous discharges of effluents. Most of the surface water drainage from yards, streets and roads in urban areas is dis- posed of to rivers and streams.This can be quite polluting in terms of sus- pended solids and organic matter content, and may contain de-icing chemicals applied to roads in severe weather. Spillages of oils or chemicals often reach watercourses via surface water drains and sewers, and the frequency of such events increases as usage, storage and transport of these materials increases. Accidents or negligence at premises discharging trade eilluent to sewers from time to time results in gross contamination of sewage flows arriving at sewage works, where they not only cause discharge of the contaminating pollution in the sewage effluent, but also sometimes render the sewage purifi- cation wholly ineffective. It is important to note that ignorance or negligence on the part of employees, and not on the part of management, is the main cause of these accidental pollutions.Usually in these cases, the only practic- able course of action is to control the pollution after it has reached the river, and to take steps to prevent repetition of the mishap. Drainage from agricultural land, particularly that discharged through under-drains, contains nitrate and phosphate (and calcium sulphate from clay soils)-much of this is derived from artificial fertilizers. This adds to the general eutrophication of rivers and other surface waters caused by dis- charges of sewage effluents. Pollution arising from the agricultural use of pesticides, apart from that caused by accident or negligence, is not as serious as may be feared.While the use of persistent pesticides obviously needs very careful control, problems arising from agricultural use of other pesticides should not become more serious than any other pollution problem unless aerial spraying, particularly by fixed-wing aircraft, becomes widespread. Wastewater purijication and disposal Though the prime movers in pollution control are the river authorities, their efforts and directions would be useless without the massive effort which is exerted by sewerage authorities, industrialists and farmers to control wastes and to purify them to river authority prescriptions. The farmer generally seeks to dispose of wastes from animal husbandry back onto the land, either by simple spreading of liquid manure or by ‘organic-irrigation’ systems of slurry disposal.These methods are very effective but are not without their difficulties from the agricultural point of view. The trend towards more Fish 113 intensive factory farming, and correspondingly more complex effluent dis- posal problems, is being regarded with some concern by river authorities and agriculturists alike. Only a very small proportion of the farm effluents pro- duced are discharged to public sewers in the same way as industrial effluents, but perhaps in the future this position will change. The purification of sewage involves three basic processes. The primary process is the sedimentation of solids in settlement tanks.The settled liquors are then bio-oxidized in percolating filters or activated-sludge plants. The latter processes incorporate sedimentation in secondary tanks to remove most of the solids produced in bio-oxidation from flocculation of colloidal matter and from saprophytic generation of the cellular material of oxidizing bacteria and higher organisms. The tertiary processes include treatment in sand- filters or microstrainers or by land irrigation for final removal of solids. The use of the tertiary processes (which should not be confused with the ‘tertiary’ processes now being applied abroad for removal of phosphate and other materials from effluents) is not usually necessary unless the final effluent is required to conform with a standard of quality better than the 30 mg 1-1 suspended solids, 20 mg 1-1 BOD5 standard.In all three processes, solids separated from the sewage are run as wet sludges (96 to 99 per cent water) which are either passed straight to under-drained beds for atmospheric drying, or are digested anaerobically to reduce the bulk of solids by methane production. Digested sludges are either dewatered by pressure or vacuum filtration, dried on under-drained beds or redistributed on farmland in the wet state. Most of the sludge produced at sewage works is disposed of on farmland as a soil-conditioner and mild manure, some is dumped at sea, and an increasing proportion is incinerated. Organic industrial effluents from the food manufacturing industries, leather industries and certain textile industries can be purified by similar techniques, with or without chemical precipitation, before discharge to watercourses.Some 90 per cent of all the industrial effluents reaching freshwater streams, including nearly all the effluents from the engineering and chemical industries which are generally intractable to bio-treatment without dilution with sewage, are disposed of via public sewers to sewage purification works. Substances in these effluents which would inhibit sewage purification or render the sewage effluent toxic or otherwise of unacceptable quality are pretreated before dis- charge to sewer by a variety of means, including rather special applications of bio-oxidation, and chemical treatment and precipitation.Research and results The third force in the control of pollution is the Water Pollution Research Laboratory at Stevenage, currently under the direction of the Minister of Technology. Over the last 40 years, this Laboratory has made an indispens- able contribution to water pollution control both at home and abroad. Its Annual report^,^ Notes on Wuter Pollutioi~,~ and the research papers it has produced for publication in water pollution control Journals5p6 give a unique record of progress in water pollution control in its broadest aspects. The results have been scantily referred to in the spate of television, radio and newspaper reporting on water pollution over the last 12 months. Since R.I.C. Reviews 114 1951, when the first part of the current pollution control legislation became operative, a vast amount of new pollution has been prevented, and a great deal of pollution of long-standing has been eliminated.For example, virtually the whole freshwater length of the River Thames and its tributaries supports fish life, and the main river provides more angling and boating amenity than any other river in the country despite the load of effluent it receives (Fig. 3). In Essex in 1958, a survey showed that about 200 miles of river and stream were clean and about 100 miles were polluted. In 1965, a second survey showed a great reduction of pollution-only 17 miles of river remained polluted. The Ministry of Housing and Local Government can take credit for reaching, through its Standing Committee on Synthetic Detergents and the co- operation of detergent manufacturers, a classical solution of the detergent problem which in the 1950s threatened to submerge our riversides in foam.Similarly, through its application of the Radioactive Substances Act 1960, it can take credit for containing effectively the problem of radioactive effluents. At the request of the Ministry of Housing and Local Government, river authorities have recently completed a comprehensive survey of the quality of rivers and streams in their areas. This survey will undoubtedly show that by far the greater part of the total length of rivers and streams in England and Wales support fish life and are providing or can provide immense quantities of 115 Fig. 3.Leisure activities on the Thames below Shepperton Lock. Fish 9 water for general supply purposes. But there are still far too many miles of river in the North and the Midlands which are fishless and unusable as sources of water supply, except for heavy industrial cooling and quenching purposes, and still too many estuaries which are fishless. Yet none of these causes significant nuisance and improvements are being planned and will be made as quickly as our capacity and preparedness for investment in effluent purification plant permits. More important than cleaning-up the remaining dirty rivers is the necessity to keep our cleaner rivers clean. This means that we must control potential pollution more effectively, particularly that likely to arise directly from the development and use of new non-degradable chemicals, and indirectly from increasing eutrophication of waters.FUTURE REQUIREMENTS Although a very great deal can be said on the subject of how best to meet the sometimes daunting challenges of water pollution control in the future, particularly in the broad aspect of protection of our environment, a number of factors of fundamental importance can be identified. First and foremost we must keep our feet firmly on the ground, or at least our heads out of the clouds, on the subject. All our environmental problems spring from the fundamental fact that, apart from in the high energy zones of nuclear reactions, matter cannot be created or destroyed and consequently we are obliged to live with the waste matter we produce or its degradation products.The pollution of water is inevitably bound-up with other forms of environmental pollution, and unfortunately the amount of freshwater, the raw material essential for our life and industry, is subject to seasonal and longer-period maxima and minima. Undoubtedly we have the capacity to produce all the clean water we want in the future by further conservation of rainfall and run-off and desalination of sea water. But the production of ever increasing quantities of clean water implies the production of ever increasing quantities of effluent which must be properly purified and disposed of, if we are not to increase our depredations of the aquatic part of the environment and the very sources of water we wish to render clean.The natural processes of waste assimilation and recovery are all recyclings, and our water use and wastewater disposal must follow these cycles. In some areas, we are still overloading the river part of the hydrological cycle with too much degradable organic pollution, and we are approaching overload on most lowland reaches of rivers with mineral salinizing or eutrophicating pollution and non-degradable organic matter generated by modern chemical manufacture. This overloading of our river systems, now and in the future, can only be controlled by treatment of used waters to remove the unaccept- able pollutants from the 99 per cent or more of water contained in the total waste.The fundamental question arising is should we carry this process to the stage where the water is recovered in a very clean state so that it may be reused, after return to rivers and aquifers, for all purposes, leaving us with only the separated pollutants or their breakdown products to be dis- posed of if not reusable, thereby limiting drastically our new demands on natural water resources ? Or should we continue our present arrangements of making increasing new calls on natural water resources and of only R.Z.C. Reviews 116 partially oxidizing and/or separating the grosser contaminants from used water, leaving the remainder to change the quality of our rivers and coastal waters gradually until they all take on a uniform ‘greyness’-neither clean nor obviously dirty, but very unnatural? Whatever basic approach is adopted, the existing identifiable deficiencies of our water pollution control arrangements will need to be made good in the very near future.The amount of investment in wastewater purification, disposal and reuse should be greatly increased in accordance with regional and nationally-approved plans. The present amount of ME90, plus about a 10 per cent increase per annum, probably needs to be doubled in annual total and annual increment within the next decade. Existing legislation must be brought into a more realistic relationship with the rate of change of development and technology. The broad principles of the law need to be laid down, with innovations as to its scope, particularly to deal with better control of waste disposal into the ground; control of pollutive development and the manufacture of dangerous new chemicals; changes in agricultural practice; and the causes and remedy of unintentional or negligent pollution.The detailed provisions could then be applied and modified as necessary by the Ministerial Order procedure, which enables necessary changes to be rapidly brought into effect. The number of sewage disposal authorities needs to be drastically reduced from the present 1400 to ensure that each authority is financially and tech- nically capable of carrying out its duties effectively. Additionally, and for the same reasons, the number of river authorities should be approximately halved, and amalgamations of small water supply authorities into viable, forward looking and scientifically directed authorities should be accelerated. Research effort into all aspects of water pollution and its control needs to be greatly increased, and more effectively co-ordinated. Finally, but probably most important, the social implications of pollution, its consequences and control need to be explained to people of all ages, with emphasis on the everyday problems and individual responsibilities as well as on the sensational occurrences and possibilities. Above all, broad teaching on this subject in the schools should be commenced on an appropriate basis. Unless determined action is taken on these lines, the considerable progress in controlling water pollution made over the last 20 years could be lost within a decade. Although we were the first gross polluters, we now have the best record in the world in water pollution control. There is no good reason why we should not maintain this lead and example for the rest of the world to follow, and there is good reason to believe that we shall. BIBLIOGRAPHY 1 L. Klein, Aspects of river pollution. London: Butterworths, 1957. 2 B. A. Southgate, Water poZlution and conservation. Harrow : Thunderbird Enterprises, 1970. 3 Water pollution research. Annual Reports. London : HMSO. 4 Notes on water pollution, 1-44. Stevenage: Water Pollution Research Laboratory. 5 Journal of the Institute of Water Pollution Control. 6 Efluent and Water Treatment Journal. 117 Fish