Water and Environment Journal

The Mersey Estuary has suffered a legacy of abuse and neglect since the beginning of the Industrial Revolution. The discharge of effluents from manufacturing processes, together with wastewater from the burgeoning centres of population, resulted in the estuary gaining the unenviable reputation of being one of the most polluted rivers in Europe. As a result of the long-awaited remedial action which has been implemented over the last fifteen years, there is now unequivocal evidence that the water quality of the river and the biology of the system have improved significantly and will continue to do so as further planned alleviation schemes are completed. This paper reviews the achievements which have been made at the half-way stage in the 25-year multi-billion pound ‘clean-up’campaign.

There Were 34 outbreaks of water-borne disease recorded in the UK between 1937 and 1986, comprising over 11794 cases and at least six deaths. A total of 21 outbreaks were due to public water supplies, 11 of them contaminated at source; in eight of these 11 the water was unchlorinated or defectively chlorinated. None of the six reported deaths was due to contamination of public supplies at source. About 1000 cases of gastro-intestinal illness were caused by consumption ofafoods, particularly milk and canned nicats, that had been contaminated by polluted water during processing. Shellfish harvested from pollutcd cstuarics gave rise to increasing numbers of outbreaks of viral gastroenteritis and hepatitis A. The recreational use of water was associated with about 400 serious infections and probably many minor illnesses. Sonie hospital infections may have hecn derived from the potable water supply. A total of 14 outbreaks of legionnaires' disease and eight of humidifier fever were associated with water in buildings. The future control of water-borne and waterassociated disease demands not only continued vigilance in the water industry but closer collaboration between public health doctors and water engineers and scientists.

Tamar Lakes is comprised of two reservoirs, which are located in South West England and in the headwaters of River Tamar at approximately 135 m above ordnance datum. Upper Tamar Lake (UTL) is a direct feed source reservoir of potable water in North Cornwall. Immediately following completion in 1975, UTL was subject to intense blue-green algal blooms that continue to the present. These blooms create operational problems for water treatment, especially in hot-dry years. Lower Tamar Lake (LTL) was constructed as a water supply reservoir in 1819 and became obsolete following UTL coming on-line. Detailed water quality investigations over a period of some 28 years have confirmed the source of nutrient enrichment that fuels the algal blooms to be agriculturally derived, corresponding with a substantial increase in livestock farming. Associated poor land management practices, such as extensive field drainage and inappropriate slurry disposal to land, are linked with substantial elevations in organic contaminants such as ammonia, biochemical oxygen demand (BOD) and suspended solids (SS) during rainfall events. Evidence demonstrates that both reservoirs act as primary treatment lagoons, substantially reducing the worst of these pollutants and providing significant environmental gain. The implications of the Common Agricultural Policy (CAP), the Water Framework Directive (WFD) and regulatory monitoring are discussed in relation to resource management.

SYNOPSISAN OUTBREAK OF gastro-enteritis in several villages to the North East of Leeds, England, in July 1980 was rapidly traced to the water supply. One of the source boreholes was found to be contaminated by sewage from faulty sewers, via the Magnesian limestone. The combination of circumstances which allowed the contaminated water to enter the supply are described, as are the ways in which systems were improved to prevent any similar incident occurring

In January 1988 the city of Truro experienced a severe flood from the River Kenwyn. The return period of this event was initially estimated at 350 years using the methodology recommended in the Flood Studies Report1. In October of the same year a second flood, of even greater magnitude, occurred. The subsequent investigations employed a variety of flood frequency estimation techniques including one which uses descriptive information on the history of flooding, obtained from local newspapers and journals, in addition to recent flow records. The return periods of the two events were reassessed to be 50 and 100 years respectively. This flood frequency behaviour was found to be markedly different from the regional average for the South West of England.

Groundwater resources of Chalk aquifers may become depleted during drought periods; major causes of this depletion include reductions in the aquifer transmissivity and the interaction between aquifers and rivers. In the East Kent aquifer there are certain catchments where difficulties are encountered in maintaining yields but, in other catchments, drought periods have little effect on the available resources. A mathematical model is developed to help understand the flow processes within the aquifer system, and the model is used to predict the consequences of possible abstraction scenarios.

During the period 1988–92, the south and east of England were subjected to drought conditions. Data from 10 catchments and three groundwater level records were analysed using runoff and groundwater deficit indices to place the drought in its historical perspective. In parts of eastern England the drought was the most extreme – in terms of runoff deficit – for at least 150 years. It was less notable in other parts of southern England, but still extreme.

Between 4 and 7 February 1990, exceptionally high river flows on the River Tay resulted in widespread flooding of land and property. Roads and railway lines were rendered impassable, and villages and farms were isolated for a prolonged period. In the Tay Valley, 42 km of flood banks were overtopped and 34 km2 of land were inundated. This paper describes the extent and effects of the flooding and reviews the relevance of various factors in terms of their likely contribution to the magnitude of flooding. Flood-mitigation measures are discussed with particular attention being given to the implementation of a flood-warning system for the Tay Valley.

The paper reviews the current methods of sludge technology, and compares them with those discussed by Ashton in 1904. The paper also plots the development of some of the current technology over the last century, particularly those methods of treatment which were mentioned by Ashton but were not in existence at the time. The 1990s have been a most interesting era, and have probably seen more changes in sludge technology than any other decade this century. The most significant impact will be due to the cessation of the sea disposal route which, at the beginning of the 1990s, was used for about 30% of the total sludge production in England and Wales and approximately 76% of the total sludge produced in Scotland.

The paper presented in 1898 by F. W. Lockwood (a) provided a detailed description of the many and varied factors contributing to the health and welfare of the population of Belfast, and (b) took a forward look as to where improvements could be foreseen. This paper considers the issues which were raised almost a hundred years ago and assesses the changes and developments in the fields of politics, legislation, demography, topography, water, sewerage, environmental health, public health, waste management and housing. It is likely that Lockwood would be satisfied by the overall improvement to people's general health and their environment, although the utopia he wished for is still some way off.

The growing importance of odour control and the failure of a high proportion of abatement schemes are discussed. A strategy for dealing with nuisance is presented, laying emphasis on a fully integrated approach, involving covering, ventilation design, and odour treatment. Some of the options for treatment are compared.

The paper by Towler(1) described the design, construction and testing of a pumping installation which incorporated a triple-expansion Cornish steam engine with an integral three-ram positive-displacement pump. This paper contrasts and discusses the developments, with pumping machinery, which have taken place during the last 100 years.

This paper describes the principles underlying water quality examination in a large modern water company, and compares these present-day techniques with the approach which was used 100 years ago. Although the analytical technology and regulatory framework for water testing has changed out of all recognition in this period, the author argues that many of the fundamental concepts remain the same. This illustrates the foresight of our predecessors. Nevertheless, despite, or perhaps because of, our modern analytical skills, public confidence in the high quality of current water supplies is being ‘strained’ by our ability to detect more and more minute trace contaminants in water. The challenge to water quality managers of today is to demonstrate to their customers that present approaches to water examination provide a very high degree of reassurance about water safety, not the converse.

The proposed privatization of the ten regional water authorities together with the accompanying reorganization of water pollution control responsibilities between the new National Rivers Authority and Her Majesty's Pollution Inspectorate, as well as the ever tightening environmental standards for the aquatic environment emanating from Brussels and from general environmental pressures, means that dischargers of industrial effluents can expect major changes both in the cost of disposing of their effluents and in terms of the legislative controls which will restrict their content. The paper examines the various factors which will influence the management of trade effluents in the 1990s and endeavours to give some indication of what the future holds both in terms of disposal costs and environmental regulation from the point of view of the discharger.

The new sludge-dewatering and fluidized-bed incineration plant at Blackburn Meadows sewage-treatment works, Sheffield, was commissioned in March 1990, replacing the former aged and costly filter presshouse and multiple-hearth incineration plant. The plant was the second in a ‘new generation’of integrated-design sewage-sludge incinerators commissioned by Yorkshire Water to meet the Company's operational, economic and environmental needs for sludge treatment and disposal at the Blackburn Meadows works. This paper details the work undertaken on the project from historical development and contractual issues to plant commissioning, reviewing the first six months’operating experience.

The paper reviews developments which have been carried out during the last hundred years in the design and construction of outlet works for water supply and river regulating reservoirs in the UK. The review covers diversion tunnels, culverts, valve towers, upstream control equipment, in-line valves, pipeline materials and flow control valves. It concludes with a brief description on the rehabilitation of the outlet works at a number of nineteenth-century reservoirs.

The report describes visits made as part of a mission to Japan which included, under the IWEM/JSWA Technology Exchange Programme, a Technical Workshop on sewage sludge technology held in Tokyo on 11–18 November 1991.

This paper describes an assessment, which was carried out during 1994, of demands and resources for public water supplies in Scotland from 1991 to 2016. The assessment is the third in a series published by The Scottish Office – the two previous studies being carried out in 1973 and 1984. In the 1994 study, demands were assessed on a component basis from 1991 to 2016 in five-year steps for each of the nine mainland and three islands councils. These were aggregated to give the all-Scotland picture, and a sensitivity analysis was carried out to determine what effect any changes in underlying assumptions might have on the forecast demands; and a demand envelope was constructed.

As environmental regulator, the Environment Agency seeks the best balance between essential needs of water supply and the environment, whilst taking into account costs and benefits; nowhere is this balance more focused than in the management of droughts. The drought of 1995–96 was the most severe on record in the North West, and presented a major challenge to both the water company and the Environment Agency in safeguarding essential water supplies and minimizing the risks to the environment. This paper describes the management of the drought from the Agency's perspective.

Prior to Easter 1998, the 1947 floods were the reference events for flood-risk management in many catchments throughout England and Wales. However, Easter flood levels were generally higher than those of 1947 in the river systems draining an area of about 5000 km2, bounded by Bedford in the east, Evesham in the west, Peterborough in the north, and Oxford in the south.The paper describes the background to the floods and the independent review, and outlines the lessons which emerged from the Easter 1998 flood experiences, particularly in relation to flood-plain management, hydrometry and flood forecasting and warning.

In 2000, the UK introduced a Cryptosporidium oocyst monitoring programme for groundwater public supplies as a consequence of a 1999 amendment to statutory water quality regulations in England and Wales. The programme, which is ongoing and was estimated to have cost c. £12 million (€17.4 million) by the end of 2005, has accumulated the largest and most comprehensive array of data on the presence of oocysts in raw groundwater in the UK to date, with 90 water treatment works subjected to continuous monitoring at one time or another between 2000 and 2005. The programme was preceded by a scrutiny of the future of over 180 groundwater supplies identified as significantly at risk by the 19 water utilities concerned. The results of this process and of the monitoring programme up to 2005 are examined and critically reviewed.

Regulations Introduced in 1999 obliged water companies In England and Wales to conduct risk assessments of their treatment works to establish whether there was a significant risk from Cryptosporidium oocysts in the water supplied. More than 330 treatment works were identified as being at risk, just over half of which were plants treating groundwater. This paper provides an overview of what water companies themselves identified as the most at-risk settings for their groundwater-based works in terms of aquifer and type of supply. Evaluation of results from the subsequent continuous monitoring regulatory regime that came into force on many of these supplies could validate the primarily qualitative nature of the initial assessments of at-risk settings. There would also be public health benefits from confirmation of whether currently-employed risk assessment methods are well-founded because similar procedures could then be applied with confidence to the many small private supplies In Britain.

The remarkable progress made in the early 20th century in improving the microbiological quality of municipal drinking water supplies is undoubtedly one of the most important factors contributing to the improved health and life expectancy of the developed world during that century. The paper highlights perceived milestones in the 19th and early 20th centuries in the scientific and technological developments in municipal water treatment practice, particularly in relation to the improvements in the chemical and biological quality of drinking water supplies. The paper concludes by summarizing key developments in the methods of measuring water quality and in the improvements in drinking water quality standards during that period.

Thirty-four million people live in Sudan, and environmental pollution is a major concern throughout the country; therefore, an integrated approach should be adopted by industry, communities, local authorities and central government, to deal with pollution issues. Most polluters pay little or no attention to the control and proper management of polluting effluents: furthermore, the imposed fines are generally too low and do not deter potential offenders.The paper discusses the overall problem and identifies possible solutions.

The protracted and widespread flooding, which was experienced across much of the UK during the autumn and winter of 2000–01, was the most severe since 1947. Catchments remained saturated for lengthy periods and the high flow regimes of many rivers were significantly redefined. There is no modern parallel to the magnitude of groundwater replenishment over the 2000–01 winter recharge season, and groundwater flooding was exceptionally protracted in the English lowlands. This paper examines the synoptic background to an extremely wet episode and uses a hydrological framework to document the magnitude, duration and extent of a flood episode outside the previous experience of the greater part of the population of England and Wales.

Extreme floods often demonstrate unanticipated characteristics that pose problems for management and response. The floods on the Tyne and Eden in January 2005 provided numerous examples of such unexpected response. This paper describes characteristics of storm rainfall and runoff generation on the River Tyne catchment, flood effects and damage. Unusual aspects of hydrological behaviour are highlighted as a basis for assessing what lessons can be learned for flood risk management. These include problems associated with coincidence of extreme wind speeds and rainfall, the retarding influence of floodplain storage on flood wave travel time in extreme flows, the influence of critical storm duration on the severity of the resulting flood on headwaters and main river, and the variety of mechanisms of flood occurrence. The occurrence of such an extreme flood provides the opportunity to validate and enhance the review process of the Environment Agency's flood zone maps.

SYNOPSISThe Paper describes the dramatic changes which have occurred in the provision of public water supplies in Bahrain over the past 21 years since an earlier paper' outlined the original situation in 1965. It shows how the serious and irreversible ramifications of the continuously declining piezometry and increasing salinity of the natural, brackish, artesian groundwaters were tackled by the Government. A massive and imaginative programme was introduced to convert almost the whole island population from groundwater to mainly desalinated water by 1986. The relative success of this expensive programme and its novel use of reverse osmosis for desalinating the deeper saline water to relieve the piezometric pressure invasions of the upper fresh water aquifers is discussed. Finally, the outlook for the future stability and management of the island's total water resources is mentioned.

The method of how surface water from highway drainage systems is assessed has been refined and the changes have been implemented towards achieving compliance with the Water Framework Directive (WFD). This directive has identified the need to significantly improve the surface water quality in the United Kingdom and Europe. Our road network plays a significant part in achieving a legacy of better environmental standards, and developments in the assessment and control of the drainage discharge, demonstrate commitment towards this. This paper discusses some of these changes and presents how the M1 Widening project addressed the requirement of obtaining appropriate source data.

Over the course of history, development in and around London has encroached significantly into the River Thames floodplain. As a result, approximately 116 km2 of heavily urbanised land between Teddington Weir and Dartford Creek is at risk of tidal flooding. This area is currently protected from overtopping for levels in excess of the 1:1000-year flood event by an integrated system of static and moveable defences. However, the residual risk due to the probability of defence failure (through breaching) and the resulting consequences of such a failure remains high. To effectively manage this risk the Environment Agency needs to be able to prioritise investment in the defence system, predict probable flood extents as a result of a breach event, issue timely warnings and ensure that the response to an event is an appropriate one. Currently, this is not possible due to a distinct lack of information regarding the propagation of floodwaters through the complex urban topography in and around London. This paper details a 2D floodplain modelling project, currently underway within the Environment Agency, which was initiated to address these issues. The paper highlights the constraints and problems associated with urban flood modelling, suggests potential solutions and outlines how this type of modelling system could be used to inform future flood risk management tools.

This paper discusses the impact on the UK water industry of EC legislation which has been adopted and proposed for the control of dangerous substances discharged to the aquatic environment. The main impact arises from the increased monitoring needs, requiring more sophisticated analytical equipment and skilled staff, together with the increased administrative burden to produce reduction programmes and to set and control consents for dangerous substances. The paper also summarizes recent initiatives which have been taken by the UK towards a more precautionary approach to pollution control, by requiring that ‘red-list’ substances should be controlled by environmental quality standards and limit values whichever are the more stringent.

Quality assurance for the water industry and its suppliers is being seen to be of ever-increasing importance as a means of meeting the demands of customers and giving confidence to regulators. The creation of the Water Industry Certification Scheme demonstrates the industry's increased level of commitment to quality assurance. This paper considers the requirements and benefits of certification of quality systems with particular reference to the BS 5750/EN 29000/ISO 9000 series of standards. The requirements for certification in the water industry are discussed in terms of corporate policy, what is stated in the standard, and how the requirements of some elements of the standard might be interpreted by a certification body.

This paper seeks to address a growing lack of historical knowledge in the water industry of how European Union (EU) water policy has developed and been responded to. It also aims to overcome the lack of comparative studies that explore the role politics has played in the development and application of EU water policy. As a result, this paper develops a historical comparative understanding of how England and Wales and the Republic of Ireland have responded to the Drinking Water Directive (80/778/EEC). It does so from the perspectives of political priority and ideology. Political ideology is shown to have had a greater impact on facilitating the achievement of the Directive's standards in England and Wales. However, it is established that the political priority national governments have accorded compliance has been central to ensuring the application and enforcement of the Directive's standards. Despite the apparent success of political ideology in England and Wales, the paper sounds a note of caution with regard to judging privatisation as being uniformly successful, for it has not, particularly if issues of water charges, customer debt and financial and reporting irregularities are considered.

The background to and technical deficiencies of the EC Drinking Water Directive are discussed. Although the inadequacies of the Directive are becoming increasingly recognized, there is no doubt that it has had a major impact on the UK water industry, much of which will be beneficial in the long term. However, it has provided a significant challenge to water suppliers on technical and environmental issues, as well as in new areas such as publicity and customer awareness. The water industry should be seen to be responding to the situation vigorously and positively to meet the spirit of the Directive, whilst seeking technical refinements which will make it a more practicable piece of legislation for the future.

ABSTRACTA new synthetic inflow record for Talla Reservoir is derived from reservoir log data for the period 1907–94. The paper describes (i) the procedures which were adopted for the derivation, based upon a reservoir water balance, and (ii) the changes in contributing area. For the years since construction of an upstream reservoir in 1968, the summer analysis draws on data from a neighbouring catchment in order to provide analysis of a more homogeneous time series. The paper also discusses the possibility of undertaking similar work for other reservoirs, as a means of improving the knowledge of the past variability of UK water resources.

Deep mining activity has totally ceased in the Durham coalfield, and withdrawal of the regional dewatering scheme is being contemplated. Consequent groundwater rebound is expected to have severe and expensive environmental consequences, which could only be entirely avoided through indefinite pumping. However, continued pumping is expensive, at about $1 million/annum. The options of either abandoning or continuing pumping have differing time streams of future costs and, consequently, direct comparison of the expenditures involved is difficult. Both options are therefore analysed using economic evaluation criteria in order to determine the lowest cost alternative for the future. The overall outcome of the economic analysis, using both net present value and equivalent annual cost criteria, demonstrates that the option of continued pumping is less expensive than the option of abandoning pumping in all cases.

The paper describes the approach and methods used during a three-year programme to improve river-water quality in an area seriously affected by agricultural pollution.Low base-flow river systems serving clay catchments exhibit flash characteristics which required long-term permanent solutions to ensure improved river water quality under all weather conditions. The approach which was used needed to identify polluters and convince them (a) that effective remedies had to be found and implemented within a reasonable time scale, and (b) that there would be serious consequences of failure to undertake improvements. The initial contact with dischargers, the attitudes adopted and responses received are considered and discussed. Progress throughout each phase of the programme, the solutions used and the degree of improvement achieved are assessed. Legislative changes during the period of the programme, other factors influencing agricultural pollution of watercourses, and likely future implications of these, are discussed.The success of the programme resulted in the elimination of all major sources of agricultural pollution.

The paper describes the design and operation of a submerged biotower, i.e. flooded upflow reactor which utilises a random-packed polypropylene medium for supporting the biomass. The process can be used for carbonaceous removal or nitrification. In the application which is described, the process has been used for tertiary nitrification of a poultry abattoir wastewater as an extension to the existing effluent-treatment plant. Details of process commissioning at low temperatures are given and results from twelve months’operation are discussed. Operating costs are compared with other processes.

The explosion at the Abbeystead valve house in May 1984, with its attendant loss of life and injury, forcibly drew the attention of the public to the dangers of methane and other natural gases. It also reaffirmed to the water industry and engineering professions the pervasive nature of the gas and the need to take appropriate measures in the construction, design and operation of any scheme which involves a possible methane presence. The investigations into the source and mechanism of the methane gas ingress, and the design of the permanent repairs and modifications to the scheme, have illustrated many of the risks and problems associated with methane and the measures for dealing with them. The paper describes the essential repairs and modifications which had to be carried out, the main lessons learned, and the recommendations which are felt to be applicable to new and existing water schemes where methane may be present.

Elevated nitrate concentrations have been documented since the 1970s within the trans-national Abbotsford–Sumas aquifer, situated in the central Fraser Valley of southern British Columbia, Canada, and northern Washington State, United States. Nitrate concentrations in excess of 10 mg/L NO3–N are commonly observed in the monitoring wells. A groundwater model is used in this study to conduct a particle tracking analysis to estimate groundwater travel times and compare these with groundwater ages determined from 3H/3He concentrations measured in several monitoring wells. Groundwater ages estimated from particle tracking show excellent agreement with measured ages (slope=1), although there is scatter (R2=0.76), reflecting the complexity of the travel pathways and ambiguities in groundwater ages because of mixing. An assessment of the efficacy of recommended nutrient management practices, which were implemented in 1992 to reduce nitrogen loading, suggests that wells shallower than about 20 m should be monitoring a decrease in nitrate concentration. However, persistent elevated nitrate concentrations even at shallow depths point to the lingering effects of a remnant manure–nitrate signature in combination with continued high loading.

The city of Aberdeen has a population of 265,000 people, which was previously served by a preliminary sewage treatment facility, Including screening and grit removal prior to discharge to the North Sea. The Nigg Waste Water Treatment Works (WwTW) was designed and built to treat the sewage from Aberdeen as part of a Private Finance Initiative (PFI) in order to achieve Urban Waste Water Treatment Directive (UWWTD) standards for BOD (25mg/l 95%ile) and COD (125mg/195%ile). A small footprint plant was required and involved lamella tube settlers for primary treatment followed by a Biological Aerated Flooded Filter (BAFF) plant for secondary treatment. The plant received loads above the design and chemical closing was applied to increase the capacity for treatment. Constant monitoring through the plant was put in place in order to optimise the performance. This paper gives details of the performance of the plant over the first year of operation.

The UK waste management industry remains committed to landfill as the principal means of disposal for a large proportion of controlled wastes. Whilst the development of landfills above ground has been practised for many years in certain countries overseas, the concept has only become more widely accepted in the UK during the 1980s. It is vital that such sites are well planned, designed, operated, and restored. In particular, such sites need to be well engineered, and the following key issues have to be addressed: (i) Site identification and assessment; (ii) Peripheral bunding; (iii) Filling and compaction; (iv) Drainage; (v) Water management; (vi) Landfill gas management; and (vii) Monitoring programmes. The practice of above-ground landfilling is gaining greater acceptance in the UK. In certain respects such sites can have advantages over conventional infilling of voids.

The ability to remove nitrogen and phosphorus by biological means in the activated-sludge process represents the most significant refinement of the process since its discovery. This paper reviews the development of the activated-sludge process in Johannesburg. Emphasis is placed on the last twenty years’research into biological nutrient removal and the successful incorporation of research findings into the design and operation of full-scale plants of up to 200 Ml/d capacity.

The separation of activated sludge in secondary settling tanks is the crucial step in biological wastewater treatment from the point of view of both final effluent quality and operation of the aeration plant. The sludge-separation problems of bulking and foaming are connected with an excessive growth of filamentous micro-organisms in the biocenosis of activated sludge. This paper (a) describes the methods which are used for the quantification of activated-sludge separation problems, and (b) summarizes the design recommendations for bulking and foaming control.

During the last thirty years, attempts have been made to increase the rate of treatment of wastewater in compact activated-sludge systems whilst ensuring (a) an adequate supply of dissolved oxygen, (b) good settleability of activated sludge, and (c) consistently high-quality effluents. This paper describes two successful systems, i.e. oxygenated activated sludge and the deep-shaft process, which are used to intensify the rate of treatment in relatively compact aeration tanks. Data are presented of full-scale oxygen activated-sludge systems, including Vitox and Unox, together with information on the operation and performance of the deep-shaft process.

The paper attempts to review current and future practices in the UK against a European background. Sludge disposal has become a subject which is developing rapidly again and, since the presentation of this paper, there have been a number of developments, e.g. the adoption by the EC of its hazardous waste Directive in December 1991. Untreated sludge or sludge which is unsuitable for use in agriculture will be classified as a hazardous waste, subject to certain criteria. This makes the work on sludge classification even more crucial.

The earliest references to the loss of nitrogen and phosphorus in activated-sludge systems indicated an awareness, but no particular interest, in the use of biological processes for the removal of nutrients. The development of extended-aeration processes in general, and of channel systems in particular, intensified the interest in denitrification as a means of reducing nitrogen in an effluent. Observations of simultaneous nitrification and denitrification led to the proposal of separate anoxic zones for optimal nitrogen removal. The discovery that biological nitrogen and phosphorus removal could be synergistic, led to an explosion of processes, differing in all but the basic underlying biochemistry, for the removal of both nitrogen and phosphorus. The development of computer models, to accurately describe the complex and inter-related reactions, makes it possible to fully exploit biological systems to achieve cost-effective nutrient removal.

This paper examines and discusses (a) the innovations of the activated-sludge process which have been developed in recent years - particularly biological nutrient-removal processes, (b) modifications to minimize the construction costs of activated-sludge systems while simultaneously incorporating biological nutrient-removal techniques, (c) innovative computer-interfaced control methodologies, and (d) proposed methods of improving the biochemical versatility of activated sludge. The paper also presents potential methods of utilizing activated-sludge processes to produce valuable by-products from wastewaters.

During the last three decades, the World Health Organization has been actively involved in assisting countries and health authorities to improve their healthcare waste management. Wide disparities exist internationally on the standards of treatment and disposal of healthcare wastes which are achievable and sustainable in individual countries and localities. Three levels of practice can be identified: (i) a ‘foundation’ level in which some improvement in hospital hygiene and public health is achieved by removing wastes from wards to simple burning grounds and landfills, (ii) an ‘intermediate’ level whereby more organized collection and treatment is possible, and (iii) a more ‘sophisticated’ level involving treatment, enforcement of strict emission standards and landfilling regulations. This paper summarizes the range of practices in use and the options for (a) thermal treatment, (b) alternative technologies, and (c) engineered landfill. Details are also given on some of the activities undertaken by the World Health Organization in the areas of advice and guidance, direct assistance and research.

The water framework Directive is proposed as a mechanism for applying river-basin management across the European Union. Proposals for River-Basin Management Plans might have an impact on the present system of Local Environment Agency Plans and on schemes which are used in the British Isles to provide river management on a catchment basis. For this study, representatives from the Environment Agency, Scottish Environmental Protection Agency and European Parliament advisors were interviewed. In addition, Local Environment Agency Plans were assessed for compatibility with the requirements of River-Basin Management Plans.