bluuebunny/crossref_metadata_2025 huggingface dataset:
Automatic Monitoring of Activated Sludge Settling Characteristics and Plant Control Applications
Authors: C. REID J. M. , NASON R. B.
Published: July 2007

A fully automatic instrument has been developed to allow the on‐line measurement of activated sludge settling characteristics. The monitor uses the derived data to calculate final sedimentation tank solids loadings and the required rates of returned activated sludge pumping. The instrument has been developed by Thames Water Utilities Limited and is now manufactured under licence by Phox Systems Ltd. It samples mixed liquor and returned sludge alternately and measures solids concentration, the initial settling rate (or rate of hindered settlement) and the stirred specific volume index. The stirred specific volume index at a standard solids concentration of 3.5 g/l is derived from the data. Actual and maximum final sedimentation tank loadings (kg/m2h) are calculated, and the required returned sludge pumping rate is predicted and may be controlled by the monitor. Tests have been carried out on a number of sewage‐treatment works during several years of development, and some of the results are presented and discussed.
Charging for Discharges and Integrated Pollution Control in Scotland
Authors: LEATHERLAND T. M.
Published: July 2007

The year 1992 saw the successful implementation in Scotland of charging schemes which recover the cost of regulating authorized discharges into water and into the atmosphere. The new schemes recover from dischargers those costs of the regulatory authorities arising directly from the regulation of consented and authorized discharges. These costs were previously part of the country's overall public expenditure. The schemes operated by the river purification authorities are particularly fair because costs and charges are balanced for every individual discharger, rather than across the regulatory function as a whole. Charges therefore vary substantially both within and between river purification board areas, but a comparison of actual charges raised by the Forth River Purification Board with estimated National Rivers Authority charges indicates that the Scottish charges are generally lower. The absence of an incentive charging element contrasts with a recent recommendation of the Royal Commission on Environmental Pollution.
Controlling the Artesian Boreholes of the South Lincolnshire Limestone
Authors: BARTON B. M. J. , PERKINS M. A.
Published: July 2007

This paper describes (i) a long‐established, serious and growing problem in a part of the Anglian Region of the National Rivers Authority due to uncontrolled leakage of groundwater from old artesian boreholes (‘wild bores’) in the South Lincolnshire Limestone aquifer, and (ii) a remedial project recently undertaken by the Authority. The paper discusses (a) the nature of the problem and its implications for water resources, (b) the means employed to carry out the work, (c) environmental considerations, and (d) the results of the project.
Accounting for Losses: The Bursts and Background Concept
Authors: LAMBERT A.
Published: July 2007

Losses of treated water occur through leakage and overflows from the pressurized pipes and fittings in water undertakers’distribution systems and customers’private supply pipes. The UK National Leakage Control Initiative was formed in 1991 to update previous published work on leakage control policy and practice in the UK.

Although some published technical relationships exist, there has been no overall methodology which attempts to provide a component‐based estimate of annual losses in different parts of the distribution system for any particular combination of local circumstances, i.e. pressure, burst frequency, burst flow rate, number of properties, length of mains, method of leakage control, standards of service, and waste notice service/enforcement policy.

The ‘bursts and background estimate’spreadsheet‐based methodology is designed to provide such estimates. It links ‘night‐flow’and ‘annual losses’concepts, and can be used for a variety of purposes. These include (a) assessment of the likely incidence of losses for different leakage control and waste notice policies, (b) identification (from night flows) of districts in which there are unreported bursts, and (c) assessment of economic target levels for leakage control. The substantial element of annual losses from service pipes, and the considerable influence of pressure on annual losses, are also discussed.
Statutory Water Quality Objectives on the River Cam
Authors: TESTER D. J.
Published: July 2007

The Government has announced its wishes to gradually introduce statutory water quality objectives in pilot catchments, commencing in late 1993. The River Cam is one of the catchments under consideration.

The paper describes the main physical features of the River Cam and its uses, which include salmonid and cyprinid fisheries, agricultural and industrial abstraction, and recreational pursuits.

Significant sewage and industrial discharges in the catchment, and their impact on water quality, are discussed, and current river quality is compared with established river quality objectives, EC requirements and proposed statutory water quality objectives. Procedures for setting the latter objectives are considered, together with monitoring and compliance assessment. Future effluent discharge standards are proposed, and options to achieve long‐term water quality targets are suggested as part of a catchment management action plan.
Wastewater Rapid‐Gravity Filtration in Severn Trent Water
Authors: LANDER J.
Published: July 2007

In Severn Trent Water, rapid‐gravity filtration is used as a tertiary treatment process on a number of large sewage‐treatment works, and is likely to find further use in meeting more stringent discharge quality limits in the future. Design maximum hydraulic loadings and average suspended‐solids loadings are identified, and average hydraulic and solids loadings for 1989–91 are presented. Established filters are hydraulically underloaded, but on average suspended‐solids loadings they are mostly overloaded due to relatively poor quality influents. High mean solids and BOD removals are achieved. Reduced medium relative density has been found to vary with the degree of fouling and causes over‐expansion of the bed and medium loss. A correlation has been demonstrated between relative density and percentage dry matter, which could be used to assess the degree of medium fouling.
The Treatment of Weathered Crude Oil in Kuwait
Authors: SHABAN H. I.
Published: July 2007

During the Gulf War about 740 oil wells were blown up by the Iraqi forces, and the unburnt oil flooded from these wells to form oil lakes. This resulted in one of the largest oil slicks in the world, causing serious damage to the marine life in the Gulf region. The oil which is exposed to atmospheric weather over a period is called ‘weathered crude oil feed stock’, and it is important to treat this oil not only from the economical point of view but also to consider the environmental pollution which is created. The Government of Kuwait, represented by Kuwait Oil Company (KOC) has made its best attempts to treat this oil, and most of the oil lakes have now been cleared. The objective of this study is to report and evaluate different treatment methods and measures to control and manage these oil lakes.
Managing Agricultural Pollution Using a Linked Geographical Information System and Non‐Point Source Pollution Model
Authors: MORSE G. , EATHERALL A. , JENKINS A.
Published: July 2007

This study documents the development of a link between a geographical information system (GIS) and a non‐point source pollution model. The GIS ARC/INFO was linked to the agricultural non‐point source pollution model and ORACLE data sources. Application of the system is demonstrated using the Bedford‐Ouse catchment as a suitable case study. Water quality impacts are predicted from source data describing topography, soils, land use and river network. The model results were in agreement with observed nitrate concentrations at the catchment outlet, and more appropriate data sources are considered to be the main priority for improving model predictive ability. Management scenarios were established to assess the impact of changing agricultural management practices on predicted water quality. The approach has significant potential for the management of agricultural pollution in the UK.
Seasonal Variations in the Quality of Spring Waters Used as Private Supplies
Authors: PETRIE A. S. , HORAN N. J. , CLAPHAM D. B. , CRAM A. G.
Published: July 2007

The quality of water issuing from four springs which act as private water supplies was monitored regularly over a twelve‐month period. Bacteriological analyses for faecal coliforms and chemical analyses for iron, manganese, aluminium and lead were carried out and related to meteorological conditions. Bacteriological quality, which was influenced by the amount and duration of rainfall, deteriorated rapidly after heavy rain and improved markedly during dry periods. Chemical quality was a function of both the rainfall and atmospheric pollution emanating from the nearby urban conurbation. The results are discussed with relation to the statutory requirements for local authorities to monitor small private water supplies.
The Effect of Chlorinated Water on the Pesticides Prometryn and Terbutryn
Authors: FAIRHEAD A. P.
Published: July 2007

The pesticides prometryn and terbutryn are shown to be broken down by the chlorination process. The reaction is rapid and pH‐dependent. By analogy, a number of similar compounds are expected to be affected in the same way. The importance of considering the breakdown products of pesticides is discussed.
An Assessment of the Impact of Inland Surface Water Input to the Bacteriological Quality of Coastal Waters
Authors: WYER M. D. , JACKSON G. , KAY D. , YEO J. , DAWSON H.
Published: July 2007

The introduction of ultraviolet disinfection in Jersey has achieved significant improvements in water quality. However, bathing waters in St Aubin's Bay and shellfish flesh have failed to comply with microbial standards. Streams and seepages from coastal structures were investigated as potential indicator organism sources (total and faecal coliforms, faecal streptococci). Seepages were an unimportant bacterial source as concentrations were low. Geometric mean concentrations in streams were up to four orders of magnitude higher than in final sewage‐treatment works effluent, and concentrations increased significantly at high stream discharge. Rainfall‐induced pulses of poor water quality occurred two to three times per week during the 1993 summer season. Natural discharges from island catchments thus contribute significantly to the bacterial load received at the coast, especially during high flow events. These observations have implications for other UK and European schemes using tertiary disinfection technology to attain water quality targets in coastal waters.
Low‐Cost Remote‐Sensing Techniques Applied to Drainage Area Studies
Authors: SCOTT A.
Published: July 2007

The paper describes a project in which colour and infra‐red video images were used as the basis for assessing the percentage impermeability of subcatchments for a WALLRUS model. The imagery was obtained from helicopter‐mounted video cameras. Computer processes were developed to convert raw data, which were in analogue format, into a format which could be manipulated and displayed by the computer. The computer was able to assess the total permeable and impermeable areas in each subcatchment. These data were used in the WALLRUS model and compared with the results obtained using manually derived data and results from the flow verification survey.
Aqueduct Management Planning: Thirlmere, Haweswater and Vyrnwy Aqueducts
Authors: CRITCHLEY R. F. , AIKMAN D. I.
Published: July 2007

Between 1988 and 1992, an asset study of North West Water Limited's three largest aqueducts was carried out to assess their condition and rehabilitation needs. About 360 km of the aqueduct system, including approximately 1700 structures, 160 km of tunnel and conduit, 700 km of pipeline and 4000 valves, were covered by the study. A wide range of survey techniques was used, some being specially developed as part of the study, and a unified system of condition assessment and prioritization of rehabilitation needs was devised.

The paper (a) describes the overall approach and survey techniques, (b) discusses the methods of assessment used, (c) summarizes the conditions of the assets whose ages vary from 20–100 years, and (d) reviews some of the rehabilitation works proposed and executed.
Foam Formation, Anaerobiosis and Microthrix Parvicella
Authors: CHACIN E. , KOCIANOVA E. , FORSTER C. F.
Published: July 2007

Microscopic examinations of the sludges associated with two incidents of foam formation in anaerobic digesters are described. In both cases, the dominant filamentous species was Microthrix parvicella. Preliminary growth studies with this species indicated that it could grow in both aerobic and anaerobic environments, but that in an anaerobic regime it did not produce polyphosphate granules. This suggests that M. parvicella may be involved in the luxury uptake of phosphate and, under strict anaerobic conditions, could compete with acetoclastic methanogens for acetate.
Sea‐Water Infiltration: The Dramatic Corrosion of Ductile‐Iron Rising Mains
Authors: LONG M. J.
Published: July 2007

Repeated failures of a ductile‐iron sewage rising main, after only three years’ use, led to an investigation into the cause of the problem. Of particular concern was the fact that a pipe failed at an operating pressure of less than a quarter of its nominal 40‐bar rating after such a short period. Serious internal corrosion, concentrated along the soffit of the rising main, resulted in tensile failure under pressure.

An analysis of the sewage revealed high concentrations of chloride and sulphate, resulting from major infiltration of sea water into the sewerage system.

The combination of the high concentrations of inorganic sulphates, and the presence of sulphate‐reducing bacteria normally found in domestic sewage, is believed to have resulted in the production of a large concentration of hydrogen sulphide which was then oxidized to sulphuric acid by air entrained at the pumping station.
The Development of a Waste Management Policy in Northern Ireland
Authors: WILCOCK D. N.
Published: July 2007

With one or two isolated exceptions, waste management in Northern Ireland is not practised as a sequential process of waste avoidance, recycling and disposal by the best practical option. In order to update waste management practice in the province, the Government proposes to implement most of the waste management provisions contained in the Environmental Policy Act, 1990. Waste regulation will be made the responsibility of central government, while waste disposal and recycling will be the responsibility of central government, while waste disposal and recycling will be the responsibility of local authorities. The policy will have to be implemented within a set of distinctive social, political, geographical and economic factors which raise a number of questions as to the best way forward.
Setting Effluent Consent Standards
Authors: ROSS S. L.
Published: July 2007

The paper outlines how consent standards are normally calculated in Scotland for both river systems and tidal waters. A background is given to the reason why a more statistical approach has been adopted in England and Wales where the use of combining distribution methods is more widespread. Comparison of the two approaches is made, particularly with regard to their potential impact on resources required for treatment plants, and also the problems of taking enforcement action. The setting of standards under the EC urban waste water treatment Directive is considered where, in addition to the implications of primary, secondary and more stringent treatment, consideration is given to storm‐sewage overflows and industrial discharges.
The East Kent Chalk Aquifer during the 1988‐92 Drought
Authors: CROSS G. A. , RUSHTON K. R. , TOMLINSON L. M.
Published: July 2007

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.
Boat Wash at Channel Banks
Authors: GADD G. E.
Published: July 2007

The general characteristics of boat wash, as affected by boat speed and water depth, are discussed. The classical deep‐water wave pattern, with the most prominent waves at the forward edges of a V‐shaped region of semi‐angle 19 1/2°, becomes modified at high speeds. The effective angle of the V is then reduced and the waves become very long‐crested.

In moderately shallow water, the level of the water surface close to the boat (on either side of it) can be depressed by an amount which is greater than the amplitude of the downstream waves. In still shallower water, for boat speeds which would cause appreciable waves in deep water, the boat squats markedly and makes very large waves.

Possible implications of these facts for bank erosion are discussed.
Computer Models for Quantifying the Hydro‐Ecology of British Rivers
Authors: JOHNSON I. W , LAW F. M
Published: July 2007

In recent years, the use of models and scoring surveys for assessing the environmental impacts associated with river‐engineering works has increased. This paper discusses the circumstances in which modelling may be needed, and gives details of some of the models currently in use and under development. River corridor surveys, HABSCORE, RIVPACS (River Invertebrate Prediction and Classification System), SERCON (System for Evaluating Rivers for Conservation) and QUASAR (Quality Simulation Along Rivers) are described, and more detailed information is given on the IFIM (Instream Flow Incremental Methodology using PHABSIM), the physical habitat simulation approach being tested for the National Rivers Authority and the Ministry of Agriculture, Fisheries and Food.
Basingstoke Canal Hydrological Study: A Water Balance
Authors: PINKETT A. J
Published: July 2007

The paper describes a hydrological study to investigate causes and potential solutions to a significant shortfall of water in the Basingstoke Canal. Canal inflows and losses were investigated under drought and average summer conditions, and spring yields, streams, piped drainage and pumped inflows were assessed. Losses included evaporation, seepage, weirs and lock usage. A computer model of the complete water balance in the canal was created for the 29 pounds† for different levels of canal usage under three meteorological scenarios. This showed the balance of water stored, and in shortfall or excess, for each month over a year of operation for each pound.

Field investigations, which were carried out to verify the model and to refine preliminary estimates, included flow measurement, site investigation, groundwater level monitoring and water‐quality testing. Recommendations were made on potential solutions to the problem of water shortage to achieve different levels of canal usage.
Pumping Machinery in the Mid‐1990s
Authors: GIBSON D. C.
Published: July 2007

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.
Design of the Thames Water Ring Main
Authors: Farrow J. P , Claye P. M
Published: July 2007

The Thames Water ring main is a 2.5 m dia. tunnel approximately 50 m below ground and 80 km long, which conveys potable water from major treatment works, located west of London, into central London. The scheme was constructed during the late 1980s and early 1990s.

In 1985, to meet increasing water demand, a gravityfed system of deep tunnels was devised by Thames Water Utilities Ltd; this involved a full ground investigation and underground obstruction survey to establish the optimum tunnel route, bearing in mind the many and various constraints.

A series of shafts was sunk to connect directly into the ring main with the purpose of either introducing water at major water‐treatment works or acting as pumpout shafts at strategic locations around the capital.

The tunnels and shafts were designed to be built in two phases. Phase 1 was constructed using conventional wedgeblock techniques, but problems were encountered which resulted in increased costs and delay.

Phase 2 therefore necessitated a different approach. The company adopted a completely new strategy by changing the form of contract, purchasing its own tunnel boring machines, and redesigning the tunnel linings.

One of the keys to the success of the ring main was the new expanded wedgeblock concrete lining. Design calculations were prepared and finite element analysis work was carried out. The new rings were subjected to build and load tests, both on individual segments and complete rings, using specially designed test rigs.
Commissioning and Operation of the Thames Water Ring Main
Authors: Edwards A.G. , Colbourne J. , Renton P. , Batchelor J.M.
Published: July 2007

In order to achieve the earliest possible benefits of the investment in the Thames Water ring main, in late 1989 it was recognized that it was necessary to establish a commissioning team. The remit for the team was to progressively commission the ring main to match the construction programme, without risking the integrity of the daily water supply.

This paper describes the methods, accountability, and achievement of the commissioning project.
The Lower Colne Improvement Scheme: Environmental Costs and Benefits
Authors: Driver A. , Pepper A. T.
Published: July 2007

ABSTRACT The Lower Colne improvement scheme, on a river system to the west of London, was the first in the Thames region to give equal importance to environmental and engineering aspects in a feasibility study which was carried out in the early 1980s. This resulted in a scheme proposal comprising sixty elements of discrete work, rather than a continuous new channel or embankments, which reduced the impact on the environment. Many of these separate elements comprise environmental mitigation and enhancement features. This paper focuses on (a) examples of different types of scheme, (b) the environmental advantages and disadvantages, and (c) the costs of incorporating such features into flood‐defence works.
Household Hazardous Wastes: Current Issues in the UK
Authors: Heaven S. , Kerrell E.
Published: July 2007

As collection programmes are now being established to manage household hazardous waste in the UK, it has become increasingly apparent that there is an urgent need for clear and consistent definitions. Also, from an assessment of definitions in current use in North America and Europe, it is evident that definitions are likely to be needed at a number of levels. This paper reviews current practice and offers some guidance on the development of definitions in the UK.
Policy and Legislation Relevant to the Conservation of Freshwater SSSIs Subject to Eutrophication
Authors: Wilson H. , Payne S. , O'Sullivan P. , Gibson M.
Published: July 2007

Although no legislation in England and Wales directly addresses the causes and effects of eutrophication of surface freshwaters, a wide range of laws may be applied to the reduction of nutrient inputs. Nature conservation laws are applicable, in that rivers, lakes, reservoirs and canals designated as ‘sites of special scientific interest’(SSSIs) are theoretically safeguarded from degradation. However, the SSSI system is not designed to protect water quality at the catchment level. Since intensive agricultural practices are responsible for significant nutrient losses, legislation aimed at extensification is also relevant. Increasingly, laws related to extensification of agriculture include environmental imperatives ‐ a trend which will inevitably extend to nutrient conservation. Basically, enrichment is a water‐quality issue, but policy and legislation in this area are not yet sufficiently developed to address the problem comprehensively. Existing regulatory systems for water quality carry the potential to work comparatively well for point sources, but appear ineffective in dealing with diffuse losses.
An Optimization Model for the Selection of Wastewater and Sludge Treatment Alternatives
Authors: Tang S. L. , Wong C. L. , Ellis K. V.
Published: July 2007

A systems analysis technique, called the ‘analytic hierarchy process’, has been employed to develop a wastewater treatment optimization model which enables consideration to be given to subjective factors such as socio‐cultural and environmental conditions as well as to technical and economic aspects. The model is particularly applicable to the developing world. Twenty and twenty‐two parameters were identified for the selection of wastewater and sludge‐treatment alternatives respectively. Forty‐six and ninety‐four treatment alternatives were formulated as decision variables for the selection for wastewater and sludge treatment respectively. The technique was then employed to select the optimum treatment procedures.
Environmental Modelling in the Hydrological Cycle: What the Client Needs?
Authors: Gardiner J.
Published: July 2007

This paper summarizes expert and user views in some of the fields which are of interest to the Environment Agency. Models have been specifically designed to fulfil the needs of particular functions such as water resources, flood defence, and water quality. There are trends towards models serving more than one function and operating to represent the ‘natural’processes in an entire catchment or the wide range of parameters influencing the habitat at one point.

Model evolution is likely to be driven partly by the client's requirements (based in turn on more stringent legislation, economics, public expectation and new phenomena) and partly by advances in computational power. The recent focus on holistic treatment of catchments and their multi‐functional issues may stimulate the development of the relatively new distributed, linked models more than their single‐function counterparts.
Energy Cost Savings in Motive Power
Authors: Falkner H.
Published: July 2007

Motive power accounts for over 65% of the average UK industrial electricity bill; however, in the water industry this percentage is nearer to 90%. During 1994, UK industry spent almost £3000 million on the energy used by motors – mainly attributable to AC induction motors, with pumps and fans being the most common motor applications.

Many techniques can be used to reduce the cost of running motors, from simple good‐housekeeping measures to sophisticated electronic controls. This technical note reviews a selection of these techniques using independent case studies from the Department of the Environment's ‘best practice programme’to illustrate the cost savings; the use of software to predict energy savings is also discussed.
Peak Demands from Spray Irrigation
Authors: Weatherhead E. K. , Knox J. W.
Published: July 2007

Although irrigation accounts for less than 2% of water use in the UK, direct abstraction for spray irrigation can be a significant user in certain catchments in dry summers. Peak demand is expected to grow nationally by 1–2% per annum on average, but this growth varies locally. Water resource planners need to know the peak demands and how they are likely to grow within each catchment or aquifer, and the likely local annual variation and timing of demand. This paper discusses how recent developments in irrigation modelling combined with the application of a ‘geographic information system’can produce such forecasts, taking into account spatial variation in soils, climate, cropping and irrigation practice.
The Use of a Mobile Sludge Dewatering Unit at Small Sewage‐Treatment Plants in Japan
Authors: Takahashi H.
Published: July 2007

The construction of small sewage‐treatment works in Japan is increasing. In most municipalities, economical and effective treatment/maintenance systems, which match the local conditions, are needed. As one of its support strategies, the Japan Sewage Works Agency has initiated and implemented ‘co‐operation’ projects. In one of these projects, a mobile sludge dewatering unit has been shown to be the most economical method of treatment. The first unit, which was commissioned in March 1992, is being used in three municipalities, and this paper appraises its use.
Cairo Sludge Disposal Study
Authors: Hall J. E. , Smith S. R.
Published: July 2007

This paper describes the establishment of the Cairo sludge disposal study which is being funded within the Mediterranean Environmental Technical Assistance Programme through the European Investment Bank and promoted by the Cairo Wastewater Organization. The study is a demonstration programme to show how the problems of sludge disposal from large, rapidly developing cities, such as Cairo, can be solved through the establishment of a practical system for the safe re‐use of sewage sludge in agriculture. It is being carried out principally through a series of demonstration field trials and the development of ettensive information. This study is of relevance to Egypt and other countries with similar agricultural and environmental conditions, where (a) sludge production is increasing, (b) water protection is essential, and (c) appropriate environmentally acceptable solutions are urgently required.
Substrate Removal by In‐Sewer Oxygenation
Authors: Malik M.
Published: July 2007

This paper describes a study which was carried out to investigate the degree of in‐sewer treatment which could be achieved by suspended heterotrophs (normally present in domestic sewage), under aerobic conditions and under different retention periods and sewage strengths.
The Use of Fertilizer‐Free Grass Buffer Strips to Attenuate Nitrate Input to Marshland Dykes
Authors: White S. K. , Cook H. F. , Garraway J. L.
Published: July 2007

Fertilizer‐free buffer strip establishment has proved to be effective in attenuating nitrates which are mobile in shallow water‐tables feeding watercourses of conservation potential. This paper demonstrates their effectiveness on reclaimed alluvial marshland soils.
Habitat Creation Opportunities for Landward Coastal Re‐alignment: Essex Case Studies
Authors: Dixon A. M. , Leggett D. J. , Weight R. C.
Published: July 2007

Relative sea‐level fluctuations during the Holocene period have combined with medieval to present saline floodplain embanking to reduce the inter‐tidal saltmarsh area in Essex from 40 000 ha to 4400 ha. The present loss by erosion is estimated at 2%/annum for the country, and the reduction in these areas is not only detrimental to related habitats but has caused an increasing requirement for flood‐defence financial investment.

Recent initiatives by the Ministry of Agriculture, Fisheries and Food, the Environment Agency and English Nature have created mechanisms and opportunities to develop sustainable flood‐control structures where coastal re‐alignment has been the preferred option.

The Orplands frontage covers 2 km of sea wall which have been deliberately breached to allow 40 ha of rare saltmarsh to re‐establish. At Abbotts Hall, an arable field of 20 ha has been converted to its former saltmarsh by creek re‐establishment and tidal inundation by reversal of existing sluices. These two schemes have (a) regenerated habitats for halophytic and semi‐halophytic plants, marine and brackish invertebrates, and (b) provided roost, feed and breeding areas for birds and nursery areas for marine fish fry. Apart from flood control and habitat creation, particular features were incorporated to provide niche locations for targeted types of wildlife.
Variations between Continuous and Spot‐Sampling Techniques in Monitoring a Change in River‐Water Quality
Authors: Hazelton C.
Published: July 2007

Following significant expenditure by Thames Water Utilities Limited at Crawley and Horley sewage‐treatment works, the quality of the final effluents being discharged to the River Mole improved considerably.

The automatic quality‐monitoring station operated by the former National Rivers Authority downstream from both discharges showed a distinct improvement in water quality which was not recorded to the same degree by the NRA's formal sampling programme. The quality of data provided by the formal sampling programme can be misleading, and such data should be used cautiously in water‐quality assessment and modelling.

The reasons why spot‐sample data were unreliable were investigated, and the possibility and benefits of developing a systematically biased continuous monitoring strategy to produce water‐quality data under comparative environmental conditions are explored.
Analysing and Forecasting Peak Demands on the Public Water Supply
Authors: Herrington P. R.
Published: July 2007

The paper examines the magnitude of present and future peaks in the public water supply in England and Wales. Current knowledge is surveyed, including recent research undertaken for the Department of the Environment. Reference to a number of surveys permits a ‘first‐cut’estimate to be made of the micro‐components of typical domestic peaks in south and east England, and judgement is used to predict peaks for 2021. Finally, evidence concerning the effect of domestic metering on peak demands is summarized, suggesting a major role for economic instruments in the reconciliation of future demands and supplies.
Effects of Plastic Support Media on the Diffusion of Air in a Submerged Aerated Filter
Authors: Hodkinson B. J. , Williams J. B. , Ha T. N.
Published: July 2007

The established procedures for quantifying the aeration capacity of diffusers used in submerged aerated filter wastewater‐treatment systems do not consider the effects of support media; this may lead to ineffective design and sizing of diffused‐air systems. The study was carried out to determine the factors affecting aeration in a submerged aerated filter containing high‐voidage random‐packed plastic media. Tests were conducted in a full‐scale model reactor with and without support media.
A Biological Key to Canal Water Quality
Authors: Ruse L. P.
Published: July 2007

Sixty sites on canalized watercourses in England were sampled using the ‘Chironomid pupal exuviae technique’, and chironomid data were related directly to associated physical and chemical characteristics of each site. A scoring system is proposed for assessing canal water quality, and scores are assigned to widely distributed, frequently occurring and easily recognizable indicator taxa. A dichotomous key, based on six of these indicators, is provided for classifying canal water quality.
Arriving at the Economic Level of Leakage: Environmental Aspects
Authors: Howarth D. A.
Published: July 2007

In England and Wales, recent droughts and the future threat posed by climate change has intensified the debate on the suitability of either resource‐development or demand‐management approaches to ensure that supply and demand are kept in balance. The need to reduce leakage from water distribution systems has gained almost universal acceptance, and discussion now centres on what should be included in the cost‐benefit analysis in determining that economic level of leakage.

This paper (a) reviews the role of the Environment Agency in leakage control and the current thinking on the economic level of leakage, (b) argues the case for the inclusion of environmental costs and benefits, and (c) explores some of the reasons why water companies appear to be reluctant to pursue the goal of further leakage reduction.
Strategies Towards Sustainable Development in Nigeria's Semi‐Arid Regions
Authors: Toro S. M.
Published: July 2007

During the last three decades, there has been a steady decline in rainfall within Northern Nigeria where the total annual amount has declined below the 30‐year mean; this could be either a permanent or temporary phenomenon. Whatever the trend, the continuous deterioration in climatic conditions, combined with uncoordinated resources planning, are paving the way for a crisis of dramatic proportions in the sub‐region. In the rush to combat this threat, like most third‐world countries, Nigeria embarked upon large‐scale constructions of dams and irrigation‐infrastructure facilities without proper planning and coordination. Consequently, the schemes have now failed to achieve their forecast output.

The paper attempts to establish the important role which the naturally available water‐resources potential of the sub‐region could play towards sustainable irrigated agricultural development under increasing risks of drought and desertification within the area.
Impacts of Sewers on Groundwater Quality
Authors: Bishop P. K. , Misstear B. D. , White M. , Harding N. J.
Published: July 2007

This paper summarizes the findings of a recent research project on groundwater contamination from leaking sewers, which was completed for the Construction Industry Research and Information Association. Fifty‐four incidents were identified in England and Wales from a combined questionnaire survey and literature review. In addition to recorded incidents, the poor quality of many urban groundwaters suggests some effects from leaking sewers. Age is considered to be the most significant characteristic governing leakage from sewers; ground conditions (predominantly aquifer vulnerability) and usage (private versus public ownership) are also important factors relating to the likelihood of groundwater pollution from leaking sewers. Recommended strategies for reducing groundwater contamination include (a) modification of existing criteria for the service performance grading of existing sewers, (b) improved construction of new sewers in appropriate areas, (c) increased groundwater monitoring, and (d) risk assessments for new groundwater sources.
An Energy‐Efficient Combustion System for High‐Moisture Organic Wastes and Biomasses
Authors: Have H. , Henriksen K. S.
Published: July 2007

A special combustion system comprising a drier, combustion unit and heat‐recovery unit, designed to produce low‐grade heat from high‐moisture fuels, was investigated using sewage sludge, animal manure and energy crops as the feed material. Part of the investigation dealt with the development of a new method of combined wet pelletizing and surface drying of sludges to facilitate simple and efficient combustion as well as easy handling of the dried product. The investigation showed that (a) drying at temperatures up to at least 950° is feasible, and (b) low‐temperature heat may be produced for space and water‐heating purposes at high thermal efficiency.
High‐Pressure Water Jetting: Avoiding Damage to Sewers
Authors: Cant J. , Trew J.
Published: July 2007

High‐pressure water jetting of sewers and drains is being undertaken in the UK using equipment which, under certain circumstances, can damage the pipes. Research was therefore carried out to provide information which would accurately identify the potential for causing damage and enable preventative measures to be undertaken.

This paper explains the key factors which control the potential to damage sewers and drains by pressure jetting, and provides details of a new jetting test for pipes.
A Review of the 1995–96 Drought in the North West
Authors: Walker S. , Smithers H. A.
Published: July 2007

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.
The Development and Use of Hybrid Aeration Processes
Authors: Chambers B. , Upton J. , Greenhalgh S. H.
Published: July 2007

Requirements to improve effluent quality have led to the establishment of better design procedures for activated‐sludge plants. The recognition that activated‐sludge aeration is responsible for a large proportion of the energy used in sewage treatment has resulted in the specification of energy‐efficient aeration systems as part of such design procedures. Fine‐bubble diffused‐air techniques are potentially more efficient than mechanical surface‐aeration systems, but low oxygen‐transfer efficiency is often observed in practice under conditions of high aeration tank solids loading. Surface‐aeration systems appear to be able to operate at reasonable aeration efficiencies under conditions of high loading, but they are not as effective as diffused‐air systems in low‐rate processes.

There is evidence that a properly designed combination of the two types of aeration system in the same process (hybrid aeration) can result in optimum energy use and good effluent quality. The paper describes the development of this concept, showing the long‐term performance of three full‐scale plants utilizing hybrid aeration.
Nutrient Removal: Experiences in Johannesburg (Abridged)
Authors: Pitman A. R.
Published: July 2007

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.
Activated Sludge: Latest Developments and a Look Into the Future (Abridged)
Authors: Randall C. W.
Published: July 2007

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.
An Assessment of Drainage Best Management Practices in Scotland
Authors: McKissock G. , Jefferies C. , D'Arcy B. J.
Published: July 2007

The study was carried out to establish the extent to which source‐control systems are being used in Scotland. An investigation into the level of knowledge of such systems was also initiated. Over 100 questionnaires were sent to organizations which have been involved in the development of surface‐water drainage schemes, and the 43 responses were analysed.

Further work was then undertaken to establish the locations of source‐control systems in use. The collated information was utilized and, with the help of the Scottish Environment Protection Agency consent files and correspondence with consultants, a database indicating the locations of sites, was compiled. Information was collected on approximately 79 examples of such systems, currently in use or proposed, in Eastern Scotland.
Estimation of Outage Allowances
Authors: Cullen N. , Fenn C. R.
Published: July 2007

A methodology is described for estimating the allowances or safety margins which can be applied to estimates of water resources to allow for outages (random or periodic interruptions to supply). The methodology follows recent published UK Government and water‐industry guidelines and provides estimates at two levels: on‐average estimates, and risk‐related estimates. Example applications are described, and advice is given on ways of improving the supply/demand balance. The final choice of any outage allowance to be used should take account of (a) patterns of demand, and (b) the consequences of failure.
The Use of Membranes for Salt Reduction in the UK
Authors: Moss P.
Published: July 2007

Reverse‐osmosis membranes, which have been used for reducing the salt content of water since the late 1960s, are available for a variety of desalination applications, ranging from seawater to brackish water and specific species removal, including hardness and organics. In recent years, major advancements have been made in the salt‐rejection capabilities and in pressure requirements, which have made the use of membrane technology in water treatment an attractive proposition.

The paper focuses on (i) seawater desalination, reviewing the present study which is being carried out by Anglian Water; (ii) brackish water desalination, in particular a project which is being undertaken by Essex and Suffolk Water, and (iii) well‐water desalination, describing a project which is being executed by Anglian Water.
Leachate Ammonia Flushing from Landfill Simulators
Authors: Purcell B. E. , Butler A. P. , Sollars C. J. , Buss S. E.
Published: July 2007

The operational management of landfills is currently being reviewed in the UK and Europe. In the UK, the ‘flushing bioreactor’ approach to landfilling involves (a) enhancing microbially mediated degradation of domestic waste to promote rapid waste stabilization, (b) increased methane recovery, and (c) reduced timescales to final landfill stabilization. Flushing oeprations under bioreactive conditions could be used to optimize the removal of ammoniacal nitrogen from landfilled waste. In this study, the flushing of ammonia from pulverized domestic waste was investigated using laboratory‐scale test cells to simulate landfill conditions. A simple mathematical model, based on test‐cell water balance, was used to describe the latter stages of ammonia reduction.
Healthcare Wastes: A World Health Organization Perspective on Waste Treatment and Disposal Options (Abridged)
Authors: Rushbrook P.
Published: July 2007

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 Application of Rubber Dams for Water Supply in Hong Kong
Authors: Tam P. W. M.
Published: July 2007

There is a long history of the use of inflatable dams (rubber dams) in Hong Kong. Three inflatable dams were constructed in the 1960s as an integral part of the Plover Cove water supply scheme which was the largest project in Hong Kong at that time. However, because most civil‐engineering structures are constructed from steel, concrete, soil and rock, the use of rubber as a construction material is subject to much scepticism. The problems and counter‐measures associated with the use of rubber are discussed, based upon the experience of several departments which have used the dams in Hong Kong, and in other parts of the world.