bluuebunny/crossref_metadata_2025 huggingface dataset:
Extreme Historical UK Floods and Maximum Flood Estimation
Authors: ACREMAN M. C.
Published: July 2007

Historical flood events recorded as flood marks on bridges and houses or reported in newspapers and journals provide valuable information on the maximum size of floods which are likely to occur in the UK. For hydrological analysis peak water level must be converted to peak discharge, which is problematic even when the flood has been recorded at a flow gauging station. This paper describes some of the methods used to calculate the magnitude of extreme floods. Sixty‐nine historical UK floods are plotted on a graph of discharge versus drainage area and compared with curves published in 1933 and 1960 which were used to estimate the Normal Maximum Flood required for dam spillway design before 1975. From that date the design standard became the Probable Maximum Flood. PMF is calculated for 17 sites where extreme floods have occurred. For six events the observed peak discharge exceeded PMF. Possible reasons for these findings are discussed.
Large‐Scale Biological Nitrate and Ammonia Removal
Authors: ROGALLA F. , RAVARINI P. , LARMINAT G. De , COUTTELLE J.
Published: July 2007

In order to treat water containing nitrogen in excess of the European Drinking Water guideline, an innovative large‐scale biological, nitrogen‐removal process has been used. After extensive pilot‐scale testing and a first full‐scale (80 m3/h) demonstration at Eragny (France), a 400 m3/h installation, serving about 50000 people, was built at Guernes‐Dennemont, near Paris. The raw water source is a combination of percolation from agricultural plains and river bank infiltration, and contains both nitrates and ammonia.

The plant consists of two fixed‐bed biological reactors in series. An anoxic filter, using ethanol as a carbon source for heterotrophic bacteria, removes nitrates at filtration rates up to 10 m/h. The denitrified water is then polished on an aerated two‐layer filter, packed with activated carbon and sand. Excess carbon from the first stage, together with reduced nitrogen (ammonia and nitrates), is oxidized at this stage before ozonation of the water.

Design data and operational performance are given for total nitrogen (NO3 and NH,), total organic carbon (TOC) and chlorinated hydrocarbons. A specific dosing method for biodegradable carbon was developed to monitor the efficiency of the post‐treatment. Special attention was paid to (a) nitrate control through improved backwash, and (b) reducing the potential for bacterial contamination and aftergrowth in the distribution network.
The EC Bathing Waters Directive as Applied to Scotland
Authors: HALCROW W. , LEATHERLAND T. M.
Published: July 2007

Some monitoring of the bacteriological quality of potential bathing waters has been carried out in Scotland since the publication of the EC bathing waters Directive’14 years ago. However, it is only since 1987 that 23 beaches in Scotland have been officially recognized as having bathing waters which should meet the environmental quality standards (EQS) laid down by the Directive. Results of the first three years’monitoring are outlined and the cost of this work has been estimated. The idea of reviewing the standards presently prescribed by the Directive is welcomed. The need to monitor both indicator and target organisms is questioned, and studies are cited suggesting that the present mandatory coliform standards may not be sufficiently stringent. Possible future requirements, including effects of the proposed Directive on the treatment of municipal waste waters, are briefly considered.
Disinfection of Sewage, Stormwater and Final Effluent
Authors: THOMAS VICKY K. , REALEY G. J. , HARRINGTON D. W.
Published: July 2007

This paper highlights the main disinfection options available for sewage, final effluents and stormwater, and is a review of the current research programme being carried out by staff of the Water Research Centre.

Disinfection is an increasing requirement, with particular emphasis on bathing and recreational water use. Laboratory and field trials are reviewed, and a wide range of disinfectants have been tested. These include peracetic acid and the Clariflow process for crude sewage; peracetic acid, ozone and UV irradiation for final effluent; and peracetic acid for stormwater.

The efficacy of the various disinfectants is evaluated and general costs are presented. Of special interest is the potential effect of sewage strength in reducing the disinfecting properties of the chemical. It is also apparent that there are wide variations in performance between processes and host organisms.
Supervision of Sewers for Adoption
Authors: COX G. C. , BUDLEIGH J. K. , JENKINS W. O.
Published: July 2007

The Water Authorities Association guide ‘Sewers for Adoption’ has achieved considerable success in unifying practice and establishing well‐understood and recognized standards for the design and construction of sewers by developers under Section 18 of the Public Health Act 1936. However, the supervision provided by the adopting authorities — particularly in relation to supervision fees — has been an area of dispute for some time.

The Construction Industry Research and Information Association (CIRIA) has recently completed a study on the optimum levels of supervision for sewer construction. The study included a national survey on the nature and extent of problems occurring during the course of Section 18 work and the supervision practices presently being undertaken. The study puts forward recommendations on the nature and timing of periodic inspections undertaken during construction. Several specific problem areas are discussed, ranging from measures required to ensure that design submissions are of an adequate standard, to the timing of any pre‐adoption closed‐circuit television inspection. This paper draws upon the contents of the report and discusses some of the principal findings and recommendations of the study.
River Flow Simulation: Research and Developments
Authors: KNIGHT D. W. , SAMUELS P. G. , SHIONO K.
Published: July 2007

The translation of recent research work concerning shear layers into practical river simulation models is explained. The equations which govern the lateral distribution of streamwise depth‐averaged velocity are formulated and solved. The analytical solution includes the effects of bed‐generated turbulence, lateral shear turbulence and secondary flows, and therefore reproduces many of the main features of river channel flow. The solution closely simulates the process involved in river gauging by the current‐meter method. Recent data from the Science and Engineering Research Council's Flood Channel Facility are used to illustrate the variation of shear stresses within the flow, and data from three river‐gauging sites are used to illustrate the potential of the model.

The steps involved in the design of a modern river simulation package are also described. It is shown how choices made during the development of a model can have a significant impact on the success of model simulations. The development of a package requires many different skills, including those of engineering, mathematics and computing.
Sheep‐Dips as a Source of Pollution of Freshwaters – A Study in Grampian Region
Authors: LITTLEJOHN J. W. , MELVIN M. A. L.
Published: July 2007

The results of organochlorine insecticide analysis of samples taken during 1984–85 from the River Ugie and its tributaries in Grampian Region showed, by the timing and the nature of the compounds found, that sheep‐dips were likely sources of pollution of freshwaters in the Region. Subsequent investigation of freshwaters and treated waters for organophosphorus insecticides typical of sheep‐dips supports this hypothesis. However, there is no evidence of serious contamination of freshwaters in the Region by phenolic compounds from sheep‐dips, even though these are present at high concentrations in sheep‐dip preparations.
Design and Construction of Bulk Storage Reservoirs – Muna, Saudi Arabia
Authors: SLEIMAN B. F.
Published: July 2007

The paper describes the background for, and the magnitude of, the unusual peak water demand (during the Haj season) in Muna and the Holy Environs of Makkah. It then summarizes the various conceptual designs of storage alternatives, which led to the selection of the ‘bulk storage’concept at high elevations in the surrounding hills, commanding the project area by gravity.

The objectives of the scheme were (a) elimination of operational and maintenance requirements during the peak demand season, (b) reduction of construction costs, and (c) aesthetic harmony with the surrounding environment.

A detailed description of the design of all the components of the two reservoirs covers: location, shape, dam section, flood protection, pipeworks, roof structure, and waterproofing, as well as the mode of operation.

Finally, the paper describes the experience associated with the first commissioning of bulk storage reservoir No. 2, and the measures that were introduced to improve the performance of the water‐proofing membrane utilized in the reservoirs.
Service Reservoir Remedial Works
Authors: SPURGEON G.
Published: July 2007

Two conventional reinforced‐concrete service reservoirs failed during initial filling, the wall sections sliding sufficiently to cause rupture of some water‐stops in the expansion joints. The paper describes the remedial works undertaken to stabilize the structures and gives details of the method used to make the expansion joints watertight.
Historical Factors and Recent Developments in Wastewater Treatment Management in Japan
Authors: KUBO T.
Published: July 2007

Japan has experienced serious water pollution problems, such as Minamata Disease (mercury poisoning) in the 1960s. Since then, comprehensive countermeasures have been implemented including establishment of a legislative framework and environmental water quality (EWQ) standards, enforcement of EWQ standards on dischargers, encouragement in the development of sewerage systems, research and technology development, and wastewater reclamation and reuse. This paper reviews the recent developments in wastewater management in this social context in Japan.
Identification, Investigation and Assessment of Contaminated Land
Authors: SMITH M. A.
Published: July 2007

The identification of contaminated land and its associated problems is a multi‐stage process covering the first suspicion of contamination through to the final assessment in which hazards and risks are determined so that appropriate remedial measures can be taken. In the UK, an effort has always been made to distinguish between the existence of ‘contamination’, and any assumption that this automatically implies the existence of a ‘problem’. The task is to identify contaminated land which might currently, or in the future, pose a threat to (a) human welfare, (b) the environment, or (c) natural resources. This can be achieved through an appropriately designed site investigation and subsequent careful assessment of the results.

This paper is intended as a broad look at identification, investigation, and assessment processes.
How the Wastewater Discharge Fee Might Become a Tool of River‐Basin Management
Authors: H.K. R. IMHOFF E.
Published: July 2007

The Federal German Water Law of 1976 postulated for the first time that a licence for the discharge of wastewater into public watercourses might only be granted when the wastewater, prior to discharge, is treated according to laid‐down standards. In 1976 it was also decided that for the residual pollution load in sewage‐treatment plant effluents a pollution fee has to be paid.

At present three pollution units have to be paid per capita and annually for untreated domestic wastewater. One pollution unit is assessed at 17/annum, but the price will be increased to 30/annum in future.

Since the pollution units encompass COD, nitrogen, phosphorus, heavy metals, and chlorinated hydrocarbon compounds, the pollution unit is a good tool to compare the effectiveness of treatment. For different drainage systems the residual pollution units (per litre and second) can also be calculated for low‐flow conditions.
Water Resources and Management in the Republic of Ireland
Authors: McCUMISKEY L. M. , TONER P. F.
Published: July 2007

Ireland is well‐endowed with water resources and has one of the higher rates of water availability in Europe. However, regional variations in rainfall and population distribution give much less favourable conditions in the east of the country compared to other areas. Pollution of waters to date has been generally localized and moderate in intensity, although there is a trend towards eutrophication of the river systems. Piped water supplies, either from public or private schemes, are now available to nearly all dwellings in the state, both urban and rural. The same position holds for sewerage facilities in the urban areas, but nearly 25% of the rural population is still unserviced in this regard. Future development of services will place more emphasis on sewerage facilities, as outlined in the recently issued national action programme on the environment.
Solid Waste Problems and their Handling in the Netherlands
Authors: LOUWMAN ING D.
Published: July 2007

The Netherlands, in common with most other countries, has a problem in disposing of solid wastes in an environmentally acceptable way. The paper reviews the historical situation, looks at the present‐day position, and explains the proposals for waste disposal in the Netherlands up to the year 2000 and beyond.
Impact in Scotland of UK and EC Sewage Legislation
Authors: ANDERSON T. A.
Published: July 2007

The EC Directive (91/271/EEC) concerning urban waste water treatment has far‐reaching financial and technological implications for local authorities in Scotland which are responsible for sewerage. Increased capital consent limits and additional financial assistance from central government are essential if the requirements of the legislation are to be met.

Although the Directive is welcomed in general terms, the sections of the legislation dealing with the identification of sensitive waters and the provision of primary treatment for coastal discharges to less sensitive waters are of limited environmental significance in Scotland.

The elimination of sewage sludge disposal at sea will create severe difficulties for Scottish authorities as a high percentage of sewage sludge is currently disposed of at sea. Each of the main alternative disposal options presents environmental, financial and technical problems and, in the case of incineration, the certainty of widespread unpopularity with the public.
Drinking Water Quality and the Consumer
Authors: FAWELL J. K. , MILLER D. G.
Published: July 2007

Public understanding of water quality is obtained primarily from the extensive media coverage of problems. This has contributed to a distrust of the water supply industry and of specific experts in this field. It is therefore important that the basis of standards for both microbiological and chemical parameters is absoulutely clear and scientifically defensible, since these are the yardsticks against which quality and safety will be judged. They are also the reference point from which political decisions on standards must be made.

It is also important that the public is given some understanding of the comparative risks involved and that a proper balance is struck between maintaining microbiological quality and achieving chemical standards, particularly for disinfection by‐products. Without this, the demand for more stringent standards in a search for absolute safety will result in more costly water, while standards approach the unachievable.
Development On and Adjacent to Landfill
Authors: CARD G. B.
Published: July 2007

This paper outlines the engineering design philosophy for development sites affected by landfill gas. The hazards of landfill gas need to be fully understood and evaluated in relation to the location and type of building structure proposed, and a comprehensive assessment and design process should be undertaken. This involves interpretation of investigation and monitoring data, prediction of future trends, selection of appropriate design parameters, evaluation of gas‐control measures, safety during construction, and long‐term serviceability and monitoring.

A description is given of the principal types of gas control measures which allow building development to take place on sites affected by landfill gas, and guidance is provided for the design of such measures. These measures include site encapsulation, gas‐venting trenches and wells, gas‐resistant membranes and barriers, natural ventilation to structures, and gas‐detection and management systems.
Groundwater Pollution in Spain: General Aspects
Authors: CUSTODIO E.
Published: July 2007

In spite of many aquifers still being in good condition, groundwater pollution is becoming a serious problem in some areas of continental and insular Spain, although it is not always recognized. Irrigated agriculture is an important source of pollutants, but industrial, mining and urban‐related problems also exist. These go in parallel with serious salinity problems of diverse origin. The degree of knowledge with regard to these problems is still poor, and in many instances low priority is given to studies, prevention, control and remedial action. Water quantity aspects still receive most of the attention and economic resources. A new Water Act includes provisions for dealing with groundwater quality and pollution; they seem adequate to cope with existing problems, but their effectiveness, feasibility and willingness to be applied is still uncertain. The success not only depends on scientific and technical issues, but mainly in achieving an administration and management structure capable of coping with real problems and able to obtain the trust and cooperation of water users.
Denitrification of Wastewater: Operating Experiences in the US and Pilot‐Plant Studies in the UK
Authors: (Fellow) J. UPTON , FERGUSSON ALISON , SAVAGE S.
Published: July 2007

Due to the EC urban wastewater treatment Directive, considerable attention has been focused on nitrogen removal, particularly from biological filter nitrified effluents. The paper presents a reliable and proven full‐scale fixed‐film denitrification system installed in the US and evaluated on pilot scale by Severn Trent Water. Methanol has been used as a carbon source dosed prior to the deep‐bed sand filter. The filter removes considerable suspended solids as well as providing the hydraulic retention and surface area for the growth of the biological denitrifying bacteria. Flow sheets of typical US installations are given and operational data with costs are presented for the pilot‐plant evaluation.
The Seaton Carew Sewerage Scheme: Design Features and Contractual Arrangements
Authors: PRICE A. C. , CLARK S. , ROE M. K. , LLOYD T. C.
Published: July 2007

Northumbrian Water Limited has thirty‐four bathing waters and a substantial investment programme to ensure that these waters meet EC standards by 1995. One project within this overall programme is the Seaton Carew Sewerage Scheme. Seaton Carew lies on the southern edge of Hartlepool which has a population of 95000. The scheme will combine existing flows into new foul and storm‐sewage outfalls. The headworks will incorporate screening, grit removal and pumping stations with substantial measures for odour control. Hydraulic operating regimes using active pump control and passive flume control have been investigated to ensure efficient treatment for a wide range of flows. The onerous design, manufacture and construction programme has required the development of new approaches to procuring the work, whilst maintaining a substantial element of competition. The various programmes have been substantially overlapped to ensure that the scheme is completed by April 1993.
Three‐Stage Treatment of Pennine Waters: The First Five Years
Authors: FRANKLIN B. C. , HUDSON J. A. , WARNETT W. R. , WILSON D.
Published: July 2007

The first full‐size three‐stage water treatment works was built at Blackmoorfoot (near Huddersfield) just over six years ago. The three‐stage treatment process involves flotation, first‐stage filtration and subsequent manganese removal in three distinct stages. The works at Blackmoorfoot has been followed by several others in Yorkshire Water. This paper (a) describes the three‐stage treatment process and its developments, (b) relates the operating experiences of the new works to date, and (c) gives some of the operating costs. The treatment process has been successful in treating upland Pennine waters and, as a result, water quality throughout the area has improved. The paper also shows that the process can be modified where water quality allows. The operating costs of the new process are affected by the economies of scale, but need not be greater than those of the older works which have been replaced.
Investigation of River Flow Failure at Sleaford
Authors: HAWKER P. J. , HARRIES K. J. , OSBORNE N. F.
Published: July 2007

The River Slea through Sleaford is fed by groundwater emanating from the Lincolnshire Limestone. In recent years, the springs have dried up periodically, causing failure of river flow through the town. The Slea is a main feature of the town and, when flowing, a valuable visual amenity. Conversely, when it is not flowing, progressive water quality deterioration in ponded sections reduces the river corridor to an eyesore. The paper describes investigations into the cause of the problem and how to overcome it.
Long‐Term Benthic Monitoring of a Dense Effluent Discharge to Sea
Authors: D. CRAIG N. C. , SHILLABEER N. , PARR J. C. W.
Published: July 2007

The paper describes and discusses the effect on the local benthic community of the discharge of a dense, saline, effluent into a nearshore area of the North Sea. The monitoring programme continued through the twenty‐year period from 1970 until 1989 and includes effectively five years pre‐discharge data. Samples were taken from fixed stations with a grab sampler and the invertebrate fauna were identified, wherever possible, to species. In addition, the particle size distribution of the sediment in each sample was determined. The discharge has had a clear effect on the benthic community.

This extensive dataset, with its clear gradient of effect, also offers the opportunity of comparing the effectiveness of species and family level identification when studying the effect of disturbance. In this case the impacted area was as readily identifiable from the family as the species level data.
The Development of a Sludge Disposal Strategy for the Hong Kong Territories
Authors: LOWE P.
Published: July 2007

Sludge arisings in the Hong Kong Territories are predicted to increase from the current level of 44 300 tDS/annum to 314000 tDS/annum. This has led to a need to examine the treatment and disposal facilities required for the future. Disposal facilities were found to be restricted, with virtually no suitable land for a liquid disposal route and a sea route limited to the present quantities. Only landfill remained as the major disposal outlet, but this is also limited by the moisture absorbence capacity of the emplaced material and limiting metal concentrations.

In order to match the sludge production to the disposal outlet capacity, a series of process options was considered. Transportation studies using pumping, road and sea networks were undertaken and the environmental impact assessment of introducing thermal technologies was reviewed. Finally the various options were evaluated using a modified version of the Water Research Centre's WISDOM model.
Groundwater Nitrate Concentrations from the Old Chalford Nitrate‐Sensitive Area, West Oxfordshire
Authors: EVANS D. , MOXON I. R. , C. THOMAS J. H.
Published: July 2007

This paper, describes nitrate concentrations in a groundwater catchment currently designated as a nitrate‐sensitive area. Although the scheme has been operational for two years, groundwater nitrate concentrations have regularly exceeded the EC maximum admissible concentration of 11.3 mg/1 NO3‐N (50 mg/1 NO3) from sources draining both arable and grassland management regimes. Nitrate levels from arable areas tend to produce a seasonal pattern of winter leaching and summer uptake, whilst no such pattern or fluctuation is observed from grassland areas. Four processes are defined which regulate nitrate inputs to the saturated zone of the Great Oolite aquifer: (i) availability of ‘free’nitrogen, (ii) variations in nitrogen uptake, (iii) leaching of nitrates from the soil environment, and (iv) limited atttenuation within the unsaturated zone.
Diffuse Sources of Pollution by Heavy Metals
Authors: ZABEL T. F.
Published: July 2007

Significant reductions in the amount of heavy metals released to the aquatic environment have been achieved by applying strict controls on point source industrial discharges. Because of these tight controls, diffuse pollution sources have increased in importance as a contribution to the total load. Diffuse inputs originate mainly from the use of chemical products. Thus control of these inputs can be achieved by refraining from or limiting the use of these products or by restricting the amount of heavy metals permitted in such products. Control of diffuse sources of heavy metals could be based on a ‘positive approval’system, permitting only those uses which do not lead to environmental harm and which could not be replaced by less harmful alternatives. Assessing the environmental impact of the alternatives will require the introduction of a ‘cradle to grave’approach.
The Occurrence and Viability of Giardia Cysts in Scottish Raw and Final Waters
Authors: SMITH H. V. , ROBERTSON LUCY J. , GILMOUR R. A. , MORRIS G. P. , GIRDWOOD R. W. A. , SMITH P. G.
Published: July 2007

The occurrence of Giardia cysts in Scottish raw and potable waters was investigated. Giardia cysts were detected in 49% of raw waters, with concentrations of up to 1.05 cysts per litre, and in 19% of final waters, with concentrations of up to 1.67 cysts per litre. In some of the positive water samples the viability of the cysts was assessed by viewing the cyst morphology and inclusion/exclusion of propidium iodide. Viable cysts were detected in a proportion of both raw waters and positive final waters studied. Further investigations at 21 water‐treatment plants revealed cysts in 9 (43%) of the raw waters, and in 4 (19%) of the final waters. Cysts were only detected in the final waters of plants in which cysts were also detected in the raw water. These data indicate that viable Giardia cysts may be ingested with potable water in Scotland.
The Influence of Unlined Boreholes on Groundwater Chemistry: A Comparative Study Using Pore‐Water Extraction and Packer Sampling
Authors: PRICE M. , WILLIAMS ANN
Published: July 2007

In the consolidated formations which form most of the major aquifers in the UK, many monitoring boreholes are left unlined (open) for their effective length. They therefore provide pathways for groundwater to flow from one part of the aquifer to another.

A borehole was core‐drilled through Triassic sandstones into Permian mudstones at a site in North Yorkshire. Pore water was extracted from the core and compared with conventional depth samples and with samples taken from intervals isolated using packer systems: (a) during drilling, (b) about one month after drilling, and (c) two years after drilling.

The study revealed that natural flow down the borehole led to rapid changes in the quality of water in some parts of the formation.

The implication is that open boreholes can act as conduits to allow flow to take place from one part of the aquifer to another. They are therefore not reliable as sampling points, and may actually accelerate the vertical spread of pollutants. However, this last effect should not be over‐stated; in this study, the flow down the borehole was equivalent to the natural flow through only a relatively small area of land.
Monitoring the Effect of Sewage Effluent on the Oxford Canal Using Chironomid Pupal Exuviae
Authors: WILSON R. S.
Published: July 2007

Collections of chironomid pupal exuviae from the Oxford Canal were taken monthly from May to October 1991 at stations above and below the sewage effluent discharge at Kidlington, near Oxford.

The chironomid exuvial assemblages showed clear changes reflecting the effects of the sewage, notably in the increased dominance of Parachironomus arcuatus and Chironomus riparius and other pollution‐tolerant species downstream from the effluent inflow. A return to the pattern of taxa seen in the upstream stations was noted below the next canal lock, 2.8 km downstream from the effluent discharge.

Environmental quality indices, calculated according to the Chironomid Pupal Exuvial Technique, also reflected the effects of the sewage inflow.

The results show that chironomid populations, as sampled by collecting pupal exuviae, are potentially valuable for monitoring organic pollution in canals.
Mapping Turbidity, Surface Temperature and Water Circulation Patterns with the Aid of Satellite Imagery
Authors: BABAN S. M. J.
Published: July 2007

Water turbidity, surface temperature and circulation of Barton and Wroxham Broads, two of the Norfolk Broads, were studied using one reflective (TM1) and the thermal (TM6) TM band. The results indicated that the through‐flowing path of the River Ant in Barton Broad is the major influence on the distribution of these parameters. In Wroxham Broad, both turbidity and surface temperature displayed a uniform distribution. This could be explained by the absence of a predominant direction of flow.
A Standardized Low‐Cost Low‐Flow Gauging Station
Authors: BARTON B. M. J.
Published: July 2007

This paper describes the origins and development of a simple, low‐cost, low‐flow stream gauging station to meet the operational requirements of a major water resource management system. The utilitarian design uses standardized, prefabricated components in order to achieve maximum economy and ease of construction without sacrificing durability or hydrometric accuracy.
Self‐Cleansing Sewer Gradients
Authors: MARRIOTT M. J.
Published: July 2007

Sewer design usually makes use of self‐cleansing velocity criteria. In some instances, however, simple gradient rules may be useful. The theoretical basis of such a rule is described and discussed with reference to research findings. Its use is suggested for quick assessment of proposed or existing sewers.
Experiences of Digested Sludge Thickening by Aercon
Authors: LYNCH M. , STEPHENSON T.
Published: July 2007

Increasing restrictions on sewage sludge disposal routes and the tightening of treatment requirements have led to an escalation of sludge‐disposal costs which are out of proportion to other sewage‐treatment costs: consequently reducing sludge volume is becoming increasingly cost‐effective. Consolidation of anaerobically digested sludge has traditionally been difficult and takes many weeks in secondary digesters or deep storage tanks. Pre‐aeration of the sludge using the Aercon process can enable consolidation to take place in days instead of weeks.

This paper reports the results of a pilot‐scale plant designed to investigate further the mechanism by which aeration speeds up consolidation. It was concluded that the rate of consolidation depended on aeration intensity and cooling of the sludge. Inhibition of anaerobiosis was more important than gas stripping in enhancing consolidation.
Examples of Groundwater Modelling in Environmental Assessment Studies
Authors: ASHLEY R. P.
Published: July 2007

The development of groundwater modelling techniques is reviewed, from analogue and early digital models to current commercial software packages. The parallel development of the application of groundwater modelling as a tool for evaluating the impact of developments and structures on hydrogeological systems is also examined. Formerly, new model programs were written for each application, requiring that the user had programming skills as well as hydrogeological expertise, and model development periods were measured in months or years. Now, a knowledge of the program details is not necessarily a prerequisite for a satisfactory model, which may be designed, constructed, calibrated and used in days or weeks. However, a thorough understanding of the conceptual model underlying a software package, and of the numerical methods used to generate the output, is as important as ever. Examples are given in the paper of the exploitation of commercial packages to produce rapid assessments of the impact on groundwater of proposed mineral workings and similar developments.
Impact of the River Maine Drainage Scheme on Hydro‐Power Generation
Authors: COCHRANE S. R. , HIGGINSON N. N. J.
Published: July 2007

A comparison is made between pre‐ and post‐drainage scheme river flows recorded on the River Maine, Co. Antrim. A method of using five‐year reference periods has been applied to the mean daily flows to smooth and eliminate, as far as possible, variations due to climatic changes.

Any loss of energy production which might have been due to changes in river flow was examined for turbine installations at a factory at Cullybackey. The quantities of usable water, and hence potential energy production, were calculated for each of the post‐scheme five‐year periods and compared with a pre‐scheme five‐year reference period. Any potential loss was then represented by a depreciation factor. It was found that no measurable loss of potential energy production has occurred on the River Maine in the post‐scheme period.
Trials Using a Mobile Ultraviolet Disinfection System in South West Water
Authors: JOB G. D , TRENGOVE R. , REALEY G. J
Published: July 2007

Ultraviolet radiation has been shown to be effective for disinfecting secondary effluents, and the National Rivers Authority has given conditional approval for its use at sites where disinfection can be justified.

This paper describes the findings of disinfection trials on five different sewage works' effluents using low‐pressure ultraviolet systems. The study examines and compares the disinfection performance of clean units and their deterioration in performance due to fouling effects. Conclusions are drawn on the effectiveness of ultraviolet disinfection in the removal of pathogens and pathogen surrogates.
The Life‐Cycle Analysis of Small‐Scale Sewage‐Treatment Processes
Authors: EMMERSON R. H. C. , MORSE G. K , LESTER J. N , EDGE D. R.
Published: July 2007

The environmental impact of small‐scale sewage‐treatment works has been evaluated using the technique of ‘life‐cycle analysis’. Three sewage‐treatment works with different process options were analysed to identify and quantify material use, energy use and environmental releases during construction, operation and demolition. This enabled (i) a comparison to be made between process options, and (ii) the identification of opportunities for the improvement of environmental performance. Subject to satisfactory sewage treatment and sludge disposal, the technique identified additional impacts of importance, which have implications for energy management, works design, supplier management and general environmental policy. Life‐cycle analysis provides a useful insight into environmental impact and has potential for wider application within the water industry.
The Pre‐design of Berenplaat Water‐Treatment Works, Rotterdam: Additional Processes to Achieve Biologically Stable Water
Authors: RODMAN D. J , VAN DE VEER A. J. , HOLMES J. F
Published: July 2007

Biological regrowth in a water distribution system can be avoided by either maintaining a free chlorine residual to suppress growth or controlling conditions which may support growth, or by a combination of both. Micro‐organisms will grow in water only if nutrients are present in sufficient amounts; conversely the reduction of biodegradable nutrients in water is vitally important in controlling the regrowth of microorganisms and zooplankton in the distribution system. The measurement of assimilable organic carbon has been developed as a way of evaluating the concentration of biodegradable material which is available to support such biological growth.

This paper describes the pilot‐plant and full‐scale studies carried out at the Berenplaat water‐treatment works, Rotterdam to (a) improve disinfection, (b) eliminate the formation of trihalomethanes and other halogenated compounds formed by chlorination, and (c) reduce the final water assimilable organic carbon concentrations to very low levels, so that a high degree of biological stability can be maintained in the distribution system.
Mechanisms of Leakage through Synthetic Landfill Liner Materials
Authors: BUSS S. E. , BUTLER A. P , SOLLARS C. J , PERRY R. , JOHNSTON P. M
Published: July 2007

The introduction of synthetic lining materials for leachate containment and the prevention of groundwater contamination was an important development in landfill technology. These materials have a low hydraulic conductivity which results in minimal leachate release by bulk fluid flow (advection) provided that the barrier (and its construction) is free from defects. However, the effectiveness of these materials as barriers cannot be confirmed unless contaminant release by diffusion is also taken into consideration.

This paper reviews the mechanisms by which transport through barriers occur. It highlights the role of diffusion as a pathway for organic compounds to migrate through synthetic liners and indicates its importance in terms of environmental impact and landfill design.
The Degradation of Atrazine and Other Pesticides by Photolysis
Authors: BOURGINE F. P , CHAPMAN J. I , KERAI H. , DUVAL J. L , GREEN J. G , HAMILTON D.
Published: July 2007

Groundwaters from chalk aquifers which are used as a supply for drinking water are often contaminated with pesticides ‐ in particular, atrazine. This paper discusses the use of an industrial‐scale ultraviolet chamber to reduce the concentration of atrazine in a chalk‐derived water which is used for drinking water supply. The concentration of atrazine varied between 0.1 μg/l and 0.5 μg/l, and the raw water was spiked when necessary. Results for other pesticides contaminants are also presented.

The efficiency of atrazine removal is dependent only on the energy input and is constant, regardless of the initial concentration. Hydrogen peroxide improves the efficiency of ultraviolet irradiation but requires high doses.
Reed‐Bed Treatment for Municipal and Industrial Wastewater in Beijing, China
Authors: LI S. R , DING T. , WANG S.
Published: July 2007

The reed‐bed system is a cost‐effective and environmentally friendly method of treating sewage from small treatment works. A pilot‐scale plant, which treated 500 m3/d of municipal and industrial waste‐water, was studied in Beijing, China. The aim of the project was (i) to test the ability of the reed beds to remove pollutants for long‐term operation in cold weather conditions, and (ii) to evaluate its environmental, ecological and financial values. The results of operation demonstrated that this system has the ability to remove the pollutants. One of the attractive features is that the reed beds can partly convert the pollutants into plant biomass with the natural energy from sunlight. The reeds can (a) be harvested each year, (b) provide a wildlife habitat, and (c) improve the quality of the ecosystem. Capital and operating costs of the system are comparatively low.
The Incidence of Cryptosporidiosis in Comparison with other Gastro‐Intestinal Illnesses in Blackpool, Wyre and Fylde
Authors: FEWTRELL L. , DELAHUNTY A.
Published: July 2007

The paper describes a study which was carried out to examine the incidence of cryptosporidiosis and other gastro‐intestinal illnesses in Blackpool, Wyre and Fylde. Information on the incidence of cryptosporidiosis, between 1987 and 1992, was collected retrospectively. Between July 1992 and June 1993, prospective information on a range of gastro‐intestinal illnesses was obtained from individual cases using a specially designed questionnaire.

In the six‐year period of the retrospective study, 497 cases of cryptosporidiosis were reported. When spatial patterns of cryptosporidiosis reporting were examined, no relationship could be found with either the water supply zone or census ward. The prospective study produced similar results to the retrospective investigation. Recreational water use and farm animal contact were identified as ‘risk factors’ for cryptosporidiosis when compared with other gastrointestinal illness aetiological agents.
Reservoir Outlet Works in the Mid‐1990s
Authors: EARP D. N. W.
Published: July 2007

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.
Cost‐Effective Water‐Quality Modelling of Potable Water Distribution Systems
Authors: LINDLEY E. , DAVIES S. E.
Published: July 2007

Before privatization of the water authorities in England and Wales in 1989, future water companies were instructed to provide auditable proof of their investment requirements by the production of asset management plans.

With respect to distribution systems for potable water, asset management plan studies have established that unlined ferrous mains are often the main cause of complaints about discoloured water. It has also been found that the investment in water mains rehabilitation, which is driven by water quality problems, overshadows similar investment requirements driven by high burst rates and poor hydraulic performance.

This paper describes how certain techniques of water quality modelling have been developed and refined to provide a rapid, cost‐effective method for identifying requirements for water‐main rehabilitation.
Uprating Water‐Treatment Works Supplying the Thames Water Ring Main
Authors: Glendinning D. J , Mitchell J.
Published: July 2007

This paper outlines the measures which were taken at Thames Water's major water‐treatment works to uprate their hydraulic capacity in meeting the projected demands of the Thames Water ring main. In addition, the integration of advanced water‐treatment processes, in the form of ozonation and granular activated‐carbon filtration, is also highlighted.
Environmental Influences on Company Valuations
Authors: Young P. J
Published: July 2007

The benefits accruing from good environmental management of companies are most often linked to economic benefit and the concept of moving towards sustainable development. However, the link between environmental liabilities, assets, or performance, and the financial valuation of a company remains obscure at best. Operational improvements, for example from implementing a waste minimization programme, can give a clear short‐term reduction in costs, and impact immediately on profits. Many environmental risk management programmes also need to deal with long‐term issues such as historical land contamination and changes in manufacturing technology. These have a much more protracted and ultimately fundamental impact on the perceived capital value and future prospects of a company. This paper seeks to describe how the relationship between environmental and financial risk management is becoming clearer, and uses examples to show how this is brought into focus during merger and acquisition activities.
Development of a Friability Test for Granular Filter Media
Authors: Humby M. S. , Fitzpatrick C. S. B. , Stevenson D. G.
Published: July 2007

ABSTRACT At present there is no generally accepted test available for characterizing the friability of granular filter media in the context of its ability to withstand handling and placing, as distinct from abrasion resistance during backwashing – which is the subject of other, existing, test methods. Most existing procedures tend to be grinding tests and have little meaning. The approach selected in this work was to adapt the ring shear test, in which a sample (large enough to be analysed by sieving) is subjected to shear under a known compression load and the change in the undersize fraction is assessed. A representative selection of dry media was submitted to the test and the results proved to be reproducible and capable of distinguishing (clearly) between friable and non‐friable resistant types. The procedure is likely to become the basis of a standard test.
Surface‐Water Abstraction Controls in Scotland
Authors: Adeloye A. J. , Low J. M.
Published: July 2007

ABSTRACT The system of abstraction controls for irrigation in Scotland is one of local control orders where, to limit abstractions from any particular watercourse, the river purification authority must apply for an order from the Secretary of State for Scotland to cover abstractions from that one watercourse and its catchment. This contrasts sharply with the heavily protective system in England and Wales where the National Rivers Authority has statutory powers to license all abstractions. The purpose of this paper is to examine the abstraction control system in Scotland with a view to highlighting its advantages and limitations, and to suggest ways by which the system can be improved or made more effective.
Refurbishment of Control Structures on the River Avon at Strensham Lock
Authors: Lewis R. I.
Published: July 2007

Three control structures at Strensham lock maintain the water level in the upstream pound of the River Avon for navigation, ecology and angling purposes. The National Rivers Authority †, which currently owns the structures, is responsible for their maintenance and for the operation of the vertical‐lift sluice gates which are opened to control flooding. Construction work has recently been completed to secure the structures, which were in a poor state of repair and in danger of collapsing. The two sluice structures were completely rebuilt and the weir was modified.

The paper describes the planning, design and construction of the works, which are located within a ‘site of special scientific interest’.
Effluent Control: The Hong Kong Approach
Authors: Holmes P. R.
Published: July 2007

Water pollution has existed for many years in Hong Kong, but the Government's strategy for pollution control is now beginning to take effect. The strategy includes planning, legislation, and the provision of sewage‐disposal systems. In the past, the main thrust has been against traditional pollutants measured by BOD, suspended solids and various nutrients, but as these are brought under control, attention will be given to the need to control toxic pollutants. The existing policy and legislation does not deal with toxic pollutants well, and past work on toxic substances in Hong Kong has concentrated on individual chemicals. The Environmental Protection Department is now seeking to (a) develop ecotoxicological expertise to identify toxicant pathways in the environment, (b) introduce water‐quality objectives for toxic substances which it can monitor effectively, and (c) improve standards for effluent control.
The Use of an Objective Index for the Assessment of the Contamination of Surface Water and Groundwater by Acid Mine Drainage
Authors: Gray N. F.
Published: July 2007

Temporal and spatial comparisons of acid mine‐drainage contaminated waters are difficult because of the complex physico‐chemical nature of the pollutant, and an objective index has been developed and evaluated for the assessment of such waters. The acid mine‐drainage index is calculated using a modified arithmetic weighted index utilizing seven parameters which are most indicative of acid mine‐drainage contamination, i.e. pH value, sulphate, iron, zinc, aluminium, copper and cadmium. Weighting is used to express the relative indicator value of each parameter. pH and sulphate are considered to be of greatest indicator value as they are unaffected by sorption processes, while sulphate is also unaffected by natural neutralization processes. The acid mine‐drainage index, as proposed, is designed to detect and quantify contamination from acid mine drainage, and to help categorize samples, quantify impact and to monitor the recovery of receiving waters.