Thames Water Research Articles

The Thames Water Ring Main: Mechanical and Electrical Installations

ABSTRACTAlong the route of the Thames Water ring main there are nine major unmanned pumping stations, in shafts, which lift the water from the tunnel and pump it into local distribution systems. Each shaft has the capacity to supply a town the size of Swindon with water, and has extensive mechanical and electrical installations ranging from large pumps to sensitive water‐quality and atmospheric monitoring systems.This paper outlines the principal features and scope of the mechanical and electrical installations in the shafts, including variable‐speed drives, pump control systems, gas‐monitoring and alarm systems, dehumidification plant, water‐quality monitoring systems, isolation and access arrangements.

Proceedings of CIWEM Symposium on ‘A Unique Approach to Metropolitan Water Supply ‐ The Thames Water Ring Main’

Water and Environment JournalVolume 9, Issue 4 p. 425-426 Proceedings of CIWEM Symposium on ‘A Unique Approach to Metropolitan Water Supply - The Thames Water Ring Main’ M. P. O'REILLY, M. P. O'REILLY (British Tunnelling Society)Search for more papers by this author M. P. O'REILLY, M. P. O'REILLY (British Tunnelling Society)Search for more papers by this author First published: August 1995 https://doi.org/10.1111/j.1747-6593.1995.tb00961.xAboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume9, Issue4August 1995Pages 425-426 RelatedInformation

Procurement of pumps via framework agreements

Thames's Water's Framework Agreements have set new standards in the partnership between pump supplier and a major utility. By considering the whole life cost of the pump both parties look likely to benefit from this initiative.

Construction of the Thames Water ring main — with particular regard to the technicalities of the surveying contribution : D. E. B. Jones & M. S. Sutton, Proceedings — ICE: Geotechnical Engineering, 113(1), 1995, pp 51–54

Construction of the Thames Water ring main — with particular regard to the technicalities of the surveying contribution : D. E. B. Jones & M. S. Sutton, Proceedings — ICE: Geotechnical Engineering, 113(1), 1995, pp 51–54

Counter-current dissolved air flotation/filtration

Thames Water Utilities has developed and patented a Counter-current dissolved air flotation/filtration (COCO-DAFF) process as a compact water treatment system designed to remove particulate material from traditional water sources. In particular it has been developed to overcome operational problems with primary filters caused by seasonal blooms of filter blocking algae such as Melosira sp., Aphanizomenon sp. andAnabaena sp. The process can be run without flotation during periods when algae are not a problem, giving operational cost savings. This process differs from co-current dissolved air flotation in that the recycle water is introduced after the inlet structure, but above the filter media. This generates an even depth bubble blanket in the flotation tank through which all the flocculated water must pass. The advantages are that in moving the recycle inlet away from the flocculated water inlet the potential for floc damage by the recycle is eliminated. Also since the entire sludge blanket is supported by a deep, even, bubble blanket, on de-sludging any fall-out of sludge that occurs near the de-sludging weirs will have to go back down through the process, leading to subsequent re-floating, and a reduced potential for spiking of the floated turbidity. Process validation experiments have been carried out on a 1.4 Ml/d pilot plant based at the Kempton Advanced Water Treatment Centre, London. These tests have identified a required flocculation time of 15 minutes prior to counter-current flotation, and insensitivity to the depth of the air injection below top water level. Dissolved air distribution is achieved using a special high volume flow rate DAF nozzle designed to lower the number of nozzles required per unit area, and to maximise the spread of the bubble cloud for optimum bubble/particle contact. Computational fluid dynamics (CFD) has been used in the scale-up of the pilot plant experience into the first full scale of this design plant to be built, by PWT Projects, at the 200 Ml/d Walton AWTW, for Thames Water Utilities.

Counter-current dissolved air flotation/filtration

Thames Water Utilities has developed and patented a Counter-current dissolved air flotation/filtration (COCO-DAFF) process as a compact water treatment system designed to remove particulate material from traditional water sources. In particular it has been developed to overcome operational problems with primary filters caused by seasonal blooms of filter blocking algae such as Melosira sp., Aphanizomenon sp. and Anabaena sp. The process can be run without flotation during periods when algae are not a problem, giving operational cost savings. This process differs from co-current dissolved air flotation in that the recycle water is introduced after the inlet structure, but above the filter media. This generates an even depth bubble blanket in the flotation tank through which all the flocculated water must pass. The advantages are that in moving the recycle inlet away from the flocculated water inlet the potential for floc damage by the recycle is eliminated. Also since the entire sludge blanket is supported by a deep, even, bubble blanket, on de-sludging any fall-out of sludge that occurs near the de-sludging weirs will have to go back down through the process, leading to subsequent re-floating, and a reduced potential for spiking of the floated turbidity. Process validation experiments have been carried out on a 1.4 Ml/d pilot plant based at the Kempton Advanced Water Treatment Centre, London. These tests have identified a required flocculation time of 15 minutes prior to counter-current flotation, and insensitivity to the depth of the air injection below top water level. Dissolved air distribution is achieved using a special high volume flow rate DAF nozzle designed to lower the number of nozzles required per unit area, and to maximise the spread of the bubble cloud for optimum bubble/particle contact. Computational fluid dynamics (CFD) has been used in the scale-up of the pilot plant experience into the first full scale of this design plant to be built, by PWT Projects, at the 200 Ml/d Walton AWTW, for Thames Water Utilities.

Enfield-Haringey artificial recharge scheme

Artificial recharge was carried out experimentally in north London by the Water Resources Board and the Metropolitan Water Board between 1953 and 1970(Boniface 1959). These trials were successful, although only small volumes of water were recharged. Research by Thames Water Authority continued between 1975 and 1984 at a larger scale in the north London area (Flavin & Hawnt 1979; Flavin & Joseph 1983). Thames Water Utilities drilled and tested 14 new production boreholes for the Enfield-Haringey Scheme along the course of the New River in north London (Fig. l, opposite). These new boreholes, together with nine existing sites, are designed to increase the strategic groundwater resources of north London by 90 Ml/d by artificially recharging the Chalk and Thanet Sands aquifer beneath London (O'Shea 1994). During an average year, demand for water is often lower than that available from the Coppermills Water Treatment Works and between 10 and 20 M1/d of this excess fully treated water can be gravity recharged to the aquifer. This will be by low-rate, trickle recharge ensuring that the volume of water stored in the aquifer is sufficient to sustain a prolonged drought abstraction for up to 200 days. When demand for water is high, as in drought conditions, groundwater can be pumped from the aquifer, using the same boreholes, directly into the New River which acts as an aqueduct taking the water back to Coppermills, via the East Reservoir at Stoke Newington for treatment and supply. The scheme will be used strategically in times of

Water treatment for public supply in the 1990's — A role for membrane technology?

Higher water quality standards and water treatment guidelines are being implemented worldwide. Conventional water treatment cannot secure compliance with all of the new standards. The use of “advanced water treatment” options, including ozonation and granular activated carbon stages, improve water quality but add considerably to complexity of operation and to costs. Disinfection by chemical inactivation is also under examination from new standards on by-products, customer complaints of chlorine tastes and its inability to be fully effective against all waterborne pathogens. Membrane technology potentially offers the water industry a simple one or two step treatment barrier to overcome all these difficulties leading to a safe, aesthetically pleasing water without chemical use. First time, treatment, with optional organics removal for small community water supplies is potentially the most economic and rapidly growing application of membrane technology in the immediate future. One example is the successful introduction of nanofiltration for the Lochgair community public water supply in Scotland during 1992. This is a research and technology demonstration project jointly funded by Strathclyde Water, PWT Worldwide and Thames Water Utilities.

Converging implementation strategies in commercial TQM initiatives: implications for the NHS.

Reports on progress in the implementation of quality improvement initiatives, which was tracked over three years at Post Office Counters and Thames Water Utilities as part of a wider evaluation of Total Quality Management (TQM) pilot projects in the NHS. Although the two companies chose very different approaches to quality improvement, tracking shows that there has been progressive convergence over the period of the research. The results suggest that in spite of major differences in cultures, structures, processes and customer bases, all organizations may, in the end, have to implement similar changes to secure continuous improvement within a TQM framework. This has implications for implementing TQM in the National Health Service.

Automatic Monitoring of Activated Sludge Settling Characteristics and Plant Control Applications

AbstractA 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.

Rising groundwater levels beneath London – an update

Follows a previous article (Structural Survey 6.3) in tracing rises in groundwater levels beneath London between 1985 and 1990, drawing particularly on a 1989 report published by the Construction Industry Research and Information Association. Points out that although no damage has been (at the time of writing) recorded in London due to rising groundwater levels, heavy expenditure has been incurred in designing contingency measures into new buildings (cites St Pancras Station, the Aldersgate Underground car park and the new British Library). Concludes that the National Rivers Authority and the Thames Water Company must address groundwater rises under London in a “careful and controlled way”.

DESIGN, INSTALLATION AND POST‐IMPLEMENTATION ASSESSMENT OF AN OPTICAL DISC BASED STORAGE AND RETRIEVAL SYSTEM FOR IMAGES OF ENGINEERING CONTRACT DOCUMENTS

A large‐scale image storage system for project records and other contract documentation has been installed in the Engineering Directorate of Thames Water Utilities. The system uses optical disc storage and a relational database for indexing and retrieval of nearly 500,000 pages in compressed image format, and provides end‐user access through seven work‐stations. It has met its design objectives in protection of vital records of engineering projects, fast access to large volumes of project files, and cost savings, mainly through reduced storage space. The REOS installation was intended both as a working system and as a pilot project to gain experience with optical disc storage technology in a technical environment. Areas where the project met real difficulties, underestimated in the feasibility study, were in physical handling and document indexing during retrospective conversion, the amount of training required for staff operating the system and the development of adequate validation processes for data entry to the INFORMIX database. The system delivers good images and is reliable, and has been relocated twice during the life of the installation without difficulty.

Thames Water's Experiences with Cryptosporidium

In February 1989 an outbreak of waterborne cryptosporidiosis associated with contaminated surface water in the upper Thames catchment was identified. Less than 0.01% of the population suffered symptoms sufficient for them to seek medical advice. Nevertheless, the impact of the outbreak on the community and the water undertakers was considerable, and an expert committee was appointed by the Secretary of State for Health to advise on research and measures to control the disease and prevent future waterborne outbreaks. One of the committee's interim recommendations was for the gathering of information on the occurrence of cryptosporidium oocysts in the aquatic environment particularly sources used for abstraction and production of drinking water. The results of monitoring in the River Thames catchment will be discussed particularly in light of observations that peak contamination events occur in rivers which pass through agricultural land but do not receive discharges from sewage treatment works.

Recent Developments in Oxygenation of the Tidal Thames

ABSTRACTIncreased polluting loads are discharged to the tidal Thames at times of heavy rainfall. This can lead to a rapid decline in dissolved‐oxygen (DO) concentrations, which, on occasions, has resulted in fish mortality. The problem is caused by the cumulative effect of surface runoff, increased flows from sewage‐treatment works, and storm‐sewage discharges from the combined drainage of Inner London.An experimental system of in‐river oxygenation has been operated by Thames Water in order to alleviate the problem. This scheme demonstrated that the river oxygenation concept is viable. There was, however, a need to increase the operating reliability of the plant and to provide extra oxygenation capacity. Thames Water carried out a detailed investigation into the various options prior to the acquisition of a new, purpose‐built, self‐propelled, oxygenation vessel, which was delivered to the River Thames in October 1988.

Raising the Standard of Operation of Small Sewage Works

Thames Water operates about 400 sewage works in the catchment area of the River Thames, over half of these serve populations of less than 2000. These small works are mainly biological filter works but also include oxidation ditches and reed beds. Most of these works discharge to the headwaters of salmonid rivers which are used as drinking water sources and therefore have to meet high standards including in many cases full nitrification and low suspended solids. The paper describes the consent standards set for the works. Currently a number of small works do not meet these standards so Thames Water has committed itself to having all works operating within standards by 1992. There are a number of reasons for failure which include, overloading due to increase in population and water use, trade effluent discharges, and operational problems. Small works may also fail to meet their standards because they are unmanned apart from infrequent maintenance visits, and thus any plant failure may go unnoticed for some days. Thames Water is adopting a two fold strategy to overcome these problems. Firstly, so that operational problems may be identified quickly a simple cost effective system of automation and telemetry is being installed and secondly, to overcome operational and facility deficiencies, a Project Management team has been set up to identify the causes of failure, to prioritise remedial work, to recommend alternative operational strategies, if appropriate, to design and build extensions or new works if appropriate, and, if remedial works cannot be built quickly enough, to install temporary plant to ensure compliance with effluent standards.

Instrument Triplication in Sewage Treatment

One of the main problems with the introduction of automation is the poor performance of same instrumentation. One possible way of improving this situation is through triplication of the instruments (that is the use of triple active redundancy). This approach should give improvements in data availability, accuracy and help identify instrument faults. Reliability theory may be used to show that gains in availability of up to 10% are possible, but if the basic instrument availability is less than 50%, then triplication will actually decrease the overall availability. The dissolved oxygen instruments at Witney STW (Thames Water) have been triplicated. Individual instruments were found to have an availability of 90% giving a theoretical triple availability of 97%. The overall availability measured was only 92%, mainly because the failures were not always random and independent. Uncertainty in the data was reduced by 40% because of the effect of averaging but drift detection was not as successful as hoped due to the presence of significant short term jitter in the DO readings. The cost of triplication can be significant in both extra hardware and extra maintenance. In the light of these points some comparisons are made with other methods of improving reliability.

The Application of ICA in Sewage Treatment – Witney Evaluation and Demonstration Facility (EDF)

The Witney Sewage Treatment Works of Thames Water has been established as the Evaluation and Demonstration Facility (EDF) for instrumentation, control and automation (ICA) in sewage treatment. The objectives of the process related EDF programme have included demonstration of the viability of computer-based process management systems, the investigation of the interactions of processes and the development of methods for their optimisation. Evaluation of process monitoring instrumentation has demonstrated that whilst severe shortcomings still exist in some areas reliable process automation can be achieved. Successful routine operation of the Witney plant has been maintained by the automatic control system and a detailed assessment of the main control functions has shown benefits which include cost savings, more accurate control and early warning of equipment failure. Progress has also been made in the modelling both of process performance and of operating costs. This work will lead to the development of software tools to aid process management and to enable process optimisation.

Taming a River with New Technology

AbstractIn response to the requirement of the Thames Water Authority for improved efficiency on all aspects of river management in general, and the New River in particular, commitment was given to look into reducing the overall unit cost and at the same time showing an improvement in effectiveness (levels of service).This paper shows how traditional methods of maintaining a river of this type and magnitude, with due consideration to its environments and physical constraints, can be revolutionized and brought into the 20th century by adopting the latest technology. In addition, and after executing a re‐appraisal of the New River activities, quite radical changes to the existing working practices together with a change in the general attitude of the individual employees were successfully implemented.

The conservation value of water supply reservoirs

AbstractThere are over 500 water supply reservoirs in England and Wales, a total water surface of 20000 hectares, much of which has been flooded this century. Waterfowl, amphibious and aquatic wildlife have all benefited from this change, especially important after so much wetland has been drained and ploughed to increase agricultural production. Modern reservoirs include landscape and conservation in their planning, construction and operation, often leading to their notification as Sites of Special Scientific Interest soon after their construction. Examples in the Anglian Water and Thames Water regions are discussed to demonstrate their value to wildlife as well as fulfilling their prime function for water supply. Pitsford Water (Northamptonshire), Rutland Water (Leicestershire), Staines Reservoirs (Surrey), and Walthamstow Reservoirs (Greater London) show varying levels of conservation planning. Protection from recreational activity is shown to be an essential part of management at these sites.

The concentrations and fate of linear alkylbenzene sulphonate in sludge amended soils

A programme of monitoring work to determine the fate of linear alkylbenzene sulphonates (LAS) in sludge amended soil is described. The concentration of LAS in soils are given for a large number of locations (24 farms and 51 fields) in the Thames Water Authority (TWA), U.K. The sites selected provide a range of soil types, frequency and concentration of sludge applications and agricultural uses (pasture/arable). In addition, the disappearance of LAS from soil with time is shown at three selected sites following different sludge application practices. A solid phase extraction-HPLC method, employing a Soxhlet extraction technique to recover LAS from soil matrices, is described for these determinations which gave an average recovery of LAS (2–15 μgg − spikes) of 97%. In fields (42) not recently spread with sludge (prior to 1987) the concentrations of LAS found in the sludge amended soil are generally less than 1 p g LAS/g soil. When this data is compared with the estimated total cumulative load based on known sludge applications the majority of the sites show losses of LAS > 98%. In fields (9) recently spread (during 1987) the concentrations of LAS in soil are in the range <0.2–20 Mg g −1 representing losses of LAS between 70 and 99% of the estimated total cumulative load. The time course studies confirm the rapid removal of LAS from sludge amended soils at three locations (5 fields) and for three different methods of application. The calculated half-lives for LAS in soil range from 7 to 22 days and agree with laboratory test results and other monitoring studies. The homologue distributions determined for LAS in soil suggest that microbial breakdown rather than leaching is the prime mechanism for its removal. Overall, the data indicate that an adequate safety margin exists between the concentrations of LAS in sludge amended soils and those likely to affect the growth of crop plants.