Colour Removal in a Reservoir and the Dredging and Dewatering of the Deposited Waterworks Sludge

T he A lbert R eservoir of the Yorkshire Water Authority was built in the 1850s as the final raw water storage in the chain of impounding and storage reservoirs which feed Halifax, Brighouse, and Elland in West Yorkshire (Fig. 1).
This paper describes the problems encountered with increasing raw water colour since the mid1970s, the action taken to pretreat the water at the Albert reservoir prior to pressure filtration at the Thrum Hall Water Treatment Works (WTW), and the resulting problems with the deposited alum sludge in Albert reservoir.     

The East Kent Chalk Aquifer during the 1988-92 Drought

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.     

Burnley Sewage-Treatment Works: Design and Operation of a High-Rate Nitrifying Filter

The paper deals with the planning, construction, operation and performance of the purpose-built nitrifying filter from its commissioning in August 1986 to the present day. Burnley sewage-treatment works consists of inlet screens, Dorr detritors, primary sedimentation tanks, surface-aeration activated sludge units, and final settlement; sludge is digested and tankered to farmland.
The filter was designed and built following the closure of several local works and subsequent diversion of flows to Burnley. It was realized that the increased volume from the extended Burnley works would reduce the dilution of the effluent by the River Calder. This would result in a deterioration in the quality of the river. As a consequence an ammonia standard of 14 mg/l was imposed on the works following the completion of the nitrifying filter.     

Managing and Engineering Rivers for the Benefit of Man

F rom earliest times flood, famine and drought have been scourges of mankind. River engineers alleviate floods, drain the land for agriculture, and conserve water resources. They construct engineering works, guide planners and developers, and provide warnings to minimize damage caused by storms over catchments and coasts. As the country becomes more developed, problems of reconciling conflicting interests require a flexible approach. This paper examines ways of providing the basic services in a climate of increasing public clamour for wildlife and landscape protection, and recreation.     

Developments in the Thermal Drying of Sewage Sludge

The application of heat to dried sewage sludge has been practised by the water industry for many years. Early technologies were effective but their utilization of energy was not so efficient. Other industries have faced up to this problem and, as a result, have developed thermal-drying techniques which are more efficient and therefore more cost effective. In recent years, the transfer of this technology to sewage-sludge drying has been taking place, and some companies have designed dryers specifically for this purpose. Commercial and legal pressures have also focused attention on the final product and its use in agriculture, horticulture, land reclamation, landfill, incineration, and as a substitute for fuel.
This paper reviews the work which has been undertaken to determine the changes which occur as sewage sludge is dried, and discusses the technology which is available at present. Factors influencing capital and operating costs and product choice are also included.     

Satisfying the Water Supply Demand of the Channel Tunnel

When Europe's largest civil-engineering construction site, the Channel Tunnel, requested a guaranteed source of water during 1988, the Folkestone District Water Company was experiencing the first signs of the drought conditions which were to prevail for the next three years. Whilst infrastructure changes allowed for supplies to be made available to the Channel Tunnel contractors, the increasing reduction of resources meant that an alternative supply of water was required.
The solution to the problem was to utilize desalination by reverse osmosis of sea water taken from the English Channel. The process design and operation of this most arduous of feed water is discussed, demonstrating the successful application of this technology.     

The Development of a Sludge Disposal Strategy for the Hong Kong Territories

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.     

Practical Experience of Borehole Performance Evaluation

S evern -T rent W ater is engaged on a programme of operational reviews within the water supply function. Standardized borehole performance tests form an essential part of the data gathering exercise. For some, particularly the older and smaller borehole sources, these tests are providing the first ever reliable documentation on their operational characteristics. The tests, linked where appropriate with geophysical and closed-circuit television (CCTV) logging, are indicating where borehole operation could be improved and where rehabilitative measures are desirable. The tests also provide the basis of the cost-output relationships necessary for modelling of the water supply system. The paper describes the programme in more detail and illustrates by examples some of the beneficial results being achieved.     

The Procurement and Testing of Process Plant for the Water Industry

The paper describes contractual procedures necessary when performance guarantees are required for process plant. It shows how the Institution of Chemical Engineers Model Form of Conditions of Contract for Process Plants (Red Book) can be suitably modified to meet the needs of the water industry.
Particular attention is given to devising suitable testing regimes to meet the contract stages – construction, completion, take-over, and performance tests. The principles underlying the proposed testing procedures are stated.