The Effect of Ozonation on Particle Removal in Drinking-Water Treatment

The effect of the introduction of additional process stages in a surface-water treatment plant was studied in order to investigate how particle removal could be optimized. Particle counting is considered to be a useful indicator of treatment performance. This paper is based on results which were obtained from trials on a water-treatment plant treating surface water; these consisted of a combination of modifications to existing full-scale plant and a specially constructed pilot plant.     

The Impact of Electricity at Work Regulations on the Operation of a Water Company

Since 1 April 1990, the Electricity at Work Regulations 1989 have placed legal requirements on employers, employees and the self-employed to take precautions against the risk of death or injury from electricity in work activities. This paper (a) examines the requirements, (b) reports on an initiative by the Lee Valley Water Company, and (c) proposes a management strategy for an organization to comply with the legislation.     

Developments in Health-Related Quality Standards for Chemicals in Drinking Water

Small differences in water quality standards can mean huge differences in costs for water treatment; difficulties which are compounded by standards for which the derivation is unclear, such as the EC drinking water Directive. Such situations give no indication of the margin of safety for a parameter or the significance to consumers of exceedances. The WHO Guidelines are being revised and will be presented so that the precise derivation of the numbers is absolutely clear. The scientific and quasi-scientific considerations can be separated and the user given the appropriate information to adapt the guidelines to particular circumstances. In deriving standards for toxicological data the factors incorporated reflect uncertainties in the data and extrapolation from animals to man. Understanding the mechanisms of toxicity or carcinogenicity can reduce the uncertainty and improve the quality of the standard, often allowing higher figures to be used with confidence that public health will not be comprised.     

Faecal-Indicator Budgets for Recreational Coastal Waters: A Catchment Approach

This paper explores the application of a catchment faecal-indicator budget approach to the examination of faecal-indicator sources impacting on coastal recreational water quality. This involves (i) the characterization of water quality in sewage effluent and riverine inputs, and (ii) measurement and estimation of input flows; the product of these components yields the input flux of indicator organisms from each source. The impact of sewage-treatment scenarios on budgets is also investigated.     

Post-Construction Effects of the Cameroonian Lagdo Dam on the River Benue

This paper examines the immediate and long-term effects of the Lagdo dam on the Upper Benue river basin in Nigeria. From routine monitoring of the River Benue, it was found that some immediate deleterious effects were (a) siltation of the river bed and channel, (b) frequent flooding events, and (c) reduction in flow. Consequently, these factors have constrained irrigation, navigation and fishing activities which were formerly undertaken along the river. Similarly, water-supply intake structures and irrigation abstraction facilities along the river have either been silted up or threatened. Allowing for assumptions on a real-time operational schedule of the dam, coupled with future water demands in north Cameroon, longterm effects of the dam on the Benue basin within Nigeria are predicted.     

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.     

Thermal Drying of Sewage Sludge

Over the next decade the UK will experience significant, imposed changes in the quantity of sewage sludge produced and in the means available for its disposal. Existing practices are being reappraised and new technologies are being explored to cope with a predicted 40% increase in the quantity for disposal. Thermal drying of sludge undoubtedly has a role to play in coping with this demand.
The two principal process types, i.e. direct and indirect heat application, are appraised in depth and a comparison is drawn. A case study is identified to examine the energy demands of the process, including the potential for heat recovery and for resource reuse. The environmental impact of a typical process is also examined.     

Maintaining Groundwater Supplies during Drought Conditions in the Brighton Area

The very low level of recharge to the chalk of the South Downs, which provide Brighton with its water supply, has meant that the groundwater levels are very low. Despite this, no restrictions have been necessary since February 1991. This is perhaps due to the instigation of public information campaigns, together with media coverage of the drought, as well as a successful programme of leakage control. This paper looks at how the growth of public water supply has been accommodated operationally while ensuring that groundwater quality is maintained. Options for the future expansion of supply, and their cost-effectiveness, are also considered.     

Surface-Water Abstraction Controls in Scotland

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.     

Characterization and Treatment of Leachates from Hong Kong Landfill Sites

Development of a large landfill site in the North-Eastern New Territories of Hong Kong, which will receive 25 million m³ of wastes during a life of about 13 years, must include the provision of a scheme to manage leachates which will arise in the tropical climate of the region.
The paper presents detailed results from a study commissioned by the Environmental Protection Department of the Hong Kong Government, to characterize and treat leachates generated by landfills in Hong Kong, in order to design a suitable management scheme. Field and laboratory trials which were carried out during 1989 showed that, although leachates from Hong Kong landfills have some specific characteristics (e.g. concentrations of amm.N to 5000 mg/l), they can be treated to high standards by aerobic biological processes.
As a result of these studies, a scheme has been designed which will provide a high degree of environmental protection in respect of leachate, as the landfill is developed.