Ozone Treatment of Sewage Works' Final Effluent

This paper describes a laboratory-based study which was designed to investigate (a) the changes in selected physico-chemical properties of a sewage-works' final effluent after ozonation, and (b) the effect of ozone on the concentration of organic halides and effluent toxicity and mutagenicity. Different conditions were studied involving the application of ozone concentrations up to 13.5% w/w and the ozonation of the effluent under both constant and variable ozonation rates.     

Comparison of RBC and SBR Systems for the Treatment of Sewage from Small Communities

This paper describes a study which was carried out to evaluate the performance of two types of small sewage-treatment plant which are commonly available in the UK, i.e. a rotating biological contactor and a sequencing batch reactor. Both systems produced an effluent quality of less than 20 mg/l BOD and 30 mg/l SS; however, the sequencing batch reactor was more consistent in producing a better effluent (i.e. BOD<10 mg/l and SS<20 mg/l) than the rotating biological contactor. The sequencing batch reactor also demonstrated a greater tendency to remove nutrients, although the special design features which were used in this study were believed to have enhanced the rate of nutrient removal     

Managing Water Services Through Service Differentiation and Pricing in an African City

A key challenge for managers of water utilities in developing countries is to provide services to the rising urban population in a financially sustainable manner. The paper examines the management of water services in an African city which piloted service differentiation and pricing. Among the key findings was that substantial improvement in the provision of water services to the urban poor was attained. Cost recovery was achieved through innovative structuring of public/private partnerships, an appropriate pricing policy, and flexible payment systems. The project demonstrates that (a) by structuring service delivery with appropriate pricing, utilities could serve more customers (including people living in informal settlements) at affordable cost and achieve financial sustainability, and (b) service differentiation and appropriate pricing has the potential to improve urban water services in low-income countries.     

Water-Recycling Technologies in the UK

Urban water recycling in the form of rain, grey or black water is becoming an important element of demand-management practice in the UK, and appropriate technology allows the use of three different water sources for similar applications. The level of pollution in the water source and the application to which it is being recycled, dictate the level of technology which is used. This paper describes current water re-use practices in the UK (in terms of water source, technology scale, type and efficiency) and examines five case studies. Of more than 150 schemes identified, most are rainwater-collection systems and these are generally sited in rural areas. There are various single-house greywater recycling sites, many of which are part of water company or Environment Agency monitoring programmes. Larger-scale schemes employ both natural and hi-tech treatment options. Operationally successful schemes utilise appropriate technology for the end-use, although the economic benefits of many of the schemes are poor.     

An Assessment of Water Demand Management Options from a Systems Approach

A systems approach is used to model the urban water and wastewater system. Scenarios are developed for the implementation of a range of water demand management measures, including (a) leakage reduction, (b) the increasing use of water metering, (c) the replacement of standard WCs by low-flow WCs, and (d) the introduction of greywater recycling systems. These measures are assessed according to the water saving, cost per unit of water saved, and other indicators of the relative contribution to the sustainability of the system. Preliminary assessments of selected environmental costs and benefits are also included.     

Considerations for Recycling Sewage Effluent in the UK

Technical, environmental, legislative and institutional considerations in relation to effluent re-use are described, with specific reference to experiences gained through the development of a scheme to augment Essex and Suffolk Water's Hanningfield reservoir with effluent from Chelmsford sewage-treatment works. Effluent standards are driven by a number of EU directives associated with protection of fisheries, recreational water quality, eutrophication and nitrate control for designated sensitive areas, and surface-water abstraction. The selection of the most appropriate strategy for re-use needs to consider public perception issues, in addition to technical feasibility and environmental concerns.     

WATER CONSERVATION AND ITS PERCEPTION IN PALESTINE: A CASE STUDY

This paper describes a pilot project, based upon a specific approach for encouraging effective water use in schools. The project included (a) constructing two low-cost sewage-treatment plants for irrigation water re-use in two schools, and (b) conducting an awareness campaign for effective water use in fifteen schools in the Jenin rural area. Data show that the campaign increased the pupils' knowledge of water and positively impacted on attitudes and practices.
Statistical analysis demonstrates that good knowledge and positive attitudes in students will result in improved effective water use. The schools with pilot sewage-treatment plants for irrigation water re-use benefited the most and encouraged students to modify their water-use practices.     

Laboratory Investigation into the Performance of an In-Sewer Vortex Flow Regulator

Aspects of the hydraulic performance of an in-sewer vortex regulator have been studied. These devices are increasingly used in stormwater management schemes, but their characteristics under a variety of prototypical situations have not been widely disseminated. The study used a full-size laboratory mockup of a section of sewer and associated manhole with facilities for measuring discharges of up to 60 1/s. The performance of a typical vortex flow regulator was investigated under both steady and unsteady flow conditions. The steady head-discharge relationship revealed the expected 'kick back'region (during rising head); however, this was less pronounced during falling head. Under unsteady conditions, vortex initiation was affected and a hysteresis effect was noted. The influence of downstream surcharge was significant at lower upstream heads. Theoretical comparison showed that to obtain equivalent performance, an orifice of 62% of the diameter of the vortex regulator would be required, and 25% savings in storage could be made.