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ABSTRACTThe 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.

ABSTRACTUtilization on agricultural land is the principal outlet for sewage sludge in the UK, accounting for about 40% of the annual production. During the last 30 years current practice has developed to maximize the benefits to farmers whilst controlling potential problems of public nuisance, water pollution, pathogen transmission and soil contamination. Until now this has been achieved by Government guidelines but, in future, utilization of sewage sludge in agriculture will have a statutory basis following the implemention of an EC Directive in June 1989.A copy of the discussion to this paper, and a copy of the full version of the proceedings of the Symposium, can be obtained from the Institution's Headquarters.

ABSTRACTStorm‐sewage overflows are one of the principal sources of urban river pollution in the UK. The paper (a) outlines the various possible pollutants and their effect on the receiving stream, and (b) identifies the features of individual overflow structures which are likely to lead to unsatisfactory performance. Since the rationalization and rehabilitation of storm‐sewage overflows should only be considered as part of a more general drainage area study, a strategy for rationalization is presented which identifies objectives for effective design and operation; it discusses, in particular, how chambers may be proportioned to give effective separation of visible pollutants. By combining field data with the results of model tests, a comparison of the performance of the main recommended types of overflow structure is given, together with a discussion of maintenance and safety aspects.

AbstractBrisbane City Council provides sewage‐treatment facilities for a population of 800 000, together with industrial effluents having an organic loading equivalent to a further 600 000 people. Three projects are described to illustrate some of the different designs and operating parameters used in Brisbane, where the sewage temperatures range from 18°C to 29°C and stormwater is collected separately. The first project is a 400 000 population equivalent augmentation to a conventional activated‐sludge plant located at Luggage Point. The two other plants have to comply, inter alia, with an effluent standard of 10 mg/l for total nitrogen. This requirement, together with site constraints and an economic evaluation of alternatives, resulted in the selection of the extended‐aeration process incorporating anoxic zones and separate mixing and aeration. These contemporary designs are specific to Brisbane conditions, and are intended to facilitate reliable operation as well as being cost effective.

Sewage Sludge Management for Environmental Sustainability: An Introduction -- Sewage Sludge Management: Analytical Methods -- Bioleaching Approach for Enhancing Sewage Sludge Dewaterability -- Potential Role of Beneficial Microbes for Sustainable Treatment of Sewage Sludge and Wastewater -- Biological and thermo-chemical treatment technologies for sustainable sludge management -- Emerging Nutrient Recovery Technologies in Sewage Sludge Management -- Biostabilization of Sewage Sludge -- Sewage Sludge Treatment and involvement of microbes -- Role of Beneficial Microbes in Sewage Sludge Management -- Sewage Sludge and Its Health Risk Assessment: Opportunities and Challenges -- Scope of Antibiotic Resistance Genes in Sewages Sludge for Therapeutic Uses -- Required Quality of Sewage Sludge as an Agricultural Soil Amendment -- Detoxification of Sewage Sludge by Natural Attenuation and Application as A Fertilizers -- Socio Economic Aspects of Sewage Sludge Use in Agriculture -- Sustainable use of sewage sludge in soil fertility and crop production -- Municipal Waste Management: Current Research and Future Challenges -- Management of Sewage Sludge for Environmental Sustainability -- Global Scenario of Sewage Sludge Management -- Biological and Thermo-Chemical Treatment Technologies for Sustainable Sludge Management.

AbstractThis study characterises the sewage sludge from 26 sewage treatment plants in India, which demonstrates the nutrient potential and highlights the associated challenges in using the sludge. The dry sludge had 2.35%–4.2% N, 2.46–3.2% phosphorus (P2O5) and 0.83%–1.24% potassium oxide (K2O), whereas sludge ash contains ~13.6% and 2.7%, P2O5 and K2O, respectively. Total nutrient potential from the sludge of the existing sewage treatment facility was 97.5 × 103 tonne/year, which is equivalent to 0.92% urea or 0.19% NPK used presently as conventional fertilisers in India. However, pre‐treatment may be required for this sludge before using it in agricultural fields as heavy metals, such as Zn, Cu, Ni, Cd, and Cr, were found higher than the compost standards. This study would be useful for the researchers and policymakers globally and would motivate them to make policies and deploy suitable technologies towards the nutrient utilisation from sewage sludge.

AbstractConsolidation is potentially the most cost‐effective of all sludge treatment processes. However, traditional design procedures have been oversimplified such that the process has not generally been fully exploited.The objective of this report is to summarize the Water Research Centre (WRc) procedure for sizing sewage sludge consolidation tanks, and explain the major design aspects which control the effective operation of the plant. The procedure provides a means of sizing tanks to consolidate any particular sewage sludge to any solids concentrations up to the maximum, and is applicable to both the batch and continuous operational modes. To obtain the predicted performance, the essential equipment such as the picket fence and control system, comprising a consolidation plant, must be suitably designed.

ABSTRACTThis 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.

ABSTRACTActivated SLUDGE SEWAGE treatment processes are often inadequate to comply with effluent criteria as promulgated in anti‐pollution legislation. Ozonation was studied as a means of improving nutrient removal activated sludge processes without the salinity and other disadvantages of the often used polyvalent metal salt addition. Direct ozonation into the aeration basin of a 150 I/d Phoredox (modified Bardenpho) system led to improved removal of organic substances. Nitrification was improved while phosphate removal was not adversely affected. Beneficial biological activity in the activated sludge was enhanced. The trihalomethane formation potential was reduced. Pollutional loads could be lessened, while an effluent with increased reuse potential was produced.