| Treatment of wastewater necessarily involves the production of sludges irrespective of the treatment processes of systems selected. Increasingly stringent environmental quality objectives and reduced outlets for disposal of sludges have focused attention on the need to consider fully the options for sludge disposal prior to taking decisions regarding the location of wastewater treatment and sludge treatment works. Before wastewater treatment systems are selected, the options for sludge disposal, transport and treatment should be fully investigated. Options must incorporate the best available technology not entailing excessive costs given local conditions and privious experience which comply with environmental quality objectives and regulations. Requirements and development methods of sludge disposal strategies are discussed based on the experiences of the authors gained while assisting fifty percent of the UK Water Plc`s. The advances in wastewater process technologies described in the paper commence with the design and function of the sewerage system, including the need to avoid odour nuisance and excessive corrosion of the sewer fabric, together with the benefits of pre-treatment of wastewaters in the sewers. The paper includes a description of recent advances in processes used for grit separation, settlement of suspended solids, secondary treatment by biological filtration (including submerged aerated filters) and activated sludge and tertiary reed bed treatment, together with some new processes for sludge dewatering, treatment and destruction. In some cases, details of performance and costs are given together with advantages and disadvantages based on operational experience. |
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