Author(s): R. M. Ashley; R. Sakrabani; T. Hvitvedjacobsen; J. Vollertsen
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Keywords: Biodegradability; Combined sewer overflows; Oxygen demand; Settling velocitysewer solids
Abstract: Much of the pollution of watercourses in urban areas originates from combined sewer systems, from which overflows relieve the highest flows. Discharges convey dissolved pollutants and solids that range from those that degrade readily to those more difficult to degrade. Studies in Denmark in the late 1970s defined the criteria for dissolved oxygen in streams affected by wet weather discharges from combined sewers and these criteria are now incorporated into the UK standards, and are utilised across Europe. These standards do not now include the latest advances in knowledge about the nature of the sewer solids being discharged from CSOs. It is clear that impacts are affected by the relative biodegradability (oxygen demand) and the behaviour of the solids being discharged; their settling characteristics, organic content and hydrolisation rates. This paper illustrates some recent results studying the biodegradability of solids in sewers and the potential for impacting on receiving waters and demonstrates a possible new approach to standards.
Year: 2003