OPTIMAL WASTE WATER SYSTEMS TORAGETANK VOLUME TO MEET RECEIVING WATER QUALITY STANDARDS

摘要

Urban wastewater systems (UWWS) consist of three main sub-systems: the urban drainage network, the wastewater treatment plant (WWTP) and the receiving water. Recent research has shown the potential benefits of considering the three systems as one entity when striving to achieve stringent water quality standards. This has become possible due to the better understanding of the systems and improvements in computer modelling of the integrated system. The particular benefit of modelling the integrated system is that the dynamic and multifaceted interactions between the individual sub-systems can be investigated and the impact of the whole system on the river water quality can be determined. Introducing storage tanks to temporarily store peak wastewater flows that would otherwise be spilled via an overflow is one measure that can be taken to reduce intermittent pollution discharge to the receiving water system. Storage tanks have conventionally been sized according to differing objectives, among which include retaining the initial 'first-foul-flush' of pollution [3], achieving a minimum dilution of overflow spill with river flow [4] and limiting the discharge of overflow spill. The use of hydraulic and hydrologic computer models has been shown to be a useful tool in determining the required storage tank volume. These models are used to determine the tank volume required to limit the volume/duration/ frequency of overflow discharge [7,8,9] and/or the total pollution impact of overflows.