Enhancement of a waste stabilisation pond system in Namibia -Effects of pre-treatment to the effluent quality

摘要

Waste stabilisation ponds are a common waste water treatment option especially for towns in arid and semi-arid regions. They present a cost-effective treatment with regard to construction, maintenance and energy consumption. Conventional pond systems consist of an anaerobic pond followed by a facultative pond and several maturation ponds. However, due to fast population growth in those areas, existing waste stabilisation ponds are often overloaded and effluents are exceeding the required standards. Thus, enlargements or upgrades that improve the water quality and enable water reuse are the means of choice, because water is scarce in many African communities and reclaimed water with still a certain nutrient level presents a valuable resource for local irrigation. To increase the capacity of an existing system mechanical and anaerobic pre-treatment can be installed to reduce input of solids and COD (chemical oxygen demand) into the ponds. This decreases sludge accumulation and methane emissions and can be achieved with the installation of UASB (upstream anaerobic sludge blanket) reactors or micro screens.