Lai, Patrick Chuen-chi (1994) An ecological study of waste stabilization ponds in Werribee, Australia, with special reference to nutrient and plankton dynamics. Research Master thesis, Victoria University of Technology.

Abstract

Werribee Treatment Complex has been regarded as a waste treatment facility which is both environmentally friendly and economically sustainable. In the treatment processes, recycling of resources is maximized while energy input is minimized. Moreover, through livestock production in the land and grass filtration areas, as much as 20% of the total operation cost of the complex is recovered. However, in terms of the volume of waste water treated per unit area, grass and land filtration are considered to be less efficient than stabilization ponds. It has been proposed that those areas currently used for land and grass filtration should be converted to stabilization ponds in order to increase the overall efficiency of the complex to meet the augmented sewage loading of the increasing population in Melboume (Lane and Peake, 1990). Clearly, more information on the operational principles and treatment efficiency of the waste stabilization ponds at the Werribee Treatment Complex is needed to allow an informed decision to be made. This study examined a waste stabilization pond series at the Werribee Treatment Complex. The nutrient dynamics and the prevailing ecological processes in the ponds were investigated. The findings showed that the quality of the effluent was largely controlled by the detention time of the system (cf Meron et al, 1965). In particular, prolonged detention would result in a significant increase in phytoplankton abundance which is a key-component in the treatment process. The algae not only stabilize the nutrients through direct uptake, they also produce oxygen via photosynthesis, facilitating aerobic degradation and nitrification by aerobic and nitrifying bacteria respectively. In the pond series at Werribee, ammonia in the raw sewage was completely removed through nitrification as well as algal cell uptake during periods of longest detention time. On the other hand, removal of phosphorus was insignificant throughout the study period. According to Gakstatter et al (1978), water bodies receiving effluent from waste water treatment facility such as Port Phillip Bay are usually nitrogen-limited for algal growth. Therefore, the control the nitrogen content in the effluent should be of greater concern than phosphorus.

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