Analysis of the Control and Performance of Algal-Wastewater Stabilization Ponds.

摘要

There has been considerable interest in recent years in controlling the thermal condition of shallow water bodies used to effect beneficial biological conversion processes. Waste heat from a power production process may be used as the energy source for this control,and specific applications include wastewater treatment and algal production. In this study mathematical models were developed to assess means of maintaining thermal control and assessing the impact on wastewater treatment and algal production. The thermal response and control of a shallow pond which uses waste heat in a closed cycle cooling system was considered. Calculations suggested a heat exchanger design involving a network of 30m long, 25mm OD pipes on 0.15m centers. The design provides a reasonable compromise between initial costs and performance and enables maintaining near-optimum pond temperatures throughout the year for climatic conditions typical of the midwest. Calculations based on a model of a completely mixed activated sludge wastewater treatment system revealed the benefits to be derived from operation at elevated temperatures. Effluent quality is improved for any increase in temperature from 10to 30 C. Calculations based on a model of algal growth at optimum temperatures predicted daily yields which are in agreement with maximum yields which have either been measured or inferred from field studies.