COMPUTER AIDED DESIGN OF SINGLE STAGE ACTIVATED SLUDGE PROCESS

Abstract

Activated sludge process (ASP) is a widely used aerobic:' waste water treatment process. However, the design of activated sludge process is quite complicated as the designer has the choice to select several combinations of design variables. In the present study, a softwater package has been developed to enable the designer to choose among various alternatives. The software has been developed by rational approach of design of component units of ASP viz. the reactor, secondary classifier and sludge recycle. Cost of anaerobic digester of excess sludge produced has also been considered. The reactor design is based on microbial kinetic concepts and continuous culture of microorganism theory. Proper considerations have been shown to temperature variation effect on kinetic coefficients, neutralization and nutrients requirements. Biomass concentration in the aeration tank and return sludge are utilized as the primary independent design variables. Secondary settling tank has been designed on solid flux theory and acceptable overflow rate. The problem has been formulated as the capital and operating cost subject to the constraints by effluent quantity criteria and process variables affectin&' the performance. Following the software, the results suggest that the unit cost increases linearly with increase in either influent BOD or efficiency, whereas it decreases sharply with increase in waste water flow.