Ecological and Comparative Performance Studies on High-rate Sewage Filter Media

Abstract

Used waters containing high concentrations of organic materials have proved difficult to treat to suitable standards for discharge to inland waters ,using conventional biological filtration, The use of two stage filtration has been shown to produce effluents of a higher standard than single stage filtration. This investigation was undertaken to determine the optimum conditions for two stage filtration where the primary stage employed various types of biological media designed to accept high organic loadings, Pilot and laboratory scale filters were designed and constructed to investigate the mechanisms of two stage filtration, The quality of effluents obtained from the pilot scale high-rate filters was examined and their effects on nitrification in laboratory scale secondary filters employing low organic loadings observed. The ecological maturation of the high-rate primary filters was monitored. The study indicated that under the loading conditions considered, the high-rate filter media developed biological films which could support carbonaceous oxidation in proportion to the media specific surface areas, Random packed media developed weights of biological film in proportion to their specific surface areas, Modular media supported significantly less film per wit of specific surface area. The dominant flora and fauna of high-rate filter films were identified, After two years of operation, -the filters had not fully matured, ‘ Suitable primary hizh-rate filter effluents could be obtained to permit full nitrification in laboratory scale nitrifying filters, Further studies are required to optimise the use of high-rate filtration,