REMOVAL OF N, P, AND COLIFORM BACTERIA IN A SINGLE SLUDGE ANOXIC-AEROBIC BIOLOGICAL PROCESS FOLLOWED BY SLOW SAND FILTER

Abstract

The investigation reported in this paper is a part of an ongoing research aimed at finding simplified wastewater treatment operations which can produce acceptable effluent quality with less cost and using processes less demanding for operating skills. A single sludge two stage anoxicaerobic biological process followed by slow sand filter was operated in the laboratory with direct feed to the anoxic zone of municipal raw wastewater. Two sizes of filter media and 3 filter bed depths were investigated. Performance evaluation of the biological process, the slow and filter, and overall system for removal of N, P, and Coliform bacteria is presented in this paper. The biological process investigated produced moderate total nitrogen and phosphorous removals, but was found highly effective for reduction of total and fecal coliform bacteria. Average removals were: total N(52 58%), total P(17-32%), total coliform (98.8%), and fecal coliform (99.4%). The slow sand filter was not effective in improving nitrogen removal, but slightly improved phosphorous removal and proved highly effective for bacteria removal. No important differences were observed in performance of the coarse and fine filter media and among the investigated filter bed depths.