Effect of food to microorganism ratio on biological treatment of textile liquid waste

Abstract

Untreated or poorly treated effluent from textile industries is severely polluting the water courses of Bangladesh. Regular operation of well design effluent treatment plant is necessary to reduce the pollution problem of Bangladesh. Lack of information on treatment efficiencies of different treatment options causes hindrance for the designers to select appropriate treatment units. This study represents an attempt to evaluate the efficiencies of Food to Microorganism ratio (F/M) on biological treatment and find out the effective FIM ratio. The study also tried to identifY simple and cost effective approach to stabilize the biological treatment method. Three approaches have been carried out for biological treatment of textile liquid waste by Aerated lagoon process. BOD, COD, TDS, TSS, colour and turbidity was taken as a indicators in the assessment of treatment efficiencies of different treatment approaches. From this approaches it was observed that pH 6 is effective for biological treatment by aerated lagoon. It was found that treatment efficiency decrease with increasing F/M ratio. The cell yield was found maximum at F/M ratio 0.48. Lower cell yield were found for higer F/M loading. The Settling performance was high since for all cases SVI value was found < 80. A comparative study between conventional activated sludge process and aerated lagoon process was carried out. The study focused in the area requirement, treatment efficiencies and operational cost aspects of those two processes. In this study BOD removal efficiency was found higher than existing ETP at Savar dyeing. But COD removal efficiency observed 7.9% lower than Existing ETP.The study result showed that Aerated Lagoon treatment is economical than full scale ETP of Savar dyeing where land cost is insignificant.