Two stage biological treatment of domestic sewage

Abstract

In this study, the experimental results of an up-flow anaerobic sludge blanket (UASB) reactor operating over a period of 6 months at ambient temperature (14-28 degrees C) to treat low strength domestic sewage were given and the effect of the anaerobic pre-treatment on the nutrient removal and sludge production in a sequencing batch reactor (SBR) was evaluated. The removal efficiencies of the UASB and SBR system were 86% for COD, 100% for NH4-N and 60% for PO4-P. The main advantages of anaerobic pre-treatment were that the anaerobic pre-treatment enhanced both the nitrification rate and efficiency, and excess sludge was not produced in the system. On the other hand the UASB-SBR system could not efficiently remove phosphorus. Therefore the pre-acidification of raw domestic sewage can be suggested to enhance PO4-P removal and to stabilize the influent SS instead of the anaerobic pre-treatment stage.