The role of the biofilm in aerobic biological filtration

Abstract

A small hybrid system for municipal wastewater treatment consisting of a jet mixed separator (JMS) used in a precoagulation/sedimentation process and an aerobic moving bed biofilter (MBB) used in a postbiological oxidation process was developed. The MBB is a type of downflow packed bed aerobic biofilter. It has an airlift mechanism, which refreshes the filter medium during its transport from the bottom to the top of filter bed and thereby prevents clogging of the medium. A majority of influent organic particles in the MBB adsorbed onto the biofilm, and the effluent BOD and SS concentration after 1 h of hydraulic retention time were < 20 and ~ 0 mg/L, respectively. The MBB could be continuously operated without removal of excess sludge. This paper describes the mechanism of biological oxidation in the MBB as deduced by measurements of the oxygen uptake rate of the biofilm attached to the anthracite medium in the MBB.