Influence of chromium and powdered activated carbon (PAC) on activated sludge microorganisms and sequencing batch reactor treatment process

Abstract

One of the possibilities of using activated carbon in wastewater treatment is the direct addition of powdered activated carbon (PAC) to an activated sludge system, thus combining adsorption and biodegradation. The aim of this study is to investigate the effects of Cr(III) and the efficacy of PAC in reducing the inhibitory effects of Cr(III) on activated sludge microorganisms under sequencing batch reactor (SBR)operation. The addition of Cr(III) into SBR system caused significant inhibitory effects on the activity of activated sludge microorganisms as shown in the drastically dropped in specific oxygen uptake rate (SOUR). The increase of Cr(III)concentration from 5 to 10 mg/l had further deteriorated the treatment performance of SBR system in terms of the total organic carbon (TOC), suspended solids (SS) and Cr(III) removal efficiencies. In the case of 0.5 g PAC/cycle addition into the SBR reactor, the TOC and Cr(III) removal efficiencies were improved from 88 to 94 % and 82 to 90 %, respectively. Coupled with the increasing mixed liquor biomass suspended solids concentration after PAC addition, the biomass apparently played the key role in the uptake of Cr(III) and kept the effluent Cr(III) concentration low.