Bioaugmentation of activated sludge with the immobilized 2-mercaptobenzothiazole-degrading bacterial consortium for rubber industrial wastewater treatment

Abstract

Effluent from the rubber industry contains 2-mercaptobenzothiazole (2-MBT) as the major persistent pollutant. To remove 2-MBT, this study investigated the bioaugmentation of activated sludge with a 2-MBT-degrading bacterial consortium, which was previously enriched from rubber wastewater sludge. The consortium was immobilized in a commercial porous carrier to increase its efficiency and stability. The 16S rRNA gene analysis showed that the dominant Pseudomonas spp. and Stenotrophomonas spp. were maintained when it was repeatedly used for 4 cycles in a minimal medium containing 300 mg L−1 2-MBT. For bioaugmentation, a stirred tank reactor containing the immobilized consortium and activated sludge at a 1:2 mass ratio was constructed and found to remove 88.2 % of 100 mg L−1 2-MBT from synthetic wastewater. When the rubber industrial wastewater was applied at an organic loading rate (OLR) range of 1.0–3.0 kg COD m−3 d−1, the bioaugmentation reactor had 2-MBT and COD removal efficiencies of 70–79 % and 83–96 %, respectively. The reactors with either immobilized consortium or activated sludge alone had lower treatment efficiency. The bacterial community and its predicted functions corresponded to the activity of the added consortium and the operation of the reactor. Consequently, bioaugmentation should be applied to activated sludge for the treatment of rubber wastewater.