Isolation of a sulfate reducing bacterium and its application in sulfate removal from tannery wastewater

Abstract

In order to remove sulfate in tannery wastewater efficiently, a sulfate reducing bacterium (SRB) was isolated in tannery anaerobic activated sludge. With biochemical and genetics method, the isolated bacterium was identified as Citrobacter freundii. Then, the isolate was inoculated to tubes containing sulfate in simulated tannery wastewater to optimize the process. The results show that the effect of C. freundii in removing sulfate was best when the temperature was 32°C, pH was 7.0, COD/SO₄^2- was 5.0 and the initial SO₄^2- concentration was 1500 mg/L. Also, the SRB was inoculated onto an up-flow anaerobic sludge bed (UASB) to remove sulfate in actual tannery wastewater. It was found that the removal rate of sulfate in actual tannery wastewater reached 89.66% which was 12.13% higher than the treatment without inoculating the isolated SRB when the initial SO₄^2- concentration was 1069 mg/L. The experiment demonstrates that C. freundii could be selected as a new biomaterial to remove sulfate in tannery wastewater.

Key words: Tannery wastewater, sulfate, Citrobacter freundii.