Comparative study of the performance of an anaerobic rotating biological contactor and its potential to enrich hydrogenotrophic methanogens

Abstract

BACKGROUND: Process upset due to volatile fatty acid accumulation is one of the major drawbacks of anaerobic treatment of wastewater. The performance of an anaerobic rotating biological contactor (AnRBC) was studied under normal operating conditions as well as shock loadings of propionic acid, for its ability to enhance the conversion of hydrogen to methane. These results were compared with those of a reactor lacking the enhanced gas-liquid hydrogen transfer mechanism, a conventional anaerobic digester. RESULT: The AnRBC exhibited lower concentrations of hydrogen in the headspace (300-600 ppm) under both normal and shock loading conditions, and also showed more hydrogenotrophic methanogens on the denaturing gradient gel electrophoresis (DGGE) profile of 16S rRNA gene amplicons, both in terms of intensity and band numbers (4 in the AnRBC and 2 in the anaerobic digester). CONCLUSION: This study showed that the AnRBC is able to maintain lower hydrogen partial pressure at both normal operating and shock loading conditions due to the abundance of hydrogenotrophic methanogens and good gas-liquid hydrogen transfer efficiency. This finding should encourage the commercial exploitation of AnRBC for the treatment of wastewaters, especially that containing easily acidifiable organic compounds, which causes instability in operation through souring.