Anaerobic digestion of wastewater and municipal sludge to isolate potent methanogen using BMP assay

Abstract

Municipal sludge production is the inevitable residue generated in enormous amounts by the wastewater treatment plants. Sludge treatments at lower handling costs are the requisites to combat the growing population, rising production of municipal sludge and increasing energy demands. Anaerobic digestion of municipal sludge ranks to be an excellent treatment in view of sludge utilization and biogas production. Numerous researches have been conducted till date to enhance the anaerobic digestion processes of sludge and to upgrade the biogas production. Applications of microbial additives are the most promising technology among the various biogas production enhancement technologies. In the present study, isolation of potent methanogens was carried out from the lab scale reactor containing anaerobically digested municipal sludge. The raw wastewater and municipal sludge (9:1) mixture was anaerobically digested after the inoculation of pure bacterial isolates to screen the potent methanogen through simple and reliable Biochemical Methane Potential (BMP) assays for a period of 45 days. Amongst the nine isolates (DWH1, DWH2, DWH3, DWH4, DWH5, DWH6, DWH7, DWH8 and DWH9), one isolate (DWH9) showed interesting results by producing maximum cumulative biogas (3.64 l kg−1 VS). Molecular characterization of the potent methanogen was carried out and the phylogeny was confirmed by the 16S rDNA sequence, the isolate was confirmed to be Methanobacterium sp. AS1.