Microbial activity and community structure in a lake sediment used for psychrophilic anaerobic wastewater treatment.

AIMS: The aim of the study was to investigate the feasibility of a continuous reactor for psychrophilic anaerobic wastewater treatment by using the sludge from cold natural environment.

METHODS AND RESULTS: Six sludge samples (S1-S6) were collected from different cold natural locations to select sludge with high anaerobic microbial activity under low temperatures. After a 225-day incubation, the maximum specific methane production rate of a waterfowl lake sediment (S1) at 15°C (70·5mLCH(4) gVSS(-1) day(-1)) was much higher than all other samples. S1 was thus chosen as the seed sludge for the reactor treating synthetic brewery wastewater at 15°C, by immobilizing the micro-organisms on polyurethane foam carriers. The chemical oxygen demand (COD) removal efficiency reached over 80% after 240-day operation at an organic loading rate of 5·3kg m(-3) day(-1), and significant enrichment of biomass was observed. Clone libraries of the microbial communities in the inoculum had high diversities for both archaea and bacteria. Along with a decrease in microbial community diversities, the dominant bacteria (79·5%) at the end of the operation represented the phylum Firmicutes, while the dominant archaeon (41·5%) showed a similarity of 98% with the psychrotolerant methanogen Methanosarcina lacustris.

CONCLUSIONS: The possibility of using anaerobic micro-organisms from cold environments in anaerobic wastewater treatment under psychrophilic conditions is supported by these findings.

SIGNIFICANCE AND IMPACT OF THE STUDY: This study enriches the theory on microbial community and the application on anaerobic treatment of sludge from cold natural environments.