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

Abstract

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. 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. The possibility of using anaerobic micro-organisms from cold environments in anaerobic wastewater treatment under psychrophilic conditions is supported by these findings. This study enriches the theory on microbial community and the application on anaerobic treatment of sludge from cold natural environments.