Field assessment of full-scale solar-powered floating biofilm reactors for improving water quality in a micro-polluted river near Lake Taihu

Abstract

Small rivers in rural areas near Lake Taihu that receive non-point-source pollutant are often used by the rural population as sources of water for domestic use. Improving water quality in situ using a floating biofilm reactor is an economically way of decreasing the health risks posed by such water to humans and improving the aquatic environment. In this study, the feasibility of using solar-powered floating biofilm reactors to improve water quality was assessed by performing field tests. An aerated reactor alone decreased the ammonium concentration, chemical oxygen demand, total nitrogen concentration, and total phosphorus concentration by 31.94%, 10.25%, 10.36%, and 9.38%, respectively. An innovative system using alternating aerated and nonaerated biofilm reactors decreased the total nitrogen concentration by up to 21.38%. A higher specific denitrification rate was found for biofilm cultured in a non-aerated reactor than for biofilm culture in an aerated reactor. The dominant bacteria responsible for removing nitrogen in biofilms on carriers and natural suspended particles in the same area were different. The biofilm on the reactor carriers were enriched in Gammaproteobacteria, but biofilms on natural suspended particles in the same zone were enriched in Deltaproteobacteria. This, and the dominance of Halomonas in the zeolite biofilms, indicating that it is essential to use appropriate biofilm carriers to enhance denitrification of polluted surface water. The degree to which water quality is improved in practice will be determined by the number and sizes of reactors used, and the flow rate and pollutant loading of the polluted river being treated.