An alternative carbon source withdrawn from anaerobic fermentation of soybean wastewater to improve the deep denitrification of tail water

Abstract The study explored an approach to improve the deep denitrification of tail water in denitrifying biofilter (DNBF) by utilizing alternative carbon sources withdrawn from the anaerobic fermentation of soybean wastewater due to its abundance and low costs. It was found in the batch tests that the alternative carbon sources could be obtained from soybean wastewater rapidly under optimal conditions. The obtained carbon sources were mainly consisted of acetic and propionic acids. The denitrification efficiency reached above 91% with the addition of fermented soybean liquids (FSL) with C/N ratio of 5 which was comparable to that of the commercial acetate. Further analysis demonstrated that the FSL was advantageous over the commercial acetate on the formation of biofilms and microbial diversity in DNBF which accounted for the satisfying performance of DNBF on the pollutants removal. Moreover, the potential environ-economic benefits could be expected by utilizing FSL as the alternative carbon source for deep denitrification which exhibited certain prospects in large-scale application.