Mixotrophic denitrification: A study on the removal of high nitrate concentration from piggery wastewater by biofilter reactors

Abstract

The treatment of piggery wastewater through anaerobic fermentation and subsequent irrigation on farmland has been found to pose a risk of nitrate-nitrogen pollution in groundwater, thereby posing potential threats to human health. The scientific investigation of employing heterotrophic/autotrophic (mixotrophic) denitrification as a means to address the issue of farm wastewater containing elevated levels of nitrate nitrogen has garnered significant attention. This study employed sulfur monomers, limestone, and corn cob as microbial carriers within a biofilter system to facilitate the heterotrophic denitrification process of piggery wastewater fermentation broth. The efficacy of mixotrophic denitrification was found to surpass that of sulfur-limestone autotrophic denitrification in the treatment of nitrate-nitrogen wastewater with elevated concentrations of nitrate-nitrogen. This was evidenced by higher rates of denitrification, as well as reduced production of sulphate ions and alkalinity. The experiments on mixotrophic denitrification reaction observed a positive correlation between the content of corn cob and the relative abundance of microbial flora. Specifically, the relative abundance of Proteobacteria at the phylum level showed an increasing trend. Additionally, there was a proportional increase in the relative abundance of various other flora at the genus level.