Effects of organic carbon and sulfide on the anammox reaction in the anoxic column in the SRDAPN process for treating high-strength wastewater

Abstract

Low energy consumption treatment of high-strength wastewater is crucial in controlling groundwater pollution and eutrophication in closed waterbodies. In this study, the sulfate reduction, denitrification/anammox, and partial nitrification (SRDAPN) process, which is an effective organic carbon and nitrogen removal process with low energy consumption for low strength wastewater, was applied to treat livestock wastewater with high COD and sulfate concentration, and microbial reaction and community were examined using an anaerobic–anoxic biological filter reactor that simulates circulation from an aerobic reactor. At a total organic carbon loading rate of 2.7–5.8 kgC/m3·day, sulfate reduction and methane production occurred simultaneously in the anaerobic column of the reactor. Specifically, sulfate reduction resulted in organic matter removal rates of 38 and 26% at ambient temperature and 25 °C, respectively. Furthermore, both heterotrophic and autotrophic denitrification occurred in the anoxic column, and when the organic loading rate in the anoxic reactor was below 0.2 kgC/m3·day, 33%–37% of ammonium and 33%–34% of nitrite were removed by the anammox reaction. Heterotrophic denitrification bacteria (Thauera, Comamonas, and Denitratisoma) and sulfur denitrification bacteria (Sulfurimonas denitrificans) grew in the lower and middle parts of the anoxic column, whereas anammox bacteria (2.5% of Candidatus Brocadia at ambient temperature and 9.4% of Candidatus Kuenenia at 25 °C) grew in the upper part of the anoxic column. These results indicate that the SRDAPN process based on sulfur cycle and anammox is useful for treatment of high strength wastewater with low energy consumption.