Effect of sulphate on nitrogen removal, sludge characteristics and microbial community structure of anammox process

Abstract

The effect of salinity, represented by SO42−, on the anammox reaction was still unclear. Therefore, the three aspects of pollutant removal, sludge characteristics, and microbial communities were investigated separately in the study. The results showed that the increasing SO42− concentration decreased the NH4+-N and NO2−-N removal efficiencies to different degrees. The nitrogen removal efficiencies were still stable above 77 % with 20 and 30 mmol of K2SO4. However, higher concentrations (40 and 50 mmol) of K2SO4 caused the nitrogen removal efficiencies to drop continuously. Both EPS (extracellular polymeric substances) (from 77.52 to 41.51 mg/g VSS) and SAA (specific anammox activity) (from 133.56 to 43.29 mg N/(g VSS·d)) of sludge were inversely related to K2SO4 concentration (from 0 to 50 mmol). The microbial community structure indicated that low concentrations of K2SO4 even promoted the abundance of Candidatus Kuenenia (2.64 % and 1.83 % increased after elevated K2SO4 concentrations in R2 (from 5 mmol increased to 20 mmol) and R3 (from 10 mmol increased to 30 mmol), respectively). In addition, higher concentrations still showed inhibition for Candidatus Kuenenia and Candidatus Brocadia.