Removal capacities and varying characteristics of substrates and microbial community structure in simultaneous...

Under the background of carbon neutrality, resource and energy utilization technologies have become the focus of future research. The paper investigated the removal efficiencies and varying characteristics of substrates and microbial community structure in the simultaneous sulfide and nitrate biological removal (SSNBR) process. The results showed that the sulfide and nitrate removal loads reached 2.998 kg m^-3∙d^-1 and 1.011 kg m^-3∙d^-1 respectively when HRT was 2.4 h. The sulfide and nitrate molar ratios (S/N ratios) hardly influenced the removal efficiencies of sulfide and nitrate. However, the reaction products sulfate and nitrite concentrations in the effluent became higher as the S/N ratios decreased. Under the S/N ratio of 5:5, when the influent sulfide and nitrate concentrations were improved from 100 mg L^-1 to 600 mg L^-1 and from 87.5 mg L^-1 to 306.25 mg L^-1, respectively, the sulfide removal efficiencies were all above 99%, but the nitrate removal efficiencies reduced from 95.53% to 55.54%. Sulfide removal effect was better than nitrate. HRT had great effect on the nitrate removal efficiencies, but hardly affected the sulfide removal. When HRT was shortened from 12 h to 2.4 h, the sulfide removal efficiencies were all above 99%, while the nitrate removal efficiencies decreased from 93.14% to 77.04%. The main functional genera included Exiguobacterium, Clostridium, Bacillus, Thiobacillus and Sphingomonas, all of which had the nitrogen and sulfur removal functions.