Experimental study on multistage bio-augmented reactor for treating coal gasification wastewater

In order to optimize the key pollutant removal mode of coal gasification wastewater, a bio-augmentated reactor composed of 4 tandem units was used to conduct pilot scale tests. The start-up procedure and water quality variation characteristics along the reactor were analyzed. In addition, the influences of hydraulic retention time and additional carbon source on the simultaneous nitrification & denitrification(SND)efficiency and removal effect were also discussed. The results indicate that under the influent quality of ρ(NH4+-N)126 to 165 mg/ L, ρ(TN)139 to 178 mg/ L, ρ(total phenol)286 to 352 mg/ L and ρ(COD)1 340 to 2 296 mg/ L, the microbial acclimation and immobilization of the reactor were completed in 27 days. Under the oxygen-limiting aeration condition and HRT 62 h, SND was achieved in all the reaction chambers from C1 to C4, and the mass concentrations of NH4+-N, TN, total phenol, COD in the last effluent were respectively 0.12-1.25, 79.1-109, 17.8-26.7, 128-196 mg/ L. The TN removal effect of the reactor was enhanced by HRT reduction in the HRT range from 38.8 h to 62 h. The TN removal rate and SND efficiency were 38.9% and 37.3% when the HRT= 62 h. For comparison, the TN removal rate and SND efficiency were 53.0% and 51.2% when the HRT= 38.8 h. The TN removal effect could be all further enhanced by the 5 modes of carbon source dosing with 300 mg/ L. The reactor achieved highest TN removal rate under the dosing mode of II. The coresponding TN removal rate and SND efficiency were 92.8% and 94.4%. The COD removal effect could be enhanced by the modes of I, II, III and IV, and the COD removal rate achieved the maximum value of 91.8% under the condition of mode I. © 2022 China Coal Society. All Rights Reserved.