Abstract: Abstract:WT5”BZIn 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(NH4+-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 NH4+-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.