Strategies for recovering inhibition caused by phenolic compounds in a short-cut nitrogen removal reactor treating coal gasification wastewater

Different strategies, including extension of hydraulic retention time (HRT), dilution, and addition of powdered activated carbon (PAC) and super-powdered activated carbon (S-PAC), were investigated for the quick recovery of nitrifying bacteria activity from the inhibition of coal gasification wastewater (CGW). A laboratory-scale short-cut biological nitrogen removal (SBNR) reactor treating CGW, achieving high levels (90%) of nitrogen removal, was used. After a shock of phenolic compounds (around 250 mg/L) and a failed performance, the results of the batch recovery tests indicated that the PAC and S-PAC addition were the best recovery strategies. In the SBNR reactor, the addition of 1 g/L PAC and S-PAC shortened the recovery time from the natural recovery of 32 days to 13 days and 10 days, respectively. Fluorescence in situ hybridization (FISH) assay and the adsorption isotherms revealed that activated carbons absorbed phenolic compounds, reducing the toxicity and allowing for the quick recovery of SBNRs treating CGW. S-PAC showed greater adsorption capacity for phenol than PAC.