Experimental Analysis of Biological Oxidation Characteristics of Hygas Coal Gasification Wastewater.

摘要

An eight month experimental study was performed to assess biological treatability characteristics of Hygas coal gasification process pilot plant wastewater comprised of cyclone and quench condensates. The study evaluated treatability characteristics of ammonia-stripped and unstripped wastewater at full strength and at 1:1dilution. It was determined that minimum pretreatment required for biological oxidation consisted of reducing wastewater alkalinity,and decreasing raw ammonia concentration by dilution or by stripping. Kinetic studies with stripped Hygas wastewater showed the waste could be processed at mean cell residence times varying from 10to 40days with hydraulic residence times of 2to 3days;the bacteriological yield coefficient was 0.11 (COD basis),and the decay coefficient was 0.02/day. The study also determined correlations for dissolved oxygen uptake,the effect of COD removal rate on zone settling velocity and sludge volume index,removal efficiencies for various constituents,and adsorption isotherms for biological effluent COD on activated carbon and process char. Nitrification was completely inhibited in this study;it was suspected that this was due to high wastewater boron concentration (80to 110mg/l),however additional testing at lower loadings is required to confirm this observation. Hygas wastewater seemed to inhibit bacteriological growth because mean cell residence times less than 10days do not appear feasible and because apparently higher yield coefficients were observed with diluted wastewater. (ERA citation 04:012039)