Simultaneous Removal of Ammonium and Sulfate in EthanolMethane Coupled System
In cassava-based ethanol-methane coupled system,distillery waste contains high concentration of sulfate and organic nitrogen which are converted to ammonia and hydrogen sulfide by conventional anaerobic biological treatment respectively.Since ammonia and hydrogen sulfide have toxic effect on microorganisms in the anaerobic treatment system,as well as negative effect on the growth and metabolism of yeast in the ethanol fermentation,it is necessary to study new technology of anaerobic simultaneous removal of ammonium and sulfate in the distillery waste.An anaerobic fluidized-bed reactor was used to study simultaneous removal of ammonium and sulfate in synthetic medium which contained sodium sulfate as electron acceptor,ammonium chloride as electron donor and glucose as carbon source for bacteria growth.The process was operated for total 83 d,and loading rates of COD was reduced to 0.4 kg/(m3.d),influent concentration of SO42-and NH4+-N reached to 676 mg/L and 200 mg/L respectively.Results demonstrated that removal rates of ammonium,sulfate and COD could reach 58.28%,67.22% and 93.50% respectively.Material balance gave a ratio of NH4+conversion and SO42-conversion of about 2:1,and sulfur was observed in the effluent and increased with time,which indicated the occurrence of simultaneous removal of ammonium and sulfate in the anaerobic fluidized-bed reactor.Reaction mechanism through analysis of experimental results in different stages was also discussed.