The Study On Anaerobic-aerobic-advanced Biological Treatment Of Bioethanol Wastewater

Biological process for treating high-strength distillery wastewater andpretreatment wastewater with high ammonia nitrogen content has been studied in thispaper, thermophilic anaerobic-mesophilic aerobic-biological filter technology wasapplied. Process wastewater from bioethanol production was of large amount withhigh COD (＞30000mg L^-1), suspended solids (＞5000mg L^-1) and ammonianitrogen (＞500mg L^-1) content, so bioreactors with high OLR, high efficiency forammonia nitrogen removal and capability of overload shock were needed.For high-strength distillery wastewater, thermophilic anaerobic treatment wasused to remove most of the organic matters in it and CH4was produced as cleanenergy. Then co-digestion of anaerobic effluents and pretreatment wastewater wascarried out by aerobic process to remove ammonia nitrogen and residual organicmatters. Aerobic effluents were finally treated in BAF to adsorb and degrade residualpollutants. Based on this, AFB-ALR-BAF technology was developed.Parameters of thermophilic anaerobic process were optimized with results asfollows: temperature53-55℃, pH7.0, liquid up flow rate8.5-9.5m h^-1, influent withCOD of30000±2000mg L^-1was reduced to2785mg L^-1after68h. AFB has beenoperated for150days to investigate its performance, under optimal condition,influents with COD of29500-35300mg L^-1was reduced by over90%at OLR of17.5g-COD L^-1d^-1. For aerobic treatment in ALR, at33-35℃, pH7.0-8.0, superficical gasvelocity8.1mm s^-1, HRT15h, COD and ammonia nitrogen removal rate has reached88.5%and96.7%. ALR has been operated for50days with influent COD andammonia nitrogen of1052^-1480mg L^-1and475-525mg L^-1, effluents with COD andammonia nitrogen of136mg L^-1and15.4mg L^-1were obtained. Aerobic effluentswere finally treated in BAF under ambient temperature （18-25℃）, gas-liquid ratio of6:1and HRT of5h, Final effluent with COD and ammonia nitrogen content of65.3mg L^-1and3.9mg L^-1were obtained, which was below primary discharging standard(GB8978^-1996, COD＜100mg L^-1, ammonia nitrogen＜15mg L^-1).