Wastewater Treatment Process Study On Treatment Of Wheat Starch Wastewater And Direct Fermentation Of L(+)-lactic Acid

Wheat starch wastewater was a kind of wastewater with high concentration organicsubstance, which contained a lot of starch, protein, carbohydrates, fat and other substances. Ifthey were discharged directly, which would pollute the environment and cause seriousresource waste.End-of-pipe treatment and using wheat starch wastewater to produceL(+)-lactic acid was determined in this paper, conclusions were as follows:1. UASB-SBR was used to treat the starch wastewater after recycling some starch asfeedstuff accrording its good biodegradability.Parameters, final effects,operation of theprocessing unit were studied.Results showed that after sedimentation, CODout concentrationof wastewater reached approximately8000mg/L, and then after UASB-SBR system, valuesof COD,suspended solids and ammonia nitrogen all corresponded to concentration limits(100mg/L,30mg/L and15mg/L,respectively) for direct discharge of water pollutant concentrationin new business according to “Discharge standard of water pollutants for starchindustry”(GB25461-2010).In addition,value of total phosphorus also corresponded toconcentration limits (5mg/L)for indirect discharge according to the same standard. UASBreactor gas-liquid-solid three-phase separator was designed showing good gas-liquidseparation effects.2. The rich nutrients in starch waste water was used as carbon source for microorganismsto produce fermentation L(+)-lactic acid. The results showed that with the plus of0.5g/Lammonium sulfate as a nitrogen source, concentration of CODcr (9500～10000mg/L), starchconcentration (18.6～22.4mg/L) of raw water can be directly used as the medium for3.866Rhizopus oryzae to produce L(+)-lactic acid fermentation. The optimum fermentationcondition of flask fermentation was as follows:seed culture(10%),work volume(20%),additionof1%CaCO3after8h fermentation, and then fermentation process continued52hours inshaker with speed of170r/min and under temperature of26℃.In the end,L(+)-lactic acidconcentration and biomass were15.28g/L and3.43g/L,respectively. After the wholefermentation process, concentration of CODout reduced from10532mg/L to1532mg/L andremoval efficiency of CODcr wheat starch wastewater reached85%.