Experimental Study Of Food Processing Wastewater Treatment By Photosynthetic Bacteria

Food processing wastewater is characterized by large discharge amount andhigh concentration of organic matters, which will cause problems such as watereutrophication if discharge into natural water without treatment. Conventionalbiological treatment process usually cause the problems of high energy consumption,complex and expensive facilities, and excess sludge disposal. Wastewater treatmentinvolving photosynthetic bacteria （PSB） seems to be a promising approach due to itshigh efficiency in pollutant removal and the reuse of PSB cell，which is non-toxicand contains high-value nutrient. However, previous researches showed that PSBwas not capable of degrading wastewater contains large amount of macromoleculesdirectly, but there are often a lot of macromolecules in food processing wastewater,which posted a limitation on the widespread use of PSB in food processingwastewater treatment.This study used Z08, a strain of Rhodobacter sphaeroides, to treat six kinds ofcommon food processing wastewater （sugar wastewater, starch processingwastewater, dairy processing wastewater, soybean protein wastewater, monosodiumglutamate wastewater and citric acid wastewater） in the sequencing batch reactor. Itcan improve the treatment effect by introducing small molecule organic compoundsinto the treatment system. The treatment conditions were also optimized. Resultsshowed that PSB could degrade soybean protein wastewater directly. Smallmolecule organic compounds could improve the treatment efficiency of sugarwastewater, starch wastewater and dairy wastewater. It can improve the treatmenteffect of monosodium glutamate waste water and citric acid wastewater by PSBafter domestication.When the inoculation amount was400mg/L, the best treatment conditions forsugar wastewater by PSB were obtained as follows: the addition amount of malicacid was900mg/L, initial pH was7.0, C/N=15, F/M=11, the treatment conditionwas natural light-microaerobic condition, the additive amount of Fe²⁺is1.5mmol/L.Under the conditions described above, COD removal rate could reach95.81%at96h, the total sugar removal rate was96.38%, biomass was1979.0mg/L. When theinoculation amount was160mg/L, The optimized treatment conditions for starchwastewater by PSB were as follows: malic acid concentration was400mg/L，dark-aerobic condition. COD removal rate at48h was84.09%.When the inoculation amount was400mg/L, the optimized treatment conditions for dairy wastewater by PSB were as follows: potassium sodium tartrateof550mg/L, C/N=10, F/M=6, dark-aerobic. COD removal rate at60h was92.74%and biomass was2500.0mg/L. The addition of malic acid could speed up the userate of soybean protein wastewater by PSB, but the final protein removal rate isalmost the same. Malic acid combined with ammonium sulphate could increase thebiomass production by1062.5mg/L under the condition of light-anaerobic. Thebest light and oxygen conditions for treating soybean protein wastewater by PSBwas dark-aerobic.When the inoculation amount was400mg/L, the best treatment conditions formonosodium glutamate waste by PSB after domestication were: C/N=10, F/M=5，natural light-microaerobic. COD removal was95.28%at40h, and the biomass was1562.5mg/L. When the inoculation amount was580mg/L, the optimized treatmentconditions for citric acid wastewater by PSB were as follows: C/N=15, F/M=4,natural light-microaerobic. Under these condition, COD removal and biomass couldreach94.72%and1762.5mg/L at60h, respectively.