Study On The Detoxification Process Of Biological Treatment For Crotonaldehyde Manufacture Wastewater

Crotonaldehyde manufacture wastewater(CMW)is a kind of refractory organic wastewater,which contains high-strenth organic pollutants and is highly toxic to microorganisms.If discharged directly into the biological treatment units,CMW could adversely affect the microbial activities and deteiorate the steady operation of biological units.The objectives of this paper are to provide intructions for pretreating CMW and reducing its toxicity to biological treatment process.This study focused on the toxicity of CMW to anaerobic digestion process and the identification of the key toxic organics;and optimized the operating conditions of the combined process of ozonation-hydrolysis acidification(HA)pretreating CMW,and discussed the mechanism of toxicity removal.The main conclusions were as follows:(1)The chemical oxygen demand(COD)of CMW was 84202±1014 mg/L.However,the50%effect concentration(EC50)of CMW to specific VFA production activity(SVA)and specific methanogenic activity(SMA)were 367 and 250 mgCOD/(gVSS),respectivety,which indicated that CMW cannot be directly treated by anaerobic process due to the high toxicity to anaerobic microorganisms.(2)The main characteristic organic matter in CMW included crotonaldehyde,(E,E)-2,4-hexadienal,3-(2-methyl-2-propylene)-5-pentanolactone,5-formyl-6-methyl-4,5-dihydropyran and ethyl sorbate.The toxic unit(TU)(calculated by the inhibition degree of SVA)of crotonaldehyde and(E,E)-2,4-hexadienal were 18.5 and 9.8,respectivety,which accounted for33.3%and 17.6%of TU(55.6)of CMW.And the TU(calculated by the inhibition degree of SMA)of them were 16.9 and 9.4,respectivity,which accounted for 40.5%and 22.5%of TU(41.7)of CMW.The results showed that crotonaldehyde and(E,E)-2,4-hexadienal were important toxic organics in CMW to anaerobes.(3)The optimum reaction parameters for ozonation uints were at reaction time of 180 min,initial pH of 3.0,temperature of 35 ~oC and ozone concentration of 30 mg/L in gas phase.The removal rate of crotonaldehyde,(E,E)-2,4-hexadienal,3-(2-methyl-2-propylene)-5-pentanolactone,5-formyl-6-methyl-4,5-dihydropyran and ethyl sorbate were 82.9%、96.7%、98.2%、93.8%、74.4%,respectivety.The TU removal rate of SVA inhibition and SMA inhibition were 56.1%and 46.8%,respectivety,which indicated that ozonation could effectively reduce toxicity of biological treatment but the further detoxification technology was needed.(4)The optimum operation parameters of HA process were influent COD of 8640±444mg/L,hydraulic retention timen(HRT)of 24 h and influent pH of 8.0.The average COD removal rate and average acidifaction degree(AD)of effluent were 40.1%and 28.7,respectively.Besides,the main characteristic oganic matters in CMW were all removed by over83.4%,and the removal rate of TU on SMA inhibition was 91.8%,which indicated that ozonation-HA process could reduce 95.5%of toxicity of biological treatment and ensure the stable operation of subsequent biological treatment process.