Biological Treatment Of Epichlorohydrin Wastewater

This paper takes the epichlorohydrin wastewater as an object,in which the influence ofchloride ion concentration's change on sludge concentration, microbial community, oxygenconsumption rate and the COD removal rate was studied by activated sludge acclimationexperiment. At the same time, the immobilized microorganisms technology was used to studythe degradation performance of immobilized halotolerant bacteria to epichlorohydrin.The experimental results of activated sludge acclimation showed that the sludgeconcentration decreased with the increase of chloride ion concentration, and finally stabilized.The activated sludge changed yellow-brown from gray-brown and had a good flocculationperformance after acclimation, which could form larger floc rapidly after cessation of aerationand the suspended solid of effluent was rare after precipitation.In the process of sludge domestication, the composition of microbes in system changedwith the increase of chloride ion concentration. At low chloride ion concentration, themicroscopic examination showed abundant microbial species associated with campanula. Athigh chloride ion concentration, the types and quantities of microorganisms were both gettingfewer. It could be found that the dominant microorganisms in activated sludge acclimated bysalt-resistent changed comparing to non-acclimated sludge through the analysis to the DNAextracted from microbial groups in acclimated and non-acclimated sludge.In the process of sludge acclimation, the COD removal rate of effluent decreased from96% to about 75% with the increase of chloride ion concentration in sludge system. The aerobicactivated sludge was used in this paper to carry out the biodegradation of epichlorohydrinwastewater. According to Grau experimental model, when chloride ion concentration was 2%and 12%.Through the study to A/O+MBBR, the parameters could be determined by experiment asfollows:the total hydraulic retention time(HRT)is 48h (anaerobic acidification unit is 24h,anoxic unit is 12h,aerobic unit is 12h), the pH in the aerobic unit should be maintained the level of 7.8-8.0. Under above conditions, the removel rate of COD was over 80%.The influence of immobilized method, carrier material and environmental conditions onthe treatment of epichlorohydrin wastewater was examined in the experiment of immobilizedmicroorganism treating epichlorohydrin wastewater.The results showed that polyvinyl alcoholalginateembedding method is superior to physical adsorption, the jellies ration of polyvinylalcohol:alginate was 10:1.5, the crosslinker H3BO3:CaCl2 was 6:1. When the wastewater's pHvalue, inoculums size, activation time, temperature were 7, 20%, 16h, 30℃,respectively, thedegradation rate of immobilized microbe to the epichlorohydrin could reach 80%.