Research On Treating Containing PAM Wastewater By Immobilized Special Functions Microorganisms

With the extensive use of polymer flooding technique,the containing polymer oilfield produced water is increasing year by year in oil field.Poly-containing wastewater high viscosity,oil droplets and suspended solids are increasing under the action of polyacrylamide and hydrolysis product,poly-containing wastewater was treated difficultly.As polyacrylami-de is held up in surface water and groundwater for a long period,polyacrylamide is degraded slowly in the environment and the toxic acrylamide monomer is given off,it would endanger human health.Microorganism method is become important topic of degradation polyacrylamide as the characterristics of high efficient and without secondary pollution.The research object is poly-containing wastewater,the innovation of this paper is processing poly-containing wastewater by immobilized microorganisms method.The immobilized microorganisms method overcomed the defects of bacteria loss,low of microbial utilization rate and difficulty to recovery,improve the microorganism activity and resistance to poisonous and harmful material.Six special functions microorganisms were screened from poly-containing wastewater,which can make use of polyacrylamide as the only nitrogen source and carbon sources.Through determining polyacrylamide degradation rate of single strain and mixed strains,the result showed that polyacrylamide degradation rate of mixed bacteria is higher than a single strains degradation rate.The influencing factors including nitrogen sources,phosphorus source,activation number,inoculation amount,temperature,salinity,pH,time were analyzed respectively.The results showed that the carbon sources was crude oil,without extraneous nitrogen source,phosphorus sources was K2HPO4-KH2PO4,the activation time was 4,the inoculation amount was 3%,incubation temperature was 30?-40?,the mineralization content was 3000-5000mg·L-1,initial pH value was 6.5-7.5,the degradation time was 3 days,the mixed bacteria had a higher degradation rate of polyacrylamide.The conditions of mixed bacteria degrading polyacrylamide was investigated by orthogonal experiment and additional experiment.The optimum process conditions were as follows:without extraneous nitrogen source,phosphorus sources was K2HPO4,the activation time was 2,the degradation time was 3 days,initial pH value was 7,the best bacteria group was number 5,incubation temperature was 35?,the mineralization content was 4000mg·L-1.Analysis of variance showed that the main factors affecting degradation rate were nitrogen source,time,pH,activation time,inoculation amount and mineralization content.Polyacrylamide degradation rate reached 62.1%,oil removal rate reached 63.6%based on the best degradation conditions.In order to reducing bacteria loss,microbial immobilization experiment was carried out by mixed bacteria embedding immobilization method.The optimum process conditions by orthogonal experiment were as follows:crosslinking agent are 2%calcium chloride and 3%boric acid,the immobilize time is 4 h immobilization in calcium chloride solution and then 20 h immobilization in boric acid solution,the volume ratio of wet bacterium and embedding medium is 1:1.The main factors affecting degradation rate is volume ratio of wet bacterium and embedding medium.Polyacrylamide degradation rate reached 83.2%,oil removal rate reached 85.2%based on the best immobilized preparation conditions.Degradation effect of polyacrylamide by immobilized bacteria was characterised by SEM and IR.SEM photos showed that polyacrylamide was transformed from bigger molecular organism into smaller molecular organism.Degradation mechanism of polyacrylamide was analysed by UV spectra,UV spectra showed that acylamino was transformed into carboxyl.In optimum process conditions,the laboratory simulation treatment on poly-containing wastewater was carried out by microbial immobilization.The results showed that after 3 days,the degradation rate of polyacrylamide in wastewater reached 79.5%,oil removal rate reached 93.4%,CODCr removal rate reached 86.4%,which attained the National Secondary Emission Standard.Through experiment was identified that P4-1 was affiliated to Bacillus sp.,P4-2 and P4-3 were affiliated to Micrococcus sp.,P4-5 was affiliated to Sporosarcina sp.,Y4-2 was affiliated to Bacillus sp.and Y4-3 was affiliated to Pseudomonas sp..