Screening Of Psychrotrophic Bacteria And Their Application Effect To Treatment Of Livestock Wastewater

Twenty-two psychrotrophic bacteria were isolated from swamp soil collected in Roigea plateau plateau,with 16S rDNA PCR-RFLP methods,14 psychrotrophic bacteria were screened,and their generation time,degrading ability of livestock wastewater CODer and phenotypic diversity was determined.Five representative strains were chosen to do 16S rRNA gene sequenc analysis,the genetic diversity and phylogeny of these bacteria were performed.The results showed as follows.The generation time of the fourteen strains was within 4.9 h to 11.6 h.Based on the generation time,9 psychrotrophic strains(NLJ1,NLJ6,NLJ7,NLJ9,NLJ10,NLJ11,NLJ12, NLJ13 and NLJ14),whose generation time was within 4.9 h to 5.6 h,were chosen to treat livestock wastewater.The results suggested that these nine strains had different COD_cr disposal ability when treating livestock wastewater singly at 6℃～9℃and 22℃～25℃for 48 h,and strains NLJ6, NLJ7,NLJ9,NLJ10,NLJ11 and NLJ13 had good ability to degrade livestock wastewater in different temperture,the COD_cr degrading rate was about 63%～75%,hence,they were used as high efficient strains;However,the COD_cr degrading rate of the other strains was less than 50%. After inoculating mixture culture of these six strains into the distilled livestock wastewater in the two different temperture,after 6 h's treating,the CODer degrading rate reached to 85.42%and 88.81%,respectively.Furthermore,in laboratory,activated sludge collected from Yaan,Dujiangyan and Chengdu were inoculated by the mixture culture of those six strains,and used to treat livestock wastewater for 6h.The results showed that the average COD_cr degrading rate was 81.67%,76.32%and 70.56%,respectively;Variance analysis showed that there was no significant differentiation between each treatment,which revealed that those six psychrotrophic strains had good adaptability to different activated sludge.The mixture of those six strains was taken into the CASS treating system pond and the COD_cr,NH₄⁺-N,TN and TP disposed rate were compared with control.The result showed that the COD_cr and TN degrading rates wre about five times higher compared with it.Phenotypic features of six strains were analyzed.The result showed that all of the six strains are typical psychrotrophic bacterias,most of them could grow in 4℃～32℃,and 50%strains could endure 4%NaCl respectively.But there were great diversities among strains in carbon utilization, endurance to extreme pH,degraded starch,gelatin and so on. 16S rDNA PCR-RFLP analysis devided these 22 psychrotrophic bacteria into 8 groups,based on the results of 16S rDNA PCR-RFLP,5 stains were selected for 16S rRNA gene sequences analysis The phylogenic tree was constructed,the results suggested that these bacteria mainly distributed in 4 phylogenetic branches,and they were genus of Pseudomonas sp, Sphingobacterium sp,Mycoplana sp and Arthrobacter sp.