Construction Of Mixed Microflora And Its Remediationof Pyrene-Cr(?) Compound Contamination In Water

The pollution of the natural environment usually consists of associated and comprehensive components,that is to say,there is a joint action between different pollutants to form the compound pollution.The inorganic pollutants in the environment are mainly heavy metals,and heavy metals which cannot be degraded naturally.Polycyclic aromatic hydrocarbons(PAHs)pollution is a kind of organic pollutants that is difficult to degrade,and it is easy to accumulate in soil and sediment.The isolation and screening of single high efficient biodegradable bacteria cannot meet the increasingly serious situation of complex pollution,so it is of great significance to create a mixture of bacteria that can repair the heavy metal and polycyclic aromatic hydrocarbons compound pollution.In this paper,a highly efficient mono-functional strain was isolated from soil,water and sediment contaminated by heavy metal and polycyclic aromatic hydrocarbons(PAHs),one of which was capable of reducing Cr(?)and degrading pyrene respectively.On basis of different proportions,of which mixed bacteria is determined,so as to explore the relationship between Cr(?)and pyrene in compound pollution.The effects of temperature,pH value and inoculation amount on the remediation of Cr(?)pyrene compound pollution is investigated by single factor experiment.Through orthogonal test,the optimum condition of mixed microbial strains was determined,and the effect of mixed bacteria on Cr(?)-pyrene compound pollution in simulated wastewater was scrutinized by laboratory simulation test.The effects of mixed bacteria on reducing the toxicity of compound pollution to crops were examined by hydroponic test.The main findings are as follows:(1)A strain of 12-2 strain with high Cr(?)reduction ability and one strain of 4-1 strain with high degradation ability of pyrene were isolated and screened.They were identified as Serratia marcescens(myxotypic Shareh bacteria)and Arthrobacter sp.(ganglia bacteria).uThe reception numbers are MK027123 and MK027124,respectively.The ratio of mixed bacteria was 1: 1,which was 47% higher than that of Cr(?)added only 12-2.When the concentration of Cr(?)increased from 40mg/L to 120mg/L,the degradation rate of 50mg/L pyrene decreased from 47.4% to 18.0%.And the Cr(?)reduction rate of 40mg/L increased first and then decreased with the increase of pyrene concentration.(2)by single factor test and orthogonal test,the optimum conditions of compound contamination remediation with mixed bacteria were 25 ?,pH9 and inoculation volume 15%.After 48 hours,the reduction rate of Cr(?)to 40mg/L was 96.9% and 7 days later,the degradation rate of pyrene to 50mg/L was 65.3%.(3)under the optimal conditions,a simulated experiment was carried out to repair Cr(?)-pyrene compound contamination in water.The Cr(?)reduction rate of 10mg/L by the mixed microbial strain was up to 100% after 7d,and the degradation rate of pyrene by the mixed microbial strain was up to 52.9% after 7d.The results of hydroponic experiments showed that Cr(?)-pyrene combined pollution had a significant toxic effect on the growth of crops.The growth of cotton,soybean and corn was 80.6%,71.3% and 70.6% of the control group.The toxic effects of Cr(?)-pyrene compound contamination on crops were reduced after the addition of mixed microbial strains.After the treatment of mixed microbial strains,the growth rates of cotton,soybean and corn were 94.7%,91.8% and 92.2%,respectively,of the blank control.