| With the continuous development of industry and science technology,the use of heavy metals and the production of PAHs in China are increasing nowadays.Through the deposition of atmospheric deposition and rain erosion,such composite pollution is finally abundant in water bodies.The formation of polycyclic aromatic PAHs and heavy metal composite pollution is becoming more and more serious.Therefore,the pursuit of low-cost,high-efficiency,environmentally friendly bioremediation technology for PAHs-heavy metal complex pollution is the fundamental goal of finding pollution control to achieve comprehensive management and ecological balance.In this research,a new plant material,loofah,was used as an immobilization carrier,and it was immobilized in a 1:1 ratio with high-efficiency Pyrene degradation bacteria 4-1(Serratia marcescens)and high-efficiency Cr(VI)reducing bacteria 12-2(Arthrobacter sp).The immobilization method and carrier conditions were studied,an efficient and stable immobilization system was established;The degradation characteristics of immobilized mixed flora on Pyrene-Cr(VI)composite pollution were studied,and the repair conditions were optimized by response surface design;The growth characteristics and degradation kinetics of degraded Pyrene and reduced Cr(VI)were studied and discussed;Finally,the experiment on the repair effect of immobilized mixed bacteria on the actual Pyrene-Cr(VI)complex pollution wastewater was carried out.The following main research results were obtained:(1)The best system for the immobilized mixed flora of loofah was determined:The relatively optimal condition is to add five 1.2 cm ×1.2 cm × 0.7 cm volume square loofah carriers for fixing at the beginning of the strain.Under this condition,50mg/L pyrene in pyrene-Cr(VI)complex pollution can be degraded by nearly 40%(168h),and the reduction rate of 30mg/L Cr(VI)can reach 100%(24h).(2)In the process of complex pollution degradation by immobilized mixed flora,the reduction of Cr(VI)promoted by low concentration pyrene and the inhibition of high concentration pyrene;Cr(VI)inhibited the degradation of pyrene.The optimum conditions for the immobilized mixed bacteria group degradation Pyrene-Cr(VI)complex pollution in the water by single factor and response surface optimization were as follows: temperature 30.08 ?,inoculum concentration 3.11%,p H 8.74,verification experiment results in experimental model within the confidence interval.(3)The growth characteristics of the free and immobilized mixed flora are fitting with the Logistic growth dynamics.The degradation of Pyrene by mixed flora fitting with the first-order degradation dynamics;When the initial concentration of Cr(VI)is medium and low,the reduction of Cr(VI)in the mixed flora is consistent with the first-order degradation dynamics.When the initial concentration of Cr(VI)is higher,it is fitting with the zero-order degradation dynamics.(4)The practical application of immobilized mixed flora: The effect of mixed flora on the treatment of seven kinds of actual wastewater containing pyrene-Cr(VI)complex pollution was studied,which indicated that the immobilized flora was more adaptable than the free flora and the removal efficiency of pollutants was high.Among them,the removal rate of Cr(VI)in four kinds of wastewater reached 100%,and the degradation rate of sputum in six kinds of wastewater exceeded 60%.The carrier loofah can be reused 7 times,and the Cr(VI)reduction rate is 96% at the 7th use,the Pyrene degradation rate is 41.5%,and the integrity of the loofah is basically unchanged.Through the removal test of Pyrene-Cr(VI)complex pollution in water,a set of high-efficiency application technology system of immobilized mixed flora was established.It provides theoretical basis and technical support for solving the bioremediation practice of PAHs-heavy metal composite pollution in water environment. |
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