Study On The Degradation Charateristics Of Bacterial Consortium QY1 And The Effective Degradation Of PAHs By Combination Of Consortium QY1 And Biochar

Polycyclic aromatic hydrocarbons(PAHs)which are the typical representatives of the persistent organic pollutants have been ubiquitous in the environment.PAHs have posed a serious threat to environment for their toxicity,bioaccumulation,carcinogenicity and so on.It is important to explore environment-friendly and effective technology to eliminate PAHs from polluted environments.Biodegradation is a low-cost and safe method to remediate organic pollutions,and microbial consortium is superior to single strains,however,there are few studies on mixed PAHs degradation by microbial consortium.Biochar has been widely applied in environmental remediation,but its adsorption abilities for pollutants were the primary concern,and research on the promotion of biochar on PAHs biodegradation is limited.In this study,phenanthrene(PHE)and pyrene(PYR)which are the modal compounds of PAHs were used as objective pollutants,an aerobic PAHs-degrading microbial consortium QY1 has been enriched from soil of an electronic waste disassembly site.The optimum degradation conditions,degradation characteristics and interaction of PHE and PYR by QY1,and microbial community shift of QY1 were investigated.Studies of the effect and synergy mechanism of biochar on the biodegradation of mixed PHE and PYR were conducted.The potential of biochar-consortium QY1 in biodegradation of PAHs coexisted with heavy metals was also investigated.The effects of biochar,free consortium QY1 and immobilized consortium QY1 on the remediation soil polluted by PAHs or PAHs-Cd were investigated.The major results in this study are as follows:(1)Microbial consortium QY1 with high capacity to degrade PHE could degrade 94.4%of PHE(100 mg/L)under optimal conditions(30?,1 g/L of wet QY1,p H 7)after 2 d.The intracellular enzyme of consortium QY1 played a key role in PHE degradation.After 7 d,QY1 could only degrade 18.4% single PYR(10 mg/L),but could degrade mixture of PHE and PYR effectively.The co-metabolic degradation of PYR was positively associated with PHE initial concentration.In the presence of 500 mg/L PHE,biodegradation efficiency of PYR and PHE achieved 99.5% and 99.3%,respectively.There was no obvious inhibition between the increase in PYE initial concentration and PHE biodegradation.Methylobacterium,Burkholderia,Stenotrophomonas and Sphingobium which were the main genera in QY1 would play key role in PAHs biodegradation.Relative abundance of Pseudomonas increased with the concentration of PHE,indicating that Pseudomonas would play a crucial part in the biodegradation of mixed PAHs with high concentration.(2)Combination of QY1 and biochar had a synergistic effect on the degradation of PHE(50 mg/L)and PYR(10 mg/L).Compared to sole consortium QY1,biochar(1 g/L)addition increased the degradation efficiencies of PHE and PYR 1.1-fold and 7.1-fold after 1 d,respectively.The coorperation mechnisms of biochar were biochar increased biomass in degradation system and enhanced degrading activity of QY1,and biochar could increase contact between PAHs and QY1 by trapping QY1,biochar also enhanced richness and diversity of QY1 and relative abundance of some potential PAHs-degrading genera,including Sphingobium and Cupriavidus.The biodegradation of PYR in the presence of Cd(II),Cu(II)or Cr(VI)could be promoted by biochar.When 10 mg/L Cu(II)co-existed,biochar-consortium QY1 could still degrade PHE and PYR completely after 7 d.(3)In PAHs single polluted soil and PAHs-Cd combined polluted soil,immobilized consortium QY1 had priority over biochar and free consortium QY1 in PHE(50 mg/kg)and PYR(10 mg/kg)mixture removal and passivated available Cd(1?10 mg/kg)effectively.The removal efficiency of PHE and PYR was decreased in the presence of Cd,and Cd affected more PYR than PHE.In addition,compared to free consortium QY1,both of biochar and immobilized consortium QY1 could enhance p H,catalase and urease activity of soil at large.However,acid phosphatase of soil reduced in biochar and immobilized consortium QY1 treatments but increased in free consortium QY1 treatments.Soil enzymes activity was suppressed by Cd,and this inhibition increased with the increase of Cd concentration.This study investigated the degradation characteristics of consortium QY1 on PAHs,analyzed the synergistic mechanism of biochar on biodegradation of mixed PAHs,and explored the effect of combination of consortium QY1 and biochar on remediation of PAHs contaminated soil.The results could provide theoretical basis for the effective remediation of PAHs pollution and the reasonable environmental applications of biochar.