Remediation Of Triclosan And Polycyclic Aromatic Hydrocarbons In Sediment By A Multifunctional Degrading Bacterium

As the organic pollutants harmful to human health,triclosan(TCS)and polycyclic aromatic hydrocarbons(PAHs)are ubiquitous in sediment environment.At the same time,heavy metal pollution usually exists in the sediment,which makes the complex pollution more complicated.However,the pollutants in the sediment will be released to the overlying water again,forming secondary pollution,or endangering human health through the food chain.Therefore,it is of great significance to remediate the complex pollution of TCS and PAHs in the sediment in the presence of heavy metals.At present,for the remediation of organic compound pollution in sediment,the most promising way is bioremediation.TCSdegB2(Pseudomonas sp.TCSdegB2,genebank: mk478803.1)is a facultative anaerobe isolated from Jinan river sediment in Fuzhou City,which has the ability to degrade the solution of TCS and PAHs under hypoxia conditions,and can tolerate heavy metal cadmium(Cd),which has a good application prospect.This paper mainly studies the remediation of TCSdegB2 in polluted sediment under the coexistence of heavy metals,which provides the basic data for the development and utilization of TCSdegB2 as microbial agent to carry out in-situ ecological restoration of polluted water.At the same time,the research on the combination of sediment microbial fuel cell(SMFC)and microbial agent,the combination of calcium nitrate and microbial agents to repair TCS and PAHs in polluted sediment provides a new method for the removal of refractory organic pollutants in the sediment.The results can not only provide reference for TCS and PAHs remediation practice in sediment,but also bring new progress to remediation technology of organic pollution in sediment.The main results are as follows.1.The degradation rates of naphthalene,fluorene,phenanthrene,anthracene,fluoranthene and pyrene in 16 priority PAHs were 100%,100%,95.8±5.9%,80.3±6.8%,40.2±6.1% and 33.5±3.7%respectively under 14 days of anaerobic pure culture solution.No significant degradation was observed in other PAHs.In 21 days of anaerobic pure culture environment,the degradation rates of phenanthrene(25 mg/L)by TCSdegB2 were 57.5±3.5%,66.7±6.4%,58.8±3.6% and 55.0±3.9%respectively at the concentrations of 0,1,5 and 10 mg/L,and the degradation rates of TCS(25 mg/L)were 13.9±0.6%,16.8±1.5%,13.3±1.6% and 12.5±0.5% respectively.Compared with 0,1 mg/L Cd could significantly promote the degradation of phenanthrene and TCS by TCSdegB2(P<0.05);5mg/L Cd had no significant effect on the degradation of phenanthrene and TCS(P>0.05);10 mg/L Cd had no significant effect on the degradation of phenanthrene(P>0.05),but significantly inhibited the degradation of TCS(P <0.05).2.TCSdegB2 was used to remediate the compound pollution of TCS and PAHs in simulated sediment(the concentrations of TCS,phenanthrene and pyrene were all 25 mg/kg)for 28 days.The results showed that the average degradation rates of phenanthrene and pyrene in simulated sediment were more than 50% when only adding calcium nitrate and calcium nitrate combined with TCSdegB2 without Cd coexistence,and there was no significant difference between the two treatments(P>0.05)The results showed that the average degradation rates of TCS,phenanthrene and pyrene in the sediment treated with calcium nitrate only were less than 55%,which were significantly lower than the average degradation rates of more than 55% in the combined treatment of calcium nitrate and TCSdegB2(P<0.05)The average degradation rates of TCS,phenanthrene and pyrene in the sediment treated with calcium nitrate alone were more than 55%,which were significantly higher than the average degradation rates of 50% in the combined treatment of calcium nitrate and TCSdegB2(P<0.05).In the absence of Cd,the average degradation rates of TCS,phenanthrene and pyrene were more than 65% under SMFC technology and SMFC technology TCSdegB2 combined treatment,and there was no significant difference between the two treatments except TCS(P>0.05);When the concentration of CD was 1 mg / kg and 10 mg / kg,the degradation rates of TCS,phenanthrene and pyrene were more than 65%,respectively.Except pyrene,there was significant difference between the two treatments(P<0.05).The above results show that the removal efficiency of SMFC on TCS,phenanthrene and pyrene in anaerobic sediment is higher than that of calcium nitrate treatment.The anaerobic environment greatly limits the activity of indigenous microorganisms in sediments.When calcium nitrate and SMFC provide electron acceptors,they can greatly stimulate the activity of indigenous microorganisms,resulting in the insignificant promotion of TCSdegB2 on the degradation of pollutants.The addition of calcium nitrate will increase the concentration of nitrate ions in the overlying water,and SMFC can not only effectively degrade PAHs in the sediment,but also generate electricity.Therefore,compared with adding calcium nitrate treatment,SMFC is a more advantageous technology to remove organic pollutants in the sediment.3.The results of remediation of PAHs in contaminated sediment by TCSdegB2 for 28 days showed that the degradation rates of fluorene,anthracene,phenanthrene and pyrene has reached more than 90% when only calcium nitrate and calcium nitrate TCSdegB2 were added,only under the combined treatment of SMFC technology and SMFC technology-TCSdegB2,under only TCSdegB2 treatment.The above results show that adding calcium nitrate,SMFC technology or TCSdegB2 is a very efficient method for field sediment remediation.The combination of TCSdegB2 with calcium nitrate or SMFC technology has no obvious effect on the degradation of PAHs in the field sediment,which may be due to the low content of PAHs in the sediment.Only adding calcium nitrate and SMFC technology can remove more than 95% of PAHs;in addition,providing electron acceptor can greatly stimulate the activity of indigenous microbial degradation bacteria,which may inhibit the activity of TCSdegB2.The results of Illumina high-throughput sequencing showed that the addition of electron acceptors can greatly stimulate the activity of indigenous microorganisms and inhibit the activity of TCSdegB2 in the treatment with TCSdegB2 only after 28 days of cultivation.TCSdegB2 can adapt to the hypoxia and complex microbial community environment in sediment,and it does not need to add electron acceptors,which is related to the existence of a large number of electron acceptors required by TCSdegB2 in sediment.Therefore,only TCSdegB2 can be added to PAHs contaminated sediment to reduce resource consumption and complicated experimental design.