Availability of electron acceptors in the persulfate slow-release treatment of petroleum pollution in karst groundwater
In situ chemical oxidation(ISCO)has the potential to combine with bioremediation techniques in the remediation of petroleum-contaminated groundwater,but it can decrease the activity of microorganisms,which may be buffered by slow-release material(SRM)techniques.To better understand the effect of SRM with persulfate(PS)on the biodegradation in the remediation of petroleum pollution in karst groundwater,a microcosm experiment under microaerobic and anaerobic conditions was conducted to explore the availability of different electron acceptors.In the test,different working conditions without or with slow release PS(persulfate/paraffin mass ratios of 0.5,1,2,and 3)were set as follows:no addition of electron acceptor,addition of 100 mg·L-1 nitrate as electron acceptor,addition of 100 mg·L-1 Fe3+as electron acceptor,the treatment of benzene,toluene,xylene(referred to as BTX)and ethanol(EtOH)was investigated,as well as the availability of electron acceptors.The results showed that the degradation rate of BTX was positively correlated with the mass ratio of SRMs,and the highest degradation rate constants occurred at persulfate/paraffin mass ratios of 2 and 3.BTX was more preferentially oxidized by PS than EtOH.BTX degradation was dominated by chemical oxidation,while EtOH dgradation was dominated by microbial action.With the presence of SRMs,nitrate reduction was more significant in microbial action,while sulfate reduction was relatively weak,iron reduction was unconspicuous.Nitrate was more readily used as an electron acceptor by microorganisms,followed by sulfate.However,the possibility of ferric iron used by microbial was slight.Different mass ratios of SRMs and different types of electron acceptors could lead to significant differences in the dominant genera.Both Sphingomonas spp.and Ralstonia spp.had higher relative abundances than others and played a major role in utilizing various electron acceptors to degrade pollutants.
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