| In recent years,excessive perchlorate dichange into surface water and ground water has caused serious environmental problems.Therefore,the development of effective perchlorate removal technologies is imminent.Biological reduction technology including heterotrophic and autotrophic process was an attractive alternative for removing perchlorate from contaminated water.However,these two methods have various shortcomings and restrict the application of the technology.Therefore,a combined heterotrophic and sulfur-based autotrophic process was developed to reduce high concentration perchlorate via anaerobic baffled reactor(ABR)systems.By the meaning of step-feeding strategy,the ABR system can improve the reduction performance of perchlorate and control the effluent sulfate.A combined heterotrophic and sulfur-based autotrophic process in the ABR system was established,and its feasibility for reducing perchlorate was explored.The results showed that the perchlorate removal efficiency reached to 99.60% at the influent concentration of 300 mg/L,the effluent sulfate concentration was approximately stabilized at 150 mg/L.In addition,the pH value of the influent and effluent can be maintained between 6 and 9 without adding alkalinity to the ABR system,which provides a suitable environment for the growth of microbial community.Therefore,the combined heterotrophic and sulfur-based autotrophic process can achieve an acid-base balance.Different C/Cl ratio has significant effects on the perchlorate reduction in ABR system.The experimental results showed that the effluent perchlorate concentration can be stabilized within 2.7 mg/L with the total removal efficieny of above 99% when the C/Cl ratio was 1.5:1 and the influent perchlorate concentration was 300 mg/L.at the same time,the effluent concentration of sulfate was about 96.40 mg/L,which is significantly lower than the national standard(GB5749-2006).In order to improve the performance of the combined heterotrophic and sulfur-based autotrophic process in ABR system,the application of step-feeding strategy is applicated.Therefore,the step-feeding ABR(SF-ABR)system and normal-feeding ABR(NF-ABR)system are established,and the differences between the two different inflow modes are discussed from performance,acid-base balance,EPS and bacterial community.The results showed that the perchlorate removal efficiency of the SF-ABR reached 97.56% and the effluent sulfate concentration was controlled under 250 mg/L at a total influent flow of 1.92 L/h when the influent perchlorate concentration was 800 mg/L.These results were significantly superior to the NF-ABR.In three components of the extracellular polymeric substances(EPS),the fluorescence intensity of the tryptophan-like component were identified by fluorescence excitation–emission matrix(EEM)spectra with parallel factor(PARAFAC)analysis,and exhibited a positive relationship with the perchlorate removal rate in the heterotrophic perchlorate reduction unit(HPR unit)of the SF-ABR and NF-ABR.Bacterial community analysis suggested the dominating perchlorate reducing bacteria and the diversity in two ABRs.The results indicated that seven bacterial genera were related to heterotrophic perchlorate reduction while four genera were associated with sulfur-based autotrophic perchlorate reduction.The step-feeding segmentation ratio of #1-#5 comartmrnts in ABR system was optimized,and the dynamic changes of perchlorate,sulfate and COD concentrations in each compartments of the ABR system were analyzed in detail.The experimental results showed that the step-feeding segmentation ratio of the #1-#5 compartments was 30.20%,20%,20%,20% and 10% when the total inflow is 1.92 L/h.The removal rate of 1300 mg/L perchlorate can reach 99.8%,which significantly improves the overall performance of the ABR system.And the effluent sulfate concentration was controlled under 240.5±12.0 mg/L.Material conservation indicates that the segmented water inflow strategy can efficiently promote the utilization of perchlorate in subsequent cells.A mass balance evaluation suggested that the step-feeding strategy can efficiently promote the reduction efficiency of perchlorate in #2-#5 compartments.The microbial community structure indicated that Acinetobacter,Longilinea and Levilinea genera were effective heterotrophic perchlorate reducing bacteria;Ferritrophicum was associated with autotrophic perchlorate reduction.In addition,the genus Chlorobaculuma is considered the dominant bacteria related to sulfur disproportionation.In summary,the research of this subject has improved the theoretical background of reducing the high concentration perchlorate in the heterotrophic combing sulfur-based autotrophic ABR system.And,the heterotrophic combing sulfur-based autotrophic technology provides an effective solution and industrial application basis for the treatment of high concentration perchlorate wastewater. |
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