The effect of step-feeding distribution ratio on high concentration perchlorate removal performance in ABR system with heterotrophic combined sulfur autotrophic process

https://doi.org/10.1016/j.jhazmat.2021.125151Get rights and content

Highlights

  • Perchlorate was treated by heterotrophic combining autotrophic processes.

  • Step-feeding improves perchlorate removal performance of ABR system.

  • Pollution removal capacities in compartments were analyzed by mass balance.

  • Bacterial communities were different between heterotrophic autotrophic processes.

  • Relationships between perchlorate removal and genera were found by PCA.

Abstract

In a lab-scale anaerobic baffled reactor (ABR) with eight compartments, the heterotrophic and sulfur autotrophic processes were combined to remove perchlorate. And then, the step-feeding distribution ratio of the heterotrophic perchlorate reduction unit (HPR unit) was optimized to achieve efficient removal of high concentration perchlorate. Under the optimized step-feeding distribution ratio, the perchlorate removal efficiency reached to 99.8% with the influent concentration of 1300 mg/L, indicating that the removal performance of step-feeding was better than that of normal-feeding. A mass balance results showed that the perchlorate removal capacity of the C1-C5 compartments were 11.8 ± 0.6, 13.2 ± 0.2, 11.7 ± 1.0, 8.8 ± 0.2 and 9.8 ± 1.0 g/d during the stage VIII, indicating that the step-feeding can effectively relieve pollutant loading of C1 compartment and improve the perchlorate removal capacity of the C2-C5 compartments. Moreover, the high-throughput sequencing analysis showed that bacterial community was significant difference between the HPR and sulfur autotrophic perchlorate removal (SAPR) units. Principal component analysis (PCA) showed that perchlorate removal was more positive correlation with the forward compartments than the posterior compartments of HPR unit. The study confirms that the optimized step-feeding ratio is beneficial to remove the high concentration perchlorate via combining heterotrophic and sulfur autotrophic processes.

Introduction

Because of aerospace and explosive-manufacturing industries, the high concentration of perchlorate pollutant is generated and discharged into external aqueous environment, which can cause human health hazard (Pleus and Corey, 2018, Shi et al., 2011). Therefore, efficient perchlorate removal from industrial wastewater needs to undergo rigorous treatment before discharging into the water environment (Gao et al., 2016). The perchlorate removal technologies mainly include adsorption (Xu et al., 2019), membrane filtration (Long et al., 2012) and biological removal (Sevda et al., 2018, Srinivasan et al., 2009) and etc. Ion exchange and membrane filtration both can effective remove perchlorate, however, these technologies are simply transferred perchlorate from the water environment, and then the high concentration secondary brine wastes is generated (Xie et al., 2018). By comparison, biological removal technology, which can transforms perchlorate into innocuous chloride, is an attractive alternative with cost-effective (Jiang et al., 2017, Yin et al., 2019).

Perchlorate can be removed by biological processes including heterotrophic and autotrophic. However, perchlorate-contaminated wastewater and groundwater were confronted with organic matter limited, which lead to inefficient removal of perchlorate via the heterotrophic removal. Therefore, addition of organic is necessary for heterotrophic perchlorate removal, which leads to increase operational cost. Thus autotrophic perchlorate removal, especially sulfur autotrophic, has been reported to be an alternative process in perchlorate-contaminated water (Zhang et al., 2018, Ucar et al., 2017). However, for high concentrations perchlorate, the sulfur autotrophic removal processes is often limited by the low perchlorate loading rate (Gao et al., 2016, Long et al., 2012). On the one hand, the H+ production is adverse to the sulfur autotrophic bacteria, thus the pH is required to keep neural via supplementation of external alkalinity (Gao et al., 2016). On the other hand, sulfate is produced in sulfur autotrophic process, which is other challenge for the high concentration perchlorate removal via this process (Wan et al., 2019). The maximum allowable sulfate concentration is limited to below 250 mg/L for drinking water (China NHC, 2007). Theoretically, the maximum of 90.25 mg/L perchlorate could be removed by sulfur autotrophic process, and the sulfate production is not exceeding the limit (Eq. (1)). Therefore, the control of excess H+ and sulfate production via sulfur autotrophic process are the challenges for high concentration perchlorate.4S+3ClO4+4H2O3Cl+4SO42+8H+

Hence, the heterotrophic and sulfur autotrophic perchlorate removal processes are combined in anaerobic baffled reactor (ABR) system to make up for the deficiencies of those two processes (Li et al., 2019). Because the ABR can provide the independent compartment for heterotrophic and autotrophic process, respectively. Meanwhile, the combined system could effectively remove perchlorate and control the sulfate formation since heterotrophic perchlorate removal bacteria shared partial function of autotrophic perchlorate removal (Li et al., 2019, Ucar et al., 2017, Zhang et al., 2018). However, the toxicity of high pollutant loading in the forward compartment of ABR resulted in inhibition of bacterial growth and metabolism. Meanwhile, the insufficient pollutant-loading in the posterior compartments limited the reaction efficiency of ABR (Yu et al., 2015). Therefore, the distribution of pollutant-loading is important to improve perchlorate removal performance. The step-feeding could effectively distribute high pollutants loading to the individual compartments of the ABR system, which enhanced the contaminants removal performance of compartments. However, the optimal step-feeding ratio and the pollutants removal capacities in compartments of the ABR are still ambiguity.

Therefore, the step-feeding was carried out to relieve the adverse effect of high concentration perchlorate on the forward compartments and increase utilization ratio of the posterior compartments in ABR with heterotrophic combined sulfur autotrophic process. The step-feeding distribution ratio was investigated in detail with purpose of improving perchlorate removal performance of ABR. And then, the contribution of every ABR’s compartment for the pollutants removal and sulfate production were calculated according the mass balance. Moreover, the dominant bacterial community members were determined during the perchlorate heterotrophic and sulfur autotrophic removal process. Finally, the relationships between the bacterial community and environmental variables were evaluated via principal component analysis (PCA).

Section snippets

Experimental set-up and operation conditions

A laboratory-scale ABR system with eight compartments was used in this study. The system with liquid volume of 46 L contains heterotrophic perchlorate removal unit (HPR unit, including C1 to C5 compartments and filling with anaerobic sludge) and sulfur autotrophic perchlorate removal unit (SAPR unit, including C6 to C8 compartments and filling with sulfur particles) (as shown in Fig. 1). The volume ratio of the upflow and downflow was 4:1 in each compartment.

In HPR unit, the anaerobic sludge

ABR performance

The effect influent flow distribution ratios of HPR unit on the ABR performance were investigated. The profiles of COD, perchlorate and sulfate concentrations of ABR’s influent and effluent were shown in Fig. 2.

Conclusions

The optimizing step-feeding distribution ratio was investigated for improving perchlorate removal performance and controlling the sulfate production in ABR systems with heterotrophic combined sulfur autotrophic process. This study demonstrated that when the distribution ratio of C1-C5 compartments were 30%, 20%, 20%, 20% and 10% respectively, the ABR could maximally remove 1300 mg/L perchlorate with the removal efficiency reaching to 99.8%. Furthermore, the mass balance calculation showed that

CRediT authorship contribution statement

Haibo Li: Conceptualization, Funding acquisition, Formal analysis, Investigation, Data curation, Writing - review & editing. Kun Li: Data curation, Writing - original draft. Jianbo Guo: Validation, Supervision, Funding acquisition, Writing - review & editing. Zhi Chen: Supervision, Funding acquisition, Writing - review & editing. Yi Han: Writing - review & editing. Yuanyuan Song: Writing - review & editing. Caicai Lu: Writing - review & editing. Yanan Hou: Writing - review & editing. Daohong

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant No. 51678387 and 51908399) and Tianjin Natural Science Foundation (Grant No. 19JCQNJC07600). We would like to thank Master Buyue Wang for her assistance in drawing of Graphical Abstract.

References (34)

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