Anaerobic biotransformation of roxarsone regulated by sulfate: Degradation, arsenic accumulation and volatilization

Rui Tang; Guangxue Wu; Zhengbo Yue; Wei Wang; Xinmin Zhan; Zhen-Hu Hu

doi:10.1016/j.envpol.2020.115602

Anaerobic biotransformation of roxarsone regulated by sulfate: Degradation, arsenic accumulation and volatilization

Environ Pollut. 2020 Dec:267:115602. doi: 10.1016/j.envpol.2020.115602. Epub 2020 Sep 6.

Authors

Rui Tang¹, Guangxue Wu², Zhengbo Yue³, Wei Wang⁴, Xinmin Zhan⁵, Zhen-Hu Hu⁶

Affiliations

¹ School of Civil Engineering, Hefei University of Technology, Hefei, 230009, China; School of Resources and Environmental Engineering, Hefei University of Technology, Hefei, 230009, China.
² Key Laboratory of Microorganism Application and Risk Control (MARC) of Shenzhen, Graduate School at Shenzhen, Tsinghua University, Shenzhen, 518055, China.
³ School of Resources and Environmental Engineering, Hefei University of Technology, Hefei, 230009, China.
⁴ School of Civil Engineering, Hefei University of Technology, Hefei, 230009, China.
⁵ Civil Engineering, College of Engineering and Informatics, National University of Ireland, Galway, Ireland.
⁶ School of Civil Engineering, Hefei University of Technology, Hefei, 230009, China; Anhui Provincial Engineering Laboratory for Rural Water Environment and Resources, Hefei University of Technology, Hefei, 230009, China. Electronic address: zhhu@hfut.edu.cn.

PMID: 33254639
DOI: 10.1016/j.envpol.2020.115602

Abstract

Roxarsone, an extensively used organoarsenical feed additive, is often pooled in livestock wastewater. Sulfate exists ubiquitously in livestock wastewater and is capable for arsenic remediation. However, little is known about impacts of sulfate on roxarsone biotransformation during anaerobic digestion of livestock wastewater. In this study, the biodegradation of 5.0 mg L^-1 roxarsone, and the accumulation and volatilization of the generated arsenical metabolites in a sulfate-spiked upflow anaerobic granular blanket reactor were investigated. Based on the analysis of degradation products, the nitro and arsenate groups of roxarsone were successively reduced to amino and arsenite groups before the C-As bond cleavage. Effluent arsenic concentration was ∼0.75 mg L^-1, of which 82.9-98.5% were organoarsenicals. The maximum arsenic volatilization rate reached 32.6 μg-As kg^-1-VS d^-1. Adding 5.0 mg L^-1 sulfate enabled 66.7% and 45.9% decrease in inorganic arsenic concentration and arsenic volatilization rate, respectively. Arsenic content in the anaerobic granular sludge (AGS) was accumulated to 1250 mg kg^-1 within 420 days. Based on the results of FESEM-EDS and XPS, sulfate addition induced arsenic precipitation in the AGS through the formation of orpiment. Arsenic in the effluent, biogas and AGS accounted for 52.9%, 0.01% and 47.1% of the influent arsenic when the reactor operated stably. The findings from this study suggest that sulfate has effectively regulatory effects on arsenic immobilization and volatilization during anaerobic digestion of organoarsenic-contaminated livestock wastewater.

Keywords: Anaerobic digestion; Arsenic; Biotransformation; Roxarsone; Sulfate.

MeSH terms

Anaerobiosis
Animals
Arsenic*
Biotransformation
Roxarsone*
Sulfates
Volatilization

Substances

Sulfates
Roxarsone
Arsenic