Impact of roxarsone on the UASB reactor performance and its degradation
Mengchuan Shui, Feng Ji, Rui Tang, Shoujun Yuan, Xinmin Zhan, Wei Wang, Zhenhu Hu
《环境科学与工程前沿（英文）》
2016年
第10卷
第6期
doi:
10.1007/s11783-016-0871-9
摘要：
Impact of continuous ROX addition on performance of UASB reactor was investigated With continuous ROX addition, severe inhibition to methanogenic activity occurred ROX addition caused the changes in the morphology and bacterial diversity of AGS A possible biotransformation pathway of ROX in the UASB reactor was proposed 60%–70% of the arsenic was discharged to the effluent, and 30%–40% was precipitated Roxarsone (3-nitro-4-hydroxyphenylarsonic acid, ROX) has been widely used for decades as an organoarsenic feed additive to control intestinal parasites and improve feed efficiency in animal production. However, most of the ROX is excreted into the manure, causing arsenic contamination in wastewater. The arsenic compounds are toxic to microorganisms, but the influence of continuous ROX loading on upflow anaerobic sludge blanket (UASB) reactor is still unknown. In this study, the impact of ROX and its degradation products on the performance of the UASB reactor and the degradation and speciation of ROX in the reactor were investigated. The UASB reactor (hydraulic retention time: 1.75 d) was operated using synthetic wastewater supplemented with ROX for a period of 260 days. With continuous ROX addition at 25.0 mg?L , severe inhibition to methanogenic activity occurred after 87 days operation accompanied with an accumulation of volatile fatty acids (VFAs) and a decline in pH. The decrease of added ROX concentration to 13.2 mg?L did not mediate the inhibition. As(III), As(V), MMA(V), DMA(V), HAPA and an unknown arsenic compound were detected in the reactor, and a possible biotransformation pathway of ROX was proposed. Mass balance analysis of arsenic indicated that 60%–70% of the arsenic was discharged into the effluent, and 30%–40% was precipitated in the reactor. The results from this study suggest that we need to pay attention to the stability in the UASB reactors treating organoarsenic-contaminated manure and wastewater, and the effluent and sludge from the reactor to avoid diffusion of arsenic contamination.
关键词：
Anaerobic digestion
Anaerobic granular sludge (AGS)
Arsenic species
Impact
Roxarsone (ROX)
UASB reactor
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