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Study on removing selenate from groundwater by autohydrogenotrophic microorganisms

Siqing XIA, Shuang SHEN, Jun LIANG, Xiaoyin XU

《环境科学与工程前沿（英文）》 2013年第7卷第4期页码 552-558 doi: 10.1007/s11783-013-0531-2

摘要： Performance of autohydrogenotrophic bacteria for bio-reduction of selenate (Se(VI)) under anaerobic conditions was investigated with batch experiments. Results showed Se(VI) was bio-reduced to selenite (Se(IV)) as an intermediate product, and then to elemental selenium (Se ). Reduction kinetics could be described by the pseudo-first-order model. In particular, the influences of pH value and temperature on Se(VI) reduction by autohydrogentrophic organisms were examined. The high degradation rate was achieved at pH 7.0 to 8.0; and the best reduction temperature was between 25°C and 35°C. This study is of help for treating groundwater with selenium contamination by autohydrogenotrophic bacteria as well as its reactor development.

关键词： autohydrogenotrophic selenate hydrogen groundwater

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Biological removal of selenate in saline wastewater by activated sludge under alternating anoxic/oxic

Yuanyuan Zhang, Masashi Kuroda, Shunsuke Arai, Fumitaka Kato, Daisuke Inoue, Michihiko Ike

《环境科学与工程前沿（英文）》 2019年第13卷第5期 doi: 10.1007/s11783-019-1154-z

摘要： Removal of selenate in saline wastewater by activated sludge was examined. Sequencing batch reactor was operated under alternating anoxic/oxic conditions. Above 97% removal of soluble selenium (Se) was achieved continuously. Major Se removal mechanism varied depending on the length of aeration period. Various Se-reducing bacteria likely contributed to coordinately to Se removal. Selenium (Se)-containing industrial wastewater is often coupled with notable salinity. However, limited studies have examined biological treatment of Se-containing wastewater under high salinity conditions. In this study, a sequencing batch reactor (SBR) inoculated with activated sludge was applied to treat selenate in synthetic saline wastewater (3% w/v NaCl) supplemented with lactate as the carbon source. Start-up of the SBR was performed with addition of 1–5 mM of selenate under oxygen-limiting conditions, which succeeded in removing more than 99% of the soluble Se. Then, the treatment of 1 mM Se with cycle duration of 3 days was carried out under alternating anoxic/oxic conditions by adding aeration period after oxygen-limiting period. Although the SBR maintained soluble Se removal of above 97%, considerable amount of solid Se remained in the effluent as suspended solids and total Se removal fluctuated between about 40 and 80%. Surprisingly, the mass balance calculation found a considerable decrease of Se accumulated in the SBR when the aeration period was prolonged to 7 h, indicating very efficient Se biovolatilization. Furthermore, microbial community analysis suggested that various Se-reducing bacteria coordinately contributed to the removal of Se in the SBR and main contributors varied depending on the operational conditions. This study will offer implications for practical biological treatment of selenium in saline wastewater.

关键词： Activated sludge Selenate reduction Saline wastewater Sequencing batch reactor Alternating anoxic/oxic conditions Selenium biovolatilization