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| Bio-reduction of arsenic and nitrogen by sulfate-reducing bacteria in bentonite |
| Received:October 06, 2022 Revised:December 19, 2022 |
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| KeyWord:arsenic;nitrogen transformation;sulfate-reducing bacteria;bentonite |
| Author Name | Affiliation | E-mail | | MENG Xinyun | College of Resources and Environment, Southwest University, Chongqing 400715, China | | | ZHAO Jia | College of Resources and Environment, Southwest University, Chongqing 400715, China | | | LIU Jing | College of Resources and Environment, Southwest University, Chongqing 400715, China | liujing-vip@163.com |
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| Abstract: |
| This paper investigates the effects of the sulfate-reducing bacteria（SRB）, Desulfovibrio vulgaris Miyazaki, exogenous N addition amount, and organic matter on the species and concentration of arsenic（As）and nitrogen（N）molecules in the bentonite solid-liquid system under anaerobic conditions, as well as the relationship between them through microcosmic experiments. The results showed that As（Ⅴ）was reduced to As（Ⅲ）from day zero, reaching 1 947 μg·L-1 on day seven, in the standard culture medium suitable for SRB growth. This is markedly higher than As（Ⅲ）concentration（1 341 μg·L-1）in ultra-pure water. Biological reduction increased NO2- and NH4+ in three different bacterial growth conditions. In the control group without nitrogen addition, As（Ⅲ）was almost undetectable. However, in the experimental groups with low and high nitrogen levels, As（Ⅲ）concentrations were 427 μg·L-1 and 1 341 μg·L-1, respectively, and ammonium formation and denitrification was evident with the addition of nitrogen. The addition of high and low levels of sodium acetate markedly increased the amount of As（Ⅴ）available for reduction. The average As（Ⅲ）concentrations obtained were 2.0 and 2.5 times higher than those of the control group, respectively. However, the addition of humic acid increased the amount of As（Ⅴ） being reduced. Further experiments to explore the relationship between NO2- and As（Ⅲ）show that the concentration of As（Ⅲ）can be increased from below the detection range to 14.6 μg·L-1 within 5 hours after sodium nitrite is directly added to As（Ⅴ）solution coexistence system, therefore NO2- can serve as an electron donor in the reaction and directly participate in As（Ⅴ）reduction reaction. |
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