Selenium (Se) is a naturally occurring trace element that is nutritionally essential for humans and animals but toxic at high concentrations. This laboratory study explored the feasibility of developing a treatment column containing municipal wastewater treatment sludge (biosolids), drinking water treatment residuals (WTRs) and agricultural solid waste wheat straw to clean up Se-contaminated industrial wastewater. High microbial activity in biosolids and wheat straw could reduce selenate (SeO42−) and selenite (SeO32−) to water-insoluble elemental Se, and the abundance of aluminum (Al), iron (Fe) and calcium (Ca) hydroxides in WTRS could sorb SeO32− from wastewater through the formation of inner-sphere complexation. A series of logically connected laboratory experiments have been conducted to test this novel concept and explore potential controlling mechanisms. Results show that, with 1 mg/L Se as selenite, the biosolid-WTR-wheat straw column reduced Se concentrations by 95% from 1 mg/L to 0.04 mg/L over three days. Selenium speciation significantly affects Se removal efficiency, more effectively with selenite than with selenate. Wastewater pH also affects selenite-Se removal efficiency, showing a descending order of acidic (pH 6.5) > neutral (pH 7) > basic (pH 8.5) wastewater treated with 1 mg/L. Five bacterial strains were isolated from wheat straw and the mixture of biosolids, WTRs and sand. All isolated bacterial strains show a good biotransformation ability to reduce SeO32- to Se0, and the strain Asc5 isolated from the mixture of the biosolid-WTR-sand treatment substrate also showed the most significant methylation to convert SeO32- to volatile Se organic compounds. Overall, this study has successfully demonstrated the feasibility of developing an environmentally sound remediation technology that uses municipal and agricultural solid waste materials to clean up Se-contaminated wastewater.
|Commitee:||Adegboyega, Nathaniel, Greenfield, Ben|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 82/3(E), Masters Abstracts International|
|Subjects:||Environmental science, Environmental engineering, Water Resources Management|
|Keywords:||Wastewater treatment, Drinking water, Selenium|
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