Abiotic, Biotic, and Bio-Enhanced Reduction of Hexavalent Chromium, Chloroform and Co-Contaminants Using Nano-Scale Zero Valent Iron in Highly Contaminated Groundwater
Master of Science in Engineering (MSE)
Civil and Environmental Engineering and Construction
First Committee Member
Second Committee Member
Third Committee Member
Fourth Committee Member
Boo Shan Tseng
Number of Pages
Investigations of groundwater in a former industrial perchlorate manufacturing site have shown high contamination with perchlorate, chlorate, nitrate, hexavalent chromium (Cr (VI)), and chloroform (CF) with levels greater than 3,000, 30,000, 300, 100, and 4 mg/L, respectively. Remediation efforts using biological reduction to desired contaminant levels at this site has been challenging due to high contaminant concentrations, and high total dissolved solids (TDS). Furthermore, removal of Cr(VI) and CF in the presence of nitrate, chlorate, and perchlorate has not been examined at the contaminated site. Nano-scale Zero-Valent-Iron (NZVI) has been effective at reducing groundwater contamination both with and without bacterial augmentation. The objective of this research was to investigate the removal of CF, Cr(VI) and co-contaminants in contaminated industrial groundwater using NZVI alone or in combination with biological reduction (bio-enhancement). The effectiveness of abiotic reduction using NZVI, biotic reduction using a 1ml bacterial sludge inoculum enriched with 20 ml/L of molasses and additional nutrients, and bio-enhanced reduction using both NZVI and bacteria was evaluated in this study. Bench-scale reactors were monitored for Cr(VI), CF, nitrate, chlorate, and perchlorate removal over 8 weeks. The use of NZVI resulted in 100% reduction of Cr(VI) in only 4 hours with doses of 5,000 mg Fe^0/L. As 100% reduction of Cr(VI) occurred at a much faster rate in abiotic treatments than biotic treatments, bio-enhancement for Cr(VI reduction relies more on NZVI reduction. For CF, removal showed 15%-40% greater results under bio-enhancement conditions than abiotic treatments. However, a bio-enhanced NZVI dose of at least 8,500 mg Fe^0/L is needed to achieve higher removal than biotic treatments alone. A bio-enhanced NZVI dose of 17,000 mg Fe^0/L resulted in 100% CF removal in 7 days. Bio-enhancement also achieved greater nitrate and chlorate removal, showing 100% removal at NZVI doses of 17,000 and 5,000 mg Fe^0/L, respectively. No abiotic perchlorate reduction was observed using NZVI. Perchlorate showed 25-50% removal only in biotic and bio-enhanced conditions. Bio-enhancement showed greater and more consistent removal for all the examined contaminants. This endorses bio-enhancement as the best treatment for groundwater from the examined site.
Bio-enhanced remediation; Bio-remediation; NZVI; Remediation
Environmental Engineering | Environmental Sciences
University of Nevada, Las Vegas
Robleto Martinez, Eduardo, "Abiotic, Biotic, and Bio-Enhanced Reduction of Hexavalent Chromium, Chloroform and Co-Contaminants Using Nano-Scale Zero Valent Iron in Highly Contaminated Groundwater" (2020). UNLV Theses, Dissertations, Professional Papers, and Capstones. 3950.
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