BIOREMEDIATION OF EFFLUENT WATER IN A COAL ASH DISPOSAL AREA: OPTIMIZING MICROBIAL SULFATE REDUCTION

Coal combustion residues (CCR) pose a serious environmental threat, even long after they are disposed of in specialized landfills, due to their complex composition and potential for leaching into waterways. This study focuses on the issue of elevated sulfate concentrations at the Martin Lake Steam Electric Station (MLSES) A-I Disposal Area in Panola County, Texas, where CCR are disposed of in a permanent landfill. This site is exceeding its regulatory limit of sulfate concentrations in its effluent and is in need of a cost-effective and sustainable solution to this problem.

This research utilized benchtop experiments to investigate sulfate reducing bacteria (SRB) mechanisms within flask wetland microcosms, simulating conditions comparable to the final pond at the disposal area. The effectiveness of acetic acid, lactic acid, mushroom compost, and cow manure were analyzed through a series of laboratory experiments treating flask wetland microcosms with varying concentrations of carbon sources to test their efficiency in improving SRB reduction. Mud substrate from an active wetland on site of the A-1 Disposal Area was used to inoculate flasks with SRB, carbon treatments, and 1000 ppm synthetic sulfate water.

Five trials were conducted testing four carbon treatments at three different ratios of chemical oxygen demand (COD) and three controls; each carbon treatment and control group were run in triplicate (n=45) for one week, four week, and eight week trials. Ultraviolet Visible (UV Vis) Spectroscopy was used to measure final sulfate concentrations using the Mettler Toledo Method.

Results show the acid substrates were successful in promoting SRB to utilize sulfate in the system, with up to 98% sulfate reduction after a 4-week experimental period. Overall, this research provided insights into long-term strategies for sulfate reduction and water quality improvement in coal ash disposal areas. By leveraging natural processes of biological sulfate reduction, this study proposes sustainable solutions for environmental remediation and regulatory compliance.