Date of Award

2020

Degree Type

Thesis

Degree Name

Master of Science in Civil and Environmental Engineering

Department

Civil and Environmental Engineering

First Advisor

Joseph E. Goodwill

Abstract

Acid mine drainage (AMD) and municipal wastewater (MWW) are two constituents that pose major environmental risks to surface waters if left untreated. Modern MWW treatment facilities are capable of removing organics and pathogens from wastewater before being discharged into surface waters. Although proven methods also exist for treating AMD, it is commonly untreated. Over the past few years, researchers have illuminated new approaches to simultaneously co-treat AMD and MWW. However, there is little research on combining the two waste streams within a conventional wastewater treatment plant for co-treatment. Co-treatment could facilitate metal removal from AMD while also improving MWW treatment processes. The city of Johnstown, PA hosts a unique opportunity for co-treatment with an urban AMD discharge in relative proximity to the city’s MWW treatment facility.

AMD often possess a high iron (Fe) content, which has the potential to benefit or disrupt MWW treatment processes. One potential risk of adding AMD is the amount of Fe that could end up in the facility’s solids (sludge) handling processes. Adding AMD to Johnstown’s MWW treatment facility at a 20% mixing ratio (the maximum AMD:MWW ratio predicted from the recorded data) could result in as much as 10 grams of Fe per kilogram of dry, dewatered sludge. This amount of Fe would fall in the low end of the EPA reported range for Fe content in dry solids. In addition, the published literature suggests the addition of Fe could be beneficial. The additional Fe content could help increase the sludge dewatering efficiency, improve the stabilization process, reduce odors produced from MWW solids, and raise the quality and marketability of the resulting biosolids currently used for land application.

Adding AMD after the biological treatment process and before the final clarification step will likely have little to no impact on MWW treatment. AMD addition likely offers improved final clarification of effluent and holds the lowest risk of disruption of the biological treatment phase. Our laboratory study examined the impact of co-treatment using raw Johnstown AMD and MWW samples at three mixing ratios with increasing amounts of AMD (1:25, 1:15, and 1:5 AMD to MWW). Results showed that co-treatment increased sludge settling at high ratios and significantly reduced effluent phosphate concentrations without impacting effluent pH, biochemical oxygen demand, or total solids. However, the effluent Fe and sulfate (SO42-) content did increase.

Co-treating AMD and MWW does have the potential to influence microbial activity in MWW treatment facilities. At the start of respiration rate trials, microbial respiration rates were lower than treatments without AMD, which suggests that AMD additions could influence biological processes in conventional wastewater treatment plants. However, as these trials progressed, the respiration rates eventually converged, suggesting that microorganisms in conventional wastewater treatment plants ought to be able to adapt to conditions with AMD.

Available for download on Friday, April 15, 2022

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