Dongyang Deng

Date of Graduation

2017

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Lian-shin Lin

Committee Co-Chair

Martin Jacob Christ

Committee Member

Leslie Hopkinson

Committee Member

Antar Jutla

Committee Member

Louis M McDonald

Abstract

Acid mine drainage (AMD) and municipal wastewater (MWW) are two major pollution sources in headwaters of Appalachia and energy producing regions worldwide. Incorporating the prevalent chemistry of the two wastes in designing treatment technologies for concurrent management of the wastes can provide multi-faceted benefits. First, alkalinity in MWW can raise the pH of AMD upon mixing, and promote chemical precipitation of metal hydroxides and carbonates. Second, low solubility of phosphate with multivalent metals (e.g., Fe and Al) can be an effective mechanism for recovering phosphate from MWW. Third, sulfate ions from AMD can serve as an electron acceptor for oxidation of organics from MWW. This can potentially eliminate the need of aeration for the biological treatment of MWW (e.g., activated sludge processes), which is the most energy-intensive operation at wastewater treatment plants. Additional benefits included significantly reduced greenhouse gas emission from the wastewater treatment and biological sludge production.;This research focuses on developing an innovative wastewater treatment method using iron as a green agent to render the above-mentioned benefits. The research consists of two parts that reflect the development of the treatment concept: co-treatment of AMD and MWW, and iron-dosed wastewater treatment. The co-treatment method involves a two-staged treatment of field-collected AMD and MWW samples, which includes aerobic mixing of the two wastes followed by a sulfidogenic treatment of the mixture solution in batch-fed experiments. This part of the research focuses on examining treatment efficiency of a wide range of pollutants originating from the two wastes. The iron-dosed wastewater treatment involves anaerobic bioreactors for continuous treatment of MWW with an option of sludge recycle. Overall, the research activities are divided into four phases: 1) evaluation of technical feasibility of co-treatment of AMD and MWW using field-collected samples, 2) investigation of relevant factors on sulfidogenic wastewater treatment kinetics and its relationship with microbial ecology, 3) developing a anaerobic technology for continuous MWW treatment with iron dosing and 4) elucidating reaction biotic and abiotic reaction mechanisms at different stages of the continuous treatment process. Corroborated by phylogenetic tree, kinetic modeling, scanning electron microscope, X-ray photoelectron spectroscopy and X-ray diffraction analysis, these bio-chemical mechanisms were studied and used to optimize the treatment process.;Results indicate that AMD and MWW passive co-treatment is a viable cost-effective approach to improve water quality and can achieve multiple treatment objectives concurrently with promising treatment efficiency. Potential toxicity of iron and other metals can be avoided and favorable sulfidogenic treatment conditions can be achieved by proper mixing of the two wastes. Sulfidogenic treatment kinetics is closely related to microbial ecology in the bioreactors and can be optimized by chemical oxygen demand (COD)/sulfate ratio of the influent to the bioreactors.;Long-term operation of continuous treatment of MWW with iron dosing and sludge recycling under a range of COD/sulfate and Fe/S ratios was successfully demonstrated. Biogeochemical transformations of the two main elements, Fe and S, in the treatment process were examined using spectroscopic and phylogenetic analyses. The analyses included 1) mass balances of Fe, S in the treatment process, 2) qualitative characterization of the chemical and biological sludge materials, 3) estimations of mass fluxes of chemical and biological materials, and 4) identification of microbial species responsible for biological transformations of Fe and S at different stages of the treatment process. This innovative treatment process was found to exhibit long-term operation stability and consistent treatment performance with COD/sulfate and Fe/S as the primary two factors affecting the overall treatment performance.

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