Efficient dewatering of acid mine drainage sludge is necessary to reduce disposal costs and improve the viability of reusing the sludge for other purposes, such as low-cost adsorbents and building…

The Office of Surface Mining Reclamation and Enforcement awarded Virginia Polytechnic Institute and State University $200,000 under the Science and Technology Projects Related to Coal Mining and Reclamation federal grant program (CFDA 15.255) from July 1, 2023 to June 30, 2025. The award will support Virginia Tech's development, optimization, and validation of an innovative acid mine drainage sludge dewatering process circuit consisting of lime neutralization, precipitate flotation, and filtration. The goal of the OSMRE Applied Science Program is to develop improved science-based technologies to address environmental and restoration topics related to coal mining. If proven effective on an industrial scale, Virginia Tech's proposed modular circuit could enhance sludge dewatering and reduce disposal costs for mining companies, helping to further the program's objectives.

Efficient dewatering of acid mine drainage sludge is necessary to reduce disposal costs and improve the viability of reusing the sludge for other purposes, such as low-cost adsorbents and building materials. Some existing dewatering circuits can generate sludge with as high as 30 WT. Solids content however, nearly all the circuits rely on sedimentation in clarifiers, which is a relatively slow process and normally takes several to tens of hours. Therefore, clarifiers are required to have a large volume to provide enough residence time, and the existing circuits usually occupy a large footprint and have a low degree of modularity, which make the circuits difficult to assemble, dissemble, and relocate. As a result, the existing dewatering circuits are not suitable when the acid mine drainage of mining companies is distributed in different areas with relatively small volumes. In this case, centralized processing or installing a new processing plant in each area is unfeasible due to high transportation and construction costs. To address this dilemma, an innovative process circuit consisting of lime neutralization, precipitate flotation, and filtration is proposed, which is advantageous over the existing circuits in several aspects, such as smaller footprint and higher modularity. The primary objective of this project is to develop, optimize, and validate the proposed circuit by conducting experimental tests and techno-economic analysis. In this project, the specific technical and economic metrics that will be achieved using the proposed circuit include: (1) solids content in the sludge is improved to greater than 30 WT. (2) the clean water generated from the proposed circuit complies with the coal mining effluent guidelines and standards formulated by the U.S. Environmental protection agency (EPA) and (3) the cost of the proposed circuit is close to or less than that of the existing circuits. The office of surface mining reclamation and enforcement (osmre) is responsible for establishing a nationwide program to protect society and the environment from the adverse effects of surface coal mining operations. The proposed project aims to develop, optimize, and validate an efficient, low-cost, and modular process circuit to enhance the dewatering of acid mine drainage sludge. Application of the circuit on an industrial scale will bring several benefits, such as reducing sludge disposal costs, increasing sludge stability, and decreasing environmental impact. Therefore, the proposed project exactly aligns with the responsibilities of osmre and will contribute to the well-being of mining states and tribes.