The LTV Steel Corporation’s Banning No. 4 mine operated until the early 1980s as a room and pillar deep mine within the Pittsburgh Seam of the Main Bituminous Coal Field on the east and west sides of the Youghiogheny River near the Borough of West Newton in Westmoreland County, Pennsylvania.

Upon closure, the mine pool increased in elevation and created a surface discharge in downtown West Newton. The Pennsylvania Department of Environmental Protection then ordered the mining company to use the two active treatment plants that were used for dewatering during active mining operations, Banning and Euclid, to reduce the mine pool to a safe elevation preventing further surface expression into West Newton and the Youghiogheny River and for treatment of the subsequent daily quantity to keep the mine pools at that elevation. Those two plants continue in that same capacity to this day but have operational difficulties due to age and antiquated technology. Banning and Euclid mine pool water quality can be characterized as anoxic, circumneutral, highly alkaline with elevated concentrations of iron, around 10 mg/l within Banning and 30 mg/l within Euclid. Normal combined plant influent flows are near 38 million liters per day.

In the first quarter of 2023, Kleinfelder Inc was awarded the design contract by the Clean Streams Foundation and the Pennsylvania Department of Environmental Protection to update treatment facility technology, improve operational flexibility through added redundancy, and to combine treatment into one larger active treatment plant strategically located downstream which will simplify future operation and maintenance.

Kleinfelder will discuss the process of developing the conceptual design for the facility and the assumptions, considerations, and risk analysis completed to effectively manage not only the pumping system to maintain the mine pool at an adequate elevation, but also treatment facility design deliverables that will offer increased redundancy and treatment operational flexibility for this planned hydrogen peroxide-based mine drainage treatment plant.

The Tioga River, a major tributary to the Upper Susquehanna River Basin, has been negatively affected by Northern Bituminous Coal Field abandoned mine drainage stemming from legacy coal mining that began in the mid-1800s, ending in the 1980s. This mine drainage loading pollution, centered around the Borough of Blossburg and the village of Morris Run in Tioga County, Pennsylvania, has rendered over 32-kilometers of the Tioga River and several tributaries as fishless due to acidity, iron, and aluminum loadings. The severe extent of the entire problem combining relatively high-flow mine drainage outfalls containing elevated acidity and metal concentrations, has created a pollution problem that was economically unfeasible to consider for treeatment as a whole historically. This economic problem was solved with the passage of the 2021 Infrastructure Investment and Jobs Act and the yearly funds allocated to Pennsylvania for mine land reclamation and mine drainage treatment.

The five deep mine discharges outfall near one another and enter the Tioga River within a eight kilometer stretch. This relative closeness of the outfalls and rural character of Tioga County allows for the capture and conveyance of these flows to a centralized active treatment plant. In 2021, the Susquehanna River Basin Commission received a Pennsylvania Department of Environmental Protection Abandoned Mine Land Economic Revitalization grant award to complete a full design to accomplish that objective. The Susquehanna River Basin Commission awarded Kleinfelder, Inc. the design contract for the Morris Run Active Abandoned Mine Drainage Treatment Plant Project in 2022, with design completion slated for first-quarter 2024.

The combination of five discharges with varying quantities and qualities creates future operational challenges that had to be managed through risk assessment design decisions. However, having nearly all watershed mine drainage now treated at one plant also allowed for considerations to be made as to where best to discharge the treated effluent to maximize stream mileage restoration gains, while also keeping the treated water cold to aid wild salmonid presence and reproduction within the Tioga River and its tributaries.

These treatment design decisions that consider the management of uncontrollable mine drainage outfall flows containing elevated acidity and metal loading, along with the applications implemented to best utilize the treated effluent to maximize stream mileage gains and protect river ecology can be replicated in other watersheds containing similar large flow and loading mine drainage discharges.

The State of Minnesota, in its efforts to protect wild rice, set a stringent sulfate standard of 10 mg/L for wild rice waters back in 1973. Achieving this standard poses a substantial challenge for small industries and municipalities due to a lack of cost-effective technologies. Membrane-based technologies, such as nanofiltration or reverse osmosis, are capable of treating water to conform with the Minnesota wild rice water sulfate standard; however, these technologies often require high capital and operation costs. Recognizing the need to develop cost-effective sulfate treatment alternatives, our project team investigated the feasibility of chemical precipitation technologies to reduce sulfate to below 10 mg/L via a combination of laboratory and field pilot testing.

Chemical precipitation using lime or barium chemicals is often used to treat mine drainage or wastewater with relatively high and medium concentrations of sulfate. However, there is a gap in research regarding water treatment at low sulfate concentrations (<200 mg/L). A treatment system has developed based on barite chemical precipitation reactions followed by ferric chloride flocculation to remove sulfate from wastewater. The lab scale batch and continuous tests examined various process parameters, including chemical dosage rates, the necessity of nucleation promotion, mixing rates, residence rates, and the influence of temperature. Using the parameters defined from the laboratory tests, a mobile pilot system was designed and manufactured.

The pilot system was deployed in three wastewater treatment plants over two summers to treat both domestic wastewater and a mixture of industrial and domestic wastewater at a flow rate of 4-7.5 liters per minute. The designed barite precipitation process successfully reduced sulfate levels from 60-350 mg/L to below 10 mg/L, with some modifications necessary for different wastewater compositions and chemistry. For instance, an excess dosage of barium chemical and the introduction of nucleation seeds were required to treat water containing sulfate with concentrations below 100 mg/L. Additionally, the presence of organic chelates interferes with the reaction, necessitating the addition of ferric chloride to remove organic chelates prior to the precipitation reaction to effectively remove these chelates.

The findings from laboratory and pilot-scale testing will be key scientific and engineering foundations to develop a full-scale or industry-relevant treatment system based on barite precipitation technology in sulfate removal. Based on process and engineering design parameters derived from the pilot testing, the project team is moving toward the development of generic designs for integrating this treatment process into existing wastewater treatment facilities.