Using our extensive industrial wastewater treatment expertise ProChemTech set about the task of creating a system that could clean acid mine drainage water enough to raise fish. Working together with William J. Sabatose of the Toby Creek Watershed Association, Inc, ProChemTech developed a treatment method. A basic design for treatment of the incoming mine discharge consisting of a diversion structure, lift station, aeration tank, flocculent polymer add/mix tank, inclined plate clarifier, multimedia filters, and sludge dewatering was proposed.
In addition to using carbon dioxide removal by aeration for pH adjustment, two other innovative processes were incorporated into the abandoned mine wastewater treatment system design, use of inclined plate clarification for removal of precipitated iron and sludge recirculation.
Inclined plate clarification has been used in industrial wastewater systems for many years as the process provides for high capacity at minimal cost in a small area. Until the recent Brandy Camp abandoned mine drainage system upgrade, this process had never been applied to treatment of acid mine drainage. Based on the excellent results obtained in the Brandy Camp project, inclined plate clarification was selected for the Blue Valley project. Specific features of the proprietary inclined plate clarifiers were designed and built specially for this project. In addition, the clarifiers are operated with no sludge blanket; all settled sludge is either recirculated or sent to the sludge holding tank.
Sludge recirculation has been used in a substantial number of industrial heavy metals treatment systems designed by ProChemTech since 1987 to obtain significant improvements in treated water clarity, improved settling rate, and denser sludge. The Blue Valley Project is the first acid mine drainage treatment system that has incorporated this innovative technology.
After going through the treatment process the water is fed into the fish tanks. There are a total of three fish tanks being solely supplied by abandoned mine water drainage. Each fish tank is 25ft diameter and contains approximately 15,000 rainbow and brook trout. The water from the fish culture tanks is then discharged to a large pond with a capacity estimated at 10 million gallons prior to flowing into the Little Toby Creek. This pond serves to remove any residual solids from the fish tanks prior to discharge and also supports a good fish population itself.
Sludge produced by operation of the Blue Valley is first pumped from the clarifiers to sludge storage tanks. From the storage tanks it is pumped to a recessed plate filter press for dewatering into a solid cake for either disposal or use as a raw material in manufacturing. This sludge cake is of high purity, and mostly iron due to lack of any alkaline reagent addition.
Note that in contrast to most abandoned mine drainage treatment projects where the removed pollutants are typically retained in open ponds subject to debris contamination, the material at the Blue Valley is both dewatered to an easily handled cake, is kept clean, and free from contamination. A clean, dewatered cake will facilitate reuse of this material in the future.
Results of the Blue Valley Project:
The first phase of the Blue Valley Fish Culture station is providing treatment of 300 to 500 gpm of abandoned mine drainage with beneficial reuse of the water as makeup to a fish culture station.
At full flow, approximately 660 lbs/day of iron hydroxide sludge will be prevented from entering the waters of the Commonwealth.
Use of inclined plate clarifier technology has been demonstrated with acid mine drainage, the results obtained, discharge turbidity generally below 0.1 ntu, are far superior to previously used clarification technology.
Pollutants, mainly iron, are reduced to a clean, easy to handle sludge cake which is suitable for future resource recovery.
The Toby Creek watershed Association continues to run the Blue Valley Project with one operator and a mix of public and private funding.