Horden Mine Water Treatment Scheme

July 2004 saw the commencement of operations at The Coal Authority’s new temporary minewater treatment plant on the site of the former Horden Colliery in Durham. This is a significant achievement for all concerned as the project took only 11 months from decision to procede to operation. Monitoring of underground water levels raised concerns that minewater levels in the East of Wear region were recovering to a point where the overlaying aquifer would be at risk of pollution by September 2004. The aquifer in question accounts for 20% of the potable water supplied to the area by Northumbrian Water. Also further pollution would be likely in the surrounding low-lying areas of the Wear Valley and adjacent coastal regions.

Investigation of the water quality indicated that the new plant may have to treat a maximum of 150 litres/sec of minewater containing up to 200 mg/litre of dissolved iron. Unipure Europe Ltd of Monmouth were engaged as Process Engineers to design the plant and oversee its construction. The plant consists of three treatment streams, each made up of two large reactor tanks, and a clarifier to separate the precipitated iron sludge from the treated minewater. The treated water is then discharged, via a pipeline to a sea outfall. The plant is fully automated, constantly monitoring and adjusting its processes to maintain the desired discharged water quality. The plant is staffed 24/7 and maintained by Engenica (TBC).

This type of plant is a first for The Coal Authority, its modular design of three independent treatment streams allowing increased flexibility regarding its future use and was a major consideration in the plants design philosophy. As the site for a permanent scheme has yet to be agreed upon, it was decided that the former Horden Colliery at Peterlee would be the most appropriate site for a temporary plant to be built. The prompt delivery of this project protects the integrity of the local water supply and alleviates the risk of a major pollution incident in the East of Wear region. It also allows the location of a permanent solution to the long term management of minewater levels in the area to be identified and implemented.