Celtic Anglian Water

Water Treatment
Sligo Water Treatment Plant, Foxes Den, Sligo
On the 1st of November 2001 Celtic Anglian Water (CAW) took over the Operations and Maintenance of the Water Treatment Plant at Foxes Den, Sligo. CAW became the first private company to be awarded a Water Treatment Operations and Maintenance Contract in the Irish Republic.

This scheme is an investment by Sligo County Council, the Government and the EU. It was designed to provide potable water for the domestic, agricultural and industrial requirements for Sligo.

The raw water source for the scheme is extracted from Lough Gill, 3 kilometres southeast of Sligo and pumped via a 500mm pipe line at a rate of approximately 550 cubic metres per hour to the main treatment works. The state of the art water treatment plant is delivering around 11 million litres of drinking water a day to the Sligo area. The water is initially dosed with alum and polyelectrolyte to speed up the flocculation process. This dosed water is then conveyed to the flocculation tanks where a paddle type mixer complete with access bridge and handrailing is provided in each tank, to again improve flocculation. The coagulated particles are mixed with a water supply partly saturated with air. These bubbles of air attach to the suspended particles and float to the surface where they are removed by a mounted surface skimmer.

The remaining water is allowed to settle and is then polished off by passing through rapid gravity filters. Following filtration the final water is pH corrected, fluoridated (by others) and chlorinated before entering the potable water supply system. A reservoir is provided on site for the storage of potable water supplies.

Water

Washwater generated during a filter backwash gravitates to the washwater holding tank where it is mixed with the particles removed by the surface skimmer. All suspended matter present in the washwater tank is completely mixed and sent to the sludge thickener. The thickened sludge is pumped to the sludge holding tank and then on to the sludge dewatering building. The sludge is dewatered using a decanter centrifuge and the 18% ds cake is removed off site to a licensed landfill site. As part of Sligo County Council’s (SCC) ongoing environmental protection policy the plant has a capability to recycle the supernatant water from the sludge plant thus reducing the amount of raw water drawn from Lough Gill.

The plant is manned by 3 local, CAW trained staff, with an advanced telemetry system remotely controlling the operation 24 hours a day.

The Water Quality is required to meet the requirements of Article 7, Monitoring of Council Directive 98/83/EC. Water quality is measured with integrated instrumentation for pH, chlorine and aluminium. The plant is currently meeting these water standards and has made a considerable improvement on previous water quality.