The Glenbeg Water Treatment Plant is designed to treat up to 3,000m3 of water per day. The plant is located on the western shore of Glenbeg Lough on the Beara Peninsula, Co. Cork, and supplies treated water to Castletownbere and its environs, including a number of fish processing companies based on Dinish Island just off Castletownbere itself.
Although Glenbeg Lough has been a source of water for the Castletownbere area for many years until the construction of the Glenbeg treatment works the raw water received only chlorination and fluoridation before being put into supply. The new treatment plant was put in place primarily to provide a barrier to cryptosporidium and to reduce elevated levels of trihalomethanes (THMs) which were being generated by the chlorination of the raw water.
However, Glenbeg Lough and the Ownagappul River which drains it, are located within the Glanmore Bog SAC and contain a population of freshwater pearl mussel (Margaritifera margaritifera). The freshwater pearl mussel is sensitive to water pollution and therefore no discharge of silt or other potential pollutants could be allowed into Ownagappul River either during construction or operation of the treatment works. Essentially this meant selecting and designing a treatment process that generated minimum waste and that no waste is discharged to Glenbeg Lough.
The works are designed to make operation and maintenance as simple as possible, with low energy costs and minimum waste. It was decided to retain as far as possible the existing infrastructure which consisted of the raw water intake, chlorination and fluoridation equipment, and the high lift pumps which deliver the water to a local reservoir. An ultraviolet sterilization system on the high lift rising main was also retained.
Low-level pumps lift the raw water onto the four newly constructed slow sand filters. The flows to each filter are controlled by automatic control valves on the inlet pipes, which maintain a constant head of water above the filter beds. A weir on the main filtered water outlet is set 50mm above the filter bed level to prevent a negative head development in the filter bed. The weir also aerates the filtered water. Filtered water from the cleaned filter is diverted to the raw water sump until the filter has matured (around 3 days) before the filtered water is returned to supply.
Operational costs for the Glenbeg Treatment Works including labour, raw water pumping, filtration and chemical dosing comes to just over half the estimated operational costs for conventional settlement and rapid gravity filter plants with similar design throughputs.