Annsborough WwTW, Co. Down

This rationalisation scheme was undertaken as part of the Integrated Wastewater Framework for NI Water by Doran Consulting designing for the BSG/ WIS JV. The contract provided a new wastewater treatment works at Annsborough in Co Down and a transfer pumping station with storm storage facilities at the works at nearby Castlewellan.

Castlewellan and Annsborough each had one Waste Water Treatment Works constructed in the early 1970s to serve the population and local industry in the adjacent towns. Castlewellan WwTW is located on the southern edge of Castlewellan town adjacent to the Burren River, whilst Annsborough WwTW is on the southern edge of Annsborough town near the Ballybannon River. The existing treatment processes consisted of percolating filters and settlement were designed to provide treatment to a mostly domestic population equivalent of 2,000 at Castlewellan WwTW and a mainly industrial population equivalent of 1,400 at Annsborough WwTW.

Preliminary studies identified that both the existing works required upgrading to meet the Urban Waste Water Treatment Regulations (Northern Ireland) 1995 and the revised discharge standards set by the Environment Agency. It was subsequently decided that a single waste water treatment works on the Annsborough WwTW site was the most cost effective solution.

The new works was designed for a population of 5,500 and use activated sludge treatment including a new inlet works, storm water storage, oxidation ditch, 2 final settlement tanks, sludge buffer and holding tanks, control building for process controls, equipment and sanitary provision. Throughout construction both the existing works continued to operate and suffered no deterioration from their existing performance.