Ballykelly Wastewater Treatment Works

Built in the 1970s, Ballykelly Wastewater Treatment Works (WwTW) was designed to serve a population of just under 8,000. However, the closure of the nearby army barracks in 2008 meant the population was halved to around 3,600, leaving the works biologically and hydraulically oversized. 

A hybrid solution, comprising conventional and natural wastewater treatment processes was designed for Ballykelly. It would not only deliver a robust long-term solution for the village but also provide an area rich in biodiversity to enhance the local land/water environment. 

Additional lands were purchased adjacent to the existing site. This was to facilitate the implementation of a greener, sustainable solution while keeping the existing WwTW operational and compliant during construction works.

Solution

We delivered the following solutions to ensure compliance:

• Activated sludge plant (ASP) consisting of two lanes with anoxic and aerobic zones with process monitoring and control
• Two final settlement tanks with automatic de-scum and de-sludge
• Return activated sludge/surplus activated sludge pumping station with flow and level control
• Final Settlement Tank (FST) scum pumping station with storage transfer option
• Sludge holding tank, storage with agitation and decent facilities
• Tertiary treatment, comprising two free-water surface wetland cells to provide a final polish with quality monitoring
• Process flows, levels, and quality monitoring
• Ancillary processes to support the main process units
• Intelligent motor control centre (MCC) with telemetry
• Programmable logic controller (PLC) and Supervisory Control and Data Acquisition (SCADA) system using HMIs (MCC No.1 and inlet works MCC)
• 91.20kWp 75KW AC solar farm
• Extensive demolition of existing WwTW
• Standby generator Installation

Sustainable treatment and enriching biodiversity

The effluent from the conventional side of the works gravitates through the ICW ponds, and together the plants, micro-organisms, sun, substrate and air interact naturally to polish the wastewater and produce a high-quality effluent.
 
With a variety of native planting, the ICW creates a wide range of habitats for creatures large and small. The shallow water depth throughout the ICW allows various macro-invertebrates to find suitable areas within the wetland to survive and a wealth of vegetated areas, where wildfowl can nest.
 
By integrating the Ballykelly ICW solution, the site is enriched with biodiversity. The paths around the ICW have wildflowers planted, and in subsequent years, NI Water plans to cover over 7,500m² of unused space around the site with trees. The ICW also has the potential to deliver on a substantial range of other ecosystem services, including flood attenuation, amenity and recreation.