Gairloch Water Treatment Upgrade Boosts Effluent Quality Ahead of Bathing Season

The Gairloch Wastewater Treatment Works (WwTW) has undergone a major upgrade to enhance effluent quality and ensure the site is fully prepared for the upcoming bathing season.

Previously, wastewater treatment at Gairloch relied on septic tanks for primary settlement, followed by fine screening and ultraviolet (UV) disinfection. However, the fine screen system was underperforming and required intensive operational input to maintain compliance with discharge standards.

To address this, a robust new treatment process was introduced. Following a successful trial of a temporary system, a Mecana Cloth Filter and Powder Activated Carbon (PAC) dosing system were permanently installed. These technologies significantly improve the quality of treated effluent, offering a more reliable and effective barrier against contaminants, which is crucial for safeguarding the water used during the May to October bathing season.

Timing was critical. All major construction had to be completed outside the regulated bathing period to avoid any impact on water quality. The upgrade involved removing the existing fine screen, which was refurbished and returned to the client for recyclability and future use, and excavating the site to install new treatment infrastructure between the septic tanks and UV system. Temporary flow diversions ensured compliance with environmental standards throughout the works.

Excavation presented a significant challenge, particularly due to groundwater infiltration and the highly viscous material with a high water content being removed. To prevent road contamination and maintain the project schedule, the team introduced “DryAdd,” a non-hazardous and biodegradable polymer that solidifies wet material, making removal cleaner and more efficient.

The new system is gravity-fed, eliminating the need for additional pumps and making use of the site’s natural elevation. A two-compartment mixing tank blends PAC with incoming effluent, which then passes through the Mecana Cloth Filter before entering the existing UV treatment stage. Quality instrumentation upstream and downstream of the filter continuously monitors turbidity and UV transmittance, enabling precise, responsive dosing control.

The PAC system is housed in a new GRP kiosk with integrated safety features, including catchpots for leak detection and an underground spill tank for overflow protection. All new equipment is centrally managed through an upgraded Motor Control Centre (MCC), fully integrated with the site’s existing control system.

These strategic upgrades mean Gairloch WwTW is now better equipped than ever to protect local bathing waters and ultimately support cleaner and safer environments for the local community.