Hybrid-SAF technology selected for Scottish Water village

Dec. 7, 2023
Tightened discharge limits moved Scottish Water to select WCS Environmental Engineering’s hybrid submerged aerated filters to treat flow at the Edgehead wastewater treatment works.

Wastewater treatment specialist WCS Environmental Engineering (WCSEE) announced that its wastewater treatment technology has been selected by Scottish Water to deliver tightened ammonia removal at a village’s treatment works.

An updated consent, which sets discharge limits, led the public utility to upgrade the Edgehead wastewater treatment works (WwTW) in Midlothian, east of Edinburgh.

The upgrade will involve the delivery and installation of two in-ground Hybrid-SAFs (submerged aerated filters) and a 4m conical humus tank. Due to the environmental sensitivity of the site, the Scottish Environmental Protection Agency has set an effluent ammonia level of 1.3mg/l of water, with a bio-chemical oxygen demand of 13.9mg/litre.

Additionally, the site has a tight footprint and is in close proximity to residential housing, both important factors considered early in the project when initial enquiries were made with WCSEE in 2017.

“The Hybrid-SAF has a modular design and 30% smaller footprint over comparable technologies, which makes it versatile and flexible for deployment in Edgehead,” said Andrew Haywood, WCSEE utility manager. “Installing the technology below ground ensures the stunning rural views go uninterrupted, and the visual impact of the WwTW is reduced, blending with the environment as much as possible.”

The company’s patented Hybrid-SAF technology employs a submerged moving-bed and fixed-film reactor. The flow balancing design in the primary tank means it can handle variable flows and loads.

WCSEE has a longstanding relationship with Scottish Water, and augmentation and improvement of the Edgehead WwTW is part of Scottish Water’s long-term water planning strategy, with the Hybrid-SAFs due to be installed in early 2024.

“It is great to be able to work with Scottish Water again and see the process through from initial enquiry to installation,” Haywood said. “WCSEE has been delivering projects for the utility over 10 years and the company is proud to be trusted to deliver such a tight ammonia consent.”

Within two weeks of installation, as the biological process becomes fully operational, the two Hybrid-SAF units will be able to handle flow rates up to 2.72 L/sec with average flows of 0.35 L/sec.