Technology from wastewater treatment specialist WPL has been selected by Scottish Water to deliver enhanced ammonia removal at a village treatment works.
Tightening environmental consents and an increasing population has led the public utility to upgrade Ferniegair wastewater treatment works in South Lanarkshire.
The site has a tight footprint and is in close proximity to residential housing, both important factors considered early in the project design phase, which was carried out by WGM Engineering Ltd. The site serves a population equivalent (PE) of 2,000, including new housing.
WPL will provide one Hybrid-SAF™ (submerged aerated filter) treatment unit, housed in a steel above-ground container to deliver additional ammonia removal at the plant. To enable the WPL Hybrid-SAF to be gravity-fed, avoiding the need for costly and energy-intensive pumping, the unit will be positioned downstream of existing SAF units and upstream of the site’s final settlement tanks.
The patented WPL Hybrid SAF treatment process creates a unique recirculating flow pattern as wastewater passes through the submerged moving media bed. The high media fill rate of 90-95% and enhanced distribution mean a more open-structured, neutrally buoyant media can be used, which reduces both the risk of the media fouling and the energy required to maintain a constant scour.
The modular nature of WPL Hybrid-SAF units also supports ease of installation where access and site footprint is constrained. This site had limited space for new equipment even with relocation of existing blowers factored in by project designers.
Built off-site and with enclosed blowers, the technology is also low on noise and odour, which is essential in residential areas to reduce any risk of customer complaints.
The Ferniegair unit will be able to treat 6.4l/s flow and provide approximately 1,000 PE of additional ammonia removal capacity. This will ensure the site maintains the Scottish Environment Protection Agency’s (SEPA) ammonia effluent requirement of 20mg/l. The agency’s regulations state the site must meet these standards at least 95% of the time.
WPL utility manager Andrew Haywood said: “As a framework supplier to Scottish Water, we are pleased to have been awarded this contract to help futureproof Ferniegair wastewater treatment works, enabling it to serve a growing population while maintaining environmental compliance.
“The design has been tailored to ensure all treatment processes are gravity-fed, with particular consideration given to the levels of pipework connecting the units. In a location with little room for manoeuvre, getting these levels right is critical if flow into and out of the treatment tanks is to be maintained and we worked in close partnership with WGM Engineering Ltd in design to achieve this. We look forward to the installation phase of this project.”
WGM Engineering Ltd director of technical & design Jason Cramb said: “As a tier one partner to Scottish Water, we were pleased to once again collaborate with WPL in the design and installation of another innovative solution. Ferniegair’s location and topography presented a number of design challenges with respect to space, hydraulics and energy consumption.
“However, working closely with all stakeholders, a robust solution was developed that will provide the necessary treatment capacity for future expansion of the local area, whilst minimising disruption to residents.”
Scottish Water project manager Richard Morris said: “This is an important scheme which will deliver enhanced ammonia removal at our Ferniegair treatment works. WPL is a framework supplier whose technology will have a key role in the site maintaining compliance.”
WPL’s onsite installation work will be taking place in the spring of 2021. Under its framework agreement with Scottish Water, the company has recently undertaken projects on wastewater treatment works in areas Newtown St Boswells, Canonbie and Winchburgh, all due to be commissioned in 2021.