Technical developments coupled with an ever-increasing expertise in cleaning mine water have helped the Coal Authority to improve the sustainability of one of its vital treatment schemes.
Enhancements to our Frances scheme in Dysart, Scotland, will significantly reduce its whole-life costs and environmental footprint:
- there will be an immediate 15 per cent reduction in chemical usage - roughly 180 tonnes every year - with the potential for more savings if dosing levels can be further cut after we review the water discharge quality
- fewer site deliveries will be needed, giving constant carbon savings and reducing greenhouse gases
- operational changes - from 'slug' dosing to a 24-hour treatment - will end the need for flushing cycles, which should reduce water consumption by more than half
- improved pumping efficiencies will lead to significant electricity savings
As the mines in the East Fife coalfield closed, the pumps used to keep them dry were switched off. Over time the water levels recovered and picked up naturally occurring minerals from the rocks, such as iron, which can impact the ecosystem.
Since 2003 our scheme at the former Frances Colliery site, part of the our work to make a better future for people and the environment in mining areas, has been collecting and treating this mine water in a series of lagoons, before it is discharged into the Firth of Forth.
Because the scheme was working at full hydraulic capacity to help control water levels across the mining block, more efficient pumps were installed in 2013 as part of ongoing refurbishments.
As a result, the scheme which now treats twice the original 80 litres a second design flow, relies on chemical dosing to reduce iron levels to meet the discharge consent.
Coal Authority project manager Mathura Pramekalan, operations manager Andrew Hargreaves, contracts manager Katie Shorrock and process engineer Waqas Ahmed have been working on the upgrade project with our contractor, Severn Trent Services. Mathura said:
This raw mine water is acidic and iron rich, and the chemistry is influenced by tidal flows. Chemical dosing helps to neutralise the acidity, enhancing the treatment and separation process, which occurs through the original cascades and settlement lagoons.
Previously chemicals were delivered for 5 hours every day, and we needed to flush the system with water between each of these batch processes, to prevent any residue crystallising when temperatures dropped, potentially blocking the pipelines.
All these factors were considered during the upgrade and informed how we approached the project to improve efficiencies and achieve more sustainable operations. Mathura added:
Process optimisation now means continuous operation of the semi-automated dosing plant to match mine water flow rates. This will cut the amount of chemicals we use to deliver significant savings - £58,000 at current prices, as prices per tonne have almost doubled in recent years.
This upgrade conforms to best engineering practices, providing the latest features to meet operational requirements and emergency operations.
The project, which ran May to December 2019, saw the installation of new hardstanding, fill point kiosk, storage tanks, pipework, dosing rig, distribution board and control panel, plus improved safety features including a better shower and eye bath.
