Tony Keeney is a water maintenance technician. He works for Oren Environmental, which is part of Severn Trent Services. On behalf of the Coal Authority, he manages the day-to-day operations at Dawdon mine water treatment plant in County Durham. A job he’s done for longer than 14 years.
However, not many people realise he’s also a tour guide for the many visitors that come to the site from across the globe. This is because of its history as a former colliery and the geothermal energy developments that are happening there.
Tony said: “I’ve got 30 people coming to look around the site tomorrow and I’m always proud to show off what the Coal Authority is doing here at Dawdon – and my role in managing the site for them.
“We’ve had the likes of Laura Tobin from ITV Tonight here and Anita Rani from BBC Countryfile. The local press has visited and so have French media outlets. We also get loads of geology students from Durham University and Newcastle University.”
About the Dawdon site
Dawdon closed its doors as an operational coal mine in 1991. Geographically, it’s located near the Durham coastline with views of the North Sea.
The disused mine shaft is around 400 metres deep. It fills up with rainwater, groundwater, and sea water very quickly. In fact, 100 litres of mine water per second is pumped out of the mine and into the plant – where it’s treated before being discharged into the North Sea. Maintaining the water levels in the shaft is key to protecting the East Durham aquifer which provides drinking water to around 20% of the population.
If left untreated, the iron-laden water could cause pollution and harm coastal habitats.
Tony adds: “The treatment plant never stops. It runs 24/7, 365 days a year.
“Of course, most of the tasks are automated now, but there’s loads to do to maintain the site. So when I’m not showing visitors around, I’m making sure the assets are clean and in fantastic working order.”
How the mine water treatment plant works
Getting the water out of the mine for treatment is a multifaceted process that takes around one and a half hours to complete. It’s this process that Tony brings to life for visitors.
Tony explains: “The mine water is pumped up from the shaft into the treatment works.
“The untreated mine water then travels across various process streams beginning with a de-gassing tank which drives off the mine gas (hydrogen sulphide) and smells like rotten eggs! We also encourage the mine water to oxidise to form particles so it’s easier to separate later.
“To stabilise the PH levels of the mine water, one tonne of lime gets pumped into the process every 24 hours. It comes in a powder form which we mix into a liquid before adding to the water.
“The mine water ends up at a final lamella settlement tank to clarify. To help it along, we use a flocculant called polymer to encourage iron particles to clump together and sink to the bottom of the tank.”
“Within the tank itself, there’s a pump that recirculates some of the thick iron ochre sludge back to an earlier stage in the process, so it grabs hold of the small particles and forces them to settle. Another pump sends the sludge into a filter press which turns it into ochre cake. In fact, our process produces around 20 tonnes of iron per week.
“Whatever water we have left in the settlement tank that’s clean, is then discharged into the North Sea.”
Why Dawdon’s been in the spotlight
Dawdon mine water treatment plant has been attracting lots of attention over the last couple of years because it uses its own mine water to heat the facility. This is a renewable energy source that’s cheaper to run and better for the environment.
Tony explains: “Underground mine water can typically be around 20 degrees Celsius. Here at Dawdon, heat exchangers transfer the heat from the mine water and use it to heat the plant. From the welfare areas right through to the offices.
“It’s planned that mine water from Dawdon will also be used to heat a nearby property development called Seaham Garden Village. The heat from the mine water can serve over 1,500 homes and some public buildings. It’s a phenomenal environmental innovation from the partners involved in the project, and I’m excited about the prospect of seeing it first-hand.”
For more information about Seaham Garden Village visit: https://seahamgardenvillage.co.uk/