Is the glass always greener?

Yorkshire Water is trialling crushed glass as a filter medium in place of sand. And early signs show that both the financial and the environmental benefits are significant.

Yorkshire Water is going green with a new system for treating wastewater that cuts emissions and saves the countryside.

The water company has teamed up with Recycling Action Yorkshire (Ray) to run an innovative 20-week trial project, managed by water treatment experts Aqua Enviro. The trial uses crushed glass as a filter medium in place of sand at Yorkshire Water’s WwTW at Malton, North Yorkshire.

The Malton works has two identical filters with 23 tonnes of filtration media. This makes the trial one of the first full-scale operational tests of a glass filtration system in the UK and is already demonstrating significant environmental and process benefits.

Traditionally, water filtration systems use sand, specifically quarried near Leighton Buzzard in Bedfordshire because if it is high silica content. For the duration of the trial, the sand in one of the two filters at the Malton site has been replaced by glass to determine the differences in performance and energy consumption between the two filtration media.

This and earlier, smaller trials have indicated that, as well as proving to be more resilient to bio-fouling, crushed glass is up to 10% more efficient than sand.This leads to financial and environmental benefits from reduced energy consumption and a longer working life.

An annual carbon emission saving of more than one tonne of CO2 per tonne of filtration media is predicted from the energy savings alone.

With around 7,500 WwTWs throughout the UK, of which 1,500 are in the Yorkshire and Humber region, there is a large-scale market opportunity to replace sand with crushed glass.

The use of crushed glass also helps to reduce quarrying, which has a significant environmental impact on the countryside and creates additional emissions.

Recycled glass

Ben Stone, glass project manager at Ray, says: “The UK recycled 740,000 tonnes of glass last year, but the glass-making industry cannot on its own use all of the green and mixed-colour glass which is collected.

“It would be an effective use of resources if this glass could be used within the emerging water filtration market, as this is complementary to the main market for recycled glass – back into glass container manufacture.

“In Yorkshire and Humber, this recycled glass could be sourced locally rather than the imported specialised silica sand, leading to extra reductions in transportation emissions.

“As well as environmental benefits, crushed glass also offers a more effective filtration medium than sand, which often requires chemical or biological additions to prevent the filter becoming blocked and eventually overflowing.”

He adds: “Concern that crushing the glass creates more carbon emissions than are saved is misplaced. The latest calculations indicate that the carbon savings from filtration energy reduction is four times greater that the energy used in the crushing process.”

Andrew Roach, Yorkshire Water catchment manager, says: “Filtration is one of the steps we take to ensure that the treated effluent will comply at all times with the standards that have been set by the Environment Agency to permit the cleaned wastewater to be released back into the regions rivers.

“Meeting the standards for wastewater treatment is an absolute requirement for Yorkshire Water. And the implications for failing are numerous, including a financial penalty levied by the courts, bad publicity, and in severe cases a custodial sentence for company directors.

“It is therefore very important that both the water utilities and industry invest a lot of time and effort in ensuring their plants meet all the stringent standards set.”

Initial evidence from the trial shows water quality is maintained or slightly improved while significant energy and carbon emission savings are achieved. Water treatment is a high-energy user making such savings doubly important given current energy prices. These drivers have the potential to unlock a sizeable market for recyclers who can process glass to the required specification.

There is limited production capacity currently which presents an exciting business opportunity to capture this market in the region, across the UK and potentially on into export markets.

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