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Street waste recycling cuts council costs

Recycling business Gwrtaith Gwynedd is licensed to recycle 25,000 tonnes of waste a year.

The company was handling green waste for Gwynedd Council, but with the Gritbuster it felt it could do a lot more. So it asked the council if it would like to trial the technology.

Welsh authorities face tough statutory recycling targets and fines of £200 for every tonne they fall below them. While Gwynedd had achieved impressive results by concentrating on domestic and commercial waste, to achieve further reductions it needed to focus on other municipal waste such as road sweepings and gully waste. So the approach from Gwrtaith Gwynedd was timely.

Processing starts with road sweepings and gully waste being tipped into the Gritbuster’s main reception hopper. It then goes into a rotating trommel screen for washing and primary separation of the recoverable and sought after sand and gravel from the general road debris, organics and so on.

The recovered sand and gravel material is dewatered and automatically discharged from the plant, while the road debris and any oversize particulates exit separately.

The washwater laden with dirty solids is then screened to recover and dewater any fine organics and fine sand present in the mix, before the washwater is de-silted in a Siltbuster water treatment plant. The treated water is stored and recycled for washing the road waste, while the fine solids from treatment are stored separately for subsequent dewatering.

To boost the recovery of materials, Gwrtaith Gwynedd is also using the Gritbuster HDS. This uses water to separate light, lowdensity particles such as organic material from dense particles such as sand and gravel. It has further applications in aggregate recovery and organics removal, glass washing and density-based material separation.

Gritbuster’s ability to transform road sweepings and gully waste into a reusable commodity offers a real solution for Gwynedd Council, according to Steffan Jones, senior waste manager.

“Before the trial, 80% of our gully waste and street sweepings used to go to landfill but, now, 90% are being recycled. That’s a huge turnaround,” he said.

This has made a massive difference to the council as it works to achieve the 58% statutory recycling target which it must achieve by March 2016. And the new approach is saving the council money. It now sends 3,000 tonnes of road sweepings and gully waste to Gwrtaith Gwynedd for recycling, saving on landfill tax.

As Jones explained: “With the recent rate increase for trommel fines and gully waste, we would be paying £80 per tonne in landfill tax. If you add on the gate fee for each tonne, the total would be around £120 per tonne.

“Obviously we are paying Gwrtaith Gwynedd to handle the waste, but it is a fraction of the landfill cost and it means we are meeting our recycling targets too.”  

Richard Coulton is chief executive of Siltbuster

The Process

What happens to the outputs?

At Gwrtaith Gwynedd, the outputs from the Gritbuster system fall into four types. The first and biggest is aggregate, which can be used for low-grade concrete production, soakaways, bedding for pipes and paving stones and even for filling sand bags that hold down roadworks signage.

Second, there is a small amount (around 4%) of compost-like output which can be used in reclamation of industrial land.

Filter cake is the third output which goes to landfill, together with the last output which is a small amount of waste such as drinks cans, tennis balls and so on.

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