Monday, 30 November 2020

Technology that’s helping save money and the planet

IN A world with limited and ever-decreasing resources, the importance of recycling is paramount.

IN A world with limited and ever-decreasing resources, the importance of recycling is paramount.

A new £1.3million materials recovery facility in Ewelme is helping to boost Oxfordshire’s recycling rates while producing new products.

It takes just minutes to treat and transform road sweepings into different-sized aggregates for a range of uses from the construction industry to road building.

The sweepings, including leaves, sand, grit and metals, from across the county are processed at the plant, which was developed by CD Enviro and is operated by Grundon.

The plant, which has just six staff, is able to process about 25,000 tonnes of sweepings a year, or 10 tonnes per hour.

It offers a cheaper way for Oxfordshire County Council to dispose of the waste and comes three years after the Environment Agency banned the composting of street leaf sweepings because of concerns about the high levels of contaminants such as nickel, copper and zinc.

The Henley Standard was shown around the plant by manager Leon Shepherd, tender manager Owen George and waste contracts officer Teresa Mitchell, accompanied by David Nimmo Smith, a Henley councillor and the county council’s cabinet member for environment and highways.

Operators acting for South Oxfordshire District Council and the county’s four other district councils deliver their road sweepings to the plant. The sweepings consist mainly of leaves and silt but the composition of the waste varies according to the time of year.

When the raw material arrives it is checked over before being deposited in a hopper.

It then travels along a belt where a magnet extracts any metal, including sweeper brushes which can damage the plant.

It then enters the “log wash” where the material is washed and separated with the organics and water pushed to one end and the aggregates the other.

The larger aggregates, ranging from 5mm to 4cm, are washed again before being sorted and stored in three sizes.

Meanwhile, the remaining matter continues into the hydro-cyclone where it is washed again to separate out organic material such as leaves and litter from sand and grit in order to recover the very small aggregates, those less than 5mm.

Dirty water is left and this needs to be treated, so it travels through a pipe where an anti-foaming agent is added.

Mr Shepherd says: “If we don’t add that we have bubbles everywhere as there’s so much movement of water. A polymer is added to the sludge, which helps it bind.”

The liquid is then transferred into a water tank with a three-weir system which means the sludge that has binded sinks rather than floats.

Four paddles at the bottom of the tank move constantly, separating the sludge from the clean water which rises.

This water is transferred to another tank where the last of the organics are caught and separated. The clean water is then circulated back around the system to start the process of cleaning the raw material once again.

Meanwhile, the sludge is pumped into a centrifuge where it is given another dose of polymer. This removes the last of the remaining water so the material becomes compacted and leaves the machine as a powder-like substance called “filter cake”. This can be used in land restoration projects.

The process means there is very little need for mains water.

Mr Shepherd says: “I’m very proud to work with Grundon and very proud to manage this new facility. I think the possibilities are endless.”

Mr George adds: “What we’re hoping to achieve is to divert the waste from landfill and produce new products. We’re producing different sizes of aggregates that can go back into road building and construction materials.

“To be honest it has worked very well. The quality of the material we’re recovering from the road sweepings is very good. It’s like a new product.

“Waste is a resource now. It is no longer acceptable or practical to send it for final disposal. What we need to do is invest in technology like this to produce new products from the waste.

“It’s turning something that was historically sent to landfill into something that is not a waste but a product that can be sold and reduces our need to rely on virgin products.

“You’ll see more and more developments in technology to turn waste products into a resource.”

He said the new process was a lot cheaper for the council than putting waste in the ground following big increases in landfill tax. Previously this kind of waste was either burnt or buried.

The county council is also keen to maintain its excellent record for recycling — in 2013/14 about 60 per cent of the county’s 300,000 tonnes of waste was recycled.

Councillor Nimmo Smith says: “The easy part was getting to the top, the difficult part was staying there. I think this is a marvellous piece of kit. This is the way forward. Resources are finite, we need to use them as best we can.”

Rebecca Harwood, service delivery manager at the council’s waste management group, said: “After the legislation changed, we had to send some road sweeper waste to landfill while the remainder went to an alternative facility outside the county.

“Obviously we were very keen to look for alternatives which would be closer to home and more environmentally friendly.

“Grundon’s new facility is not only very impressive but offers the capability to handle all of the county’s road sweeper waste in one central place.”

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