Investment in an innovative new receiving station has enabled Cornwall’s oldest liquid waste disposal contractor to increase its throughput by over 30%.
At Pellows Waste Disposal Services, near Truro, a typical 4.5m3 tanker (1,000 gallons) that used to take over 20 minutes to empty, can now get back out on the road to collect more liquid waste after less than three minutes discharge time.
The turnaround is due to ‘The Beast,’ made by SAVECO, that with a fully integrated 5mm screen, conveyor and compactor, all in one unit, removes harmful debris and dewaters it prior to discharge. It can handle 200 m3/h and up to 6-8% solids as a plug-and-play system.
Payback is expected in just four months, as Pellows’ Director, James Martin, explains:
“The Beast has far exceeded our expectations,” he said. “It injects water to accelerate the process, and is so much more efficient and robust than our previous system. Investing in The Beast is part of a major upgrade that we’ve put into place to address the big changes that have happened in Cornwall’s collection and disposal of liquid waste.”
The upgrade at Pellows, which includes a centrifuge, aeration, and larger tanks, has enabled the company (established in 1964) to expand its customer-base by offering a complete in-house service. It will also provide a potential lifeline to other contractors who collect liquid waste from the holiday parks, factories, hotels and many thousands of homeowners in Cornwall that are not connected to the sewer network.
The closure in April 2022 of what turned out to be two large disposal sites that were trading illegally, has forced contractors into sending their vehicles long distances away to discharge their collected waste. The headache has been partly alleviated by being able to take some liquids to be treated by South West Water, but during heavy rainfall and storm events, the water company has had to keep its gates closed because capacity has been reached.
“Storms and flooding from prolonged rainfall is all too common these days,” continued James Martin from Pellows.
“We couldn’t just stop working for long periods due to the weather, letting our customers down, or keep sending our vehicles miles and miles away to unload. We had to act to protect and grow our business, so first contacted Centri-Force, who make very good decanter centrifuges. They gave us plenty of good advice about how we could become independent by treating the collected waste ourselves, which included a strong recommendation of The Beast from SAVECO.”
The pneumatic press (with de-stoner) that had been in operation at Pellows not only took far longer to receive incoming waste, but, according to Richard Montanaro, Managing Director of Centri-Force, was too small and far less sturdy, with too many areas where the process would require costly maintenance or be likely to slow or fail.
‘Environmental wet waste is a big issue’
“In comparison, The BEAST is very well designed,” he said. “It is a great product that integrates very well with other parts of a plant to provide an excellent front-end pre-screen. With a centrifuge as part of a process, it gives us exactly what we’re looking for, and has helped Pellows greatly increase productivity and take this important step to becoming a liquid waste contractor with its own treatment facility. Environmental wet waste is a big issue, and Cornwall, with far less infrastructure and sewer connections than many counties, faces some big challenges, so it is good to see Pellows play a big part in reducing the environmental impact of septic tank liquids.”
Rotating around its axis, The Beast’s cylindrical filter conveys screenings into a loading hopper placed in the centre, whilst a set of spray nozzles washes the filter during operation. A screw, placed inside the conveying pipe (with its top inside the discharge hopper), conveys the screenings towards the treatment stages, during which organic substances are washed out. Subsequently, solids are compacted and dewatered in the compacting and drainage area, before exiting through a discharge chute.
Despite septic tank contents often containing solidified calcium, rocks, stones, and sanitary products, installation of The Beast now sees Pellows’ 27-tonne artics discharge waste in less than 13 minutes, compared previously (depending on the thickness of the liquid) to 45-minutes, up to one hour.
‘Screening, washing, conveying and dewatering – all in one unit’
Craig Webb, SAVECO’s Municipal Sales Engineer, commented: “We have worked closely with Pellows and Centri Force to bring about a big improvement in treating liquid waste. Allowing effluent to be put directly through The Beast, which avoids placing further stress on an existing plant, is also a huge benefit to water companies. Liquid waste contractors and the water industry can see that by screening, washing, conveying and dewatering – all in one unit – there is a reduction in risk, and the opportunity to make big savings by removing the need for multiple pieces of equipment.”
‘Better biosolids too’
James Martin from Pellows, continued: “The whole system is so much better now. We get better biosolids too at the end of the process. Apart from South West Water, we’ve now become the first company in the County who have the capability to treat liquid waste for safe disposal into the foul sewer main.”