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A bioresources trial by United Utilities (UU) using scaled-up novel technology has shown “significant” energy savings compared to traditional sludge processing by centrifuge.
The 12-month trial funded through the Department for Business, Energy and Industrial Strategy (BEIS)’s Industrial Energy Efficiency Accelerator (IEEA) has shown power savings of up to 84 per cent compared to typical centrifuge traditionally used in the process.
It is the first time the Volute system, which revolves twice a minute compared to centrifuges that reach up to 3,500 revolutions per minute, has been used at commercial scale in the UK.
Pat Horne, bioresources head of strategy and commercial services at UU, who is overseeing the trial at Davyhulme sewage works in Manchester, said the results from the first nine months of the trials “had been excellent”.
Horne explained: “Compared to traditional de-watering processes we have seen a reduction in the power consumption of sludge de-watering from 23kWh per tonne of solids, to less than 4kWh, depending on the throughput setting. For a site the size of Davyhulme that equates to potential cost savings in the hundreds of thousands of pounds a year.”
The technology had previously been used at smaller wastewater sites in the UK but this is the first time it is used at a large regional processing centre.
Together with Evergreen Water Solutions, UU received a grant from BEIS’ IEEA, managed by the Carbon Trust, for the commercial-scale trial.
Paul McKinney, senior manager at the Carbon Trust, said the initial results showed the technology had the potential to have a significant impact on reducing energy consumption and the carbon impact of wastewater treatment.
“We are looking forward to seeing further uptake of the technology within UK industry.”
So far, UU has tested Volute on large volumes of raw sludge, digested sludge and centrate returns. The next part of the trial will involve using it with direct dewatering activated sludge (SAS) to produce a manageable sludge cake.
Horne said the next step was important as the system had outperformed traditional centrifuges in significant ways, but did require additional polymer in some dewatering processes.
Data from the finished trials will be assessed and whole life cost modelled before the Carbon Trust releases the full results at the end of the year.
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