Better biogas feed as Borger’s pump solves rectangular tank mixing headache
An innovative new Borger pump at Cliff Quay Wastewater Treatment Works is significantly improving the blend of liquified sludge and cake for Anglian Water’s anaerobic digestion (AD/biogas) process.
Working closely alongside Anglian Water and long-stablished engineers, Panks, Borger have also helped meet the challenge of mixing a rectangular tank that was proving far too difficult for existing equipment.
Jon Hooper, Cliff Quay Treatment Manager for Anglian Water, said: “As well as bringing about a better, more consistent product to feed the AD process, Borger and Panks have effectively helped us solve a problem without needing to install a new tank”.
He added: “Mixing sludge in a rectangular tank is always a difficult task, but a paddle mixer at the deep end had difficulty coping with the solids, while the vortex pump at the shallow end of the tank (20m by 10m, 550m3) kept air-locking”.
To put the Borger EL rotary lobe pump to the test – and ensure that a new set-up would work for Anglian Water – Panks first tried pumping through the existing pipework, but there was too much pressure at the jet end”.
Chris Bone, Contracts Manager at Panks, explained: “We then tried with some temporary pipework in a different configuration and this mixed the tank much, much better.
“Despite the considerable limitations of a rectangular tank, there was no doubting the capability of the Borger pump, so together with Anglian Water, we agreed to install additional stainless-steel pipework with three injection points at strategic locations”.
Now, with cake that comes in at 17% solids, with the surplus activated sludge (SAS) at approximately 3% to 4%, Anglian Water are able to achieve the optimum level of 8% solids – without the previous air-locking and burn-out issues.
Anglian Water’s Jon Hooper added: “The mix of cake and liquified sludge is quite gritty, but since the installation by Panks of the new Borger pump, we’ve successfully improved the blend – which is quite an achievement with it running 24/7 and dealing with such high volumes – around 35 tonnes per day”.
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