April 2019

Progressive cavity pump specialist SEEPEX has developed a new system to improve dewatered sludge handling, enabling long distance transfer with reduced operational costs by using a combination of PC pump technology and dense-phase conveying. The technology has already been trialled by Thames Water at its Reading Sewage Treatment Works (STW) and is now being installed as part of the new Thames Water Riverside project, providing an energy-efficient, high- performance alternative to conventional sludge handling systems. PWE reports. Energy-reducing sludge solution T hames Water’s interest in Smart Air Injection (SAI) was linked to a new project at Riverside STW to handle dewatered sludge. Following a visit by Thames Water representatives to observe SAI in action in Sweden, the company decided to measure the potential energy savings it could make by installing a trial SAI system at its Reading Sewage Treatment Works (STW). This site had previously used piston pumps, but as a result of process limitations and high operating costs, Thames Water switched to SEEPEX’s multistage PC pumps in 2014. This solution halved Thames Water’s energy use, as well as reducing transport and maintenance costs. Four years on, it was time required. The trial concluded the energy saving with SAI compared to a multistage PC pump without air injection was 15%. Compared to the original piston pumps, the energy saving was an astonishing 61%. However, there were even greater savings to be made by switching to a single stage SAI pump fitted with SEEPEX’s Smart Conveying Technology (SCT), instead of the multistage pumps currently in use. Air usage data from a working SAI installation using SCT pumps in Belgium, enabled SEEPEX to produce an estimate for Thames Water, based on the trial results from Reading. It concluded that, if SCT single stage pumps were used in place of multistage pumps, the energy saving at Reading STW would be approximately 40%. When 30 | Plant & Works Engineering www.pwemag.co.uk April 2019 Process, Controls & Plant Focus on: Pumps & Valves to see if SAI could improve things further. The SAI Reading trial set out to not only prove the technology, but to quantify the additional energy savings that could be delivered by pumping the dewatered biosolids from the centrifuge discharge to the storage silo. An SAI trial unit, including full controls and monitoring, was installed on the SEEPEX multistage PC pumps for a trial period and the results were recorded. Superior energy savings During the trial, energy use and discharge pressure measurements were taken. Using these figures, together with the volume and height of the discharge pipework, SEEPEX engineers could then calculate the optimum amount of air CASE STUDY The SEEPEX solution has allowed Thames Water to significantly reduce pump length and installed motor power, and has the added benefit of ease of maintenance