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13/01/2012
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A 520 DuN/REM high pressure peristaltic pump has met the immediate needs of three chemical dosing schemes implemented recently at various Severn Trent Water facilities.
 Deployed as part of a temporary dosing rig constructed by engineering group Costain, the pump's success is helping to pave the way for future consideration of peristaltic technology in place of conventional metering pumps.
"Until recently, Severn Trent Water consistently used a specialist manufacturer of chemical dosing systems, all of which featured metering pumps," confirms Paul Pearson, process commissioning engineer at Costain.
"However, in the past few months, aware that there may be even greater savings available, this arrangement has been relaxed and it's given us the opportunity to run trials at Severn Trent using a peristaltic pump," he adds.
Pearson explains that the Watson-Marlow Pumps system has already proved successful on three Severn Trent Water schemes. And he adds that there are at least a further half-dozen such applications planned for the coming 12 months, all of which will also use peristaltic technology – although some are larger schemes that might demand a higher flow rate specification than the existing 520 DuN/REM model (108 litres/hour at 4.1 bar).
The three schemes to date have seen the peristaltic pump used for ferrous chloride and ferric sulphate dosing. These coagulants bind with phosphates for wastewater processing. The Urban Wastewater Treatment Directive has meant that water companies have to be very stringent about the level of substances such as phosphates recorded in treated water: hence accurate dosing is of paramount importance.
"In my mind there are so many things that can go wrong with a metering pump," explains Pearson, "but with peristaltic, the potential for failure is reduced massively because there are no valves, stators, diaphragms, seals or glands.
"It makes maintenance extremely straightforward. Only the tubing requires replacement, which is quick and inexpensive. Provided this is done at the recommended intervals, there won't be any problems. We've certainly had no issues so far."
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Author
Brian Tinham
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