Peristaltic Technology Delivers Trouble-free Lime Slurry Metering at Three Stage WTW
16 July 2008
Peristaltic pumps supplied by Watson-Marlow Bredel are delivering trouble-free, 24-hour operation of lime slurry metering at the Blackmoorfoot WTW near Huddersfield.
Serving over 400,000 people, the WTW at Blackmoorfoot was the first full-size, three-stage water treatment works to be built by Yorkshire Water. Pumping around 30Ml of water a day, the three-stage process involves flotation, first-stage filtration and subsequent manganese and chlorine removal in three distinct stages. This has been successful in treating upland Pennine waters and, as a result, water quality throughout the area has improved.
A critical aspect of the water treatment process at Blackmoorfoot is the addition of lime slurry, to control the pH of the water. Water enters the works with a pH of around 6 and is then dosed with ferric sulphate and brought to a pH of 3.5. Lime is then added to aid flocculation at the first stage of filtration – bringing the water to pH 4.2 before more lime is dosed, which brings the level to pH 6.8. At the second stage of filtration before the water leaves the site, further alkaline lime slurry is metered to the supply in order to maintain the required pH level. The lime raises the pH to around 9.2, which assists in the removal of naturally occurring manganese.
According to the Joe Kelly, process engineer at the Blackmoorfoot Works, the peristaltic technology offers distinct advantages over other types of pump. “We’ve been using the Watson-Marlow Bredel pumps on site for at least seven years and they have truly delivered trouble free operation. This cannot be said of all of the peristaltic pumps we have installed on other sites. We have found that pumps from other well known suppliers are often prone to failure – particularly the inverters and motors. This results in unnecessary downtime and high maintenance costs.”
The process control engineers at Blackmoorfoot WTW use six separate Watson-Marlow Bredel SPX 40 hose pumps to handle the lime dosing. Three of the pumps run 24hr a day and the remaining three pumps are used as duty stand-by units.
With a maximum flow 6000l/h and discharge pressure 16bar, the Watson-Marlow Bredel SPX 40 is part of the company’s family of SPX direct-coupled hose pumps. Designed to provide all of the performance, reliability and ease-of-maintenance benefits of bareshaft (long-coupled) designs with the compact advantages of close-coupled pumps, the SPX range is available in sizes ranging from 10mm to 100mm.
Unlike close-coupling, Watson-Marlow Bredel's patented direct-coupled design permits the drive to be removed and replaced without the need to dismantle the pumphead.
