Peristaltic pumps supplied by Bredel are delivering trouble-free, 24 hour operation of lime slurry metering.
Pumping around 30 megalitres 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 waters and, as a result, water quality throughout the area has improved.
A critical aspect of the water treatment process 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 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 Process Engineer at the Works, peristaltic technology offers distinct advantages over other types of pump. “We’ve been using the 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.”
Six separate Bredel 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.