Peristaltic technology from Watson-Marlow Bredel has benefited a Severn Trent water treatment works (WTW) with accurate chemical dosing, reduced maintenance and reliable operation for over twenty years.
By replacing rotor and stator pumps with peristaltic pumps from Watson-Marlow Bredel, process engineers at a Severn Trent water treatment works (WTW) were able to optimise performance at the site.
The Bamford WTW located near the historic Derwent Water Reservoir pumps 160 megalitres of water per day.
Lime slurry is added as an integral part of the water treatment process at Bamford to control the pH of the water.
Water entering the works is dosed with ferric sulphate and a polyelectrolyte, and brought to a pH of between 4.7 and 5.1. Lime dosing is done if the water’s pH is lower than this level.
The water is then fed from the clarifiers onto a bank of RG filters and sodium hypochlorite is added as a disinfectant.
Just before the water leaves the site, alkaline lime slurry is metered to the supply in order to maintain the required pH level, which raises the pH to around 8/9, assisting in the removal of naturally occurring manganese.
Bamford WTW, which is owned and operated by Severn Trent Water had previously been using rotor and stator pumps for this purpose although two Watson-Marlow Bredel pumps had been used on the site for kalic dosing for several years.
The rotor and stator pumps were removed as part of the AMP3 capital programme to upgrade the site and were replaced with a range of Watson-Marlow Bredel peristaltic hose pumps.
The hose pumps have been in operation since the 1988 upgrading programme.
According to the Works Manager at Bamford Works, the peristaltic pumps supplied by Watson-Marlow offer significant advantages over the previous pumps.
A primary benefit is that there are no leaks since peristaltic pumps do not have glands.
Additionally, tube replacement involves a simple single-step operation.
The process control engineers at Bamford WTW opted for a range of Watson-Marlow Bredel SPX hose pumps to handle the lime dosing.
While larger pumps are installed at the north end of the site where the dosing demand is high, the smaller units are used at the south end of the plant.
The peristaltic pumps at Bamford WTW include:
- SPX40 with maximum flow of 6000 l/h and discharge pressure of 16 bar
- SPX32 with maximum flow of 3400 l/h and discharge pressure of 16 bar
- SPX10 with maximum flow of 105 l/hr and discharge pressure of 7.5 bar
- SPX15 with maximum flow of 375 l/hr and discharge pressure of 7.5 bar
- SPX25 with maximum flow of 1800 l/hr and discharge pressure of 16 bar
The Works Manager is convinced of the benefits of peristaltic technology over alternative pump types for demanding chemical dosing applications, especially in pumping viscous and high density fluids.
The low maintenance requirement is also a key benefit with the hose or tubing being the only wearing part and which can be quickly replaced without dismantling the pump.
The design of Watson-Marlow Bredel peristaltic pumps prevents backflow, which means that no valves are required, thereby significantly reducing blockages.
Accuracy of the delivered volume and flow rate are parameters that can be fully tailored through the size of the pump, the rotor speed and the tube diameter.
A number of safety features are incorporated at the Bamford WTW including pressure relief switches that ensure any excess force is pumped back into the suction system to do a full circle while pressure sensors indicate whether the system is running correctly.