Advanced pump solutions for advanced water treatment works

Tasked with replacing ageing pumps for disinfectant and coagulant processes at Thames Water’s Advanced Water Treatment Works (AWTW) in Walton, Surrey, engineering, consulting and construction company Black & Veatch opted to install a number of 520 series and 620 series peristaltic models from Watson-Marlow Pumps Group. Offering continuous, high pressure and quick release functionality, the new pumps have slotted comfortably into their high-tech surroundings at Walton, which is one of Thames Water’s flagship process plants.

Although a water treatment works has existed on the site at Walton-on-Thames since 1926, it was a £47 million upgrade in the 1990s that pushed the facility into the premier league of process plants. The upgrade included the adoption of new advanced water techniques such as the CoCoDAFF (counter-current dissolved air flotation and filtration) system, which offers the enhanced solids separation capability of dissolved air flotation, while providing the cost benefits of DAF and granular media filtration – all within the same footprint.

Several processes reliant on pumping operations are vital to the advanced water treatment process at Walton. For instance, pre-ozonated water is mixed with a coagulant in the flocculators to aid the production of large flocs, which are floated more easily in the subsequent CoCoDAFF process. The addition of coagulant is today facilitated by newly installed 620 series pumps from Watson-Marlow.

“While the previous 504 series pumps for the coagulant process were reaching the end of their natural life, they had performed well so it was decided to continue with this type of pump,” explains Black & Veatch’s project M&E co-ordinator at the Walton site.

The water is then treated using CoCoDAFF and passes through post-ozone and granular activated carbon (GAC) contactors, as well as slow sand filters before arriving at the disinfection stage, where sodium hypochlorite is introduced to contact tanks in doses using 520 series Watson-Marlow pumps, before being pumped into the supply.

A total of 10 Watson-Marlow 520 and 620 Series pumps at Walton since June 2009. According to Philip Bolton, Water Industry Specialist at Watson-Marlow, “These are advanced peristaltic pumps serving advanced water treatment processes. There is little margin for error where drinking water is involved, which is why the customer needed high reliability in terms of continuous operation and dosing accuracy.”

Watson-Marlow 520 pumps are designed for the specific needs of the process sector. The models at Walton feature LoadSure elements, which fit into position for simple, error-free tube loading. Using the patented LoadSure D-connectors and easy-grip clutched rotor, the element can be changed in lass than one minute without the need for special skills.

“The quick-release LoadSure elements are a blessing at a plant such as Walton, where any downtime can have significant consequences,” says Mr Bolton.