Articles & Case Studies


Posted: Monday 7th March 2011

A £17 million programme to improve drinking water quality for 50,000 Welsh Water customers in the Swansea valley has included investment in innovative Lamella plate separation technology from Hydro International.

To process increased volumes of backwash water generated by the major upgrade to clarification and filtration facilities at Crai Water Treatment Works, a Hydro Lamella Plate Clarifier was chosen by construction and consulting company Black & Veatch Ltd.

“With its small footprint design, the Lamella plate settlement process provided a compact solution in a sensitive national park location in the Brecon Beacons,” said Black & Veatch Chief Mechanical Engineer, Malcolm Bamsey.

A major upgrade to the Crai WTW was required to address the need for Manganese removal from the drinking water. The additional clarification and filtration plant incorporates a new CoCoDAF process upstream of existing filters, new media in existing filters and new chlorine and lime dosing points.

Dirty washwater from the new filtration plant is collected and fed at 14 litres per second through the Hydro Lamella plate clarifiers. The supernatant liquor is returned to the balancing tanks, whilst the separated solids are fed through existing sludge thickeners before being removed for agricultural use.

“With the Hydro Lamella plant we will achieve a high quality of supernatant liquors and achieve the required volumetric throughput for the dirty washwater process to deal with the increased loading of the plant. The Hydro Lamella plates are a highly efficient way of maximising solids removal from the supernatant before subsequent sludge thickening and removal,” said Chris Day, General Manager of Hydro Wastewater.

“By providing 10m2 of settling area per one metre of ground area, Hydro Lamella Plate Clarifiers provide a footprint up to 90% smaller than conventional settlement tanks. So they were ideal to provide a compact solution at Crai, minimising the impact on the surrounding national park landscape.

“By using Lamellas to process backwash water, the Crai WTW now has highly efficient fine solids removal, achieving a top quality clarification process with good operational reliability and low maintenance.”

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