WET News

BETWEEN FREE PASSAGE AND HYDRAULIC EFFICIENCY The SE and SL ranges offer the highest total efficiency yet in a wastewater pump Highest wire-to-water efficiency: The best yet, reducing your total costs and making life easier Best hydraulic efficiency: No compromise on free passage, meaning better solids handling and greater non-clogging capabilities Continual operation: Unprecedented reliability from high motor and mechanical efficiency, with all aspects of pump operation controlled intelligently The SE and SL ranges of wastewater pumps provide the highest total efficiency currently available. Innovative technologies from Grundfos bring together intelligence, motors, hydraulics and functionality to meet the challenges of modern wastewater, maximising the hydraulic, electrical and mechanical efficiency of your pumps. See more at uk.grundfos.com/no-compromise.html NO COMPROMISE 10697_SE_SL_annonce_285X405_WETNEWS_ART01_JW.indd 1 4/14/14 10:34 AM 9 WET NEWS MAY 2014 The filter block excavations had to be 5m deep in places to ensure the structure height limit was met Eliminating the risk factor at Dee Valley's Llwyn Onn WTW • Llywn Onn WTW was built more than 70 years ago but when structural issues meant it was ap- proaching the end of its life, the facility moved up the risk ladder. It had to be replaced. Maureen Gaines reports TECHKNOW • Second stage rapid gravity filters containing polarite media have been installed for manganese removal, which is a problem in the area • The DAF de-sludge is a hydraulic operation in the new works • Sulphuric acid is used to de-alkalise the water, preventing the lime from precipitating out within the dosing lines • A recycling facility has been established so a lot less water is put to waste D ee Valley Water's Llwyn Onn Water Treatment Works (WTW) played host recently to local dignitaries as well as Minister for Natural Resources and Food Alun Davies. They were there for two reasons − to cele- brate Dee Valley Water's 150th an- niversary, and to officially open Llwyn Onn WTW, which has un- dergone an extensive rebuild. The £17M project has been Dee Valley Water's largest project ever, and will ensure the supply of quality water to about 4w7,000 domestic and commercial cus- tomers in and around Wrexham. The rebuild was necessary because of structural issues with the existing facility, which was built in 1940 to supply water to a munitions factory during World War II. The 18Ml onsite reservoir was built about the same time, featur- ing four compartments – one for treated water and three for raw water. The first quarter was cov- ered and gradually the rest of the compartments were transferred to treated water storage. The whole reservoir is now covered, with raw water now stored off-site at nearby Marchwiel Reservoir. Dee Valley Water took owner- ship of the facility in 1951 and modified it over the years, includ- ing adding DAF facilities and adopting GAC filters to replace the sand filtration system. Allan Reef, capital programme manager, explains that as early as PROJECT SPECS • Rebuild Llwyn Onn WTW • Establish a recycling facility to reduce the amount of water going to waste THE VERDICT • The facility represents resilience and green growth • It provides a sustainable and high quality supply of drinking water to the local community ONSITE ASSET MANAGEMENT the 1970s cracks were discovered at the works, the leaks from which were causing sand underneath the structure to wash away. Repairs were carried out but at the end of the 1990s two filters "actu- ally fell through the floors into voids that had developed in the foundations", says Reef. Again, repairs were carried out but Reef says that "in the early noughties two further filters col- lapsed", confirming that the facil- ity had reached the end of its structural life. As a result, plans were made to replace the treatment works. "The treatment works climbed the lad- der and became one of the highest risks the company had," says Reef. "It was planned that in AMP5 it would be replaced." The project was incorporated into Dee Valley Water's PR09 busi- ness plan for approval by regula- tor Ofwat, and the work was put out to tender in March 2010. Thir- teen joint ventures and compa- nies went through the pre-qualifi- cation process and Dee Valley Water pre-qualified six, one of which dropped out, says Reef. All five tenders were of a high quality with considerable thought having gone into the process and layout of the proposed works. Also, the construction process had to be sustainable, in line with Dee Valley Water's policy. Specific requirements were detailed in the contract addressing issues such as waste arising from The construction process had to be sustainable, in line with Dee Valley Water's policy

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