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Whittle Dene Clarifier Refurbishment

Whittle Dene Water Treatment Works is Northumbrian Water’s fourth largest treatment works with a deployable output of 118Ml/d, supplying 228,000 properties. Located in Northumberland, 13 miles west of Newcastle, it is a strategically important works to Newcastle, Gateshead, North Tyneside, South Northumberland and Tyne Valley regions. Raw water at the site comes from adjacent reservoirs supplied by a number of impounding reservoirs in Northumberland and is further supplemented by the River Tyne. The treatment process at the works comprises; (i) clarification, (ii) filtration, (iii) GAC filters and (iv) disinfection and emergency disinfection. An asset need has been identified to address the very poor condition of the internal walls and floors of the clarifier units which have been subject to excessive concrete degradation in the 24 years since their construction in 1992. Project need The clarifiers comprise a large hexagonal footprint containing six separate chambers in an above-ground reinforced concrete structure. A structural survey identified the deterioration had resulted in an estimated 5 to 10 years residual asset life with only 5 years for the structural columns. Beyond this the structure would have a high risk of being irreparable and would require a full replacement at a high capital cost. The scope proposed by this project comprises refurbishment of the tanks to prolong their asset life and safeguard the treatment process into the future. The agreed scope identified in the Asset Need also includes for replacement of the launder channels which are in very poor condition and contribute to increased algal growth, causing problems in the downstream process. Undertakings Following agreement of a price of £2.5m NWG commissioned Stonbury to deliver the defined solution through an NEC 3 Option B re-measurable three-year contract. This commenced in January 2017 with the release of the first of the 6 (No.) compartments by reducing the works deployable output to 97MLD. Stonbury then commenced the initial clean down of the residual sludge in the compartment before building a scaffold platform with two working levels for the full height of the 6m high walls. The work required close coordination with Operations due to the connectivity between each compartment to prevent any overtopping of the common outlet channel discharging into the isolated chamber. Mortar repair In order to comply with the specification to meet the requirements of the Secretary of State for the Environment under Regulation 31(4) (a) for products used in contact with potable water Stonbury proposed the use of MasterSeal products. The chosen products were MasterEmaco S420 which is a rapid setting, high strength repair mortar in conjunction with MasterSeal 586 which is a smooth finish waterproof render. This was applied to the floors and walls of the clarifier in climatically controlled conditions to ensure adequate curing conditions were achieved. Launder channels In addition to the concrete repair work the existing launder channels were to be replaced due to their inoperability caused by their design which results in algal growth blocking the outlet holes. A new ‘V’ notch design was agreed which would provide a more even distribution of the clarified water for a more even and consistent discharge of the settled water. Phased refurbishment Following completion of Clarifier No. 6, Stonbury was handed No.1 to commence the second phase of the contract. Through a lessons-learned review Stonbury was able to improve their working methods and hence shorten the programme for the next phase. Whittle Dene WTW Clarifer RefurbishmentDesigners, contractors & suppliers Client Northumbrian Water Main Contractor Stonbury Limited Designer Wood Group LLP Main Supplier MasterSeal Wind bracing assessment The Fluid Group Climate control for the curing Polygon   Wind assessment and bracing Finally following feedback from Operations on the performance of the clarifiers due to their exposure to prevailing winds The Fluid Group was commissioned to carry out an assessment of the existing wind bracing. Following their assessment, it was established that the existing mesh panel arrangements were set at the optimum height and they were then replaced like for like due to their deteriorating condition. Progress to date At the time of writing (May 2018) the work on the Clarifier No.1 is substantially complete but due to operational constraints work has been suspended since January to allow the works to increase its deployable output to meet network resilience demands. It is envisaged that work will recommence in June 2018 to complete No.1 and move on to the next compartment in due course. During the outage of each compartment the opportunity was taken to carry out further refurbishment work to the outlet valves and rotorks as they were also at the end of their asset life. In addition, non-compliant handrailing is being replaced to allow future public access visits to recommence on site.

Water Industry Asset and Quality Conference 2018

150 delegates, including representatives from 15 UK water utilities, took part in Stonbury’s seventh annual Water Industry Asset & Quality Conference on 20 November 2018. The event took a deep dive into water quality issues as they relate to maintenance of drinking water structures. Water companies have many challenges in AMP7 (the asset management period which runs from 2020-25) and Ofwat is putting ever more pressure on water companies to drive up customer satisfaction. Customers were very much in the minds of the speakers at the Stonbury event, which took place at the Hilton St George’s Park, training ground of the England football teams. Speakers from Anglian Water and Northumbrian Water opened up about two incidents that had attracted customer complaints about taste and odour in drinking water. In both cases the cause was contractors’ failure to follow instructions for use (IFUs) – on a filler and a lining product. The companies have collaborated with Stonbury to develop a code of practice (CoP) for the application of specialist materials to drinking water structures, which will be rolled out following the approval from Water UK.  Anglian Water’s head of water quality, Clair Dunn urged people to get a copy of the CoP and give feedback. Alan Brown, scientific support officer at Northumbrian Water said, “This isn’t just about the contractor, it’s about the water undertaker as well. We need to have the right information and the confidence that the process we’re working within works for us as well.” Delegates were struck by the opportunities presented by the use of flow cytometry to measure water quality in distribution service reservoirs. Aidan Marsh, flow cytometry project leader, Northumbrian Water said, “What we’re hoping to do is produce a more biologically consistent water which will be more robust to pathogens by a lower chlorine dose. It’s that consistency that’s going to lead to customer satisfaction.” Zoe Kellock, Severn Trent Water’s lead on distribution service reservoirs and tank coordination, described the multiple challenges the utility faces as it moves to a more proactive clean-inspect programme. “We’re still investing a lot of money in our reservoirs, we’ve still got a lot of reservoirs we need to take out an inspect,” she said. “One of the most common failures we find is ingress around the hatch, so we are investing in a hatch improvement programme – it’s a simple thing, but it really boils down to better planning.” James Stonor, CEO of Stonbury said, “I’m thrilled with the day’s event and the interaction we’ve had from everybody  - the speakers on the platform and the questions from the floor." “We’ve heard a lot of concern about sustainability of assets and a lot of honesty about the challenges utilities are facing. There doesn’t seem to be a common approach to resolving that, so going forward I think the key issue is water company strategy - the strategies they’re going along with at the moment might not be fit for the future." “I was particularly pleased to hear Aidan’s presentation on flow cytometry – that is the start of something really game-changing in terms of being proactive and predicting events, learning from that and building in machine-learning. I noticed there was a lot of note-taking during that session.” Summing up Stonor said, “This is the seventh year for our Water Industry Asset & Quality Conference and I think we’ve seen some great initiatives today and some really interesting shares. The attitude of the water companies here - where they’re actually giving out their information, their data, is to be welcomed and I think it’s the next step-up – a big credit to them.” Video Summary

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