WET News

Planned maintenance acti- vities and lifting strategies had to be considered during the design stage 12 WET NEWS FEBRUARY 2016 T ransportation and a very tight timescale featured among the challenges when it came to upgrading the inlet works at Scottish Water's Meadowhead Sewage Treatment Works (STW) at Irvine. The refurbishment project has been completed, and Huber Technology contracts engineer Kelly Nightingale comments: "Although this was a challenging project from the offset, the end result proved very rewarding, achieved through close working and collaboration by all parties involved, the outcome being a successfully, maintainable solution." The upgrade by Huber involved the installation of 4-off RakeMax 6300/2752/19 coarse screens and 2-off 12m3/hr WAP-L Washpress Screening Handling units for the coarse screens; and 2-off 15m3/hr WAP-L Washpress Screening Handling units to be retrofitted into the existing inlet works for handling screenings from the fine screens. The existing works at the Meadowhead treatment works comprised both coarse screening and fine screening areas with the coarse screenings located in an enclosed ATEX- rated building. The problem that was presented to Huber was that the 4-off large grab screens had to cope with large variations in flow from catchment pumping stations that are located around a very flat area. The old screens were proving unreliable and required continual maintenance and tender loving care in order to keep them running. Investigate In addition to the coarse screen issue Huber was also asked to look at a problem that Scottish Water was having with its existing fine screens screenings handling units. The water firm approached Huber to investigate potential solutions available to solve the issue regarding these large flow variations, high screenings removal rates, improve the equipment reliability, and fit any new equipment within the existing building with limited space whilst complying to the ATEX zoning requirements. Because of reliability issues with the existing screens Scottish Water gave Huber a very tight timescale in order to carry out the necessary investigation, discussions, and agreement on type of screens. AŸer assessing the works along with investigations and observations regarding the nature of the flow and screenings being presented to the site, Huber established that the best solution for the works would be its RakeMax Multi- raked bar screen. Huber had already installed a number of Challenging project completed ahead of time ONSITE REFURBishmEnt these units throughout the UK and in particular the large inlet works at Belfast (Duncrue Street). To give Scottish Water operatives and engineers confidence in the units a site visit to Northern Ireland took place. During the design phase, significant focus was placed on the issue of handling the large volumes of screenings being presented to the screens, and how this would be addressed when presenting the screenings into any launder trough. Unlike large grab screens the RakeMax unit has multiple screenings removal rakes so more, smaller volumes of screenings are removed from the screen face and placed into the launder trough. Project costs Huber assessed each application with regards to the number of rakes fitted to ensure that sufficient small volumes of screenings are presented to the launder trough and flow, allowing them to be easily transported and removed from the discharge area. The company also looked at the merits of reusing existing equipment (launder, access platforms and sundry items) to enable the most cost-effective solution to be given. From layouts and calculations, it was found that the existing launders with some minor modifications could be used, reducing the overall project costs to Scottish Water. Huber was awarded the contract and immediately started work on the project, reducing the project time from March delivery to December, improving the installation date by three months. One of the major challenges on this site (in addition to compliance with ATEX zonings of the existing building) that Huber also had to consider during the design of the works, were issues with planned maintenance activities and liŸing strategies caused by constraints arising from utilising the existing building, gantry, launder system and existing civils. As a result, a great deal of thought and consideration had to be taken at the design and installation phase. Transportation of the four large RakeMax 6300/2752/19 from Huber's parent company in Germany required careful consideration as well. The most cost-effective way entailed splitting the RakeMax into sections for transportation with re-assembly on site. The RakeMax installation had to be completed through the roof of the building. To reduce delivery times, Huber had the RakeMax units shipped straight to the site. This meant, however, Huber needed • the inlet upgrade at scottish Water's meadowhead treatment works proved a challenge from the start. projEcT SpEcS • Area of catchment and contributing towns: major towns included within the catchment are Ayr, Prestwick, troon, Kilmarnock and irvine • the number of contributing pumping stations is six • Dry weather flow: 1,000-1,500l/sec • maximum Flow: 4,500-5,500l/sec Rakemax allows smaller volumes of screenings to be removed

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