Water & Wastewater Treatment

20 | december 2014 | WWT | www.wwtonline.co.uk Yorkshire Water ceO Richard Flint (le ) opens the plant with community engage- ment manager John bond and bradford mayor mike Gibbons Project focus: Wastewater treatment efficiency of consumption to see if we can become fully sustainable under all operating conditions. We're nearly there." Overall, the upgrade will reduce Yorkshire Water's carbon footprint by 9,000 tonnes and save £1.3 million a year in energy costs. "There is scope for similar projects in Yorkshire," concludes Calvert. "We're still evaluating options for our region, but we still have two sites with incin- erators and, at some point, these will need to be replaced with a more cost effective and sustainable solution." The plant treats a mixture of prima- ry and secondary sludges - produced both at the Esholt works itself as well as sludge imported from other sites – and the variable nature of the sludge required some subtle modifications to the plant's design. Meanwhile, the main engineering challenge was how to incorporate the new technology into the existing site. The complexity of the new plant, and the question of how to integrate it into existing assets, meant that the final detail design took longer than anticipated. "Retrofitting a new process into an existing plant o‹en leads to con- straints or compromises," says Paul Allsop, Batch Manager for the Morgan Sindall Grontmij joint venture. "At Esholt we were fortunate in that there was available space in the middle of the existing plant for the THP plant itself, but we were compromised in that the new energy centre had to be located on the other side of the main access road." Construction started on the site in January 2012, with process commis- sioning starting in July 2013. The fact that the build took place in the centre of the Esholt works pre- sented both logistical and health and safety challenges, and meant that the project team needed to work particu- larly closely with Yorkshire Water's operational team, says Allsop. "The challenges were managed by close collaboration with the Yorkshire Water site operations, greatly helped by the familiarity of the joint venture team," he says. "The entire project team worked from a co-located office on the Esholt site and two Yorkshire Water key technicians were effectively seconded into the project commission- ing team." The biogas produced by the anaero- bic digestion process fuels an on-site combined heat and power (CHP) plant, which provides for the most efficient use of this biogas, says Yorkshire Water's Calvert. "The electricity produced from the biogas is used to power the plant - both the sludge treatment plant and the associated sewage treatment plant," says Calvert. "Once the site is fully powered, if we produce extra electricity, this can be exported to the grid. We're able to do this at times of peak generation and low site demand - for example, on dry days when less sewage flow is pumped across the site - but not under storm conditions yet. We're looking at further optimisation of both our generation and the site • Perspectives bradford Lord mayor cllr mike Gibbons: "The innovative tech- nology which Yorkshire Water is now harnessing is hugely impressive. I'm delighted that the Esholt site is now the first self- powered sewage plant in Yorkshire and is leading the way in the industry with this new technology." richard Flint, Yorkshire Water ceO: "This is a massive step for us as a company and it is good news for the environment, the agricul- ture industry and also our customers because it will help us keep bills down. The technology being used on this site truly is some of the most cutting edge around and it's play- ing a major part in an 80% increase in the amount of renewable energy being generated by Yorkshire Water in the last year." An aerial view of the completed site at esholt. © Suave Air Photos copyright Suave Air Photos "Thermal hydrolysis produces an excellent quality product for recy- cling and optimises the amount of energy we can generate from the sludge" Andrew calvert, Yorkshire Water

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