Water & Wastewater Treatment Magazine
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22 | AUGUST 2018 | WWT | www.wwtonline.co.uk The Works: Water treatment A n online, automated system that allowed Severn Trent to optimise its use of coagulant in real time was named the Most Innovative Use of an Existing Technology at the Water Industry Awards 2018. The Online Zetasizer WT measures the surface charge – or zeta potential – of raw water every 15 minutes using a fully automated sampling system. This information is relayed in real time to the supervisory control and data acquisition (SCADA) system at the treatment works, where it is used to automatically determine the most appropriate dose of coagulant chemicals to use in the treatment process. The system is the result of a collaboration between Severn Trent and Malvern Panalytical, which began in 2010 and culminated in the installation of the Online Zetasizer at four surface water treatment works within the Severn Trent region. "We have a duty to our customers to make sure we optimise our use of chemicals, and have in place robust processes at our water treatme nt works," Emma Sharp, operational business lead at Severn Trent, says. "The use of the Online Zetasizer is all about moving our water treatment works operations to a new level, with increased monitoring in real-time, so we can continue to ensure our treatment processes are optimised to produce wholesome water to the best standard at the lowest cost for our customers." The measurement of zeta potential as a parameter used to inform coagulation and clari' cation processes is not new, and has been an integral part of Severn Trent's water treatment strategy since the introduction of bench-top units at a number of speci' c sites for this purpose in 2008. However, laboratory- based sampling and measurement for zeta potential can only provide a daily snapshot of water quality, or a retrospective view once conditions have changed. When dealing with source water that is subject to rapid changes in quality, this can mean that chemical doses are increased proactively in order to ensure no additional operational risk. Installing the Online Zetasizer provided Severn Trent with the capability to optimise coagulant use with an increased level of precision, but without any corresponding increase in risk. While the use of an online analyser alone is still reliant on the plant operator to execute a recommended action, the The recent Water Industry Awards saw Severn Trent and Malvern Panalytical recognised for the development of the Online Zetasizer, a system that uses real-time data to ensure the correct dose of coagulant is used at water treatment works By James Brockett Real-time data enables spot-on coagulant dosing The Zetasizer was used at Severn Trent's Tittesworth WTW, which draws water from Tittesworth reservoir WINNER