Rotork intelligent electric valve actuators with Profibus DP open control system connectivity are helping Wessex Water to improve the sewage treatment regime and protect the popular tourist beaches on the UK’s Somerset coast at Highbridge. Two new storm tanks have been built to double the storage capacity of the existing installation, which receives the flow from eight pumping stations in the surrounding area. The plant expansion is being designed, installed and commissioned by the principal contractor, M.J. Gleeson, in order to meet strict new consent targets introduced by the Environment Agency to minimise the risk of untreated discharges to sea. At the same time new screens, filters, aeration tanks, settlement tanks and ultra-violet treatment plant have been installed at the West Huntspill STW, which receives the outflow from the Highbridge site, at a controlled rate of no more than 300 litres/second. Rotork IQ actuators control the flow rate through the Highbridge plant as well as the sequence of filling and emptying the storm tanks when the full flow to site rate is exceeded. At this point the additional volume is automatically diverted into the storage tanks until the flow rate returns to normal. All the processes at Highbridge are controlled on Profibus two-wire networks, linked to a new Mitsubishi Q2AS-S1 PLC utilising a software programme written by Wessex Water automation.
