The sewage treatment works at Cardigan, Wales, are the focus of a multi-million investment scheme undertaken by Dwr Cymru Welsh Water, designed to bring environmental benefits to the Teifi Estuary and local watercourses.
Improvements at Cardigan STW are centred around the introduction of two Copa membrane bioreactor (MBR) treatment plants, producing a high quality disinfected effluent without the need for additional filtration or ultra-violet treatment.
With 64 membrane sets, the Copa installation is the largest in the Welsh Water region and probably the largest in the UK. A feature is its compactness, enabling throughput to be increased within the boundaries of the existing site. Rotork IQ and IQT intelligent electric actuators are installed on the valves that control the flow and processes in all new equipment areas, linked on three Profibus 2-wire segments to the new MBR control room.
Sewage flows through new inlet screens and grit removal tank to a central flow split tank in front of the reactors. At times of heavy rainfall, excess flow is diverted to enlarged storm tanks. The sequence of these operations, including the supply of air to the MBRs from new duty and standby blowers, the operation of effluent outfall modulating valves and the daily air diffuser MBR cleaning programme are controlled with the Rotork valve actuators. The actuators' integral data loggers store operating data including valve torque profiles, internal trips and alarms.
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