Rotork in the UK Water Industry - Some Recent Highlights

Rotork IQ intelligent electric valve actuators are installed throughout the advanced new Reading Sewage Treatment Works, described by Terry Bane, Project Director at Thames Water as "one of Thames Water's flagship projects, where some of the most innovative technology has been used to design and build the site."

Built on former waste disposal land adjacent to several new business parks, the new plant serves a population approaching 300,000 as well as a local brewery, necessitating an emphasis on odour control, biological nutrient removal, energy recovery and sludge recovery that is unique to this site.

The facility's buildings are therefore designed to blend with future developments in the area, whilst acting as an envelope to capture emissions, conceal processing plant and minimise noise. The site features four distinctive 20 metre high egg-shaped aluminium clad digesters and extensive landscaping, including 20,000 trees and shrubs. The technically advanced equipment that it houses matches the state-of-the-art appearance of the site.

Approximately 150 Rotork actuators control the movement of flows throughout the site, from the fully enclosed inlet works to the tertiary filters from where the treated wastewater is returned to the local watercourse in line with the latest EU and Environment Agency standards.

Rotork in the UK Water Industry

Data loggers in the actuators store historical operating data and valve torque profiles, information that can be downloaded and analysed utilising Rotork IQ-Insight software. The collected data can help to optimise plant performance by identifying potential problems and facilitating predictive maintenance.

An equally advanced control system has been installed, utilising twenty-three Profibus 2-wire segments for the instrumentation, actuators and package plant, which are linked to several latest generation PLCs situated throughout the site.

The PLCs communicate between each other and with the SCADA central control room using Ethernet over fibre optic cable, facilitating the use of simple web browsers for viewing SCADA screens in the control room or at other onsite and offsite locations. The central focus of the control room is a 50 inch wide screen plasma display, whilst workstations in the control room and touch screens within the plant itself facilitate centralised and local access to SCADA displays.

Virtually all of the Rotork actuators installed are IQ multi-turn or IQT quarter-turn models, the majority factory fitted with the Rotork Profibus DP card. Reading Sewage Treatment Works is the first Thames Water site to make extensive use of the Profibus protocol, which was selected as being the fieldbus system that is most universally available from equipment suppliers. Designed and built by the Target Alliance, a team formed by Thames Water, Taylor Woodrow and Black & Veatch, the plant was officially opened in January 2005.

Rotork IQ intelligent valve actuator installations at Thames Water Reading STW.From top: Digesters,Pasteurisation plant, Bioreactors.

Assistance with Severn Trent's improved water quality programme

Rotork IQT intelligent electric actuators for quarter-turn valves are a central feature of a filter improvement project at the Severn Trent Ogston water treatment plant in Derbyshire. The plant was first opened in 1946 to treat water from the adjacent Ogston Reservoir, now distinguished as where round-the-world record breaking yachtswoman Ellen Macarthur first learnt to sail.

Norwest Holst Construction Ltd has carried out the complete upgrade of twelve rapid gravity filters at Ogston, including the fitting of Tetra block filtration flooring, replacing the old sand and gravel media with an improved sand and anthracite formula and installing a new clean backwash water main. The project also involved fitting new butterfly and plug valves with Rotork IQT actuators in virtually all areas of the plant to automatically control the filtration and backwashing sequence of operations. The actuators are connected to refurbished PLCs and linked to a new master MCC (Motor Control Centre) that runs the plant, treating up to 40 ml/day (megalitres a day) for consumers in the surrounding areas.

Kevin Rodenby, Norwest Holst's M & E Supervisor on the project, appreciates features of the IQT actuator which assist the commissioning and running of the new plant. "Rotork's hand-held, non-intrusive setting tool is especially helpful in simplifying and speeding up commissioning, eliminating the time-consuming effort of removing electrical covers." he said. "Quick and easy to follow setting instructions are clearly displayed on the actuator's indication screen, which also provides local valve position and status information."

IQT actuators also incorporate on-board data loggers where commissioning settings, historical operational data and valve operating torque profiles are stored. This information can be downloaded over the non-intrusive link for analysis and review using Rotork IQ-Insight PC software to maximise plant utilisation and eliminate the threat of unexpected breakdowns.

The IQT actuators operating filtered water outlet and backwash water inlet valves are factory fitted with the Rotork CPT (Current Position Transmitter), enabling partial valve movements to be controlled and indicated in response to an analogue current signal from the MCC. CPTs were also retrofitted to the only actuators retained from the original plant - Rotork AQ units on the forward rinse valves - enabling them to be included in the new control regime and eliminating the need to replace them.

Ogston is the latest in a programme of water treatment plant upgrade projects, undertaken by Norwest Holst Construction Ltd and utilising Rotork actuators, designed to bring improved water quality to users in the Severn Trent Water area.

Rotork IQT valve actuators in two areas of the filtration plant at Ogston:
1.Clean backwash water main
2. Filter air scour valves

Help with Welsh Water's environmental improvements at Cardigan

The sewage treatment works at Cardigan are the focus of a £7million investment scheme undertaken by Dwr Cymru Welsh Water, designed to bring environmental benefits to the Teifi Estuary and other local watercourses. The scheme, designed and built by Morrison Construction and Meica Process Ltd, involves upgrading the capacity of the existing sewerage network and improving the quality of bathing water in the area in line with the latest EU consents.

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, together with other improvements that will increase the works' designed flow to treatment to 100 litres/second. Meica Process Site Manager Mike Hendy explains that, with 64 membrane sets, the Copa installation is: "the largest in the Welsh Water region and probably the largest in the UK.

A major feature is its compactness, enabling throughput to be significantly 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. A Mitsubishi PLC and customised Copa software developed by Meica Process and General Panel Systems has been introduced to run the plant fully automatically. Telemetry also links all the data from the PLC to the central control room for Welsh Water's operations.

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, which is constantly monitored by the PLC.

Effluent from the MBR is clean enough to be discharged directly into the estuary. Sludge is thickened on-site prior to being tankered away. A new standby generator has been installed to operate the site in the event of mains power failure, ensuring uninterrupted operation to further safeguard the environment.

The introduction of Rotork IQ and IQT actuators with Profibus connectivity has been well received at Cardigan. Simon Stone from General Panel Systems, responsible for software design, configuration and commissioning, draws particular attention to the savings achieved by reduced cabling and the benefit of having a large amount of operating information available from the actuators, whilst Dave Harding, Meica Process Commissioning Engineer, appreciates the speed and convenience of Rotork's non-intrusive actuator commissioning and interrogation system.

Mike Hendy concludes: "The Rotork actuators have played their part in the successful introduction of this innovative new plant. There have been very few problems, which have been promptly and efficiently rectified, contributing to the punctual final commissioning of the project."