Rotork's innovative CVA electric control valve actuation technology has been selected for a demanding duty involving continuous modulation at what is described as a "new generation" waste water treatment plant in southwest France.

The plant is one of the largest in France as well as one of the most energy efficient. Designed for increased rainwater and effluent treatment capacity with improved treatment quality and reduced environmental impact, the plant incorporates a range of integrated energy saving and energy recovery processes. These include solar water heating, heat pumps, heat recovery from final effluent and biogas production from sludge digestion processes. Significant biogas production generates the daily equivalent of 27,000 kWh, which is used as the energy source for a district heating scheme in the local area. 

The biogas is produced in a process which uses a combination of solids filtration and biological aeration to remove pollutants including ammonia. The Rotork CVA actuators are installed on butterfly valves to regulate the continuous supply of air to the process. Accurate air regulation enables the plant to run efficiently and reduces air wastage. 

On previous installations pneumatic actuation was used for this application, but the more accurate positional performance available with the CVA has enabled the adoption of the electrical solution on this site. Engineers from Rotork and the local Rotork distributor SERIC explained that the CVA offers very precise control valve operation, with repeatability and resolution performance within 0.1% of full scale. The actuator also features quick and easy non-intrusive setting and commissioning using wireless Bluetooth® communication technology, whilst an integral data-logger stores an extensive record of operational and maintenance related information, including valve torque profiles and dwell times. There are plans to use the same technology at more installations in the future.

This CVA application is similar to a recent project at a sewage treatment and district heating plant in Sweden. For that contract, CVA actuators were retrofitted to replace motorised isolating and manually operated regulating valves to increase the efficiency of a biological aeration process at a municipality-owned site