MCerts device helps Premier Foods cut effluent costs.

Malvern, UK -  A Premier Foods operation in Newport has substantially reduced effluent charges following an investment in MCerts-certified flow metering equipment, as part of an open channel measurement project. The ultrasonic  transducer array from Pulsar Process Measurement (PPM) was installed at the site by Siris Environmental of Co. Durham.

Companies are now charged on both the volume and quality of the effluent discharges, but according to PPM, many either fail to appreciate the importance of accurate measurement or simply don’t know how to achieve a high standard of accuracy. The MCERTS scheme has introduced a way to benchmark the accuracy of a complete installation.

"Many companies see the MCERTS Certification Scheme as another additional expense, they often don’t appreciate that the scheme ensures accurate measurement of their effluent discharge and in this case we have proved that a well implemented installation can save real money," Simon Richardson of Siris.

Paul Wiggins of the Environment Agency added: "It is excellent news that an industrial effluent flow monitoring installation meeting MCERTS requirements and using a MCERTS certified flow meter has had such a positive impact. Managing flow is crucial to effective effluent treatment, protecting the environment and can have considerable financial benefits to the industry"

Siris led the project, supplying and installing the primary measurement device together with the flow and sampling equipment. Controlling upstream flow conditions was vital to achieving the most accurate flow measurement system, so the design and the installation of the weir tank and associated equipment had to meet very high standards.  For example, the weir tank was constructed to be very rigid, the weir plate was reinforced and the chamfering of the edges of the weir plate was closely controlled.

Pulsar’s DUET non-contacting ultrasonic transducer array was chosen for its high accuracy. Ultrasonic systems work by bouncing a sound pulse from the surface being measured and calculating the distance from the time taken for the pulse to return to a transducer. The accuracy of the measurement depends on the speed of sound, which can vary with temperature. Temperature changes can be compensated for, but a temperature compensation circuit can’t respond immediately and there may be temperature variations in the column of air below the transducer face.

DUET uses two transducers a known distance apart, and by comparing the returning signal from both transducers, variations in the speed of sound are dynamically compensated for. This was critical to the success of the project. A 2mm variation in measurement accuracy would result in an error of 40 cubic metres per day.