Keeping water clean in South West England

Nomenca Ltd
200T Scada Outstation
Waste water treatment monitoring
Industry / Vertical:


Formed in 1998, Nomenca Ltd, is a Mechanical, Electrical, Instrumentation, control and Automation (MEICA) contractor. Nomenca’s scope includes the mechanical and electrical design, supply, installation and project management of MEICA and turnkey works in the Water, Power, Rail, Defence and Industrial sectors. Nomenca has seven UK offices, more than 350 employees with a turnover of in excess of £50m.


South West Water supplies water services to around 97% of people in Devon, Cornwall and small parts of Dorset and Somerset. It also provides sewage services to around 88% of its customers in this region. An important part of this service includes the safe treatment of waste water. The treatment of sewage is the process of removing toxins and pollutants from waste water, household sewage and industrial effluent to produce products safe for disposal or reuse.

South West Water operates 39 water treatment works around the region. For the primary filtration process, the company’s smaller sewage treatment plants deploy filter beds and rotating ‘distributor’ arms. As the sewage feeds into the filter beds via an overhead pipe, the rotating arms revolve to evenly distribute the effluent and begin the separation of the solid contaminants. During the filtration process, the arms also sprinkle water in the bed to help loosen the effluent solids and prevent clogging. Once this process is complete the liquid is siphoned for purification while the settled sediment is ‘run off’ into sludge tanks for further treatment and eventual use in the production of fertilisers and methane gas.

The unbroken rotation of the distributor arm is not only critical for effective and efficient waste water treatment but also to avoid any long lasting environmental damage to the surrounding area from over spill. With South West Water contracting the installation and management of the plant to Nomenca, it required a remote monitoring system to be implemented in order to track the operational status of the rotating distributor arms and maintain an efficient service. Nomenca approached Wood & Douglas to provide the reliable radio telemetry units for this system.


Designed to be used in waste water treatment works, Wood & Douglas deployed its 200T transmitter and OpenNET 6000 central controller. With an onboard digital compass module that detects movement through the earth’s magnetic field, the 200T was fitted to each rotation arm, transmitting a coded pulse over a low-cost, secure VHF wireless to a centrally located OpenNET 6000, for every arm rotation.

If at any time during operation the rotating arm slows down, or ceases to revolve altogether, the 200T will instantly alert the central hub, so swift action can be taken.

With a battery life of over five years, the 200T is designed for ‘hands off’ operation in remote areas, carrying out radio health check every 15 or 60 minutes to ensure continuous successful operation. Housed in an IP68-protective enclosure that is dust and water tight, the 200T is also built to work seamlessly in all weather conditions, temperatures and tough isolated environments while guaranteeing a reliable wireless performance where obstructions may cause radio communication problems.

Wood & Douglas’ 200T transmitter and OpenNET 6000 system enables consistent, stable and secure wireless monitoring at low cost. In the event of a mechanical failure of a rotational arm, South West Water was able to carry out rapid maintenance, avoiding any major service interruption and prevent adverse environmental incidents.

  • Reliable, low-cost and secure radio link allows critical remote monitoring of rotation distribution arm operation
  • Robust radio unit designed to work in tough environments while ‘hands off’ operation and regular health checks to insure on-going operation.

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