Leachate pumping control system uses radio links

Landfill leachate treatment must be optimised to ensure efficient operation of the plant and that discharge consents are not breached. The better the control over the leachate, the easier it is to optimise the treatment process.

The strength of leachate from different cells in a site will depend on many factors including the content, its age and water ingress. However, the cells of a site are spread over a wide area that is hostile to conventional monitoring methods. Cables break as waste settles and they are vulnerable to damage by the movement of heavy plant. Manual data collection and control is slow, labour intensive and potentially hazardous.

These problems were faced by Vinod Mehroke, Operations Manager for Brett Waste Management, at its site near Canterbury, who decided to use an automated system with plcs at monitoring and control points around the site communicating by radio with a SCADA system at the treatment works.

The layout of the site was not too “radio friendly”. The leachate treatment works is low at one side of the site and the required monitoring points could be anywhere on site, often at other low points behind substantial amounts of clay and waste. To tackle this, the radio unit at the treatment works communicates with a relay station placed on a high point located centrally on the main part of the site. This provides reliable communications to all parts of the site.

In a 30-second cycle time the system contacts every remote point gathering data and setting a pumping time for those pumps that are required to run. Using the control system the operator can control the pumping flow from each of the pumps situated around the site. The control system allows the operator to blend the various leachates into a balance tank for final processing.

The system has been operating for around two years and has been expanded during that time. Brett says that similar systems will be considered for future sites.
The automation system was designed and supplied by Phoenix Electrical Engineering and the Radio Equipment was supplied by Radio Data Technology (RDT) of Witham, Essex.

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