Due to continuing elevated leachate levels within the landfill cells at a Landfill site, FRS instructed OIS to investigate the site's leachate collection system.

OIS carried out the investigation and found the following:

• Maintenance of the leachate pumps was split between the energy contractor and FRS operatives
• There were a number of pneumatic pumps, maintained by the energy contractor that were either abandoned or faulty
• There were a number of electrical pumps that were incorrect for the installations, these failed regularly due to the size and specification of the pump
• The code for the PLC's and the HMI were incorrect with faults
• The calibration of the SCADA was incorrect
• The control systems were in poor condition and/or faulty
• When a leachate pump failed, 4 FRS operatives, 1 plant operator and an excavator were required to remove a single pump
• Most of the combined leachate and gas wells, along with the leachate compliance wells were in poor condition.
• Operatives were having operate most pumps manually, and walk the collection system to take daily leachate level dips, in all weather conditions.

OIS recommended a single type pump be used for all installations excluding phase 1, the type of pump should be a rubber worm drive or similar, with the intake mounted above the electrical motor to assist with ATEX compliance. Each pump was also fitted with a level sensor to record leachate levels and also to act as a failsafe to stop any pump running dry. In addition, the pumps would discharge through flow metres, which would record flows and also act as another failsafe. Should the SCADA system detect a no flow after a period of time, the system would stop the pump from operating and raise an alarm. FRS instructed OIS to proceed with the works.

The leachate collection system installed by OIS now consists of a fully automated control system including HMI's, control panel and PLC's to control the 23 leachate pumps across the site. The pumps are also fitted with level sensors to show the true leachate levels, which are used for the Compliance Team's PPC required reports.

Daily reportThe leachate collection system improvements installed by OIS ensures PPC compliance, assists with the reduction in odour escape and increases landfill gas yields from the landfill cells. As an example, when all of the piggy back leachate and gas wells are operational, the value of landfill gas recovery from these wells is around £1900 per week.

In summary, the improvement works carried out by OIS have yielded the following benefits:

• Improved PPC compliance
• Reduced operating cost
• Increased revenue from landfill gas recovery