Pneumatic pumps extract the leachate

GeoRemediation (part of the SetPoint Europe group of companies based in Leamington Spa), has recently completed the supply, installation and commissioning of what is believed to be the largest pneumatically operated leachate borehole pumping system in Europe.

Waste management contractor Cleanaway Ltd, which operates the Rainham Landfill site in Essex, had been looking to install an effective leachate removal system. The leachate project which includes, 100 bore holes, pump units, pipework infrastructure and specifically designed leachate treatment plant, has been managed by Cleanaway’s Environmental Projects Team based at Southend-on-Sea.

After intensive field trails of various pneumatic leachate extraction pump technologies, QED Hammerhead pump units were successfully selected. Performance during the trial, track record and overall capacity ensured that GeoRemediation were awarded the pump supply contract. Installation took place in three phases.

The H4 Hammerhead Controllerless pump requires 3.5 ft or more of liquid above the pump bottom to pump. When first submerged, the pump fills due to static head pressure over the pump inlet. The inlet check ball lifts and liquid fills the pump body. As liquid enters the pump body, the pump float is lifted upward. Air displaced by the liquid exits the pump body through the exhaust port and tubing. The inlet ball falls down into its seat when the pump is full.

Once the float rises to the top of the pump it moves the hammer drive mechanism into the pump discharge position. In this position supply air enters the pump body pushing the liquid up the discharge tube. During the discharge the discharge check ball rises up to allow the passage of the liquid. During discharge the exhaust port is sealed off to seal the pump body.

The float drops back down as the liquid is discharged from the pump. At the lowest position the weight of the unsubmerged float pulls the hammer drive mechanism back into the refill position, allowing the pump to vent and begin another refill cycle as described above. As long as liquid is available the H4 continues to fill and discharge. If the liquid source recovers slowly the pump will slow its cycles automatically, shutting off in cases where liquid recharge stops.

Slight variations in the pump units having been made to deal with the specific requirements of each particular phase of the Rainham installation and, as a result, the Hammerhead pumping system is currently extracting over 200,000 litres of leachate a day. To ensure this performance is maintained Cleanaway personnel have attended specially organised operation and maintenance seminars by GeoRemediation to ensure peak performance of the leachate extraction pumps.

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