Leachate pumps are instrumental in the removal of contaminated groundwater from solid-waste landfill sites. Two different types of pumps are typically used in the extraction of leachate: pneumatic pumps, where compressed air displaces the fluid, and piston pumps, where a surface-driven piston displaces the fluid.
Pneumatic well pumps are fully-submersible pumps used for the extraction of contaminated groundwater from wells. The water is pumped by displacing it with air, producing much less fluid shear and emulsification than electrically-driven pumps. The pump is set in the well with an air supply line, an air exhaust line, and a water discharge line running to the surface. Water in the well enters the pump, either through the top or bottom, pushing open the fluid check valve, raising the float, and displacing the air in the pump. As the float reaches the top of the pump, a lever is triggered, closing the air exhaust and opening the air supply. The compressed air enters the pump, closing the fluid check valve and displacing the water and forcing it to the surface. When the water is displaced and the float falls to the bottom, the air supply is closed, the air exhaust is opened, and the cycle begins again. The pump is self controlled – it only consumes air and pumps water when the pump is full.
For difficult leachate-pumping applications, piston pumps are an alternative. The down-well portion of a piston pump is composed of a bored-out piston within a cylinder. The piston is driven by a reciprocating air cylinder at the surface; the piston and driver are connected by a fiberglass rod. Air supplied to the reciprocating cylinder begins the pumping process: the piston is pulled up, forcing a check valve against the top of the piston and pulling water from the well into the cylinder; the piston reaches the top of its stroke, and the cylinder is full of water; the piston is pushed down, forcing the check valve open and allowing the piston to lower; as the piston is pulled up again, the water now on top of the piston is forced up the pipe and to the surface. Unlike pneumatic pumps, piston pumps require some form of external control to avoid pumping when no water is present.
When selecting a pump for leachate removal, the required flow rate, well depth and diameter, and inlet location are the most important factors to consider. The type of well and site constraints will help determine which style of pump is best for the application
MLE Equipment uses the QED AP series pneumatic well pumps and IronHorse Series piston pumps. Please see the provided specification sheets and manuals for more detailed information on pumps for leachate removal.
