A range of submersible mixers and mixer/aerators are used to optimize aeration efficiency and oxygen transfer. Sufficient mixing is required to enable the solids to remain suspended and thoroughly mixed with oxygen enriched effluent, thus enhancing aerobic digestion and improving process efficiency and final effluent quality.

The type of mixer/aerator required depends upon how the leachate is being held.

When stored in a tank (either steel or concrete) venturi aerator/ cutter pumps are most common. They have the ability to draw in the required oxygen with a venturi and mix large volumes of leachate with the attached pump. The other advantage of having the submersible aerator is the heat transfer from the pump/motor which helps to keep the leachate and activated sludge (bacteria) at their optimum temperature.

External venturi aerator cutter pumps are also available enabling easy access for installation, maintenance and repair. These also remove the need for high level walkways when accessing submersible pumps.

Lagoons are also quite common in the storage and pre-treatment of leachate. Floating aerators are the most favourable choice as they can be positioned and removed simply with the aid of guide ropes.