As wastewater flows through this component, suspended solids and some elements settle to the bottom, other nutrient elements are absorbed by the plants, and much of the nitrogen is converted to nitrate and then converted to nitrogen gas. Microbes in the water use oxygen from the air or plant roots to convert the nitrogen, destroy the pathogens, and decompose organic pollutants to carbon dioxide gas which is released to the atmosphere. This component is used when soil depth or soil water movement is a restricting factor with a more conventional system, and where additional treatment beyond the septic tank is needed to reduce pollutants going to the drainfield. When site features prevent gravity flow from the septic tank, a pump chamber must be added to deliver wastewater to this component. This component receives wastewater by gravity from the septic tank.
Controls consist of both a timer and a float for low liquid cutoff.
This component increases system cost due to special electrical needs, the pump, and its controls. It is most commonly used with the constructed wetlands or modified mound treatment components. This may be used where soil depth poses a severe limitation to conventional systems. It requires an experienced soil evaluator, designer, and installer to successfully implement its use. The perforated pipe receives wastewater from a pump chamber.