Because of graywater's lower flow volume, reduced oxygen demand, and lower suspended solids, the size of the septic tank and field can be reduced significantly. Alternatives to the septic tank, such as a roughing filter or forced aeration system, can enhance treatment before infiltration. Leach water can be used to irrigate nonfood plants. A diverse collection of aquatic plants is grown in a layer of gravel in a lined shallow trench. The root zone of these plants provides an aerobic environment for bacterial treatment of the flowing graywater.
Treated water infiltrates the soil from an unlined portion of the trench.
Nutrients can be recovered through biomass removal. Aerobic infiltration bed. A coarse organic cover isolates the treatment area while allowing air exchange and providing a large surface area for biological activity and freeze protection. Increased longevity and significant nutrient recovery can be effected by alternating between two beds. In cold climates, the treatment can occur within a greenhouse.