Greywater can be treated in various possible ways. Of the several
different ways used, the most preferable is the aerobic method of
treatment by constructing wetlands. Constructed wetlands can be
broadly classified into four major groups, based on the type of
plants being used: free floating plants, floating leaved plants,
emergent plants and submerged plants. Emergent plants can be
used for surface flow and sub-surface flow wetlands (Vymazal,
2007). Constructed wetlands with surface flow consist of basins
or channels. Sub-surface flow wetlands move effluent through a
gravel or sand medium on which plants are rooted. Sub-surface flow wetlands can also be further sub divided into horizontal and
vertical types on the basis of direction of flow of effluents (Vymazal,
2007).