Exponential population growth,
coupled with rapid industrialization and urbanization, has generated an
increasing amount of wastewater, which results in health risks and
environmental damage. Recently, increased attention has been focused on the practice of wastewater, under strict hygiene regulations, for forest-irrigation
purpose.
Land application technology, including irrigation, becomes a viable
solution when the cost of a typical tertiary treatment process is high. Soil and vegetation act as filters that encourage the entrapment of particulate contaminants from wastewater, and then the treated effluent is allowed to drain through the
soil profile (via gravity). Some communities in the arid and semi-arid tropics
use sewage, after primary treatment, for the irrigation of woodlots and other
species, such as Casuarina glauca, Eucalyptus camaldulensis and Tamarix
aphylla. These communities need forest plantations, greenbelts and amenity
trees for protection against sandstorms and desiccating winds.