In the modern industrialised society, continued availability of clean water makes it desirable or even necessary to recycle and re-use water, nutrients and other natural resources.
Municipal or industrial effluents re-use for irrigation as well as direct reuse of irrigation water is sometimes constrained by problems of salinity and alkalinity. In some rivers salinity increases because of contributions from irrigation practice to increase efficiency and reduce return flows.
Zoller (1980) and his associates have studied the composition of untreated, recycled irrigation water in Israel and concluded that any re-use of such waters for flood irrigation could affect agriculture adversely.
Image Source: upload.wikimedia.org
ADVERTISEMENTS:
In some situations, industrial wastewater can be re-used for irrigation. Food industry wastewaters provide good opportunities for irrigation re-use. Stehlik and Musil (1979) describe how crops of clover, lucerne, corn and potatoes can be successfully raised with irrigation from starch plant effluents.
Certain species of Eucalyptus and Casuarina are significantly tolerant to high concentrations of dissolved solids in winery effluents. Sauze (1980) has discussed the conversion of solarenergy into methane by wastewater culture of algal biomass followed by methanogenic digestion.
Some workers have advocated the raising of fathead minnows in wastewater lagoons, as a method of recycling of wastewater. Others have recommended mass-culturing of protein-rich algae such as Spirulina, Euglena and Scenedesmus in wastewater.
ADVERTISEMENTS:
Eder (1979) has advocated the use of wastewater from distilleries and breweries, after suitable evaporation and drying, as feedstuffs and has claimed that such re-use may be economically feasible provided that process energy consumption could be minimized.
Although some headway has been made in the re-use of wastewater for inigational or industrial applications, direct potable re-use of reclaimed wastewater remains a controversial issue.
Perhaps the available water reclamation technology may be quite adequate for direct potable re-use but the social and economic aspects of such re-use are still causing obstacles.
Milne (1979) has suggested the feasibility of nonpotable re-use of domestic wastewaters, such as storm drainage, for a variety of applications including toilet flushing and kitchen garden irrigation.