ABSTRACT
Water is becoming scarcer and scarcer in developing countries and also in parts of some industrialized countries. In arid and semi-arid areas especially, but in fact everywhere, wastewater is simply too valuable to waste. It contains scarce water and valuable plant nutrients, and crop yields are higher when crops are irrigated with wastewater than with freshwater (Table 21.1). Farmers also save on artificial fertilizers: in Mexico, for example, this saving is around US$135/ha year, which is a significant amount of money for subsistence farmers (Future Harvest, 2001*).
