This text offers information on the theory of major drinking water treatment processes and contains real-life practical examples. It aims to create guidelines for the design of unit processes that operate within an overall framework for water treatment plants.

Areas in relatively dry climates often have water shortages and there is competition between municipal and agricultural (irrigation) water use. The problem can be alleviated by using the water twice, first for the cities and then for agriculture after the municipal wastewater has been properly treated. There are now two sets of water quality standards for irrigation with wastewater: a stringent set for developed countries, and a less stringent set for developing countries. Also, more and more cities will have to use their wastewater internally for irrigation of parks, etc., and even for drinking. The latter requires advanced wastewater treatment. Part of this treatment can be supplied inexpensively by a groundwater recharge and recovery system, which also provides storage and enhances the aesthetics of direct potable reuse of wastewater by breaking the pipe-to-pipe connection. The renovated water from a recharge or “soil-aquifer treatment” system generally can be used as such for unrestricted irrigation, but potable use requires additional treatment.