Advanced water treatment as a tool in water scarcity management

The water resource is under increasing pressure, both from the increase in population and from the wish to improve the living standards of the individual. Water scarcity is defined as the situation where demand is greater than the resource. Water scarcity has two distinctly different dimensions: water availability and water applicability. The availability is a question of quantitative demand relative to resource. The applicability is a question of quality suitability for the intended use of the water. There is a significant difference in this regard with respect to rural versus urban use of water. In the former case, the water is lost by evaporation and polluted. In the latter case, the water is not lost but heavily polluted. With increasing scarcity, the value of water and the need for controls increase. In this situation, water reuse becomes an option that has been considered exotic until recently. This paper sets the stage with respect to perspective and management options related to implementation of water reuse. Water treatment has to be interpreted as the means by which to purify the water from any degree of impurity to any degree of purity that fits the desired use, including reuse. The historical distinction between processes used in water treatment for water supply versus processes used in water treatment of used water (wastewater) will fade, because it will all be unit processes and operations in combinations to fit the purpose of water use. Water can be purified to any degree of purity - except zero. The challenge of future reuse will be to account for the attitudes related to trace chemicals in water. How precautious is it prudent to be? Risk analysis is no longer an elitist business. It will involve the perception of the public, politicians (and the press).