The world population is expected to increase up to 8 billion by 2015. Most of the cities in the world are scattered around the fresh water resources. These cities and villages have their own interests and they constitute a power order. Therefore, we have been trying to harmonize these cities and villages in the usage of fresh water resources and the discharging of wastewater as well, by using an engineering means of water treatment. However, fresh water resources, which are essential to our lives, have a constant amount of circulation with a period of one week to ten days.
The science and technology of the water environment should recognize the limit of fresh water resources for the sustainable development of society, because the water service industries are the essential infrastructure of the community. In order to implement an appropriate risk management it is necessary to identify the goal of environmental management considering the social, natural and economical conditions. The energy-dependent technologies should be reconsidered to consume less energy and undertake more resource conservation engineering. Water science and technology cannot supply all the answers, therefore more comprehensive water management systems should be developed by other sectors, such as the food production industry.
