Applying sustainable water management concepts in rural and urban areas: some thoughts about reasons, means and needs.

Serving the world population with adequate drinking water and sanitation is an important prerequisite, not only to hygienic safety, but to prosperity and political stability as well, and will foster the adaptive capacity of the societies in the developing countries and beyond. To avoid hygienic and political disasters impacting the world economy, investment in water supply and sanitation must urgently be made. Whether the classical system of urban water supply and sanitation is appropriate to satisfy the needs of the developing world, however, and whether this system meets the general criteria of sustainability is questionable. The costs and the time needed for installation of sewers and wastewater treatment plants are tremendous. In water shortage areas, the amount of tap water required to transport pollutants to the treatment plant is hardly affordable. Recovery and re-introduction of valuable substances, including water, into the urban cycle of materials is impossible because of mixing and dilution effects inherent in the system. Decentralized water and wastewater management should be seriously taken into account as an alternative. Source separation of specific fractions of domestic and industrial wastewater, separate treatment of these fractions and recovery of water and raw materials including fertilizer and energy are the main characteristics of modern high-tech on-site treatment/reuse systems. Mass production of the key components of the system could reduce the costs of the treatment units to a reasonable level. On-site units could be installed independently of the development stage of the urban sewer system. In conjunction with building new housing complexes a stepwise improvement of the hygienic situation in urban and peri-urban areas could be achieved, therefore. Remote control of the satellite systems using modern telecommunication methods would allow reliable operation, and comfort for the users. Intensive research is required, however, to develop this system and bring it to a standard allowing efficient application worldwide.