Continued population growth, contamination of both surface water and groundwater, uneven distribution of water resources and periodic droughts have lead to a search for new sources of water supply. One must discuss, not only in developing and threshold countries, how the objectives and requirements for wastewater and sludge disposal are in accord with a possible water reuse or whether they exclude each other. Early developments in the field of water reuse are synonymous with the historical practice of land application for the disposal of wastewater.
One can observe that already in the second half of the 19th century a number of sewage farms existed, which were used primarily for waste disposal, but also made use of the water for crop production and other beneficial uses. Considerable amounts of treated wastewater were recycled, either directly using agricultural irrigation or were returned to the natural cycle by infiltration.Biological processes such as the percolation of wastewater in the upper layers of the soil were used as models for the first water treatment devices for example trickling filters, while more sophisticated treatment methods such as aeration systems were not invented until later. Since nowadays highly advanced wastewater treatment systems exist, guaranteeing a safe treatment and disposal of wastewater, one must reconsider whether an agricultural reuse of wastewater and sludge is still sensible and considering its risks, can be tolerated. Basically one must state that all man-made wastewater treatment processes only copy those processes which also occur naturally compressing them in time and space. There is therefore actually no qualitative difference between the natural and the man-made technical processes. Hence natural wastewater treatment processes, such as irrigation systems and sludge and wastewater reuse, should always be kept in mind especially for developing and threshold countries. Considerable amounts of municipal wastewater have been reused successfully in agriculture in the towns of Braunschweig and Wolfsburg, Germany, without having caused any ecological risks. In western industrialized countries wastewater treatment is normally not combined with a reuse of the reclaimed water, but 30% of all municipal sewage sludges are reused in agriculture.
Copyright: | © Universität Braunschweig - Institut für Siedlungswasserwirtschaft | |
Quelle: | Abwasserreinigung (Januar 2005) | |
Seiten: | 20 | |
Preis inkl. MwSt.: | € 10,00 | |
Autor: | Prof. Dr.-Ing. Norbert Dichtl | |
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