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Water is a critical resource
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In nature water flows through a natural water cycle
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During the water consumption cycle pollutants are added to
the water that may make it harmful to the environment or human health
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A current trend in Europe is that the withdrawal of water
from the sources is declining
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Most water has to be purified before it can be used for
human consumption
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A systematic and scientific evaluation of wastewater
handling begun in England around 1850
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To control water-borne diseases it is necessary to separate
sewage from drinking water
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The deterioration of water quality in marine environments as
eutrophication and toxic pollutants show the need for improved wastewater
treatment
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Sewage water in cities can be treated as storm water and
sanitary waste water. Industrial wastewater may be toxic and pre-treatment
may be necessary before it is treated in wastewater plants
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Wastewater discharged into an ecosystem will normally but
slowly be transformed by self-purification
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Different technical methods focus on the possibilities of
intensifying biological, chemical or physical separation processes to
diminish space and residence time
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Sewage treatment methods may be classified as physical,
chemical and biological
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An advanced sewage treatment system includes: pre-treatment,
physical treatment, biological treatment, complementary treatment, sludge
treatment and sludge disposal
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An alternative to the technical treatment of sewage water is
an ecological treatment
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New technologies aim at continue decreasing the need for
water in the society and also to diminish the emissions of harmful chemicals
into the wastewater.
