Biological Methods of Water Purification
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Biological methods of water purification and disinfection of waste water (using mainly bacteria - aerobic or anaerobic) ensure the transfer of harmful substances in insoluble or gaseous form. Conditions for the effective use of biological methods are based on biochemical mineralization and decomposition of organic matter by micro-organisms. It is very important to provide acidity environment in the course of biochemical processes, which should be within the pH 6.5-8.5.
Aerobic processes of water purification commence by filing the processed flow with enough oxygen to ensure microbial life. In general, in the biocenosis active sludge is composed of diverse groups of microorganisms: mesophilic, thermophilic, aerobic and anaerobic.
When the sufficiency of oxygen and temperature of the sewage environment within 20-30°C biocenosis is dominated by mesophilic aerobe (mesophilic oxidization), and at 30-40° C - thermophilic (thermophilic oxidization).
Depending on the conditions, one group of microorganisms may prevail through the primary process. The rest of the group of microorganisms in this case are related, they provide the core group microorganisms with necessary nutrients.
In aerobic process of water purification almost no unpleasant smell is produced, the method of microorganism reproduction is more simple and adapted to the changing composition of waste. With this process self-heating of the bio-mass occurs of up to 70° C, i.e. its disinfection commences.
If the sewage lacks oxygen, then the anaerobic fermentation occurs, which may be either methaneous or hydrogenous. When the mass temperature reaches 30-35° C the biocenosis is dominated by mesophilic anaerobic bacteria, and when the temperature of the water is 50-55° C - thermophilic bacteria. The process is accompanied by the provision of biogas, which consists mainly of methane, hydrogen and carbon dioxide.
Sewage disposal system must meet the following conditions:
♦ construction and commissioning of facilities for the storage and disposal of wastewater must precede the introduction of sewage systems;
♦ liquid effluents should be prepared to make to the ground before the frost in large doses during a period of 2-3 years;
♦ working in the wastewater in the soil in an area, which may run-off into open waters;
♦ to prevent the dumping of waste water of fish complex in water environment, regardless of their degree of purification.
Widespread use of biological ponds for water purification are for: the full treatment of water sewage effluent, for after-treatment effluent, after the last biological treatment; for fish ponds.
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