Baltic Coastal Zone No 5 • 2001

METHODS OF BIOLOGICAL SEWAGE TREATMENT

Wira J., Wira D.

Department of Water Environment Engineering,

echnical University of Szczecin,

50 Piastow Ave.,

70-311 Szczecin, POLAND,

Baltic Coastal Zone No 5, pp. 35-39, ISSN 1643-0115

Abstract

Biological sewage treatment is the process basing on the microbes activities, which use the dissolved organic pollutants, or those being brought to that form, partially as the energy source and partially as the structural material for the new cellular substance. This way the contaminations are removed from wastes. Products of pollutants decomposition can have solid, liquid and gas form. Processes of the biochemical oxidation (oxy-processes) take place if there is the sufficient quantity of the oxygen dissolved in the microbes’ activity environment. In the presence of oxygen, the organic matters decomposition is quicker in comparison with the oxygen-free conditions. On that reason, to the biological sewage treatment plants it is supplied oxygen as the rule. Biological sewage treatment is the process basing on the microbes activities, which use the dissolved organic pollutants, or those being brought to that form, partially as the energy source and partially as the structural material for the new cellular substance. This way the contaminations are removed from wastes. Products of pollutants decomposition can have solid, liquid and gas form. Processes of the biochemical oxidation (oxy-processes) take place if there is the sufficient quantity of the oxygen dissolved in the microbes’ activity environment. In the presence of oxygen, the organic matters decomposition is quicker in comparison with the oxygen-free conditions. On that reason, to the biological sewage treatment plants it is supplied oxygen as the rule. There are substances being biologically degradable in short time, and other in long time. Some organic compounds are practically biologically non-degradable (e.g. humus substances). In light of the most up-to-date researches, the answer to a question whether the particular compound is easily or hardly soluble can be obtained only after taking into account sometime just phenomenal adaptation ability of the biological purification system [3]. As the biocenosis adaptation is understood the micro flora and micro fauna adaptation to the changing environment properties, in which those organisms exist. That phenomenon is possible because of the fact that one or few substances of the wastes act as the stimulus provoking production of enzyme, or a group of enzymes, necessary to decompose and use of the nutrients being in that environment. The microbes adaptation time is differentiated, sometime it amounts to few days and sometime that process lasts for many weeks e.g. the active sludge needs about 20 days to convert into using aniline as the sole source of coal and energy for living processes. Biological sewage treatment can be conducted in natural, semi-natural and artificial conditions. Biological sewage treatment in natural conditions consists in disposing them into lakes, rivers, water reservoirs or sea. It is used here the possibility of self-purification of the superficial waters. It is the way used as a rule in relation to wastes being already biologically treated in artificial conditions and it can be used as the process giving the properties similar to natural waters for the wastes. Biological treatment in semi-natural conditions consists in the purposeful adaptation, using technological means, of the natural water or soil environment to the wastes receipt, what enables in its turn some natural process of the biological decomposition of the organic substances contained in the wastes. For such kind of sewage treatment are used waste ponds, soil and field systems (irrigated fields, soil filters and filtrating trenches). Sewage treatment in artificial conditions consists in the multiple intensification of biochemical processes of the organic matters decomposition taking place in natural or semi-natural conditions through using the relevant technological equipment and creating the optimal growing conditions for the complex of living organisms constituting some part of the natural environment therein. To the biological sewage treatment in artificial conditions are used: bio-filters, active sludge plants, fermentation chambers.