Biological Sewage Treatment Plant
Sewage treatment plant is a specialized plant that makes use of biological component to achieve effective response and to discharge safely. Once the non-biodegradable materials or solids are removed, raw sewage is passed to an aeration chamber, where diffusers supply air. This promotes aerobic bacterial action that works to break down the sewage into inorganic waste, water and carbon dioxide.
A purifying technique of domestic and industrial sewage, comprising biochemical decomposition by microorganisms of organic substances mixed and emulsified in sewage. Microorganisms use the mixed substances in sewage as a food and energy source for their life processes. The microorganisms respiration process involves oxidization of organic substances and release of the energy needed for their life functions. A part of the energy generated is used for synthesizing cellular substances processes, which is for increasing bacteria mass, active sludge quantity and biologic film thickness in the purifying structures. Bacteria participating in the process of organic compounds mineralization in sewage can be divided into two groups, based on their relationship to oxygen:
Aerobes (that makes use of oxygen mixed in water for respiration)
Anaerobes (that develops in the absence of free oxygen)
Apart from dissolved organic substances, there are oils, tars and suspended substances in the sewage, that have to be removed before biologic treatment. In this process, sand traps, gratings and settling tanks are used. In the accomplishment of aerobic biological purification is possible under natural conditions, in biologic ponds, irrigation fields, filtration fields, and when microorganisms' life processes become intensified, in a man-made created environment, in bio-filters, aero-filters and aero-tanks. Methane tanks are used in the anaerobic method of purification. Selection of structure type is made by quanity and character of sewage, local conditions and requirements as to purified sewage quality and so on. The complete purification results in virtual elimination of biochemically oxidized organic substances from the water. As the water loses its putrefy ability, it becomes transparent and bacterial contamination decreases. Biologic treatment is apt for sewage that contains a sufficient quantity of biogenic elements needed for the life processes of microorganisms.