Biotreatment

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 A type of treatment that uses substances made from living organisms to treat disease. These substances may occur naturally in the body or may be made in the laboratory. In cancer, some biological therapies stimulate or suppress the immune system to help the body fight cancer. Biological treatment processes in wetland systems depend on supplying colonies of micro-organisms with optimum quantities of air and nutrients to achieve the same reactions that occur in natural self-purification processes, at a maximum benefit to cost ratio. The three changes that occur during self-purification include coagulation of colloidal solids passing through the primary sedimentation stage; oxidation of carbon, hydrogen, nitrogen, and phosphorus; and nitrification.




The basic biological treatment processes used in the system include waste stabilization ponds and constructed wetland systems, trickling (or percolating) filter systems, and activated sludge systems. An aerobic stabilization pond is a large and shallow excavation in the ground, where the treatment of the waste occurs by natural processes involving the use of both bacteria and algae. In aerobic ponds, oxygen is supplied by natural surface re-aeration and by algal photosynthesis. Higher animals such as rotifers and protozoa are also present in the pond.

Their main function is to predate on the bacteria, and to a lesser extent on algae, which helps in controlling the suspended solids (SS) concentration in the effluent. Ponds in which the stabilization of wastes is brought about by a combination of aerobic, anaerobic, and facultative bacteria are known as facultative stabilization ponds. The three zones in such ponds include a surface zone where aerobic bacteria and algae exist in a symbiotic relationship, an intermediate zone that is partly aerobic and partly anaerobic in which the decomposition of organic matter is carried out by facultative bacteria, and an anaerobic bottom zone in which accumulated solids are decomposed by anaerobic bacteria.

Biological treatment usually is divided into aerobic and anaerobic processes. “Aerobic” refers to a process in which oxygen is present, while “anaerobic” describes a biological process in which oxygen is absent. Scientists have been able to control and refine both aerobic and anaerobic biological processes to achieve the optimal removal of organic substances from wastewater.

Biological wastewater treatment often is used as a secondary treatment process to remove material remaining after primary treatment with processes including dissolved air flotation (DAF). In the primary water treatment process, sediments and substances such as oil are removed from the wastewater.


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