Biology micro-organisms

NON-THERMAL PLASMA STERILIZATION OF AIR STREAMS KINETICS OF PLASMA INACTIVATION OF BIOLOGICAL MICRO-ORGANISMS... 

Corrosion associated with the action of micro-organisms present in the corrosion system. The biological action of organisms which is responsible for the enliancement of corrosion can be, for instance, to produce aggressive metabolites to render the environment corrosive, or they may be able to participate directly in the electrochemical reactions. In many cases microbial corrosion is closely associated with biofouling, which is caused by the activity of organisms that produce deposits on the metal surface. 

The biological contamination and the hardness of underground water are the two very serious problems of water. Dissolved salts deteriorate water quality and may cause diseases related to joints and bones, while infected water may cause many water-borne diseases such as cholera, dysentery, typhoid etc. Ultrasound may disinfect the potable water by blasting off micro organisms such as zooplanktons, phytoplanktons, pathogenic bacteria and produce germ-free water in few minutes of... 

The main pathways of the breakdown of fatty acids in biological systems involve oxidation at various points along the chain or oxidation at certain double bonds of specific unsaturated fatty acids (Coultate, 2001 90-98). The main forms of oxidation are termed a-, (3- and to-. They are named depending on which carbon of the chain is attacked. Of these (3-oxidation is the most general and prevalent. Degradation proceeds by the liberation of two-carbon (acetyl-CoA) fragments from the chain. The enzymes responsible for oxidation are widely found in plants, animals and micro-organisms. 

The flow rate and concentration of wastewater do not remain constant but vary during the course of the day and are also dependent on the time of year. If the flow rate is too high, loss of micro-organisms by washout may occur in secondary treatment processes. If the flow rate is too low, then the lack of nutrients will lead to a reduction of the micro-organism population. Wastewaters entering a treatment plant usually flow first into an equalisation basin, so that the flow rate out of the basin is maintained constant, or between prescribed limits, to protect the subsequent processes. The equalisation tank also reduces the effect of toxic shocks on the biological processes within the main treatment plant. 

The activated sludge process, depicted in Fig. 1, involves basically the aeration and agitation of an effluent in the presence of a flocculated suspension of micro-organisms which are supported on particulate organic matter. After a predetermined residence time (usually several hours) the effluent is passed to a sedimentation tank where the flocculated solids are separated from the treated liquid. A reduction of BOD from 250-350 mg IT1 to a final value of 20 mg L-1 is achieved under typical operating conditions. Part of the settled sludge is usually recycled to the aeration tank in order to maintain biological activity. 

For the past 50 years the determination of the sanitary quality of water has been based on the enumeration of indicator micro-organisms (e.g. coliform bacteria). The adequacy of coliform enumeration methods for this purpose has been questioned [21]. The current trend of year-round disinfection of waste water effluents and the increasing discharge of both toxic substances and heat from industrial outfalls cast further doubt on the accuracy of biological indicator systems [22]. 

Work has also been done on the absorption and inactivation of organomercurials by micro-organisms that tolerate and even thrive on mercurials [26, 27]. It has been postulated that inactivation occurred by the uptake of fungicide by micro-organisms, followed by metabolic breakdown and by possible utilization of portions of the byproducts. However, whether or not biological inactivation and mercury evolution occur together has not been determined. 

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