The micro-organisms utilize the contaminated substances as necessary food for their production and their preservation. The aspect for this mass of micro-organisms is that of sludge, from which we have taken the name of the process. The activated sludge pilot allows the study and the comprehension of sewage treatment by activated sludge. This Activated Sludge Sewage Treatment Pilot Plant is an intermediate stage between the physical treatments or grid iron, and primary sedimentation and the final sterilization and chlorination stage, in a sewage treatment station. The conditioning process takes place in a tank where the organic load is removed by microorganism which are cultivated under aerobic conditions by blowing in air or sometimes also pure oxygen. After the pollutant elimination phase it is necessary to divide the clarified water from the sludge, operation which is carried out in the settling tank (stating separator). Its purpose is to eliminate the contaminated organic substances which are present in the sewage water after the above mentioned physical treatment. The organic load is measured in BOD (Biological Oxygen Demand) unit and it also causes a partial elimination of COD (Chemical Oxygen Demand).
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