Secondary treatments

摘要

The primary effluent treatments are comparatively simple unit operations, although of very high significance from the point of view of easy and efficient reduction in the overall pollution load. The mechanical forms and chemical agents used in the primary treatment remove the suspended matter and, to some extent, even colour. The subsequent treatment is the biological treatment, called secondary treatment, to break down the complex organic molecules to simpler substances. Such secondary treatments are categorised into Aerobic and Anaerobic. During aerobic treatment presence of oxygen at least to 0.5 ppm is essential all the time and the microorganisms of aerobic type cause degradation of the organic matter through combination with oxygen. On the other hand, during anaerobic treatment the microorganisms or anaerobic type break down the organic matter without the presence of oxygen. In this case carbon dioxide and methane are the degradation products.