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Sewage
Disinfection - Whether it is wastewater treatment process or drinking water purification process the ultimate aim is to provide a water which is free from any pathogenic microorganisms. Sewage disinfection is defined as the process of destroying pathogenic microorganisms in the wastewater stream by physical or chemical means.
The main aim of sewage disinfection is to prevent the spread of diseases. Sewage disinfection is also aimed to protect potable water supplies, bathing beaches, receiving waters used for boating and water contact sports and shellfish growing areas.
Complete disinfection of wastewater is undesirable because removal of most of the microorganisms may inhibit the self-purification process taking place in the receiving waters.
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Disinfection process is affected by various factors which are given below:
1. The nature of water to be disinfected-if the water contains particulate matter, especially of colloidal and organic nature, disinfection will be less efficient.
2. The temperature of the water to be disinfected. Disinfection will be more rapid when the temperature is high.
3. The pH is either acidity or alkalinity of the water.
4. The nature and number of the organisms to be destroyed.
5. The type and concentration of the disinfectant employed.
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6. Mixing of water and the disinfectant. - Good mixing ensures proper dispersal of the disinfectant throughout the water. This promotes the disinfection process.
7. The time of contact. The disinfection will be more effective when the disinfectant remains in contact with the water for a longer time.
Disinfection can be done effectively using chemical agents such as aqueous solution of chlorine, chlorine dioxide, ozone or by a combination of these agents.
There are also other means of disinfection which are rarely used with varying degrees of success. For example, ultraviolet radiation, gamma radiation, sonics, heat and silver ions.
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