Water Purification and Sewage (Wastewater) Management

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Turbidity of water means the reduction in cleanliness, clarity, and transparency of water because it contains suspended soil and other soluble substances. Turbid water looks less clear and less pure.

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Turbid rainwater is not waste. If it is kept still for some time, its turbidity decreases. Adding the right amount of alum also reduces turbidity, so the water can be purified instead of discarded.

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The Secchi's disc experiment is used to measure the turbidity of water. A circular disc painted white and black is lowered into water until the colours are no longer visible.

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Average length = (A + B)/2. Here, A is the point where the white and black parts of the disc disappear, and B is the point where the white part reappears while pulling the rope up.

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A Nephelometer measures turbidity of water. The unit is NTU, which means Nephelometric Turbidity Units.

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The main stages are pumping, air mixing, coagulation, flocculation, sedimentation, sand filtration, and disinfection. Each stage removes a different kind of impurity or germ from water.

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Water is pumped from the source through pipelines to the purification plant. Wire mesh is used to prevent fishes and small plants from coming out of the tap while pumping.

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Air mixing helps remove unwanted gases and substances that cause bad smell. The principle of gravity is used, and water is allowed to fall from a height so that air and oxygen mix with it.