These chemicals are known as coagulants and the process is called sedimentation with coagulation.Įxamples of coagulants are (Al₂SO₄)₃, AlSO₄, odium aluminate, etc. Therefore we need certain chemicals to add in the water to remove such impurities which are not removed by plain sedimentation. Particles of sizes 0.006 mm required 10 hours to settle in plain sedimentation. When the suspended particles are separated under the action of gravity only, it is called plain sedimentation.įine suspended particles and colloidal impurities are not removed by plain sedimentation. Sedimentation can be achieved in two ways. Sedimentation tanks are designed to reduce the velocity of the flow of water so that the suspended particles get settled under the action of gravity. The particles whose specific gravity is greater than that of water gets settles down under the action of gravity. So to remove such particles sedimentation is done. The water after screening may contain various suspended impurities like silt and clay particles. The process of the removal of suspended particles by gravitational settling is called sedimentation. The fine screen is used to remove smaller, floating, and suspending matter of size smaller than removed by the coarse screen. They have a wider opening and are placed in front of the fine screen to remove large, floating, and suspended materials. The bar screen is also called the coarse screen. To increase the efficiency of the successive. To work as a protective device for successive treatment.ģ. To remove large suspended as well as floating matter such as leaves, branches, dead animals, etc.Ģ. When water derived from the surface contain large suspended as well as floating matters which may be sticks, branches, leaves, etc the screens are fixed in the intake works or at the entrance of the treatment plant to remove the suspended as well as floating matters like branches, leaves and sticks.ġ. Methods of the water treatment process are explained below. The water treatment process generally adopted depends upon the quality of raw water and the quality of water derived. The water treatment process includes many operations like screening, aeration and sedimentation, sedimentation with coagulation, softening, filtration, disinfection, etc. To make it suitable for a wide variety of industrial purposes such as steam generation, drying, etc.Ģ. To eliminate the corrosive nature of water affecting the pipe.ĥ. To reduce the objectionable color, odor, turbidity, and hardness.Ĥ. To reduce the impurities to a certain level that does not cause harm to human health.Ģ. Some of the main objectives of the water treatment process are:ġ. Objectives of the Water Treatment Process Dissolved Impurities – a size smaller than 10⁻⁶ mmġ. Colloidal Impurities – a size between 10⁻³ mm to 10⁻⁶ mmģ. Suspended Impurities – a size larger than 10⁻³ mmĢ. There are various impurities having sizes as :ġ. The degree of treatment depends upon the quality of water desired or required. The process of removal of undesirable matters and pathogens from water is called the water treatment process. Water from any source may contain various suspended, colloidal and dissolved impurities which may be harmful or useful for drinking purposes.
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