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             What is the Water treatment process and its steps?

                   In this article, I will illustrate and review the water treatment process and how steps are used in the treatment of water. After reading this article you will be able to treat the polluted water and used it for the drinking process.

1. What is the water treatment process?

        The Water Treatment process is that the process that used for the removal of drugs (physically, chemically) that are harmful to the availability of water for human and domestic purposes. A water treatment process that is used for the removal of all contaminants, undesirable substances creates health effects from the water that is used for consumption. This process converts the polluted water to pure water after the removal of contaminants from the water and becomes odorless, colorless, etc. The water treatment process is used to remove the disease-causing agents from the water that is used for drinking and other use. A water treatment process that is used to purify water after removal of contaminants from the water to make it capable of drinking because impure water has adverse effects on the health of humans.

STEPS THAT INCLUDE IN THE WATER TREATMENT PROCESS:

1. Screening.

2. Aeration.

3. Coagulation and Flocculation.

4. Sedimentation.

5. Filtration.

6. Chlorination.

7. Supplementary Treatment.

1. Screening:

                 First of all, it is necessary to use screens to remove floating and large solid particles from the water. To protect the water treatment plant for efficient working and operation we use screening because these particles obstruct the flowing of water. Material likes leaves, papers, pulps, and debris could obstruct the flow of water and damage the equipment of the plant. There are two types of screens like coarse and fine screens.

Coarse Screen:

       Coarse screens are made of erosion-safe steel bars divided 5–15 cm separated, which are utilized to prohibit coarse materials (like logs and fish) from entering the treatment plant. The screens are situated at a point of 60º to work with eliminating the gathered material by mechanical raking.

Fine Screen:

       Fine screens, which come after the coarse screens, keep out material that can obstruct pipework at the plant. They comprise steel bars that are divided 5–20 mm separated. A variety of the fine screen is the miniature sifter, comprising of a pivoting drum of treated steel network with a tiny lattice size (going from 15 µm to 64 µm, i.e., 15–64 millionths of a meter). Suspended matter as little as green growth and tiny fish (infinitesimal creatures that buoy with the ebb and flow in water) can be caught. The caught solids are unstuck from the texture by high-pressure water jets utilizing clean water and diverted for removal.

2. Aeration:

         Aeration is the second step after screening and removal of large suspended particles from the water. Water is aerated in the open air the remove carbon dioxide and hydrogen from the water by the supply of oxygen from the air. This process expels out all the acidic gases and removal of corrosive material from the water. By the process of Aeration iron and manganese remove from the water. Iron and manganese convert into their insoluble solution by the process of oxidation due to aeration and the solution of insoluble iron and manganese remove by filtration from the water.

   If algae are in an excess condition in raw water, the growth of algae blocking the sand filter that down the water treatment process so we use chlorination process in addition to aeration for the removal of algae and kill the algae this process is also known as pre-chlorination process.

3. Coagulation and Flocculation:

        Coagulation is the process in which we remove fine particles of size less than 1µm. In this process, we used chemicals that known as coagulants that have a positive change that neutralize the fine particles that have negative charges and due to these coagulants fine particles collect together and forming soft particles called flocs. In this process, coagulants mix in the tank and a high-speed impeller rapidly disperse the coagulants in the water. The most common use chemicals for coagulation are ferric chloride and aluminum sulfate.

     The subsequent stage is flocculation. Here the water is delicately blended by paddles during a flocculation bowl, and therefore the flocs inherit contact with each other to shape bigger flocs. The flocculation bowl regularly has various compartments with diminishing blending speeds as the water propels through the bowl. This compartmentalized chamber permits progressively enormous flocs to shape without being fallen to pieces by the blending cutting edges.

4. Sedimentation:

          When huge flocs are formed, they should be settled out, and this happens in an interaction called sedimentation (when the particles tumble to the floor of a settling tank). The water (after coagulation and flocculation) is kept in the tank for a few hours for sedimentation to occur. The material gathered at the lower part of the tank is known as sludge; this is eliminated for removal. Flocs due to their large weight lie down to water supply is called sedimentation.

5. Filtration:

         Filtration is the process where solids are isolated from a fluid. In water treatment, the solids that are not isolated in the sedimentation tank are taken out by going the water through sand and rock beds. With a stream pace of 4–8 cubic meters for every square meter of channel surface each hour, fast gravity channels are frequently utilized. At the point when the channels are brimming with caught solids, they are discharged. In this interaction, clean water and air are siphoned back up the channel to unstick the caught pollutants, and the water conveying the soil (alluded to as discharge) is siphoned into the sewerage framework in case there is one. On the other hand, it very well might be released once more into the source stream after a settlement stage in a sedimentation tank to eliminate solids.

6. Chlorination:

       Chlorination is the process that is used to purify water through the removal of contaminants by using chemicals. In this process, the water is sanitized to dispense remaining pathogenic organisms. The most regularly utilized sanitizer (the synthetic utilized for sterilization) is chlorine, a fluid (like sodium hypochlorite, NaOCl), or a gas. It is generally modest and easy to utilize. At the point when chlorine is added to water, it responds with any poisons present, including miniature organic entities, throughout a given timeframe, alluded to as the contact time. The measure of chlorine left after this is called remaining chlorine. This stays in the water through the circulation framework, shielding it from any miniature creatures that may enter it until the water arrives at the purchasers. World Health Organization (WHO, 2003) proposes the greatest remaining chlorine of 5 mg l–1 of water. The base lingering chlorine level ought to be 0.5 mg l–1 of water following 30 minutes of contact time (WHO, n.d.). There are alternate methods of cleaning water (e.g., utilizing the gas ozone, or bright radiation). In any case, these don't shield it from microbial defilement after it has left the water treatment plant. Following sterilization, the treated water is a siphon.

7. Supplementary Treatment:

    Supplementary treatment of water is essential for the benefit of the population. In this process, fluorine is added in the treatment of water because according to point of view of WHO fluorine is a very effective measure for the health of the public due to this fluoridation is very significant and use where it is possible. If we converse about the optimum level of fluoride this is 1mg per liter of water. Water fluoridation is the process of removal of contaminants from the water and prevents tooth and dental decay.