Water Treatment is a process to improve water quality to make it appropriate for a specific purpose or end use. Specific end use may be for drinking, water supply to the local area, supply to the industrial and commercial use, irrigation, safe discharge to the environment, recreation purpose and so on. Water treatment removes contaminants or undesirable substance or reduce their concentration from water to make them to use for a specific purpose. Water treatment is very essential for human health and to safe environment.
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| A Drinking Water Treatment Plant. |
DRINKING WATER TREATMENT:
Drinking water treatment is to remove contamination/impurities from raw water to make it pure enough for safe human consumption. The treatment process involves reduces the concentration of contaminants such as suspended particles, parasites, Bacteria, algae, virous and fungi etc. It involves reduction of suspended solids including Iron and manganese. These metals are great harm for public health of several developing countries.
PROCESS:
Several steps are to be flowed for water treatment to get it desired qualities. The process are as below;
- Lifting of Raw Water,
- Aeration,
- Pre-Chlorination,
- Coagulation and flocculation,
- Sedimentation,
- Filtration,
- Disinfection and,
- Storage.
Lifting of Raw Water:
This stage of water treatment process involves "lifting of raw water". It includes sources (May be Ponds, Lakes, Dams, River and so on) Raw Water Lifting Pump ( may be different capacity and power to meet treatment quantity) and Over Head Storage Tank from where designed quantity of water to be release for treatment.
Screening is not required, because raw water will be pumped from deep of the resources.
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| Raw Water Lifting. |
In this stapes, raw water is to passes through "Aeration" system to increase DO (Dissolved Oxygen) into the water to expel soluble gasses as CO2, H2S, both of the gasses are acidic in nature and aeration helps the system equipment's less corrosive. Aeration also helps to remove organic gasses which give undesirable taste to the water. Iron and manganese, which give peculiar taste and stain to clothing will be remove by oxidation. Open Air Cascade are generally used to meet the aeration.
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| Over head Tank |
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| Cascade Aerator. |
Pre-Chlorination:
Algae in the raw water can block filters by it colonial growth. To over come this situation, chlorination is done to kill algae after aeration and the system called "Pre-Chlorination".
Coagulation and Flocculation:
To remove fine particle less than 1µm size, suspended in the raw water will be removed by "Coagulation" and a chemical (positive charges) is used called Coagulant neutralise negative charges of fine particles. This process performs in a rapid mixing tank called "Flush Mixture". The quantity of coagulant will be decide by pH of the raw water and suspended solids which will be decide by JAR test. Flocculant are dosed in the last step of flush mixture to help colloid and any other suspended solids bind together to form them heavier called "flocks".
The next step is "Flocculation" where water are stirred gently.
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| Coagulation and Flocculation. |
Sedimentation:
The flocks are generated in coagulation and flocculation would settled in a tank called "clarifier" or "settled Tank" and the process are called "Sedimentation" Here coagulated and flocculated water kept for predetermined times to settle flocks at the bottom of the tank. Flocks (Sludge) will be wash out from the bottom of the tan several times in the water treatment process.
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| Sedimentation. |
Filtration:
The flocks which are not trapped in the sedimentation process and over flowed will be trapped in the gravels and sand bed called "Rapid Gravity Filter" and the process are called "Filtration". The RGF will be back wash by air and freshwater passing through lower portion of the bed several times in a day, otherwise it will chocked.
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| Rapid Gravity Sand Filter. |
"Disinfection" done after Filtration to get final treated water. The wager is disinfected to kill pathogenic micro organism and for this, most commonly used material is liquid Sodium Hypo Chloride (NaOCl) or Chlorine Gas. Chlorine is added over a period of time refer as "Contact Time". The amount of chlorine left after this is called "Residual Chlorine". This residual chlorine stay in the water through the distribution system to protect growth of micro organisms. Now a days other UV ray , Ozonation are used for disinfection.
Finally treated water stores in a storage tank from where it will be distributed through the locality. In broad term referring there will be two type of storage tank, one for treated water for consumption and another for non treated water for agriculture.
Supplementary Treatment:
Supplementary Treatment may be needed for benefits of the population. For this, fluoride are added to the water to prevent dental decay. As per WHO guideline, optimum level of fluoride will be around 1mg/l.
Conclusions:
On the end of this discussion, it is said to be flow specific standard to produce safe drinking water for the safety of public health. Many developed countries specify their standard for safe drinking of water for safety of their public health. Those country not achieve their standard should follow WHO published standard.
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