Purification systems to clean water

There are plenty of purification systems to clean water today. The most common methods and techniques are mentioned below. Methods are chosen as per the type of water and the cost of purification. Pre-treatment processes involve containment and storage of water as well as pumping the water from the source into the storage/holding tanks. All physical infrastructures should be made or constructed with the appropriate materials so as to eliminate accidental contamination.

Screening is one of the first steps in purifying water. This is done to remove large debris like leaves, sticks and other trash from the water. Groundwater that is deep does not generally need screening. Water from rivers is also stored in reservoirs on the banks for a particular period so as to allow natural/biological purification. This step is important if the treatment is carried out by the use of slow sand filters. Preconditioning of hard water is done by treating the water with sodium carbonate/soda-ash that precipitates and pushes out the calcium carbonate by using the effect of “common-ion”.
Pre-chlorination is done by using chlorine to destroy the microorganisms in the tanks and pipes, but this type of purification is being discontinued considering the adverse effects of chlorine.

Flocculation clarifies the water and removes all color or turbidity from it making it colorless and clean. This is done by formation of a precipitate in the water that can be removed by using methods that are simple. Particles stick to one another forming larger particles in this process when the water is stirred. Most suspended matter is filtered out with the coagulated precipitate. Flocculating/coagulating agents like Iron III hydroxide, Aluminum hydroxide, Poly-DADMAC etc are used.

Sedimentation is also used in the purifying process. A large tank is used to allow the materials to settle down to the bottom of the tank. This tank should be placed near the flocculation tank so that the purification process is made easier. The particles form sludge on the tank floor that has to be removed and also treated. The use of cleaning devices that are mechanical can be used to clean the tank floor whenever necessary.

Filtration is another purification system which is the final stage for removing the suspended particulate matter in the water. The rapid sand filter is the most common. Water goes through the sand vertically. The sand has anthracite coal or activated carbon above it. This helps to remove organic compounds etc. Most of the particles get trapped in between pores and stick to the sand particles. Back washing and back flushing is used to remove particles that are embedded. Air scouring that involves compressed air being blown through the filter to break up filter media and aid the process of backwashing. Some of the purification systems use pressure filters that work like the gravity filters.

Purification systems to clean water using rapid gravity filtration systems have plenty of advantages:
* Smaller particles than the sand and paper filters are removed
* Liquids flow through them very easily
* They can stand pressure differences and are quite strong
* They can be reused and cleaned

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