Since most water sources and water supply have contaminants present in them a simple water purification system is necessary in your home. Purification of water is the process of taking out or removing chemicals, biological contaminants and other materials that are undesirable from water. The aim of most water purifiers is to produce water that is fit for specific purposes – be it domestic or medical, chemical or industrial use. Drinking water is mostly purified by using different methods and techniques.
The methods used generally include chemical processes like flocculation or chlorination; physical processes like sedimentation and filtration; biological processes like activated sludge and slow sand filters and also the use of ultraviolet light (electromagnetic radiation) etc.
The simple purification process reduces the concentration of suspended particulate matter (SPM), parasites, algae, fungi, bacteria and viruses etc. Governments and other agencies set standards for drinking water and water used for other purposes. Simple water purification systems include various stages of purification. Some of them are:
1. Storage and pumping of water: As the water needs to be pumped from the source through pipes to the storage tank, a physical infrastructure should be constructed with the right materials so as to avoid extra contaminants being added to the water causing accidental and additional contamination.
2. Screening: This is one of the first steps taken to take out large pieces of debris like leaves, sticks and other particles from the water. Usually groundwater from deep sources does not generally need this screening process.
3. Other storage: River water is stored in reservoirs on banks for a period of time so as to facilitate biological/natural purification. Here slow sand filters are used to treat the water.
4. Pre-chlorination and pre-conditioning: Chlorination is the process to reduce the growth of micro-organisms in the tanks and pipes. Due to the adverse effects of chlorine this has been discontinued to a great extent. Hard water is treated with sodium carbonate/soda ash to remove calcium carbonate via common-ion effect.
These techniques are used to remove the micro-organisms, dissolved organic and inorganic materials and also fine solids in the water. The quality standards, cost of a particular treatment and the type of water that is being treated will determine the method or technique of purifying the water.
A simple water purification system also involves the processes of flocculation which removes the color or turbidity in the water making it colorless and clear. A precipitate is formed in the water that can be taken out easily. The particles form big particles when the water is stirred and can be removed. This way suspended particulate matter also gets stuck to the coagulated precipitate and is removed. The next process is sedimentation which allows any matter that is still left in the water to slowly settle down at the bottom of the tank. Larger particles settle faster than the smaller particles and they help to clean them out as they settle forming “sludge” at the bottom of the tank. This sludge is removed and treated. Mechanical devices to clean the tank floor are used when necessary.