* Water treatment - describes those industrial-scale processes used to make water more acceptable for a desired end-use. These can include use for drinking water, industry, medical and many other uses. Such processes may be contrasted with small-scale water sterilization practiced by campers and other people in wilderness areas. The goal of all water treatment process is to remove existing contaminants in the water, or reduce the concentration of such contaminants so the water becomes fit for its desired end-use. One such use is returning water that has been used back into the natural environment without adverse ecological impact.
The processes involved in treating water for drinking purpose may be solids separation using physical processes such as settling and filtration, and chemical processes such as disinfection and coagulation.
* Physical Processes:
* Settling is the process by which particulates settle to the bottom of a liquid and form a sediment. Particles that experience a force, either due to gravity or due to centrifugal motion will tend to move in a uniform manner in the direction exerted by that force. For gravity settling, this means that the particles will tend to fall to the bottom of the vessel, forming a slurry at the vessel base. * Filtration is commonly the mechanical or physical operation which is used for the separation of solids from fluids (liquids or gases) by interposing a medium through which only the fluid can pass. Oversize solids in the fluid are retained, but the separation is not complete; solids will be contaminated with some fluid and filtrate will contain fine particles (depending on the pore size and filter thickness).
* Chemical Processes
* Disinfectants are substances that are applied to non-living objects to destroy microorganisms that are living on the objects. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than sterilisation, which is an extreme physical and/or chemical process that kills all types of life.
* Flocculation, is a process wherein colloids come out of suspension in the form of floc or flakes by the addition of a clarifying agent. The action differs from precipitation in that, prior to flocculation, colloids are merely suspended in a liquid and not actually dissolved in a solution. In the flocculated system, there is no formation of a cake, since all the flocs are in the suspension.
Potable water purification
* Water purification is the removal of contaminants from untreated water to produce drinking water that is pure enough for the most critical of its intended uses, usually for human consumption. Substances that are removed during the process of drinking water treatment include suspended solids, bacteria, algae, viruses, fungi, minerals such as iron, manganese and sulphur, and other chemical pollutants such as fertilisers. * Measures taken to ensure water quality not only relate to the treatment of the water, but to its conveyance and distribution after treatment as well. It is therefore common practice to have residual disinfectants in the treated water in order to kill any bacteriological contamination during distribution.
Processes for drinking water treatment
* A combination selected from the following processes is used for municipal drinking water treatment worldwide: * Pre-chlorination - for algae control and arresting any biological growth * Aeration - along with pre-chlorination for removal of dissolved iron and manganese * Coagulation - for flocculation
* Coagulant aids, also known as polyelectrolytes - to improve coagulation and for thicker floc formation * Sedimentation - for solids separation, that is, removal of suspended solids trapped in the floc. * Filtration - removing particles from water
* Desalination - Process of removing salt from the water * Disinfection - for killing...