Permanent water chlorination began in 1905, when a faulty slow sand filter and a contaminated water supply led to a serious typhoid fever epidemic in Lincoln, England.[44] Dr. Alexander Cruickshank Houston used chlorination of the water to stem the epidemic. His installation fed a concentrated solution of chloride of lime to the water being treated. The chlorination of the water supply helped stop the epidemic and as a precaution, the chlorination was continued until 1911 when a new water supply was instituted.[45]

In 1946, some maple syrup producers started using reverse osmosis to remove water from sap before the sap is boiled down to syrup. The use of reverse osmosis allows about 75–90% of the water to be removed from the sap, reducing energy consumption and exposure of the syrup to high temperatures. Microbial contamination and degradation of the membranes must be monitored.
Despite its efficiency in killing microorganisms, UV radiation will not remove heavy metals and particles. Something else to consider is the high maintenance requirement for a UV purification system. Frequent cleaning and proper part replacement are necessary requirements in maintaining a properly functioning system. Read our article on UV water purification systems for home to find out more.
The ultraviolet rays of the sun can be extremely destructive to microorganisms. We as humans avoid it as much as possible as it can cause skin cancer and other diseases. But we have learned to harness its power and use it to our advantage, especially in decontaminating our water from harmful bacteria and pathogens. UV light has been a standard in the disinfection of water supplies at the municipal level for decades but has recently become available for home use.
DO: Avoid shark-infested waters, unless you are Andy Casagrande. As for bears, always carry repellent pepper spray when hiking; it can stop a charging bear from as much as 30 feet away. To reduce the risk of an attack, give bears a chance to get out of your way. "Try to stay in the open," says Larry Aumiller, manager of Alaska's McNeil River State Game Sanctuary. "If you have to move through thick brush, make noise by clapping and shouting."

Boiling: Bringing water to its boiling point (about 100 °C or 212 F at sea level), is the oldest and most effective way since it eliminates most microbes causing intestine related diseases,[21] but it cannot remove chemical toxins or impurities.[22] For human health, complete sterilization of water is not required, since the heat resistant microbes are not intestine affecting.[21] The traditional advice of boiling water for ten minutes is mainly for additional safety, since microbes start getting eliminated at temperatures greater than 60 °C (140 °F). Though the boiling point decreases with increasing altitude, it is not enough to affect the disinfecting process.[21][23] In areas where the water is "hard" (that is, containing significant dissolved calcium salts), boiling decomposes the bicarbonate ions, resulting in partial precipitation as calcium carbonate. This is the "fur" that builds up on kettle elements, etc., in hard water areas. With the exception of calcium, boiling does not remove solutes of higher boiling point than water and in fact increases their concentration (due to some water being lost as vapour). Boiling does not leave a residual disinfectant in the water. Therefore, water that is boiled and then stored for any length of time may acquire new pathogens.

The high pressure pump supplies the pressure needed to push water through the membrane, even as the membrane rejects the passage of salt through it. Typical pressures for brackish water range from 1.6 to 2.6 MPa (225 to 376 psi). In the case of seawater, they range from 5.5 to 8 MPa (800 to 1,180 psi). This requires a large amount of energy. Where energy recovery is used, part of the high pressure pump's work is done by the energy recovery device, reducing the system energy inputs.
My first path was to go with a Pelican combination whole house filter and salt free water softener. My plumber and others said whole house filter was the way to go for pure water and clear ice, not so much. Even Pelican suggested RO was not needed with the whole house filter. While I’m pleased with the Pelican system, the water is indeed soft and clean throughout my home, my faucets don’t ... full review

Drinking water sources are subject to contamination and require appropriate treatment to remove disease-causing agents. Public drinking water systems use various methods of water treatment to provide safe drinking water for their communities. Today, the most common steps in water treatment used by community water systems (mainly surface water treatment) include:
In the normal osmosis process, the solvent naturally moves from an area of low solute concentration (high water potential), through a membrane, to an area of high solute concentration (low water potential). The driving force for the movement of the solvent is the reduction in the free energy of the system when the difference in solvent concentration on either side of a membrane is reduced, generating osmotic pressure due to the solvent moving into the more concentrated solution. Applying an external pressure to reverse the natural flow of pure solvent, thus, is reverse osmosis. The process is similar to other membrane technology applications.
Water Waste Unlike traditional water filters, not all of the water that is pumped through a reverse osmosis filter comes out the other side as drinkable water. Only a relatively small percentage—50 percent or less—is filtered, and the rest is considered waste. When possible, avoid units with 75 percent or more waste, especially if you are treating a high volume of water per day.
The pore size of the filter, usually measured in microns, will determine what will be filtered through. While a standard micron size of 0.2 is small enough to block heavy metals such as lead and copper and large parasites such as Cryptosporidium, it will not block viruses. The National Sanitation Foundation sets a standard for effective water filtration products so look for an NSF stamp when selecting a filter to purchase.