Water Filters

A water filter removes impurities from water by means of a fine physical barrier, a chemical process or a biological process. Filters cleanse water to various extents for irrigation, drinking water, aquariums, and swimming pools.

Water treatment plant filters

Types of water filters include media filters, screen filters, disk filters, slow sand filter beds, rapid sand filters and cloth filters.

Point-of-use filters

Filters for home use include granular activated carbon filters (GAC) used for carbon filtering, metallic alloy filters, microporous ceramic filters, carbon block resin (CBR) and ultrafiltration membranes. Some filters use more than one filtration method. Jug filters can be used for small quantities of drinking water. Some kettles have built-in filters, primarily to reduce limescale buildup.

Portable water filters

Water filters are used by hikers, by aid organizations during humanitarian emergencies, and by the military. These filters are usually small, portable and light (1-2 pounds/0.5-1.0 kg or less), and usually filter water by working a mechanical hand pump, although some use a siphon drip system to force water through while others are built into water bottles. Dirty water is pumped via a screen-filtered flexible silicon tube through a specialized filter, ending up in a container. These filters work to remove bacteria, protozoa and microbial cysts that can cause disease. Filters may have fine meshes that must be replaced or cleaned, and ceramic water filters must have their outside abraded when they have become clogged with impurities.

These water filters should not be confused with devices or tablets that are water purifiers, some of which remove or kill viruses such as hepatitis A and rotavirus.

Homemade water filters
A homemade waterfilter for making drinking water

Water filters can be made on-site using local materials such as grass, charcoal (e.g. from burned firewood), and sand. These filters have been used by soldiers and outdoor enthusiasts. Due to their low cost they can be made and used by anyone, including the poor, who often do not have access to safe drinking water. Regrettably such filters do little if anything to mitigate against pathogens and other harmful constituents and can give a false sense of security that the water so produced is potable.

Water Cooler

A water cooler (commonly spelled “watercooler” as a compound word) is a device that cools and dispenses water. They are generally broken up in two categories: bottle-less and bottled water coolers. Bottle-less water coolers are hooked up to a water supply, while bottled water coolers require delivery (or self pick up) of water in large bottles from vendors. The most common form of the watercooler is wall mounted and connected to the building’s water supply for a continuous supply of water and electricity to run a refrigeration unit to cool the incoming water, and to the building’s waste disposal system to dispose of unused water. Some versions are freestanding floor models, which are becoming more popular in countries where it is not common to drink water straight from the tap. Traditional water fountains In the standard wall-mounted cooler, also commonly referred to as a water fountain or drinking fountain, a small tank in the machine holds chilled water so the user does not have to wait for chilled water. Water is delivered by turning or pressing a button on a spring-loaded valve located on the top of the unit, that turns off the water when released. Some devices also offer a large button on the front or side. Water is delivered in a stream that arches up allowing the user to drink directly from the top of the stream of water. These devices usually dispense water directly from the municipal water supply, without treatment or filtering. A newer, free-standing design involves bottles of water, usually treated in some way, placed spout-down into the dispensing machine. To install the bottle, the bottle is tipped upside down and set onto the dispenser, a probe punctures the cap of the bottle and allows the water to flow into the machine’s internal reservoir. These machines come in different sizes and vary from table units, intended for occasional use to floor-mounted units intended for heavier use. Bottled Water normally is delivered to the household or business on a regularly basis, where empty bottles are exchanged for full ones. Commonly a cup dispenser can be mounted to the side of the unit to keep disposable paper or plastic cups handy for use. The bottle size varies with the size of the unit with the larger versions in the US using 5 gallon bottles. The standard size elsewhere is 18.9 litres. Some units offer a refrigeration function to chill the water. These units do not have a place to dump excess water, only offering a small basin to catch minor spills. On the front, a lever or push button dispenses the water into a cup held beneath the spigot. When the water container is empty, it is lifted off the top of the dispenser, and automatically seals to prevent any excess water still in the bottle from leaking. These gravity-powered systems have a device to dispense water in a controlled manner. Some versions also have a second dispenser that delivers room temperature water or even heated water that can be used for tea, hot chocolate, or instant coffee. The water in the alternate hot tap is generally heated with a heating element and a hot tank (much like the traditional hot water heaters used in residential homes). Additionally, the hot tap is equipped with a push-in safety valve to prevent burns from an accidental or inadvertent pressing of the lever. Table top or kitchen worktop versions are available which utilise readily available five liter water bottles from supermarkets. For example the one by design house Warwick Design shown. These coollers use air pumps to push the water into the cooling chamber and peatier devices to chill the water.

Water Treatment

Water treatment describes those processes used to make water more acceptable for a desired end-use. These can include use as drinking water, industrial processes, medical and many other uses. 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 such as settling and filtration, chemical such as disinfection and coagulation.

Biological processes are also employed in the treatment of wastewater and these processes may include, for example, aerated lagoons, activated sludge or slow sand filters.