Water

A globule of liquid water, and the concave depression and rebound in water caused by something dropping through the water surface.

Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a solvent). It is vital for all known forms of life, despite providing neither food, energy, nor organic micronutrients.

A number of natural states of water exist. It forms precipitation in the form of rain and aerosols in the form of fog. Clouds consist of suspended droplets of water and ice, its solid state. When finely divided, crystalline ice may precipitate in the form of snow. The gaseous state of water is steam or water vapor. Water covers about 71% of the Earth's surface, mostly in seas and oceans, about 96.5%.

Fishing in salt and fresh water bodies is a major source of food for many parts of the world, providing 6.5% of global protein. Large quantities of water, ice, and steam are used for cooling and heating, in industry and homes. Water is an excellent solvent for a wide variety of substances both mineral and organic; as such it is widely used in industrial processes, and in cooking and washing.

Collection

Wells

Dams

Snowmelt

Rain Basin

Evapotranspiration

Treatment

Three wastewater clarifiers from above, with skimmers shown

Water treatment is extremely important to human health, especially in high density environments, and is responsible for one of the largest gains in human life expectancy, on par with antibiotics and germ theory.

At its core, water treatment consists of 3 component processes. These are: settlement, filtration, and disinfection.

Settlement

Settlement operates mainly on the principle of gravity, and focuses on channeling water into large containers called clarifiers with high volume and surface area. Water spends a long time in the clarifier, where solid particles suspended in the water are allowed to settle to the bottom and accumulate, forming a sludge layer that can be removed at a later time. A preparatory step to this process called flocculation is key to settlement, because it is during this step that coagulants are added to the water, allowing small particles to bind together and form larger, heavier particles that will settle to the bottom of the clarifier more quickly. The water in a clarifier is cleanest near the top, where the surface can be skimmed of any floating particles and where the water can be allowed to flow over a weir an into the next process station.

During filtration, water passes through filters, some made of layers of sand, gravel, and charcoal that help remove even smaller particles.

Filtration

The next step is filtration. Filtration has two components, biological and physical. Physical filtration is relatively straightforward. Water is flown over a semi-permeable surface, such as cloth or a bed of sand and crushed charcoal. Particles that remain in the water after clarification are then caught either because they are too large to fit through the holes in the surface or because they bind to the surface of the sand/charcoal. The sand/charcoal bed also provides a medium for friendly bacteria to form colonies and make biofilms, so that they can process any dissolved nutrients such as nitrogen or phosphorus out of the water and release it as carbon dioxide. In order to treat waters that contain dissolved metals, a bed of ionic sand can be used, which form bonds with the dissolved metals and capture them in the process. In treatment of extremely nutrient dense waters such as wastewater, aeration may be effective in feeding these bacteria oxygen, accelerating the rate at which they digest these nutrients.

Shown here is a simple distillation apparatus, where the dirty water is heated by the burner, turns to steam, and then condenses in the second bulb, which is kept cool by the water from the tap.

Disinfection

The last component is disinfection. Disinfection generally is done one of three ways, either using chlorination, ozone, or ultraviolet light. However, these methods are generally quite complicated to implement in a scenario where a manufacturing base is not readily available. Therefore, the simplest way to disinfect water is to boil and capture the resulting steam, thus distilling it. Although it is energy intensive, distillation can kill bacterial pathogens and denature viral threats quite effectively.

See also

• Hydrogen
• Oil
• Oxygen

References

This article uses material from the Wikipedia article Water, which is released under the Creative Commons Attribution-ShareAlike 3.0 Unported License (view authors).