Raw water is water found in the environment that has not been treated and does not have any of its minerals, ions, particles, bacteria, or parasites removed. Raw water includes rainwater, ground water, water from infiltration wells, and water from bodies like lakes and rivers.
Raw water is generally unsafe for human consumption due to the presence of contaminants. A major health problem in some developing countries is use of raw water for drinking and cooking.
Without treatment, raw water can be used for irrigation, construction, or cleaning purposes. Farmers use it for watering their crops and give it to livestock to drink, storing it in man-made lakes or reservoirs for long periods of time. Construction industries can use raw water for making cement or for damping down unsealed roads to prevent dust rising. Raw water can also be used for flushing toilets and washing cars, as well as any other purposes that do not require it to be consumed by humans. Water in this form is considered raw, as opposed to water which has been treated before consumption, such as drinking water or water which has been used in an industrial process, such as waste water.
Raw water flushing is a method of water conservation where raw water is used for flush toilets.
Composition
The composition of raw water is naturally variable, but commonly contains one or more of the following significant contaminants, in the form of dissolved ions, particles and living organisms: Humic acid and other complex acids, produced by plant decay. These occur in peat and soil and may cause discoloration and metallic taste of water. Minerals which make water hard. Most common are carbonates of calcium and magnesium. Particles of clay and silt. Pathogenic bacteria, viruses, protozoa and their cysts. (waterborne diseases) Salt, which makes water brackish, having more salinity than fresh water, but not as much as seawater. Other, less common, contaminants of raw water include: Natural radioactive particles. Perfluorinated alkyl acids, such as perfluorooctanoic acid, which are group of pollutants that have been found in wastewater throughout Europe. There are concerns these chemicals could contaminate raw water sources that are commonly used for drinking water. Endocrine disruptor compounds; chemicals that can interfere with the endocrine system causing cancerous tumors, birth defects, and other developmental disorders. These contaminants can be harmful to humans if they drink raw water containing them, or if the water is not treated properly before consumption. The contaminants can also have an effect on the local ecosystem. For example, endocrine disrupting chemicals can have harmful effects on fish populations living in natural lakes and rivers. These growing health concerns have led to the development of guidelines, such HACCP (Hazard Analysis and Critical Control Points), for the production of safe drinking water from wastewater and raw water, and research into sustainable water supply alternatives
Treatment
Raw water can be used for many purposes, such as cooling water, water for rinsing and chemical production, purified water, and drinking water. However, due to the possible contaminants, raw water must be treated before it is allowed for human consumption or industrial use. There are several steps involved in the treatment of raw water, and different methods in which it can take place.
Reverse osmosis
Reverse osmosis has been used for the production of demineralised water for over 30 years. In reverse osmosis, water is transported across a membrane under high pressure, leaving a product that consists mainly of water and a concentrate containing most other components such as minerals and unwanted residues. Many contaminants, including iron, manganese, ammonium, traces of pesticides and medicines, organic micro pollutants, and radioactive particles can be removed with reverse osmosis alone. This efficiency has made reverse osmosis the primary method of water purification, often being used in combination with other methods, as a final treatment. A downside to reverse osmosis is that the removing of most minerals from water can have negative effects on its taste. Minerals are sometimes added to drinking water that was already filtered to improve its taste.