Raw water

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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.

Contents

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. [1]

Without treatment, raw water can be used for irrigation, construction, or cleaning purposes. [2] 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: [3]

Other, less common, contaminants of raw water include:

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. [7] 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. [8] [9]

Treatment

Water treatment plant of Braganca, Portugal Braganca43.jpg
Water treatment plant of Bragança, Portugal

Raw water can be used for many purposes, such as cooling water, water for rinsing and chemical production, purified water, and drinking water. [10] However, due to the possible contaminants, raw water must be treated before it is allowed for human consumption or industrial use. [11] 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. [10] 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. [12] Many contaminants, including iron, manganese, ammonium, traces of pesticides and medicines, organic micro pollutants, and radioactive particles can be removed with reverse osmosis alone. [4] [12] 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. [12] Minerals are sometimes added to drinking water that was already filtered to improve its taste.

Conventional pre-treatment

The conventional treatment method for water purification is a complex, multistage process that was used for many years. [10] It generally consists of five primary steps. [11] First, raw water is adjusted for alkalinity and pH with the addition of hydrated lime and carbon dioxide. Second, particulate matter is congregated with aluminum sulphate and other coagulants, such as polymers, which the water flows in a cascade that mixes the chemicals and raw water with the coagulants. Third, the water is slowly mixed in clarifiers where larger particles settle down to the bottom and are periodically removed (sedimentation). Fourth, water is directed from the clarifiers to the filters (e.g. anthracite and sand filter) to entrap any smaller particles that survived the clarification process. Finally, sodium hydroxide is added to adjust the final pH/alkalinity, sodium hypochlorite for disinfection and fluoride for fluoridation. This process is often used as a pre-treatment method while another processes, such as reverse osmosis, is used for the final treatment. [10] A disadvantage of this method is its use of chemicals, such as ozone, flocculents, hydrogen peroxide, lime, and chlorine for the filtration process. [10] These chemicals could be dangerous if used incorrectly or if they remained in the water after complete treatment. This requires special precautions, and each step of the process has to be controlled to achieve an overall optimal performance. [10] The need for a complex control system for conventional treatment can result in it being financially costly. [10] This has led to the development of alternative pre-treatment and treatment methods for raw water.

Ultrafiltration

Drinking water treatment of 300 m /h using ultrafiltration in Grundmuhle waterworks (Germany) Ultrafiltration Grundmuhle.jpg
Drinking water treatment of 300 m /h using ultrafiltration in Grundmühle waterworks (Germany)

Ultrafiltration is a membrane filtration process and provides an alternative to conventional pre-treatment. [10] In this method water is only pre-filtered with a common screen filter before being filtered at high pressure through a membrane, separating the water from contaminants within it. Ultrafiltration can be used on its own for water purification or as a pre-treatment for reverse osmosis. Its advantages over conventional pre-treatment include: very high water quality independent of the contaminants in the initial raw water, a plant that is simpler in design and more flexible, which makes it easier to automate, lower use of chemicals, and final product free of viruses and microorganisms.

Biofilm pre-treatment and Bio-diatomite Dynamic Membrane Reactor

The biofilm membrane filtration method is used to remove harmful chemical by-products, such as NH4+-N, total nitrogen, and dissolved organic matter, that could form from disinfection processes. [13] Biofilm Pre-treatment is a necessary step for water treatment in many parts of world due to its low operation cost and effectiveness at pollutant removal. In this process microorganisms remove contaminants in raw and wastewater that are harmful to humans, but nutrients to them. [13] Bio-diatomite dynamic membrane reactor filtration combines dynamic membrane technology for wastewater treatment, and microbial colonies that form diatomite particles to purify water. [14] These methods are under development in China as part of addressing the country's pollution problems.

Turbidity

Turbid water Turbid.jpg
Turbid water

Turbidity is how murky or hazy water seems due to suspended particles. The more suspended particles, the higher the turbidity. Turbidity is used to visually measure water quality, being most common in unfiltered raw water. [15] High amounts of turbidity in raw water can occur due to: [15]

Turbidity and health concerns

During high turbidity peaks, pathogens are more commonly found in raw water. This can contribute to the spread of illnesses. [16] When turbidity increases, reported hospital visits for the elderly (65+) with gastrointestinal illnesses also increase. Even places with water filtration systems that meet standards can have an endemic of gastrointestinal illness, or waterborne infectious diseases. Those hospitalized represent a small percentage of total morbidity caused by these illnesses. [9]

Controlling turbidity

Controlling the land surrounding raw water reservoirs and other sources is key to reducing turbidity. Areas of high sediment resuspension and erosion need attending regularly, and screens and other devices are needed to catch suspended particles. Screens that trap particles and debris must be cleaned consistently. Flushing out water pumps should be done when demand is lowest. This gives time for the water to settle, and decrease turbidity before is it needed in high amounts. "Turbidity reduction is best achieved when the water is run through a series of chemical and physical treatment methods before reaching the filter". [17]

Waterside of Saint Lawrence River near Kamouraska QC - Ufer Sankt Lorenzstrom bei Kamouraska.jpg
Waterside of Saint Lawrence River near Kamouraska

Raw water dieting

Around 2017, untreated spring water, described as "naturally probiotic" raw water, became a commercial product distributed through health food shops, but experts have raised public health concerns about the possible occurrence of harmful bacteria, viruses, and parasites such as Giardia . The products are associated with a fad diet of "raw water fasting", [18] [19] reportedly finding purchase among the "health-conscious elite" of Silicon Valley, including figures such as the raw vegan founder of Juicero Doug Evens. [20] [21] One doctor compared the movement's rejection of established science to the anti-vaccination movement. [22] One raw water business in the United States has even claimed that methods used by bottled and spring water producers could change the molecular structure of water. [23] [24]

The fad was mocked on The Daily Show in April 2018 in a segment that included an interview with Marion Nestle. [25] [26]

See also

Related Research Articles

<span class="mw-page-title-main">Filtration</span> Process that separates solids from fluids

Filtration is a physical separation process that separates solid matter and fluid from a mixture using a filter medium that has a complex structure through which only the fluid can pass. Solid particles that cannot pass through the filter medium are described as oversize and the fluid that passes through is called the filtrate. Oversize particles may form a filter cake on top of the filter and may also block the filter lattice, preventing the fluid phase from crossing the filter, known as blinding. The size of the largest particles that can successfully pass through a filter is called the effective pore size of that filter. The separation of solid and fluid is imperfect; solids will be contaminated with some fluid and filtrate will contain fine particles. Filtration occurs both in nature and in engineered systems; there are biological, geological, and industrial forms. In everyday usage the verb "strain" is more often used; for example, using a colander to drain cooking water from cooked pasta.

Water purification is the process of removing undesirable chemicals, biological contaminants, suspended solids, and gases from water. The goal is to produce water that is fit for specific purposes. Most water is purified and disinfected for human consumption, but water purification may also be carried out for a variety of other purposes, including medical, pharmacological, chemical, and industrial applications. The history of water purification includes a wide variety of methods. The methods used include physical processes such as filtration, sedimentation, and distillation; biological processes such as slow sand filters or biologically active carbon; chemical processes such as flocculation and chlorination; and the use of electromagnetic radiation such as ultraviolet light.

<span class="mw-page-title-main">Water treatment</span> Process that improves the quality of water

Water treatment is any process that improves the quality of water to make it appropriate for a specific end-use. The end use may be drinking, industrial water supply, irrigation, river flow maintenance, water recreation or many other uses, including being safely returned to the environment. Water treatment removes contaminants and undesirable components, or reduces their concentration so that the water becomes fit for its desired end-use. This treatment is crucial to human health and allows humans to benefit from both drinking and irrigation use.

Ultrafiltration (UF) is a variety of membrane filtration in which forces such as pressure or concentration gradients lead to a separation through a semipermeable membrane. Suspended solids and solutes of high molecular weight are retained in the so-called retentate, while water and low molecular weight solutes pass through the membrane in the permeate (filtrate). This separation process is used in industry and research for purifying and concentrating macromolecular (103–106 Da) solutions, especially protein solutions.

Microfiltration is a type of physical filtration process where a contaminated fluid is passed through a special pore-sized membrane filter to separate microorganisms and suspended particles from process liquid. It is commonly used in conjunction with various other separation processes such as ultrafiltration and reverse osmosis to provide a product stream which is free of undesired contaminants.

<span class="mw-page-title-main">Industrial wastewater treatment</span> Processes used for treating wastewater that is produced by industries as an undesirable by-product

Industrial wastewater treatment describes the processes used for treating wastewater that is produced by industries as an undesirable by-product. After treatment, the treated industrial wastewater may be reused or released to a sanitary sewer or to a surface water in the environment. Some industrial facilities generate wastewater that can be treated in sewage treatment plants. Most industrial processes, such as petroleum refineries, chemical and petrochemical plants have their own specialized facilities to treat their wastewaters so that the pollutant concentrations in the treated wastewater comply with the regulations regarding disposal of wastewaters into sewers or into rivers, lakes or oceans. This applies to industries that generate wastewater with high concentrations of organic matter, toxic pollutants or nutrients such as ammonia. Some industries install a pre-treatment system to remove some pollutants, and then discharge the partially treated wastewater to the municipal sewer system.

<span class="mw-page-title-main">Sand filter</span> Water filtration device

Sand filters are used as a step in the water treatment process of water purification.

Electrocoagulation (EC) is a technique used for wastewater treatment, wash water treatment, industrially processed water, and medical treatment. Electrocoagulation has become a rapidly growing area of wastewater treatment due to its ability to remove contaminants that are generally more difficult to remove by filtration or chemical treatment systems, such as emulsified oil, total petroleum hydrocarbons, refractory organics, suspended solids, and heavy metals. There are many brands of electrocoagulation devices available, and they can range in complexity from a simple anode and cathode to much more complex devices with control over electrode potentials, passivation, anode consumption, cell REDOX potentials as well as the introduction of ultrasonic sound, ultraviolet light and a range of gases and reactants to achieve so-called Advanced Oxidation Processes for refractory or recalcitrant organic substances.

There are many uses of water in industry and, in most cases, the used water also needs treatment to render it fit for re-use or disposal. Raw water entering an industrial plant often needs treatment to meet tight quality specifications to be of use in specific industrial processes. Industrial water treatment encompasses all these aspects which include industrial wastewater treatment, boiler water treatment and cooling water treatment.

<span class="mw-page-title-main">Nanofiltration</span> Filtration method that uses nanometer sized pores in biological membranes

Nanofiltration is a membrane filtration process that uses nanometer sized pores through which particles smaller than about 1–10 nanometers pass through the membrane. Nanofiltration membranes have pore sizes of about 1–10 nanometers, smaller than those used in microfiltration and ultrafiltration, but a slightly bigger than those in reverse osmosis. Membranes used are predominantly polymer thin films. It is used to soften, disinfect, and remove impurities from water, and to purify or separate chemicals such as pharmaceuticals.

Depth filters are filters that use a porous filtration medium to retain particles throughout the medium, rather than just on the surface of the medium. Depth filtration, typified by multiple porous layers with depth, is used to capture the solid contaminants from the liquid phase. These filters are commonly used when the fluid to be filtered contains a high load of particles because, relative to other types of filters, they can retain a large mass of particles before becoming clogged.

Reverse osmosis (RO) is a water purification process that uses a semi-permeable membrane to separate water molecules from other substances. RO applies pressure to overcome osmotic pressure that favors even distributions. RO can remove dissolved or suspended chemical species as well as biological substances, and is used in industrial processes and the production of potable water. RO retains the solute on the pressurized side of the membrane and the purified solvent passes to the other side. The relative sizes of the various molecules determines what passes through. "Selective" membranes reject large molecules, while accepting smaller molecules.

<span class="mw-page-title-main">Membrane</span> Thin, film-like structure separating two fluids, acting as a selective barrier

A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. Biological membranes include cell membranes ; nuclear membranes, which cover a cell nucleus; and tissue membranes, such as mucosae and serosae. Synthetic membranes are made by humans for use in laboratories and industry.

Ultrapure water (UPW), high-purity water or highly purified water (HPW) is water that has been purified to uncommonly stringent specifications. Ultrapure water is a term commonly used in manufacturing to emphasize the fact that the water is treated to the highest levels of purity for all contaminant types, including: organic and inorganic compounds; dissolved and particulate matter; volatile and non-volatile; reactive, and inert; hydrophilic and hydrophobic; and dissolved gases.

Membrane technology encompasses the scientific processes used in the construction and application of membranes. Membranes are used to facilitate the transport or rejection of substances between mediums, and the mechanical separation of gas and liquid streams. In the simplest case, filtration is achieved when the pores of the membrane are smaller than the diameter of the undesired substance, such as a harmful microorganism. Membrane technology is commonly used in industries such as water treatment, chemical and metal processing, pharmaceuticals, biotechnology, the food industry, as well as the removal of environmental pollutants.

Sex is influenced by water pollutants that are encountered in everyday life. These sources of water can range from the simplicity of a water fountain to the entirety of the oceans. The pollutants within the water range from endocrine disruptor chemicals (EDCs) in birth control to Bisphenol A (BPA). Foreign substances such as chemical pollutants that cause an alteration of sex have been found in growing prevalence in the circulating waters of the world. These pollutants have affected not only humans, but also animals in contact with the pollutants.

<span class="mw-page-title-main">Water reuse in California</span>

Water reuse in California is the use of reclaimed water for beneficial use. As a heavily populated state in the drought-prone arid west, water reuse is developing as an integral part of water in California enabling both the economy and population to grow.

Contaminants of emerging concern (CECs) is a term used by water quality professionals to describe pollutants that have been detected in environmental monitoring samples, that may cause ecological or human health impacts, and typically are not regulated under current environmental laws. Sources of these pollutants include agriculture, urban runoff and ordinary household products and pharmaceuticals that are disposed to sewage treatment plants and subsequently discharged to surface waters.

There are many water purifiers available in the market which use different techniques like boiling, filtration, distillation, chlorination, sedimentation and oxidation. Currently nanotechnology plays a vital role in water purification techniques. Nanotechnology is the process of manipulating atoms on a nanoscale. In nanotechnology, nanomembranes are used with the purpose of softening the water and removal of contaminants such as physical, biological and chemical contaminants. There are variety of techniques in nanotechnology which uses nanoparticles for providing safe drinking water with a high level of effectiveness. Some techniques have become commercialized.

Diatomaceous earth filtration is a special filtration process that removes particles from liquids as it passes through a layer of fossilized remains of microscopic water organism called diatoms. These diatoms are mined from diatomite deposits which are located along the Earth's surface as they have accumulated in sediment of open and moving bodies of water. Obtained diatomaceous earth is then purified using acid leaching or liquid-liquid extraction in order for it to be used in any form of application. The process of D.E. filtration is composed of three main stages: pre-coating, body feed, and cleaning.

References

  1. ↑ Huq, A; et al. (July 1996). "A simple filtration method to remove plankton-associated Vibrio cholerae in raw water supplies in developing countries". Applied and Environmental Microbiology. 62 (7): 2508–2512. doi:10.1128/AEM.62.7.2508-2512.1996. PMC   168033 . PMID   8779590.
  2. ↑ Perth W.A. (2016) What is Raw Water?. Vintage Road Haulage. http://www.vintageroadhaulage.com.au/faq/what-is-raw-water/
  3. ↑ Safe Drinking Water Committee (1980), "Raw water quality", Drinking Water and Health, vol. 2, National Academies, pp. 7 et seq
  4. 1 2 Manu, A., Santhanakrishnan, V., Rajaram, S., & Ravi, P. M. (2014). Concentration of natural radionuclides in raw water and packaged drinking water and the effect of water treatment. Journal of Environmental Radioactivity, 138, 456-459
  5. ↑ Happonen, M., Koivusalo, H., Malve, O., Perkola, N., Juntunen, J., & Huttula, T. (2016). Contamination risk of raw drinking water caused by PFOA sources along a river reach in south-western finland. Science of the Total Environment, 541, 74-82
  6. ↑ Falconer, I. R. (2006). Are Endocrine Disrupting Compounds a Health Risk in Drinking Water? International Journal of Environmental Research and Public Health, 3(2), 180–184
  7. ↑ Mills, L. J., & Chichester, C. (2005). Review of evidence: Are endocrine-disrupting chemicals in the aquatic environment impacting fish populations? Science of the Total Environment, 343(1–3), 1-34
  8. ↑ Dewettinck T, van Houtte E, Geenens D, van Hege K, Verstraete W. HACCP (Hazard analysis and critical control points) to guarantee safe water reuse and drinking water production. A case study. Water Sci. Technol. 2001; 43: 31–38
  9. 1 2 Rodriguez, C., Van Buynder, P., Lugg, R., Blair, P., Devine, B., Cook, A., & Weinstein, P. (2009). Indirect Potable Reuse: A Sustainable Water Supply Alternative. International Journal of Environmental Research and Public Health, 6(3), 1174–1209
  10. 1 2 3 4 5 6 7 8 Clever, M., Jordt, F., Knauf, R., Räbiger, N., Rüdebusch, M., & Hilker-Scheibel, R. (2000). Process water production from river water by ultrafiltration and reverse osmosis. Desalination, 131(1–3), 325-336
  11. 1 2 Bertone, E., Stewart, R. A., Zhang, H., & O'Halloran, K. (2016). Hybrid water treatment cost prediction model for raw water intake optimization. Environmental Modelling & Software, 75, 230-242
  12. 1 2 3 Vingerhoeds, M. H., Nijenhuis-de Vries, M. A., Ruepert, N., van der Laan, H., Bredie, W. L. P., & Kremer, S. (2016). Sensory quality of drinking water produced by reverse osmosis membrane filtration followed by remineralisation. Water Research, 94, 42-51
  13. 1 2 Yang, G., Feng, L., Wang, S., Zhou, J., Guo, C., Xia, T., Sun, W., Jiang, Y., Sun, X., Cao, Lian., Xu, X., Zhu, L. (2015). Potential risk and control strategy of biofilm pretreatment process treating raw water. Bioresource Technology, 198, 456-463
  14. ↑ Chu, H., Cao, D., Dong, B., & Qiang, Z. (2010). Bio-diatomite dynamic membrane reactor for micro-polluted surface water treatment. Water Research, 44(5), 1573-1579
  15. 1 2 Gauthier, V., Barbeau, B., Tremblay, G., Millette, R., & Bernier, A. (2003). Impact of raw water turbidity fluctuations on drinking water quality in a distribution system. Journal of Environmental Engineering and Science, 2(4), 281-291
  16. ↑ Schwartz, J., Levin, R., & Goldstein, R. (2000). Drinking water turbidity and gastrointestinal illness in the elderly of Philadelphia. Journal of Epidemiology and Community h, 54(1), 45–51
  17. ↑ Satterfield, Z. (2006). Turbidity Control. Tech Brief, 6(2), 1-4
  18. ↑ Bever, Lindsey. "Why 'raw water' could help you lose weight, in a bad way", Sydney Morning Herald , 4 January 2018.
  19. ↑ Mosia,Lebohang. "Why is there such a thirst among influencers for ‘raw water’?", Independent Online , 10 November 2022.
  20. ↑ Turton, William. "The Juicero founder is really into raw water", Vice News , 7 March 2018.
  21. ↑ Mole, Beth. "Meet “raw” water—ludicrously priced unfiltered water with random bacteria", Ars Technica , 2018.
  22. ↑ Morris, David Z. "Silicon Valley’s Next Big Idea: Untreated Drinking Water", Fortune.com , 31 December 2017.
  23. ↑ Bever, Lindsey (4 January 2018). "'Raw water' is the latest health craze. Here's why drinking it may be a bad idea". Washington Post. Retrieved 4 January 2018.
  24. ↑ Bowles, Nellie (29 December 2017). "Unfiltered Fervor: The Rush to Get Off the Water Grid". The New York Times.
  25. ↑ "Video: A Deep Dive into the "Raw Water" Craze - The Daily Show with Trevor Noah (Video Clip)". Comedy Central. 18 April 2018. Archived from the original on April 22, 2018.
  26. ↑ "A Deep Dive Into The "Raw Water" Craze — The Daily Show (YouTube)". 30 March 2022.

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