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83-853: The stream rises on the grounds of the Chevy Chase Country Club and flows through Chevy Chase to the Somerset neighborhood, where it crosses through Vinton Park and the Willard Avenue Park. After crossing under the Little Falls Parkway it joins Willett Branch and then flows through the Little Falls Stream Valley Park to Brookmont, the Chesapeake and Ohio Canal and into the Potomac River . The name, "Powder Mill Branch"

166-440: A "cold" electrical discharge. To use ozone as a disinfectant, it must be created on-site and added to the water by bubble contact. Some of the advantages of ozone include the production of fewer dangerous by-products and the absence of taste and odour problems (in comparison to chlorination ). No residual ozone is left in the water. In the absence of a residual disinfectant in the water, chlorine or chloramine may be added throughout

249-569: A 20 acre purchase on both sides of Massachusetts avenue in 1946. In 1948, the Maryland-National Capital Park and Planning Commission was authorized to purchase parkland around Little Falls Branch and Willett Branch under the Capper-Cramton Act of 1930. The Little Falls Parkway was eventually built from Glenbrook Road to Massachusetts Avenue , but plans to extend the parkway south to MacArthur Boulevard were dropped in 1970 and

332-745: A campus in Chevy Chase. For decades, a six-block stretch of Wisconsin Avenue in Friendship Heights and Chevy Chase has been the only place partially or wholly in Washington, D.C., with multiple traditional department stores , namely, Bloomingdale's , Saks Fifth Avenue , Lord & Taylor and Neiman Marcus . The latter two closed in 2020, as did the indoor shopping center at the Chevy Chase Pavilion. As of 2022, two department stores remain, both on

415-595: A distribution system to remove any potential pathogens in the distribution piping. Ozone has been used in drinking water plants since 1906 where the first industrial ozonation plant was built in Nice , France. The U.S. Food and Drug Administration has accepted ozone as being safe; and it is applied as an anti-microbiological agent for the treatment, storage, and processing of foods. However, although fewer by-products are formed by ozonation, it has been discovered that ozone reacts with bromide ions in water to produce concentrations of

498-778: A hotel at 7100 Connecticut Avenue; it opened it in 1894 as the Chevy Chase Spring Hotel and was later renamed the Chevy Chase Inn. "The hotel failed to attract sufficient patrons, especially during the winter months," wrote the Chevy Chase Historical Society, and in 1895, the Land Company leased the property for a year to the Young Ladies Seminary. Part of the original Cheivy Chace patent had been sold to Abraham Bradley , who built an estate known as

581-472: A late-19th-century effort to create a new suburb that its developer dubbed Chevy Chase after a colonial land patent . Primarily residential, Chevy Chase adjoins Friendship Heights , a popular shopping district. It is the home of the Chevy Chase Club and Columbia Country Club , private clubs whose members include many prominent politicians and Washingtonians. The name is derived from Cheivy Chace ,

664-537: A powerful oxidising agent which is toxic to most waterborne organisms. It is a very strong, broad spectrum disinfectant that is widely used in Europe and in a few municipalities in the United States and Canada. Ozone disinfection, or ozonation, is an effective method to inactivate harmful protozoa that form cysts. It also works well against almost all other pathogens. Ozone is made by passing oxygen through ultraviolet light or

747-465: A primary disinfectant. When used in this manner, chloramines provide an effective residual disinfectant with very few of the negative effects of chlorination. Over 2 million people in 28 developing countries use Solar Disinfection for daily drinking water treatment. Like UV, ionizing radiation (X-rays, gamma rays, and electron beams) has been used to sterilise water. Bromine and iodine can also be used as disinfectants. However, chlorine in water

830-598: A residual disinfectant in the water. Therefore, water that is boiled and then stored for any length of time may acquire new pathogens. Granular activated carbon is a form of activated carbon with a high surface area. It adsorbs many compounds including many toxic compounds. Water passing through activated carbon is commonly used in municipal regions with organic contamination, taste or odors. Many household water filters and fish tanks use activated carbon filters to purify water. Household filters for drinking water sometimes contain silver as metallic silver nanoparticle . If water

913-401: A result of the absorption , scattering , and shadowing caused by the suspended solids. The main disadvantage to the use of UV radiation is that, like ozone treatment, it leaves no residual disinfectant in the water; therefore, it is sometimes necessary to add a residual disinfectant after the primary disinfection process. This is often done through the addition of chloramines, discussed above as

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996-421: A steel vessel and the water is forced through it under pressure. Advantages: Slow sand filters may be used where there is sufficient land and space, as the water flows very slowly through the filters. These filters rely on biological treatment processes for their action rather than physical filtration. They are carefully constructed using graded layers of sand, with the coarsest sand, along with some gravel, at

1079-569: Is a by-product regulated to low allowable levels in the United States. Chlorine dioxide can be supplied as an aqueous solution and added to water to avoid gas handling problems; chlorine dioxide gas accumulations may spontaneously detonate. The use of chloramine is becoming more common as a disinfectant. Although chloramine is not as strong an oxidant, it provides a longer-lasting residual than free chlorine because of its lower redox potential compared to free chlorine. It also does not readily form THMs or haloacetic acids ( disinfection byproducts ). It

1162-557: Is a popular cationic (positively charged) organic polymer used in water purification plants. Waters exiting the flocculation basin may enter the sedimentation basin , also called a clarifier or settling basin. It is a large tank with low water velocities, allowing floc to settle to the bottom. The sedimentation basin is best located close to the flocculation basin so the transit between the two processes does not permit settlement or floc break up. Sedimentation basins may be rectangular, where water flows from end to end, or circular where flow

1245-425: Is a toxic gas, there is a danger of a release associated with its use. This problem is avoided by the use of sodium hypochlorite , which is a relatively inexpensive solution used in household bleach that releases free chlorine when dissolved in water. Chlorine solutions can be generated on site by electrolyzing common salt solutions. A solid form, calcium hypochlorite , releases chlorine on contact with water. Handling

1328-557: Is from the centre outward. Sedimentation basin outflow is typically over a weir so only a thin top layer of water—that furthest from the sludge—exits. In 1904, Allen Hazen showed that the efficiency of a sedimentation process was a function of the particle settling velocity, the flow through the tank and the surface area of tank. Sedimentation tanks are typically designed within a range of overflow rates of 0.5 to 1.0 gallons per minute per square foot (or 1250 to 2500 litres per square meter per hour). In general, sedimentation basin efficiency

1411-455: Is held in the carbon block for longer periods, microorganisms can grow inside which results in fouling and contamination. Silver nanoparticles are excellent anti-bacterial material and can decompose toxic halo-organic compounds such as pesticides into non-toxic organic products. Filtered water must be used soon after it is filtered, as the low amount of remaining microbes may proliferate over time. In general, these home filters remove over 90% of

1494-594: Is needed. Chemical and microbiological analysis , while expensive, are the only way to obtain the information necessary for deciding on the appropriate method of purification. The goals of the treatment are to remove unwanted constituents in the water and to make it safe to drink or fit for a specific purpose in industry or medical applications. Widely varied techniques are available to remove contaminants like fine solids, micro-organisms and some dissolved inorganic and organic materials, or environmental persistent pharmaceutical pollutants . The choice of method will depend on

1577-714: Is not a function of detention time or depth of the basin. Although, basin depth must be sufficient so that water currents do not disturb the sludge and settled particle interactions are promoted. As particle concentrations in the settled water increase near the sludge surface on the bottom of the tank, settling velocities can increase due to collisions and agglomeration of particles. Typical detention times for sedimentation vary from 1.5 to 4 hours and basin depths vary from 10 to 15 feet (3 to 4.5 meters). Lamella clarifiers , inclined flat plates or tubes can be added to traditional sedimentation basins to improve particle removal performance. Inclined plates and tubes drastically increase

1660-562: Is often used. After coagulation and flocculation processes, water flows to DAF tanks where air diffusers on the tank bottom create fine bubbles that attach to the floc resulting in a floating mass of concentrated floc. The floating floc blanket is removed from the surface and clarified water is withdrawn from the bottom of the DAF tank. Water supplies that are particularly vulnerable to unicellular algae blooms and supplies with low turbidity and high colour often employ DAF. After separating most floc,

1743-472: Is over three times more effective as a disinfectant against Escherichia coli than an equivalent concentration of bromine , and over six times more effective than an equivalent concentration of iodine . Iodine is commonly used for portable water purification , and bromine is common as a swimming pool disinfectant . Portable water purification devices and methods are available for disinfection and treatment in emergencies or in remote locations. Disinfection

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1826-402: Is passed quickly upward through the filter, opposite the normal direction (called backflushing or backwashing ) to remove embedded or unwanted particles. Prior to this step, compressed air may be blown up through the bottom of the filter to break up the compacted filter media to aid the backwashing process; this is known as air scouring . This contaminated water can be disposed of, along with

1909-421: Is possible to convert chlorine to chloramine by adding ammonia to the water after adding chlorine. The chlorine and ammonia react to form chloramine. Water distribution systems disinfected with chloramines may experience nitrification , as ammonia is a nutrient for bacterial growth, with nitrates being generated as a by-product. Ozone is an unstable molecule which readily gives up one atom of oxygen providing

1992-506: Is served by the Montgomery County Public Schools . Residents of Chevy Chase are zoned to Somerset, Chevy Chase or North Chevy Chase Elementary School, which feed into Silver Creek Middle School, Westland Middle School and Bethesda-Chevy Chase High School . Private schools in Chevy Chase include Concord Hill School, Oneness-Family School , and Blessed Sacrament School. Rochambeau French International School formerly had

2075-406: Is significant, often 3 to 5 per cent of the total volume of water to be treated. The cost of treating and disposing of the sludge can impact the operating cost of a water treatment plant. The sedimentation basin may be equipped with mechanical cleaning devices that continually clean its bottom, or the basin can be periodically taken out of service and cleaned manually. A subcategory of sedimentation

2158-644: Is that chlorine from any source reacts with natural organic compounds in the water to form potentially harmful chemical by-products. These by-products, trihalomethanes (THMs) and haloacetic acids (HAAs), are both carcinogenic in large quantities and are regulated by the United States Environmental Protection Agency (EPA) and the Drinking Water Inspectorate in the UK. The formation of THMs and haloacetic acids may be minimised by

2241-517: Is the addition of chemicals to assist in the removal of particles suspended in water. Particles can be inorganic such as clay and silt or organic such as algae , bacteria, viruses , protozoa and natural organic matter . Inorganic and organic particles contribute to the turbidity and colour of water. The addition of inorganic coagulants such as aluminium sulfate (or alum ) or iron (III) salts such as iron(III) chloride cause several simultaneous chemical and physical interactions on and among

2324-465: Is the oldest and most effective way since it eliminates most microbes causing intestinal disease, but it cannot remove chemical toxins or impurities. For human health, complete sterilisation of water is not required, since heat resistant microbes do not affect intestines. The traditional advice of boiling water for ten minutes is mainly for additional safety, since microbes start expiring at temperatures greater than 60 °C (140 °F). Though

2407-534: Is the primary goal, since aesthetic considerations such as taste, odour, appearance, and trace chemical contamination do not affect the short-term safety of drinking water. Other popular methods for purifying water, especially for local private supplies are listed below. In some countries some of these methods are used for large scale municipal supplies. Particularly important are distillation ( desalination of seawater ) and reverse osmosis. Bringing water to its boiling point (about 100 °C or 212 F at sea level),

2490-483: Is the removal of particulates by entrapment in a layer of suspended floc as the water is forced upward. The major advantage of floc blanket clarifiers is that they occupy a smaller footprint than conventional sedimentation. The disadvantages are that particle removal efficiency can be highly variable depending on changes in influent water quality and influent water flow rate. When particles to be removed do not settle out of solution easily, dissolved air flotation (DAF)

2573-611: Is to produce water that is fit for specific purposes. Most water is purified and disinfected for human consumption ( drinking water ), 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

Little Falls Branch (Potomac River tributary) - Misplaced Pages Continue

2656-404: Is treated with lime ( calcium oxide ) and/or soda-ash ( sodium carbonate ) to precipitate calcium carbonate out of solution utilising the common-ion effect . Electrodeionization : Water is passed between a positive electrode and a negative electrode. Ion-exchange membranes allow only positive ions to migrate from the treated water toward the negative electrode and only negative ions toward

2739-446: Is usually a high energy, rapid mix unit process (detention time in seconds) whereby the coagulant chemicals are added followed by flocculation basins (detention times range from 15 to 45 minutes) where low energy inputs turn large paddles or other gentle mixing devices to enhance the formation of floc. In fact, coagulation and flocculation processes are ongoing once the metal salt coagulants are added. Organic polymers were developed in

2822-601: The United States District Court for the District of Columbia . When the trail design was approved from Bradley Boulevard to Albemarle Street, the neighborhood group sued again. In 1980 the Washington Suburban Sanitary Commission built the sewer line through the park, replacing one that was leaking and in 1981 a bike trail was added on top of it. The bike trail was originally planned to follow

2905-579: The boiling point decreases with increasing altitude, it is not enough to affect disinfection. 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

2988-495: The watershed . 38°56′08″N 77°07′11″W  /  38.935667°N 77.119701°W  / 38.935667; -77.119701 Chevy Chase, Maryland Chevy Chase ( / ˈ tʃ ɛ v iː tʃ eɪ s / ) is the colloquial name of an area that includes a town , several incorporated villages , and an unincorporated census-designated place in southern Montgomery County , Maryland ; and one adjoining neighborhood in northwest Washington, D.C. Most of these derive from

3071-441: The 1960s as aids to coagulants and, in some cases, as replacements for the inorganic metal salt coagulants. Synthetic organic polymers are high molecular weight compounds that carry negative, positive or neutral charges. When organic polymers are added to water with particulates, the high molecular weight compounds adsorb onto particle surfaces and through interparticle bridging coalesce with other particles to form floc. PolyDADMAC

3154-544: The Bradley Farm. In 1892, Newlands and other members of the Metropolitan Club of Washington, D.C., founded a hunt club called Chevy Chase Hunt, which would later become Chevy Chase Club. In 1894, the club located itself on the former Bradley Farm property under a lease from its owners. The club introduced a six-hole golf course to its members in 1895, and purchased the 9.36-acre Bradley Farm tract in 1897. In 1906,

3237-554: The Chevy Chase Country Club barred "Negroes" and "one ethnic group of Caucasians" from membership. In response, Club president Randall H. Hagnar denied that the club excluded Black or Jewish people; he said that no members were African-Americans but that several were Jewish. In 1903, Lea M. Bouligny bought the old Chevy Chase Inn and founded the Chevy Chase College and Seminary . The name was changed to Chevy Chase Junior College in 1927. The National 4-H Club Foundation purchased

3320-491: The Chevy Chase Land Company blocked a proposed subdivision called Belmont after they learned its Black developers aimed to sell house lots to other African Americans. In subsequent litigation, the company and its affiliates argued that those developers had committed fraud by proposing "to sell lots...to negroes." By the 1920s, restrictive covenants were added to Chevy Chase real estate deeds. Some prohibited both

3403-551: The Dalecarlia drinking water treatment plant in Washington, D.C., and occasionally has received overflow discharges from the plant. According to a study conducted by the county government, the water quality of the stream and its tributaries is poor, due to water pollution from urban runoff , as well as the channelization described above. The county and the Town of Somerset have installed several stream restoration projects throughout

Little Falls Branch (Potomac River tributary) - Misplaced Pages Continue

3486-576: The Dalecarlia Reservoir and the branch stopped providing water to the city. In 1897, the Department of Agriculture purchased a farm located along a tributary of Little Falls Branch from Henry Bradley Davidson for use by the Bureau of Animal Indusctry's animal disease station. It was used until the 1930s when sub-urbanization brought neighbors who complained about the smells. It was moved to Beltsville and

3569-652: The District of Columbia, for the purpose of developing a residential streetcar suburb for Washington, D.C. , during the expansion of the Washington streetcars system. Newlands and his partners founded The Chevy Chase Land Company in 1890, and its holdings of more than 1,700 acres (6.9 km ) eventually extended along the present-day Connecticut Avenue from Florida Avenue north to Jones Bridge Road. Newlands, an avowed white supremacist , and his development company took steps to ensure that residents of its new suburbs would be wealthy and white; for example, "requiring, in

3652-503: The Maryland side: a freestanding Saks Fifth Avenue and a Bloomingdale's in a multiuse center that also includes a Whole Foods Market , boutiques, and residential and office space. Along the D.C. stretch of Wisconsin Avenue are: On the Maryland stretch are: Water purification Water purification is the process of removing undesirable chemicals, biological contaminants, suspended solids, and gases from water . The goal

3735-466: The area turned into a park. In 1951 it was transferred from the Department of Agriculture to the Maryland-National Capital Park and Planning Commission which first added it to the Little Falls Parkway, but then turned it into Norwood Park, named for the nearby St. John's Episcopal Church, Norwood Parish. Planning for the Little Falls parkway started in the mid-1940's and the county began buying land with

3818-399: The boiling solution. Even distillation does not completely purify water, because of contaminants with similar boiling points and droplets of unvapourised liquid carried with the steam. However, 99.9% pure water can be obtained by distillation. Direct contact membrane distillation (DCMD) passes heated seawater along the surface of a hydrophobic polymer membrane. Evaporated water passes from

3901-763: The bottom and the finest sand at the top. Drains at the base convey treated water away for disinfection. Filtration depends on the development of a thin biological layer, called the zoogleal layer or Schmutzdecke , on the surface of the filter. An effective slow sand filter may remain in service for many weeks or even months, if the pretreatment is well designed, and produces water with a very low available nutrient level which physical methods of treatment rarely achieve. Very low nutrient levels allow water to be safely sent through distribution systems with very low disinfectant levels, thereby reducing consumer irritation over offensive levels of chlorine and chlorine by-products. Slow sand filters are not backwashed; they are maintained by having

3984-404: The chlorine in a glass of treated water. These filters must be periodically replaced otherwise the bacterial content of the water may actually increase due to the growth of bacteria within the filter unit. Distillation involves boiling water to produce water vapour . The vapour contacts a cool surface where it condenses as a liquid. Because the solutes are not normally vaporised, they remain in

4067-579: The completion of the Washington Aqueduct , the Potomac River became the city's principal water source, instead of Little Falls Branch; however, muddy water from Little Falls Branch continued to flow into the reservoir, and a bypass pipe was built to channel the aqueduct water to another city reservoir, the Georgetown Reservoir . In 1895 construction was completed to fully divert the stream from

4150-640: The concentrate stream is fed to the RO inlet. Disinfection is accomplished both by filtering out harmful micro-organisms and by adding disinfectant chemicals. Water is disinfected to kill any pathogens which pass through the filters and to provide a residual dose of disinfectant to kill or inactivate potentially harmful micro-organisms in the storage and distribution systems. Possible pathogens include viruses , bacteria, including Salmonella , Cholera , Campylobacter and Shigella , and protozoa , including Giardia lamblia and other cryptosporidia . After

4233-481: The deed to the land, that only a single-family detached house costing a large amount of money could be constructed. The Chevy Chase Land Company did not include explicit bars against non-white people, known as racial covenants, but the mandated cost of the house made it impractical for all but the wealthiest non-white people to buy the land." Houses were required to cost $ 5,000 and up on Connecticut Avenue and $ 3,000 and up on side streets. The company banned commerce from

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4316-473: The effective removal of as many organics from the water as possible prior to chlorine addition. Although chlorine is effective in killing bacteria, it has limited effectiveness against pathogenic protozoa that form cysts in water such as Giardia lamblia and Cryptosporidium . Chlorine dioxide is a faster-acting disinfectant than elemental chlorine. It is relatively rarely used because in some circumstances it may create excessive amounts of chlorite , which

4399-424: The geology of the drainage basin or aquifer and the influence of contaminant inputs ( acid rain ). If the water is acidic (lower than 7), lime , soda ash , or sodium hydroxide can be added to raise the pH during water purification processes. Lime addition increases the calcium ion concentration, thus raising the water hardness. For highly acidic waters, forced draft degasifiers can be an effective way to raise

4482-399: The hot side through pores in the membrane forming a stream of cold pure water on the other side. The difference in vapour pressure between the hot and cold side helps to push water molecules through. Reverse osmosis involves mechanical pressure applied to force water through a semi-permeable membrane . Contaminants are left on the other side of the membrane. Reverse osmosis is theoretically

4565-465: The intended use of the water. A visual inspection cannot determine if water is of appropriate quality. Simple procedures such as boiling or the use of a household activated carbon filter are not sufficient for treating all possible contaminants that may be present in water from an unknown source. Even natural spring water —considered safe for all practical purposes in the 19th century—must now be tested before determining what kind of treatment, if any,

4648-422: The introduction of any chemical disinfecting agent, the water is usually held in temporary storage – often called a contact tank or clear well – to allow the disinfecting action to complete. The most common disinfection method involves some form of chlorine or its compounds such as chloramine or chlorine dioxide . Chlorine is a strong oxidant that rapidly kills many harmful micro-organisms. Because chlorine

4731-601: The name of the land patented to Colonel Joseph Belt from Charles Calvert, 5th Baron Baltimore , on July 10, 1725. It has historic associations with a 1388 chevauchée , a French word describing a border raid, fought by Lord Percy of England and Earl Douglas of Scotland over hunting grounds, or a " chace ", in the Cheviot Hills of Northumberland and Otterburn . The battle was memorialized in " The Ballad of Chevy Chase ". The area known as Chevy Chase includes several entities in southern Montgomery County : It also includes

4814-632: The neighborhood of Chevy Chase in northwest Washington, D.C. The United States Postal Service also uses "Chevy Chase" for some postal addresses that lie outside these areas: the town of Somerset , the Village of Friendship Heights , and the part of the Rock Creek Forest neighborhood that lies east of Jones Mill Road and Beach Drive and west of Grubb Road. In the 1880s, Senator Francis G. Newlands of Nevada and his partners began acquiring farmland in unincorporated areas of Maryland and just inside

4897-475: The pH, by stripping dissolved carbon dioxide from the water. Making the water alkaline helps coagulation and flocculation processes work effectively and also helps to minimise the risk of lead being dissolved from lead pipes and from lead solder in pipe fittings. Sufficient alkalinity also reduces the corrosiveness of water to iron pipes. Acid ( carbonic acid , hydrochloric acid or sulfuric acid ) may be added to alkaline waters in some circumstances to lower

4980-459: The pH. Alkaline water (above pH 7.0) does not necessarily mean that lead or copper from the plumbing system will not be dissolved into the water. The ability of water to precipitate calcium carbonate to protect metal surfaces and reduce the likelihood of toxic metals being dissolved in water is a function of pH, mineral content, temperature, alkalinity and calcium concentration. One of the first steps in most conventional water purification processes

5063-428: The parkway to Bradley with a spur following Willett Branch to Hillandale Road and that road to a different point on Bradley, but the entire trail was never built. Instead the 3.5 miles (5.6 km) Little Falls hiker-biker paved trail is on road on the Little Falls Parkway between Massachusetts and Dorset. North of Dorset it follows Willett Branch north to Hillandale and east to Norwood Drive. In Little Falls Stream Valley

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5146-539: The particles. Within seconds, negative charges on the particles are neutralised by inorganic coagulants. Also within seconds, metal hydroxide precipitates of the iron and aluminium ions begin to form. These precipitates combine into larger particles under natural processes such as Brownian motion and through induced mixing which is sometimes referred to as flocculation . Amorphous metal hydroxides are known as "floc". Large, amorphous aluminium and iron (III) hydroxides adsorb and enmesh particles in suspension and facilitate

5229-400: The positive electrode. High purity deionised water is produced continuously, similar to ion-exchange treatment. Complete removal of ions from water is possible if the right conditions are met. The water is normally pre-treated with a reverse osmosis unit to remove non-ionic organic contaminants , and with gas transfer membranes to remove carbon dioxide . A water recovery of 99% is possible if

5312-464: The property in 1951, turning it into the group's Youth Conference Center. For decades, the center hosted the National 4-H Conference, an event for 4-Hers throughout the nation to attend, and the annual National Science Bowl in late April or early May. The National 4-H Club Foundation sold the center in 2021 for $ 40 million; as of 2022, it is to be replaced by a senior living development. Chevy Chase

5395-526: The quality of the water being treated, the cost of the treatment process and the quality standards expected of the processed water. The processes below are the ones commonly used in water purification plants. Some or most may not be used depending on the scale of the plant and quality of the raw (source) water. Pure water has a pH close to 7 (neither alkaline nor acidic ). Sea water can have pH values that range from 7.5 to 8.4 (moderately alkaline). Fresh water can have widely ranging pH values depending on

5478-521: The removal of particles by subsequent processes of sedimentation and filtration . Aluminum hydroxides are formed within a fairly narrow pH range, typically: 5.5 to about 7.7. Iron (III) hydroxides can form over a larger pH range including pH levels lower than are effective for alum, typically: 5.0 to 8.5. In the literature, there is much debate and confusion over the usage of the terms coagulation and flocculation: Where does coagulation end and flocculation begin? In water purification plants, there

5561-453: The residential neighborhoods. Leon E. Dessez was Chevy Chase's first resident. He and Lindley Johnson of Philadelphia designed the first four houses in the area. Toward the northern end of its holdings, the Land Company dammed Coquelin Run , a stream that crossed its land, to create the manmade Chevy Chase Lake . The body of water furnished water to the coal-fired generators that powered

5644-404: The river. Membrane filters are widely used for filtering both drinking water and sewage . For drinking water, membrane filters can remove virtually all particles larger than 0.2 μm—including Giardia and Cryptosporidium . Membrane filters are an effective form of tertiary treatment when it is desired to reuse the water for industry, for limited domestic purposes, or before discharging

5727-580: The sale or rental of homes to "a Negro or one of the African race." Others prohibited sales or rentals to "any persons of the Semetic [ sic ] race"—i.e., Jews . By World War II, such restrictive language had largely disappeared from real estate transactions, and all were voided by the 1948 Supreme Court decision in Shelley v. Kraemer . In 1964, Arthur Krock wrote an article for The New York Times alleging that

5810-404: The sludge from the sedimentation basin, or it can be recycled by mixing with the raw water entering the plant although this is often considered poor practice since it re-introduces an elevated concentration of bacteria into the raw water. Some water treatment plants employ pressure filters. These work on the same principle as rapid gravity filters, differing in that the filter medium is enclosed in

5893-403: The smallest suspended particles, so simple filtration is not enough. Most particles pass through surface layers but are trapped in pore spaces or adhere to sand particles. Effective filtration extends into the depth of the filter. This property of the filter is key to its operation: if the top layer of sand were to block all the particles, the filter would quickly clog. To clean the filter, water

5976-473: The solid, however, requires more routine human contact through opening bags and pouring than the use of gas cylinders or bleach, which are more easily automated. The generation of liquid sodium hypochlorite is inexpensive and also safer than the use of gas or solid chlorine. Chlorine levels up to 4 milligrams per litre (4 parts per million) are considered safe in drinking water. All forms of chlorine are widely used, despite their respective drawbacks. One drawback

6059-500: The southern section became Little Falls Stream Valley Park. In 1978, the National Capital Planning Commission approved a trail to run the length of the park, along with a replacement sewer line to be built south of Massachusetts Avenue. This action prompted neighbors to go to court to attempt to stop construction of the trail. Later that year the southern part of the trail and the sewer project were approved by

6142-423: The streetcars of the Land Company's Rock Creek Railway . The streetcar soon became vital to the community; it connected workers to the city, and even ran errands for residents. The lake was also the centerpiece of the Land Company's Chevy Chase Lake trolley park , a venue for boating, swimming, and other activities meant to draw city dwellers to the new suburb. Similar considerations led the Land Company to build

6225-436: The surface area available for particles to be removed in concert with Hazen's original theory. The amount of ground surface area occupied by a sedimentation basin with inclined plates or tubes can be far smaller than a conventional sedimentation basin. As particles settle to the bottom of a sedimentation basin, a layer of sludge is formed on the floor of the tank which must be removed and treated. The amount of sludge generated

6308-501: The suspected carcinogen bromate . Bromide can be found in fresh water supplies in sufficient concentrations to produce (after ozonation) more than 10 parts per billion (ppb) of bromate—the maximum contaminant level established by the USEPA. Ozone disinfection is also energy intensive. Ultraviolet light (UV) is very effective at inactivating cysts, in low turbidity water. UV light's disinfection effectiveness decreases as turbidity increases,

6391-404: The top layer of sand scraped off when the flow is eventually obstructed by biological growth. In bank filtration , natural sediments in a riverbank are used to provide the first stage of contaminant filtration. While typically not clean enough to be used directly for drinking water, the water gained from the associated extraction wells is much less problematic than river water taken directly from

6474-498: The trail is next to the Capital Crescent Trail . Though opponents of the bike trail were concerned the trail would bring crime to the neighborhood, a later review showed that crime dropped after the trail was opened. Today Little Falls Branch flows through a highly urbanized area, and parts of the stream have been altered through construction of underground pipes, culverts and open concrete channels. The stream runs near

6557-652: The use of coagulants. The type of membrane media determines how much pressure is needed to drive the water through and what sizes of micro-organisms can be filtered out. Ion exchange : Ion-exchange systems use ion-exchange resin - or zeolite -packed columns to replace unwanted ions. The most common case is water softening consisting of removal of Ca and Mg ions replacing them with benign (soap friendly) Na or K ions. Ion-exchange resins are also used to remove toxic ions such as nitrite , lead, mercury , arsenic and many others. Precipitative softening : Water rich in hardness ( calcium and magnesium ions)

6640-513: The use of electromagnetic radiation such as ultraviolet light . Water purification can reduce the concentration of particulate matter including suspended particles , parasites , bacteria, algae , viruses, and fungi as well as reduce the concentration of a range of dissolved and particulate matter. The standards for drinking water quality are typically set by governments or by international standards. These standards usually include minimum and maximum concentrations of contaminants, depending on

6723-463: The water into a river that is used by towns further downstream. They are widely used in industry, particularly for beverage preparation (including bottled water ). However no filtration can remove substances that are actually dissolved in the water such as phosphates , nitrates and heavy metal ions. Ultrafiltration membranes use polymer membranes with chemically formed microscopic pores that can be used to filter out dissolved substances avoiding

6806-403: The water is filtered as the final step to remove remaining suspended particles and unsettled floc. The most common type of filter is a rapid sand filter . Water moves vertically through sand which often has a layer of activated carbon or anthracite coal above the sand. The top layer removes organic compounds, which contribute to taste and odour. The space between sand particles is larger than

6889-484: Was derived from the Loughborough Mill, which was built and operated alongside the stream in the 19th century. In the mid-19th century, the stream served as an interim water source for Washington, D.C. The Dalecarlia Reservoir was built on the Washington, D.C.–Maryland border next to Little Falls Branchin 1858 and a dam was built on the stream with water diverted into the reservoir starting in 1859. In 1864, with

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