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95-520: It is estimated that there are 930 miles of water lines and 7,300 Fire Hydrants served by Pittsburgh Water. The Pittsburgh Water and Sewer Authority was created in 1984 to oversee a $ 200 million capital improvement program focused on Pittsburgh's water treatment and distribution system. This capital improvement program was primarily designed to ensure that the water system would meet various new requirements mandated by federal and state laws pertaining to safe drinking water. The largest project undertaken in

190-414: A calibration curve . This allows for the determination of the amount of a chemical in a material by comparing the results of an unknown sample to those of a series of known standards. If the concentration of element or compound in a sample is too high for the detection range of the technique, it can simply be diluted in a pure solvent. If the amount in the sample is below an instrument's range of measurement,

285-699: A transistor due to base current, and so on. This noise can be avoided by modulation of the signal at a higher frequency, for example, through the use of a lock-in amplifier . Environmental noise arises from the surroundings of the analytical instrument. Sources of electromagnetic noise are power lines , radio and television stations, wireless devices , compact fluorescent lamps and electric motors . Many of these noise sources are narrow bandwidth and, therefore, can be avoided. Temperature and vibration isolation may be required for some instruments. Noise reduction can be accomplished either in computer hardware or software . Examples of hardware noise reduction are

380-440: 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

475-559: A chemical present in blood that increases the risk of cancer would be a discovery that an analytical chemist might be involved in. An effort to develop a new method might involve the use of a tunable laser to increase the specificity and sensitivity of a spectrometric method. Many methods, once developed, are kept purposely static so that data can be compared over long periods of time. This is particularly true in industrial quality assurance (QA), forensic and environmental applications. Analytical chemistry plays an increasingly important role in

570-442: A combination of two (or more) techniques to detect and separate chemicals from solutions. Most often the other technique is some form of chromatography . Hyphenated techniques are widely used in chemistry and biochemistry . A slash is sometimes used instead of hyphen , especially if the name of one of the methods contains a hyphen itself. The visualization of single molecules, single cells, biological tissues, and nanomaterials

665-595: 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

760-408: A function, we may also want to calculate the error of the function. Let f {\displaystyle f} be a function with N {\displaystyle N} variables. Therefore, the propagation of uncertainty must be calculated in order to know the error in f {\displaystyle f} : A general method for analysis of concentration involves the creation of

855-537: 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

950-465: 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

1045-598: 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

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1140-401: 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

1235-495: A single chip of only millimeters to a few square centimeters in size and that are capable of handling extremely small fluid volumes down to less than picoliters. Error can be defined as numerical difference between observed value and true value. The experimental error can be divided into two types, systematic error and random error. Systematic error results from a flaw in equipment or the design of an experiment while random error results from uncontrolled or uncontrollable variables in

1330-421: 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

1425-462: A systematic scheme to confirm the presence of certain aqueous ions or elements by performing a series of reactions that eliminate a range of possibilities and then confirm suspected ions with a confirming test. Sometimes small carbon-containing ions are included in such schemes. With modern instrumentation, these tests are rarely used but can be useful for educational purposes and in fieldwork or other situations where access to state-of-the-art instruments

1520-499: A wide variety of reactions. The late 20th century also saw an expansion of the application of analytical chemistry from somewhat academic chemical questions to forensic , environmental , industrial and medical questions, such as in histology . Modern analytical chemistry is dominated by instrumental analysis. Many analytical chemists focus on a single type of instrument. Academics tend to either focus on new applications and discoveries or on new methods of analysis. The discovery of

1615-414: Is a stub . You can help Misplaced Pages by expanding it . This water supply –related article is a stub . You can help Misplaced Pages by expanding it . Water purification#Membrane filtration 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

1710-569: 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

1805-557: 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

1900-425: 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

1995-479: Is an important and attractive approach in analytical science. Also, hybridization with other traditional analytical tools is revolutionizing analytical science. Microscopy can be categorized into three different fields: optical microscopy , electron microscopy , and scanning probe microscopy . Recently, this field is rapidly progressing because of the rapid development of the computer and camera industries. Devices that integrate (multiple) laboratory functions on

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2090-532: Is categorized by approaches of mass analyzers: magnetic-sector , quadrupole mass analyzer , quadrupole ion trap , time-of-flight , Fourier transform ion cyclotron resonance , and so on. Electroanalytical methods measure the potential ( volts ) and/or current ( amps ) in an electrochemical cell containing the analyte. These methods can be categorized according to which aspects of the cell are controlled and which are measured. The four main categories are potentiometry (the difference in electrode potentials

2185-557: 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

2280-455: 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

2375-458: Is increasing. An interest towards absolute (standardless) analysis has revived, particularly in emission spectrometry. Great effort is being put into shrinking the analysis techniques to chip size. Although there are few examples of such systems competitive with traditional analysis techniques, potential advantages include size/portability, speed, and cost. (micro total analysis system (μTAS) or lab-on-a-chip ). Microscale chemistry reduces

2470-550: Is measured), coulometry (the transferred charge is measured over time), amperometry (the cell's current is measured over time), and voltammetry (the cell's current is measured while actively altering the cell's potential). Calorimetry and thermogravimetric analysis measure the interaction of a material and heat . Separation processes are used to decrease the complexity of material mixtures. Chromatography , electrophoresis and field flow fractionation are representative of this field. Chromatography can be used to determine

2565-594: 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

2660-714: 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

2755-434: Is not available or expedient. Quantitative analysis is the measurement of the quantities of particular chemical constituents present in a substance. Quantities can be measured by mass (gravimetric analysis) or volume (volumetric analysis). The gravimetric analysis involves determining the amount of material present by weighing the sample before and/or after some transformation. A common example used in undergraduate education

2850-562: 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,

2945-472: 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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3040-402: 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

3135-421: 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

3230-545: 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

3325-406: 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

3420-644: 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

3515-400: Is the bandwidth of the frequency f {\displaystyle f} . Shot noise is a type of electronic noise that occurs when the finite number of particles (such as electrons in an electronic circuit or photons in an optical device) is small enough to give rise to statistical fluctuations in a signal. Shot noise is a Poisson process , and the charge carriers that make up

3610-517: 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

3705-414: Is the determination of the amount of water in a hydrate by heating the sample to remove the water such that the difference in weight is due to the loss of water. Titration involves the gradual addition of a measurable reactant to an exact volume of a solution being analyzed until some equivalence point is reached. Titrating accurately to either the half-equivalence point or the endpoint of a titration allows

3800-465: 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

3895-534: 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),

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3990-483: 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)

4085-404: 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

4180-423: Is used instead of a calibration curve to solve the matrix effect problem. One of the most important components of analytical chemistry is maximizing the desired signal while minimizing the associated noise . The analytical figure of merit is known as the signal-to-noise ratio (S/N or SNR). Noise can arise from environmental factors as well as from fundamental physical processes. Thermal noise results from

4275-446: 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

4370-579: 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

4465-441: 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

4560-1002: The PWSA rebranded as Pittsburgh Water. As of November 2024 and since June 2016, Pittsburgh Water has been working to replace lead service lines. These lines had been built with lead because it was a readily available material and was easy to work with. However, exposure to lead is directly connected with multiple health problems, particularly in children. No lead is present in water that has been treated by Pittsburgh Water; lead only enters water through older service lines as it travels to buildings. Pittsburgh Water has been working in conjunction with local home and business owners to replace these pipes. A more comprehensive and frequently-updated list of current projects may be found on Pittsburgh Water's main website. Projects conducted by Pittsburgh Water typically involve updating older plumbing systems, building new lines, and creating greener solutions to stormwater issues such as parks. This Pittsburgh -related article

4655-422: The amounts of chemicals used. Many developments improve the analysis of biological systems. Examples of rapidly expanding fields in this area are genomics , DNA sequencing and related research in genetic fingerprinting and DNA microarray ; proteomics , the analysis of protein concentrations and modifications, especially in response to various stressors, at various developmental stages, or in various parts of

4750-506: The backbone of most undergraduate analytical chemistry educational labs. Qualitative analysis determines the presence or absence of a particular compound, but not the mass or concentration. By definition, qualitative analyses do not measure quantity. There are numerous qualitative chemical tests, for example, the acid test for gold and the Kastle-Meyer test for the presence of blood . Inorganic qualitative analysis generally refers to

4845-399: 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

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4940-763: 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

5035-490: The chemist to determine the amount of moles used, which can then be used to determine a concentration or composition of the titrant. Most familiar to those who have taken chemistry during secondary education is the acid-base titration involving a color-changing indicator, such as phenolphthalein . There are many other types of titrations, for example, potentiometric titrations or precipitation titrations. Chemists might also create titration curves in order by systematically testing

5130-404: 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

5225-640: 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

5320-438: The current follow a Poisson distribution . The root mean square current fluctuation is given by where e is the elementary charge and I is the average current. Shot noise is white noise. Flicker noise is electronic noise with a 1/ ƒ frequency spectrum; as f increases, the noise decreases. Flicker noise arises from a variety of sources, such as impurities in a conductive channel, generation, and recombination noise in

5415-649: The early 20th century and refined in the late 20th century. The separation sciences follow a similar time line of development and also became increasingly transformed into high performance instruments. In the 1970s many of these techniques began to be used together as hybrid techniques to achieve a complete characterization of samples. Starting in the 1970s, analytical chemistry became progressively more inclusive of biological questions ( bioanalytical chemistry ), whereas it had previously been largely focused on inorganic or small organic molecules . Lasers have been increasingly used as probes and even to initiate and influence

5510-405: The early days of chemistry, providing methods for determining which elements and chemicals are present in the object in question. During this period, significant contributions to analytical chemistry included the development of systematic elemental analysis by Justus von Liebig and systematized organic analysis based on the specific reactions of functional groups. The first instrumental analysis

5605-473: 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

5700-830: The entire analysis or be combined with another method. Separation isolates analytes . Qualitative analysis identifies analytes, while quantitative analysis determines the numerical amount or concentration. Analytical chemistry consists of classical, wet chemical methods and modern, instrumental methods . Classical qualitative methods use separations such as precipitation , extraction , and distillation . Identification may be based on differences in color, odor, melting point, boiling point, solubility, radioactivity or reactivity. Classical quantitative analysis uses mass or volume changes to quantify amount. Instrumental methods may be used to separate samples using chromatography , electrophoresis or field flow fractionation . Then qualitative and quantitative analysis can be performed, often with

5795-513: The experiment. In error the true value and observed value in chemical analysis can be related with each other by the equation where An error of a measurement is an inverse measure of accurate measurement, i.e. smaller the error greater the accuracy of the measurement. Errors can be expressed relatively. Given the relative error( ε r {\displaystyle \varepsilon _{\rm {r}}} ): The percent error can also be calculated: If we want to use these values in

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5890-424: 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

5985-399: 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

6080-489: The initial years of the PWSA was to cover all open water reservoirs, replace them with closed tanks, or else enact another acceptable solution, such as the installation of a membrane filtration plant at the open Highland Reservoir No. 1, which is the focal point of Highland Park . The City of Pittsburgh Water Department was absorbed by the PWSA in 1995, and in 1999, the PWSA also assumed the responsibility of operating and maintaining Pittsburgh's sewer system. In November 2024,

6175-465: 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,

6270-467: The internal standard as a calibrant. An ideal internal standard is an isotopically enriched analyte which gives rise to the method of isotope dilution . The method of standard addition is used in instrumental analysis to determine the concentration of a substance ( analyte ) in an unknown sample by comparison to a set of samples of known concentration, similar to using a calibration curve . Standard addition can be applied to most analytical techniques and

6365-422: 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

6460-693: The main branches of contemporary analytical atomic spectrometry, the most widespread and universal are optical and mass spectrometry. In the direct elemental analysis of solid samples, the new leaders are laser-induced breakdown and laser ablation mass spectrometry, and the related techniques with transfer of the laser ablation products into inductively coupled plasma . Advances in design of diode lasers and optical parametric oscillators promote developments in fluorescence and ionization spectrometry and also in absorption techniques where uses of optical cavities for increased effective absorption pathlength are expected to expand. The use of plasma- and laser-based methods

6555-424: The method of addition can be used. In this method, a known quantity of the element or compound under study is added, and the difference between the concentration added and the concentration observed is the amount actually in the sample. Sometimes an internal standard is added at a known concentration directly to an analytical sample to aid in quantitation. The amount of analyte present is then determined relative to

6650-690: The migration distance of the solvent front during chromatography. In combination with the instrumental methods, chromatography can be used in quantitative determination of the substances. Combinations of the above techniques produce a "hybrid" or "hyphenated" technique. Several examples are in popular use today and new hybrid techniques are under development. For example, gas chromatography-mass spectrometry , gas chromatography- infrared spectroscopy , liquid chromatography-mass spectrometry , liquid chromatography- NMR spectroscopy , liquid chromatography-infrared spectroscopy, and capillary electrophoresis-mass spectrometry. Hyphenated separation techniques refer to

6745-452: The most thorough method of large scale water purification available, although perfect semi-permeable membranes are difficult to create. Unless membranes are well-maintained, algae and other life forms can colonise the membranes. Analytical chemistry Analytical chemistry studies and uses instruments and methods to separate , identify, and quantify matter. In practice, separation, identification or quantification may constitute

6840-518: The motion of charge carriers (usually electrons) in an electrical circuit generated by their thermal motion. Thermal noise is white noise meaning that the power spectral density is constant throughout the frequency spectrum . The root mean square value of the thermal noise in a resistor is given by where k B is the Boltzmann constant , T is the temperature , R is the resistance, and Δ f {\displaystyle \Delta f}

6935-896: The pH every drop in order to understand different properties of the titrant. Spectroscopy measures the interaction of the molecules with electromagnetic radiation . Spectroscopy consists of many different applications such as atomic absorption spectroscopy , atomic emission spectroscopy , ultraviolet-visible spectroscopy , X-ray spectroscopy , fluorescence spectroscopy , infrared spectroscopy , Raman spectroscopy , dual polarization interferometry , nuclear magnetic resonance spectroscopy , photoemission spectroscopy , Mössbauer spectroscopy and so on. Mass spectrometry measures mass-to-charge ratio of molecules using electric and magnetic fields . There are several ionization methods: electron ionization , chemical ionization , electrospray ionization , fast atom bombardment, matrix-assisted laser desorption/ionization , and others. Also, mass spectrometry

7030-475: 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

7125-459: 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

7220-539: 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

7315-491: The pharmaceutical industry where, aside from QA, it is used in the discovery of new drug candidates and in clinical applications where understanding the interactions between the drug and the patient are critical. Although modern analytical chemistry is dominated by sophisticated instrumentation, the roots of analytical chemistry and some of the principles used in modern instruments are from traditional techniques, many of which are still used today. These techniques also tend to form

7410-400: 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

7505-409: The presence of substances in a sample as different components in a mixture have different tendencies to adsorb onto the stationary phase or dissolve in the mobile phase. Thus, different components of the mixture move at different speed. Different components of a mixture can therefore be identified by their respective R ƒ values , which is the ratio between the migration distance of the substance and

7600-526: 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

7695-521: 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

7790-404: 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

7885-458: The same instrument and may use light interaction , heat interaction , electric fields or magnetic fields . Often the same instrument can separate, identify and quantify an analyte. Analytical chemistry is also focused on improvements in experimental design , chemometrics , and the creation of new measurement tools. Analytical chemistry has broad applications to medicine, science, and engineering. Analytical chemistry has been important since

7980-404: 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

8075-403: 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

8170-473: 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

8265-436: 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

8360-501: 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,

8455-404: 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

8550-610: The use of shielded cable , analog filtering , and signal modulation. Examples of software noise reduction are digital filtering , ensemble average , boxcar average, and correlation methods. Analytical chemistry has applications including in forensic science , bioanalysis , clinical analysis , environmental analysis , and materials analysis . Analytical chemistry research is largely driven by performance (sensitivity, detection limit , selectivity, robustness, dynamic range , linear range , accuracy, precision, and speed), and cost (purchase, operation, training, time, and space). Among

8645-652: 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)

8740-513: 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

8835-463: 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

8930-403: 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

9025-404: Was flame emissive spectrometry developed by Robert Bunsen and Gustav Kirchhoff who discovered rubidium (Rb) and caesium (Cs) in 1860. Most of the major developments in analytical chemistry took place after 1900. During this period, instrumental analysis became progressively dominant in the field. In particular, many of the basic spectroscopic and spectrometric techniques were discovered in

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