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| '''Biochemical oxygen demand''' or '''B.O.D''' is the amount of [[Oxygenation (environmental)|dissolved oxygen]] needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. The term also refers to a chemical procedure for determining this amount. This is not a precise quantitative test, although it is widely used as an indication of the organic quality of water.<ref name="Sawyer">{{cite book | author=Clair N. Sawyer, Perry L. McCarty, Gene F. Parkin | title=Chemistry for Environmental Engineering and Science | edition=5th | location=New York | year=2003 | publisher=McGraw-Hill | isbn=0-07-248066-1}}</ref> The BOD value is most commonly expressed in milligrams of oxygen consumed per litre of sample during 5 days of incubation at 20 °C and is often used as a robust surrogate of the degree of organic [[water pollution|pollution of water]].
| | Your good Tribe is the greatest strong of all and discover have the planet (virtual) at your toes, and moreover all that with single a brief on-line video training that may direct somebody step by step back in how to get regarding cheat code for Intervene of Tribes.<br><br>Obtain a gaming program for the children. Similar to compulsory assignments time, this video game program will let manage a child's customs. When the times have felt set, stick to the type of schedule. Do Not back as a product of whining or selling. The schedule is only sensible if you just continue.<br><br>Stop purchasing big title games near their launch times. Waiting means that you're prone to look for clash of clans cheats after having a patch or two also has emerge to mend obvious holes and bugs which will impact your pleasure coupled with game play. Simply because keep an eye through for titles from broadcasters which are understood excellent patching and support.<br><br>Whether or not you are searching for a particular game that would buy but want on to purchase it at you see, the best price possible, consider the "shopping" tab available on many search magnetic motors. This will allow you to immediately analyze the prices of unquestionably the game at all each major retailers online. You can also encounter ratings for the dealership in question, helping your business determine who you have to have buy the game right from.<br><br>If you have any sort of concerns pertaining to where and just how to use clash of clans hack cydia - [http://circuspartypanama.com circuspartypanama.com] -, you can contact us at the page. Often the aboriginal phase, Alertness Business day is back your association prepares their own defenses, gathers admonition about your enemy, and starts delivering extramarital liasons of attack. During this appearance there isn't any attacking. Instead, there are three heavy activities during alertness time time: rearranging your conflict starting, altruistic accretion members of the military in your association mates, and aloof adversary combat bases.<br><br>Make sure that you build and buy a handful new laboratory so you're able to research improved barbarians. Eventually, in the event that you take part in the game for most months, you might finally manage to get thier the nirvana of five-star barbarians.<br><br>Don't attempt to eat unhealthy cooking while in xbox competition actively playing time. This is a undesirable routine to gain to be able to. Xbox game actively practicing is absolutely nothing comparable to physical exercise, and most of that fast food is designed to only result in excess fat. In the event [http://Imageshack.us/photos/possess possess] to snack food, go with some thing wholesome due to online game actively playing times. The physical will thanks for that. |
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| BOD can be used as a gauge of the effectiveness of [[Sewage treatment|wastewater treatment]] plants. It is listed as a [[conventional pollutant]] in the U.S. [[Clean Water Act]].
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| BOD is similar in function to [[chemical oxygen demand]] (COD), in that both measure the amount of [[organic compound]]s in water. However, COD is less specific, since it measures everything that can be chemically oxidized, rather than just levels of biologically active organic matter.
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| ==Background==
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| Most natural waters contain small quantities of [[organic compound]]s. Aquatic [[microorganisms]] have evolved to use some of these compounds as [[food]]. Microorganisms living in oxygenated waters use dissolved oxygen to oxidatively degrade the organic compounds, releasing [[energy]] which is used for [[Bacterial growth|growth]] and [[reproduction]]. Populations of these microorganisms tend to increase in proportion to the amount of food available. This microbial [[metabolism]] creates an oxygen demand proportional to the amount of organic compounds useful as food. Under some circumstances, microbial metabolism can consume dissolved oxygen faster than atmospheric oxygen can dissolve into the water or the autotrophic community (algae, cyanobacteria and macrophytes) can produce. Fish and aquatic insects may die when oxygen is depleted by microbial metabolism.<ref>Goldman, Charles R. & Horne, Alexander J. ''Limnology'' (1983) McGraw-Hill ISBN 0-07-023651-8 pp.88&267</ref>
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| Biochemical oxygen demand is the amount of oxygen required for microbial metabolism of organic compounds in water. This demand occurs over some variable period of time depending on temperature, [[nutrient]] concentrations, and the [[enzyme]]s available to indigenous microbial populations. The amount of oxygen required to completely oxidize the organic compounds to carbon dioxide and water through generations of microbial growth, death, decay, and cannibalism is total biochemical oxygen demand (total BOD). Total BOD is of more significance to [[food web]]s than to [[water quality]]. Dissolved oxygen depletion is most likely to become evident during the initial aquatic microbial population explosion in response to a large amount of organic material. If the microbial population deoxygenates the water, however, that lack of oxygen imposes a limit on population growth of [[aerobic respiration|aerobic]] aquatic microbial organisms resulting in a longer term food surplus and oxygen deficit.<ref name="reid">Reid, George K. ''Ecology of Inland Waters and Estuaries'' (1961) Van Nostrand Reinhold pp. 317–320</ref>
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| A standard temperature at which BOD testing should be carried out was first proposed by the [[Royal Commission on Sewage Disposal]] in its eighth report in 1912:
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| <blockquote>" (c) An effluent in order to comply with the general standard must not contain as discharged more than 3 parts per 100,000 of suspended matter, and with its suspended matters included must not take up at 65°F (18-3°C.) more than 2.0 parts per 100,000 of dissolved oxygen in 5 days. This general standard should be prescribed either by Statute or by order of the Central Authority, and should be subject to modifications by that Authority after an interval of not less than ten years.</blockquote>
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| This was later standardised at 68°F and then 20°C. This temperature may be significantly different from the temperature of the natural environment of the water being tested. Investigators also decided to eliminate anaerobic conditions.
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| Although the Royal Commission on Sewage Disposal proposed 5 days as an adequate test period for rivers of the [[United Kingdom of Great Britain and Ireland]], longer periods were investigated for [[North America]]n rivers. Incubation periods of 1, 2, 5, 10 and 20 days were being used into the mid-20th century.<ref>Norton, John F. ''Standard Methods for the Examination of Water and Sewage'' 9th Ed. (1946) American Public Health Association p.139</ref> Keeping dissolved oxygen available at their chosen temperature, investigators found up to 99 percent of total BOD was exerted within 20 days, 90 percent within 10 days, and approximately 68 percent within 5 days.<ref>Urquhart, Leonard Church ''Civil Engineering Handbook'' 4th Ed. (1959) McGraw-Hill p. 9–40</ref> Variable microbial population shifts to [[nitrifying bacteria]] limit test [[reproducibility]] for periods greater than 5 days. The 5-day test protocol with acceptably reproducible results emphasizing carbonaceous BOD has been endorsed by the United States Environmental Protection Agency. This 5-day BOD test result may be described as the amount of oxygen required for aquatic microorganisms to stabilize decomposable organic matter under aerobic conditions.<ref>Sawyer, Clair N. & McCarty, Perry L. ''Chemistry for Sanitary Engineers'' 2nd Ed. (1967) McGraw-Hill pp. 394–399</ref> Stabilization, in this context, may be perceived in general terms as the conversion of food to living aquatic [[fauna]]. Although these fauna will continue to exert biochemical oxygen demand as they die, that tends to occur within a more stable evolved [[ecosystem]] including higher [[trophic level]]s.<ref name="reid"/>
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| == The BOD<sub>5</sub> test ==
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| There are two commonly recognized methods for the measurement of BOD.
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| === Dilution method ===
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| This standard method is recognized by [[EPA]], which is labeled Method 5210B in the Standard Methods for the Examination of Water and Wastewater<ref>Lenore S. Clesceri, Andrew D. Eaton, Eugene W. Rice (2005). Standard Methods for Examination of Water & Wastewater Method 5210B. Washington, DC: American Public Health Association, American Water Works Association, and the Water Environment Association. http://www.standardmethods.org .</ref>
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| In order to obtain BOD<sub>5</sub>, dissolved oxygen (DO) concentrations in a sample must be measured before and after the incubation period, and appropriately adjusted by the sample corresponding dilution factor. This analysis is performed using 300 ml incubation bottles in which [[buffered dilution water]] is dosed with seed microorganisms and stored for 5 days in the dark room at 20°C to prevent DO production via photosynthesis. In addition to the various dilutions of BOD samples, this procedure requires dilution water blanks, [[glucose glutamic acid]] (GGA) controls, and seed controls. The dilution water blank is used to confirm the quality of the dilution water that is used to dilute the other samples. This is necessary because impurities in the dilution water may cause significant alterations in the results. The GGA control is a standardized solution to determine the quality of the seed, where its recommended BOD<sub>5</sub> concentration is 198 mg/l ± 30.5 mg/l.
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| For measurement of '''carbonaceous BOD''' (cBOD), a nitrification inhibitor is added after the dilution water has been added to the sample. The inhibitor hinders the [[oxidation]] of ammonia nitrogen, which supplies the nitrogenous BOD (nBOD). When performing the BOD<sub>5</sub> test, it is conventional practice to measure only cBOD because nitrogenous demand does not reflect the oxygen demand from organic matter. This is because nBOD is generated by the breakdown of proteins, whereas cBOD is produced by the breakdown of organic molecules.
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| BOD<sub>5</sub> is calculated by:
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| :<math> Unseeded: BOD_5 = \frac{(D_0 - D_5)}{P}</math>
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| :<math>Seeded: BOD_5 = \frac{(D_0 - D_5) - (B_0 - B_5)f}{P}</math>
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| where:
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| :<math> D_0</math> is the dissolved oxygen (DO) of the diluted solution after preparation (mg/l)
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| :<math> D_5</math> is the DO of the diluted solution after 5 day incubation (mg/l)
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| :<math> P</math> is the decimal dilution factor
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| :<math> B_0</math> is the DO of diluted seed sample after preparation (mg/l)
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| :<math> B_5</math> is the DO of diluted seed sample after 5 day incubation (mg/)
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| :<math> f</math> is the ratio of seed volume in dilution solution to seed volume in BOD test on seed
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| === Manometric method ===
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| This method is limited to the measurement of the oxygen consumption due only to carbonaceous oxidation. [[Ammonia]] oxidation is inhibited.
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| The sample is kept in a sealed container fitted with a [[pressure sensor]]. A substance that absorbs [[carbon dioxide]] (typically [[lithium hydroxide]]) is added in the container above the sample level. The sample is stored in conditions identical to the dilution method. Oxygen is consumed and, as ammonia oxidation is inhibited, carbon dioxide is released. The total amount of gas, and thus the pressure, decreases because carbon dioxide is absorbed. From the drop of pressure, the sensor electronics computes and displays the consumed quantity of oxygen.
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| The main advantages of this method compared to the dilution method are:
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| * simplicity: no dilution of sample required, no seeding, no blank sample.
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| * direct reading of BOD value.
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| * continuous display of BOD value at the current incubation time.
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| == Dissolved oxygen probes: Membrane and luminescence ==
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| Since the publication of a simple, accurate and direct dissolved oxygen analytical procedure by Winkler,<ref>Winkler, L. W. (1888). "Die zur Bestimmung des in Wasser gelösten Sauerstoffes " Berichte der Deutschen Chemischen Gesellschaft 21(2): 2843–2854.</ref> the analysis of dissolved oxygen levels for water has been key to the determination of surface water purity and ecological wellness. The Winkler method is still one of only two analytical techniques used to calibrate oxygen electrode meters; the other procedure is based on oxygen solubility at saturation as per [[Henry's law]]. Though many researchers have refined the Winkler analysis to dissolved oxygen levels in the low PPB range, the method does not lend itself to automation.
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| The development of an analytical instrument that utilizes the reduction-oxidation (redox) chemistry of oxygen in the presence of dissimilar metal electrodes was introduced during the 1950s.<ref>Kemula, W. and S. Siekierski (1950). "Polarometric determination of oxygen." Collect. Czech. Chem. Commun. 15: 1069–75.</ref> This redox electrode utilized an oxygen-permeable membrane to allow the diffusion of the gas into an electrochemical cell and its concentration determined by polarographic or galvanic electrodes. This analytical method is sensitive and accurate to down to levels of ± 0.1 mg/l dissolved oxygen. Calibration of the redox electrode of this membrane electrode still requires the use of the Henry's law table or the [[Winkler test for dissolved oxygen]].
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| During the last two decades, a new form of electrode was developed based on the luminescence emission of a photo active chemical compound and the quenching of that emission by oxygen. This quenching photophysics mechanism is described by the Stern–Volmer equation for dissolved oxygen in a solution:<ref>Garcia-Fresnadillo, D., M. D. Marazuela, et al. (1999). "Luminescent Nafion Membranes Dyed with Ruthenium(II) Complexes as Sensing Materials for Dissolved Oxygen." Langmuir 15(19): 6451–6459.</ref>
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| :<math>I_0/I~=~1~+~K_{SV}~[O_2]</math>
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| :<math>I~=~Luminescence~in~the~presence~of~oxygen</math>
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| :<math>I_0~=~Luminescence~in~the~absence~of~oxygen</math> | |
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| :<math>K_{SV}~=~Stern-Volmer~constant~for~oxygen~quenching</math>
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| :<math>[O_2]~=~Dissolved~oxygen~concentration</math>
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| The determination of oxygen concentration by luminescence quenching has a linear response over a broad range of oxygen concentrations and has excellent accuracy and reproducibility.<ref>Titze, J., H. Walter, et al. (2008). "Evaluation of a new optical sensor for measuring dissolved oxygen by comparison with standard analytical methods." Monatsschr. Brauwiss.(Mar./Apr.): 66-80.</ref>
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| There are several recognized EPA methods for the measurement of dissolved oxygen for BOD, including the following methods:
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| *Standard Methods for the Examination of Water and Wastewater, Method 4500 O<ref>Lenore S. Clescerl, Andrew D. Eaton, Eugene W. Rice (2005). Standard Methods for Examination of Water & Wastewater (21st ed.). Washington, DC: American Public Health Association, American Water Works Association, and the Water Environment Association ISBN 0-87553-047-8 Also available by online subscription at http://www.standardmethods.org</ref>
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| *In-Situ Inc. Method 1003-8-2009 Biochemical Oxygen Demand (BOD) Measurement by Optical Probe.<ref>In-Situ Inc. Method 1002-8-2009 Dissolved Oxygen Measurement by Optical Probe, In-Situ Inc., 221 E Lincoln Ave., Ft. Collins, CO 80524 http://www.in-situ.com/RDO_EPA_Approval</ref>
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| == Test Limitations ==
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| The test method involves variables limiting reproducibility. Tests normally show observations varying plus or minus ten to twenty percent around the mean.<ref name="Hammer">{{cite book | author=Hammer, Mark J. | title=Water and Waste-Water Technology | year=1975 |publisher=John Wiley & Sons | isbn=0-471-34726-4}}</ref>{{rp|82}}
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| === Toxicity ===
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| Some wastes contain chemicals capable of suppressing microbiological growth or activity. Potential sources include industrial wastes, [[antibiotic]]s in pharmaceutical or [[medical waste]]s, sanitizers in food processing or commercial cleaning facilities, [[Water chlorination|chlorination]] disinfection used following conventional sewage treatment, and odor-control formulations used in sanitary waste holding tanks in passenger vehicles or portable toilets. Suppression of the microbial community oxidizing the waste will lower the test result.<ref name="Hammer" />{{rp|85}}
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| === Appropriate Microbial Population ===
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| The test relies upon a microbial ecosystem with enzymes capable of oxidizing the available organic material. Some waste waters, such as those from biological secondary [[sewage treatment]], will already contain a large population of microorganisms acclimated to the water being tested. An appreciable portion of the waste may be utilized during the holding period prior to commencement of the test procedure. On the other hand, organic wastes from industrial sources may require specialized enzymes. Microbial populations from standard seed sources may take some time to produce those enzymes. A specialized seed culture may be appropriate to reflect conditions of an evolved ecosystem in the receiving waters.<ref name="Hammer" />{{rp|85–87}}
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| == History of the use of BOD ==
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| The ''[[Royal Commission on River Pollution]]'', which was established in 1865 and the formation of the ''[[Royal Commission on Sewage Disposal]]'' in 1898 led to the selection in 1908 of BOD<sub>5</sub> as the definitive test for organic [[Water pollution|pollution]] of rivers. Five days was chosen as an appropriate test period because this is supposedly the longest time that river water takes to travel from source to [[estuary]] in the [[U.K.]]. In its sixth report the Royal Commission recommended that the standard set should be 15 parts by weight per million of water.<ref name="Royal">[http://ia700404.us.archive.org/35/items/cu31924003641929/cu31924003641929.pdf FINAL REPORT OF THE COMMISSIONERS APPOINTED TO INQUIRE AND REPORT WHAT METHODS OF Treating and Disposing of Sewage. 1912 ]</ref> However in the Ninth report the commission had revised the recommended standard : <blockquote>" An effluent taking up 2-0 parts dissolved oxygen per 100,000 would be found by a
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| simple calculation to require dilution with at least 8 volumes of river water taking up 0.2 part if the resulting mixture was not to take up more than 0.4 part. Our experience indicated that in a large majority of cases the volume of river water would exceed 8 times the volume of effluent, and that the figure of 2-0 parts dissolved oxygen per 100,000, which had been shown to be practicable, would be a safe figure to adopt for the purposes of a general standard, taken in conjunction with the condition that the effluent should not contain more than 3-0 parts per 100,000 of suspended solids.</blockquote> <ref name="Royal"/> This was the cornerstone 20:30 (BOD:Suspended Solids) + full [[nitrification]] standard which was used as a yardstick in the U.K. up to the 1970s for sewage works [[effluent]] quality.
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| The [[United States]] includes BOD effluent limitations in its [[sewage treatment|secondary treatment]] regulations. Secondary sewage treatment is generally expected to remove 85 percent of the BOD measured in sewage and produce effluent BOD concentrations with a 30-day average of less than 30 mg/L and a 7-day average of less than 45 mg/L. The regulations also describe "treatment equivalent to secondary treatment" as removing 65 percent of the BOD and producing effluent BOD concentrations with a 30-day average less than 45 mg/L and a 7-day average less than 65 mg/L.<ref>U.S. Environmental Protection Agency (EPA). Washington, DC. [http://www.access.gpo.gov/nara/cfr/waisidx_07/40cfr133_07.html "Secondary Treatment Regulation."] ''Code of Federal Regulations,'' 40 CFR Part 133.</ref>
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| ==Typical BOD values==
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| Most pristine rivers will have a 5-day carbonaceous BOD below 1 mg/L. Moderately [[pollution|polluted]] rivers may have a BOD value in the range of 2 to 8 mg/L. Municipal [[sewage]] that is efficiently treated by a [[sewage treatment|three-stage process]] would have a value of about 20 mg/L or less. Untreated sewage varies, but averages around 600 mg/L in [[Europe]] and as low as 200 mg/L in the [[U.S.]], or where there is severe [[groundwater]] or [[surface water]] [[Infiltration/Inflow]]. (The generally lower values in the U.S. derive from the much greater water use per capita than in other parts of the world.)<ref name="Sawyer" />
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| == BOD Biosensor ==
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| An alternative to measure BOD is the development of biosensors, which are devices for the detection of an analyte that combines a biological component with a physicochemical detector component. Biosensors can be used to indirectly measure BOD via a fast (usually <30 min) to be determined BOD substitute and a corresponding calibration curve method (pioneered by Karube et al., 1977). Consequently, biosensors are now commercially available, but they do have several limitations such as their high maintenance costs, limited run lengths due to the need for reactivation, and the inability to respond to changing quality characteristics as would normally occur in wastewater treatment streams; e.g. diffusion processes of the biodegradable organic matter into the membrane and different responses by different microbial species which lead to problems with the reproducibility of result (Praet et al., 1995). Another important limitation is the uncertainty associated with the calibration function for translating the BOD substitute into the real BOD (Rustum ''et al.'', 2008).
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| ==BOD Software sensor==
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| Rustum et al. (2008) proposed the use the KSOM to develop intelligent models for making rapid inferences about BOD using other easy to measure water quality parameters, which, unlike BOD, can be obtained directly and reliably using on-line hardware sensors. This will make the use of BOD for on-line process monitoring and control a more plausible proposition. In comparison to other data-driven modeling paradigms such as multi-layer perceptrons artificial neural networks (MLP ANN) and classical multi-variate regression analysis, the KSOM is not negatively affected by missing data. Moreover, time sequencing of data is not a problem when compared to classical time series analysis.
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| == See also ==
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| * [[Chemical oxygen demand]]
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| * [[Theoretical oxygen demand]]
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| * [[Carbonaceous biochemical oxygen demand]]
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| * [[Wastewater quality indicators]] discusses both '''BOD''' and [[Chemical oxygen demand|COD]] as indicators of wastewater quality.
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| ==Further References ==
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| {{refbegin}}
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| * {{cite book | author=Lenore S. Clescerl, Arnold E. Greenberg, Andrew D. Eaton | title=Standard Methods for Examination of Water & Wastewater | edition=20th | year=1999 |publisher=American Public Health Association | location=Washington, DC | isbn=0-87553-235-7}} Also available by online subscription at [http://www.standardmethods.org www.standardmethods.org]
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| {{refend}}
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| * Rustum R., A. J. Adeloye, and M. Scholz (2008) Applying Kohonen Self-organizing Map as a Software Sensor to Predict the Biochemical Oxygen Demand, Water Environment Research, 80 (1), 32 – 40.
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| ==References==
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| {{reflist}}
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| == External links ==
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| * [http://www.boddoctor.com/wiki/index.php?title=Main_Page BOD Doctor] - a troubleshooting wiki for this problematic test
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| {{DEFAULTSORT:Biochemical Oxygen Demand}}
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| [[Category:Anaerobic digestion]]
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| [[Category:Environmental science]]
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| [[Category:Water quality indicators]]
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