Only chemically digest able matter can be determined by the cod test. Additional analyses of water samples for chemical oxygen. A cod test can be used to easily quantify the amount of organics in water. In environmental chemistry, the chemical oxygen demand cod test is commonly used to indirectly measure the amount of organic compounds in water. Chemical oxygen demand cod is the amount of oxygen necessary to oxidize all of the organic carbon completely to co2 and h2o. Cod test the chemical oxygen demand cod test uses a strong chemical oxidant in an acid solution and heat to oxidize organic carbon to co 2 and h 2 o. Determination of chemical oxygen demand of wastewater. The quantity of organic matter or the demand of oxygen is calculated by determining how much oxidizing chemical was consumed during the test. Chemical oxygen demand can be used to estimate biochemical oxygen demand and determine the dilutions needed for the bod fiveday test. Cod often is used as a measurement of pollutants in wastewater and natural waters. An aliquot of 10 ml sample was transferred into a test tube. Chemical oxygen demand cod is the total amount of oxidisable organics biodegradable and nonbiodegradable and both dissolved and particulate, measured by the amount of oxygen. Biochemical oxygen demand bod is the amount of dissolved oxygen needed i. Prepare a new blank when the absorbance has changed by approximately 0.
It can, however, pose an indirect threat to living organisms by reducing the level of dissolved oxygen. Corrosionpedia what is a biochemical oxygen demand bod. At the boiling point, the solubility of oxygen is zero. Samples with higher cod concentrations may be processed by appropriate dilution of the sample. Biochemical oxygen demand bod testing and measurement in. How to reduce chemical oxygen demand cod in wastewater. Test method b micro cod by sealed digestion and spectrometry. The bod electrode method is suitable for determining the bod of water and wastewater.
Chemical oxygen demand analysis of anaerobic digester. How to reduce chemical oxygen demand cod in wastewater written by aos treatment solutions on november 1, 2018. The bod determination is an empirical test in which standardised laboratory procedures are used to determine the relative oxygen requirements of wastewaters, effluents and polluted. The chemical oxygen demand cod test is commonly used to indirectly measure the amount of organic compounds in water.
This oxygen transaction is the source of the tests name. The cod test is often used to monitor water treatment plant efficiency. Biological oxygen demand 28 ps2829a the bod 5 test is used to measure the potential of wastewater and other waters to deplete the oxygen level of receiving waters. Chemical oxygen demand cod is used to determine the quantity of pollution in water after wastewater treatment. The determination of chemical oxygen demand in waters and effluents 2007 methods for the examination of waters and associated materials this booklet contains guidance on methods for the determination of chemical oxygen demand using potassium dichromate solution, and notes for the disposal and recovery of selected reagents. Dilutions are determined by estimating the amount of biochemical oxygen demand bod in the sample using the measured chemical oxygen demand cod or another suitable surrogate. The amperometric determination of chemical oxygen demand cod reported by quan xies group electrochem commun 9. Recent advances in oxygen demand research haveexpanded the number of options available for testing. Chemical oxygen demand testing, via the dichromate or mercuryfree method, is an efficient alternative or complementary method to the bod test for wastewater monitoring. This test is based on the fact that a strong oxidizing agent, under acidic conditions, can fully oxidize almost any organic compound to carbon dioxide. The determination of chemical oxygen demand in waters and effluents 2007 methods for the examination of waters and associated materials this booklet contains guidance on methods for the determination of chemical oxygen demand. The quantity of oxidant consumed is expressed in terms of its oxygen equivalence. Water for cod chemical oxygen demand application water. The chemical oxygen demand cod test is an empirical test that is a measure of the potential oxygen consumption of waste waters.
It is a significant parameter to determinate water characteristic. Standard test methods for chemical oxygen demand dichromate. Allow the brown precipitate to settle out to the bottom. Chemical oxygen demand in the pulp and paper industry the pulp and paper industry uses large quantities of water at nearly every stage in the manufacturing process. It is a measurement of the oxygen equivalent of the materials present in the wastewater that are subject to oxidation. Pdf on feb 15, 2019, haleem khalaf and others published study of chemical oxygen demand. Put the blank vial that is used in the test procedure into the instrument and record the absorbance value.
A bod test is often used in conjunction with a chemical oxygen demand cod test to provide an indication of the oxygen demand, usually in a waste stream, effluent or surface water such as a river. The cod test is often used in conjunction with the bod test to estimate the amount of nonbiodegradable organic material in a wastewater. Chemical oxygen demand in the pulp and paper industry. Biochemical oxygen demand and chemical oxygen demand. Aug 15, 2019 biochemical oxygen demand bod is a chemical procedure for determining the amount of 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. Estimation of chemical oxygen demand in wastewater using uv. It is based on the use of thermo orion test kits cat. The cod test has been used for a very long time as one of the components of the method that water utilities use to charge dischargers for their part of the effluent. The purpose of this technical bluebook is to 1 provide.
By statistical significance test, the results of determination were compared with those of standard methods with no significant difference at 0. The bod value is most commonly expressed in milligrams of oxygen. Biochemical oxygen demand bod and chemical oxygen demand pdf. Chemical oxygen demand cod in wastewater i real tech water. The chemistry of chemical oxygen demand chemical oxygen. Oxygen demand is an important parameter for deter mining the amount of organic pollution in water. Cod determination takes less time than the biological oxygen. The key difference between bod and cod is that the bod is the oxygen demand of microorganisms to oxidize organic matter in the water under aerobic conditions while the cod is the oxygen demand.
Cod chemical oxygen demand cod is the most popular alternative test to bod for establishing the concentration of organic matter in wastewater samples. Rugged ph and bod meter for outstanding and flexible field or laboratory water testing. Pdf study of chemical oxygen demand cod in relation to. This oxygen transaction is the source of the tests name, chemical oxygen demand. Finding excessive levels of one or more of these parameters can serve as an early warning of potential pollution problems. Its relatively quick turnaround time, simplicity and correlation to bod make it a valuable tool for those analyzing wastewater for pretreatment planning or process monitoring. Set up and use the hi9146 portable dissolved oxygen meter duration. The term also refers to a chemical procedure for determining this amount. All organic compounds may convert into carbon dioxide, water and ammonia. Chemical oxygen demand cod analysis science classes. Determination of chemical oxygen demand cod using an alternative wet chemical method free of mercury and dichromate.
Oxygen demand is a measure of the amount of oxidizable substances in a water sample that can lower do concentrations nemerow, 1974. Biochemical oxygen demand bod testing and measurement in water. Most applications of cod determine the amount of organic. Jan, 2017 chemical oxygen demand indicates the amount of oxygen required to oxidize all soluble and particulate organic substances in water under specific conditions. Determination of chemical oxygen demand of water hard and. Mihelcic encyclopedia of life support systems eolss summary biochemical oxygen demand bod is a measure of the dissolved oxygen. Mantechs pecod analyzer technology provides chemical oxygen demand cod, biochemical oxygen demand bod and natural organic matter nom results in under 15 minutes in a simplesafeeffective manner. Method of sampling and test physical and chemical for water and wastewater, part 44. Downscaling the chemical oxygen demand test article pdf available in environmental technology 35912. Other related analytical values are biochemical oxygen demand bod, total organic carbon toc, and total oxygen demand. For a soluble cod, the samples are filtered through a 0. Understanding biochemical oxygen demand test new delhi, may 1999 csmrs building, 4th floor, olof palme marg, hauz khas, new delhi 11 00 16 india tel.
Other related analytical values are biochemical oxygen demand bod, total organic carbon toc, and total oxygen demand tod. Chemical oxygen demand is a measure of the oxygen required to oxidize all organic material present into water and carbon dioxide, and thus a measure of the amount of organic material within a substance 7. The chemical oxygen demand cod is an important parameter. Chemical oxygen demand cod is the total amount of oxidisable organics biodegradable and nonbiodegradable and both dissolved and particulate, measured by the amount of oxygen in the form of oxidising agent required for the oxidation of organic matters by heating the sample in strong sulphuric acid containing potassium dichromate 14. It measures the capacity of water to consume oxygen during. A chemical oxygen demand cod test is a test that is used to measure the organic compounds in water. Hence, do analysis is a key test both in natural waters and water pollution control practice. D biochemical oxygen demand bod is the amount of 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. Higher cod levels mean a greater amount of oxidizable organic material in the sample, which will reduce dissolved oxygen. Chemical oxygen demand an overview sciencedirect topics. Bod testing biochemical oxygen demand hill laboratories.
Because oxygen demand is not a pollutant, it poses no direct threat to fish or other life. The dissolved oxygen do of the sample is measured initially after mixing the solution and again after five days for the bod 5 or after one day for the bod 1 test. Pdf determination of chemical oxygen demand cod using an. Closely related to biochemical oxygen demand bod, chemical oxygen demand.
Difference between bod and cod compare the difference. Chemical oxygen demand titrimetric, high level for saline waters analyte. Odell inorganic chemistry branch chemistry research division. Simultaneous determination of chemical oxygen demand cod. The method determines chemical oxygen demand see definitions, section 3. Colorimetric analysis works because the two chromium ions absorb in the.
Because of its unique chemical properties, the dichromate ion cr2o7. During the fiveday period of a bod test, the bacteria oxidize mainly the soluble organic matter present in the water. The chemical oxygen demand cod is a measure of water and wastewater quality. The cod test only takes a few hours to complete, giving it a major advantage over the 5day bod test. A brownish cloud will appear in the solution as an indicator of the presence of oxygen.
To determine and measure of oxygen requirement of the sample waste water through chemical oxygen demand cod process. In essence a cod test determines the amount of carbon based materials by measuring the amount of oxygen the sample will react with. Pecod chemical oxygen demand analyzer configurations mantech. Organic matter is oxidized into carbon dioxide and water in an acidic condition. Chemical oxygen demand is an aggregate property of water, and no cas. Jun 18, 20 biochemical oxygen demand measures the quantity of oxygen consumed by microorganisms during the decomposition of organic matter. Cod or chemical oxygen demand is a measurement of all compounds in the water that can be oxidized. Understanding chemical oxygen demand test new delhi, may 1999 csmrs building, 4th floor, olof palme marg, hauz khas, new delhi 11 00 16 india tel. Chemical oxygen demand is an important water quality parameter because, similar to bod, it provides an index to assess the effect discharged wastewater will have on the receiving environment. Pdf worldwide, the standard methods for the determination of the important wastewater. If there is a large quantity of organic waste in the water supply, there will also be a lot of bacteria present working to decompose this waste. The higher value of chemical oxygen demand indicates the higher organic pollution in the water sample. Biological oxygen demand bod is a measure of the oxygen used by microorganisms to decompose this waste. The science of chemical oxygen demand hach lange pdf.
A chemical oxygen demand test is used to measure the amount of organic compounds in a water sample. Test method a macro cod by reflux digestion and titration. Biochemical oxygen demand, or bod, is a chemical procedure for determining the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down. Chemical oxygen demand testing is typically performed using a strong oxidizing chemical. The test for biochemical oxygen demand bod is a bioassay procedure that measures the oxygen consumed by bacteria. Chemical oxygen demand cod vs biological oxygen demand. Chemical oxygen demand testing is a useful measure of water quality. A chemical oxygen demand cod test is used to measure the amount of organic compounds in a water sample. The determination of chemical oxygen demand in waters. Methods chemical oxygen demand, method 5220 d, closed reflux, colorimetric method. Biochemical oxygen demand measures the quantity of oxygen consumed by microorganisms during the decomposition of organic matter.
The determination of chemical oxygen demand in waters and. Running the biochemical oxygen demand bod test ebs. How does one measure the cod of wastewater in the presence. In environmental chemistry, the chemical oxygen demand cod is an indicative measure of the amount of oxygen that can be consumed by reactions in a measured solution. The test for biochemical oxygen demand bod is a bioassay procedure that measures the oxygen. There are three widelyused methods of measuring oxygen demand. It is most commonly used to measure the amounts of organic compounds in surface water, such as rivers and lakes, and wastewater. Chemical oxygen demand cod is a critical waste treatment measurement in everything from municipal systems to food manufacturing waste streams. Mar 03, 2017 photoelectrochemical chemical oxygen demand pecod analyzer system configurations.
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