The chemical oxygen demand cod is a parameter used widely to determine the amounts of. Water for cod chemical oxygen demand application water. By means of a funnel, transfer the measurement solution into the graduated measuring flask. The standard method for indirect measurement of the amount of pollution that cannot be oxidized biologically in a sample of water. It is considered in the planning and controlling of treatment, as well as assessing its efficiency, thus forming the basis for the calculation of waste water charges. Expressed as parts per million, the higher the cod of the sample. Estimation of chemical oxygen demand in wastewater using uv. Other than that, they are really the identical process.
Determination of chemical oxygen demand of water hard. A measure of the oxygen equivalent of the organic matter content of a sample that is susceptible to oxidation by a strong chemical oxidant, usually reported as cod as mg o2l. Where the concentration is greater than 400mgl, dilute the sample. Biochemical oxygen demand bod is the amount of oxygen, expressed in mgl or parts per million ppm, that bacteria take from water when they oxidize organic matter. Nearinfrared spectrometry, wastewater, biological oxygen demand, chemical oxygen demand. It can be expressed in milligrams per liter mgl also referred to part per million ppm which indicates the mass of oxygen consumed per liter solution. Chemical oxygen demand cod is a measure of the ability of chemical reactions to oxidize matter in an aqueous system. It is a significant parameter to determinate water characteristic.
The invention relates to a measuring method for determining the content of a chemical element, particularly carbon andor nitrogen andor phosphorus, or of another water quality parameter, particularly the total oxygen demand, tod, in freshwater or wastewater, wherein a sample of the freshwater or wastewater is fed to a reaction in a carrier gas flow containing oxygen, and the. The chemical oxygen demand, cod, of water as determined by this dichromate method can be considered as an approximate measure of the theoretical oxygen demand, i. Pdf study of chemical oxygen demand cod in relation to. This test is based on the fact that a strong oxidizing agent, under acidic conditions, can fully oxidize almost any organic compound to. The cod test is often used to monitor water treatment plant efficiency. The chemical oxygen demand cod is a measure of water and wastewater quality. Estimation of chemical oxygen demand in wastewater using. Chemical oxygen demand cod is a second method of estimating how much oxygen would be depleted from a body of receiving water as a result of bacterial action. A method for testing water quality by measuring the amount of organic compounds, or pollution, in a sample of water taken from a lake or river. Chemical oxygen demand testing is used to determine the amount of oxidation that will occur and the amount of organic matter in a water sample.
The carbohydrates cellulose, starch, sugars, proteins, petroleum hydrocarbons and other materials that comprise organic matter get into water from natural sources and from pollution. The chemical oxygen demand cod indicates the amount of oxygen which is needed for the oxidation of all organic substances in water and is thus an important indicator for water analysis. 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. A novel spectrophotometric assay method using homemade reagents that can be used to determine the chemical oxygen demand cod in real wastewater was described in the study of jun li et al. In environmental chemistry, the chemical oxygen demand cod is an indicative measure of. Measurements that include nitrogenous demand generally are not useful for assessing the oxygen demand associated with organic material. The most common application of cod is in quantifying the amount of oxidizable pollutants found in surface water or wastewater. Biological oxygen demand bod5 is the amount of oxygen. The determination of chemical oxygen demand in waters and. Chemical oxygen demand testing is also used to determine the amount of inorganic chemicals in a sample. Method specified is applicable to water with a value between 30 mgl and 700 mgl. Jun 18, 20 biochemical oxygen demand measures the quantity of oxygen consumed by microorganisms during the decomposition of organic matter. Benchmark limits developed by epa the benchmarks are the.
Chemical oxygen demand measure of oxygen equivalent of the organic matter content of the sample that is susceptible to oxidation by a strong chemical. The bod value is most commonly expressed in milligrams of oxygen consumed per litre of sample during 5 days. For domestic and some industrial wastewater cod is about 2. This oxygen transaction is the source of the tests name, chemical oxygen demand. Epa on march 31, 2005 for wastewater compliance monitoring. Chemical oxygen demand cod is the amount of oxygen consumed by the organic compounds and inorganic matter which were oxidized in water. All organic compounds may convert into carbon dioxide, water and ammonia. Chemical oxygen demand testing is a useful measure of water quality. It can, however, pose an indirect threat to living organisms by reducing the level of dissolved oxygen. Simultaneous determination of chemical oxygen demand. Laboratory experiments are conducted for investigating the effect of treatment time, adsorbent dose, ph of the media, initial cod concentration, agitation speed and particle size of adsorbents on the cod reduction from the domestic. Chemical oxygen demand cod reduction in domestic wastewater. Biochemical oxygen demand definition of biochemical. Biological oxygen demand definition is biochemical oxygen demand.
Biochemical oxygen demand definition and meaning collins. Definition of chemical oxygen demand in the dictionary. Biochemical oxygen demand definition of biochemical oxygen. But we cannot get a clear picture of all type of organic substances from the bod values alone whereas cod values gives a better result. The term also refers to a chemical procedure for determining this amount. Chemical oxygen demand cod is the amount of oxygen necessary to oxidize all of the organic carbon completely to co2 and h2o. Finding excessive levels of one or more of these parameters can serve as an early warning of potential pollution problems. Biochemical oxygen demand bod and concentration of ammonium in rivers. There are three widelyused methods of measuring oxygen demand. Biological oxygen demand definition of biological oxygen. A cod test can be used to easily quantify the amount of organics in water. Biochemical oxygen demand bod and chemical oxygen demand pdf.
Chemical oxygen demand titrimetric, high level for saline waters analyte. The chemical oxygen demand cod test is commonly used to indirectly measure the amount of organic compounds in water. Chemical oxygen demand cod is used as a discharge standard parameter in wastewater treatment plant design, environmental modelling and many other applications. Typically this measurement is used to monitor and control oxygenconsuming pollutants, both inorganic and organic, in domestic and industrial wastewaters. Study of chemical oxygen demand cod in relation to biochemical oxygen demand bod in tigris river at missan governorate. The quantity of organic matter or the demand of oxygen is calculated by determining how much oxidizing chemical was consumed during the test. Because of its unique chemical properties, the dichromate ion cr2o7. The biochemical oxygen demand bod determination is an empirical test. Bod measures the amount of oxygen required or consumed for.
Jun 06, 2014 the chemical oxygen demand cod is a parameter used widely to determine the amounts of organic pollutants in wastewater. Chloride interference is an important problem of cod measurement for wastewaters containing low organic matter and high chloride concentrations. If the value exceeds 700 mgl, the water sample is diluted. Pdf determination of chemical oxygen demand cod using. Chemical oxygen demand is the amount of oxygen needed to oxidize the organic matter present in water. Chemical oxygen demand is an important water quality parameter as like bod.
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. 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. View chemical oxygen demand research papers on academia. Worldwide, the standard methods for the determination of the important wastewater parameter chemical oxygen demand cod are still based on the use of the hazardous chemicals, mercury sulfate and. Chemical oxygen demand cod vs biological oxygen demand. The test is performed by adding the oxidizing solution to a sample, boiling the mixture. The standard method for indirect measurement of the amount of pollution that cannot be oxidized biologically in a sample. Chemical oxigen demand 11 of 8 interpretation of results the cod of the given sample of water 288 mgl. Determination of chemical oxygen demand of water hard and. Jun 10, 2006 the potential of fly ash, brick kiln ash and commercial activated carbon is determined for the reduction of chemical oxygen demand cod from domestic wastewater. The mercury in the cod vials is derived from mercuric sulfate. The degree to which the test results approach the theoretical. Biochemical oxygen demand bod is the amount of dissolved oxygen needed i.
A measure of the oxygen equivalent of the organic matter. Chemical oxygen demand testing is typically performed using a strong oxidizing chemical. Worldwide, the standard methods for the determination of the important wastewater parameter chemical oxygen demand cod are still based on the. The result of a chemical oxygen demand test indicates the amount of waterdissolved oxygen expressed as parts per million or milligrams per liter of water. Chemical oxygen demand an overview sciencedirect topics. Determination of biochemical oxygen demand bod omnilab. 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. With water pollution becoming a serious issue, water quality assessment and pollutant control have become global imperatives 1,2. Cod measurements are commonly made on samples of waste waters or of natural waters contaminated by domestic or industrial wastes. Definition what does chemical oxygen demand cod mean. Why are the vials without mercury not epa approved. Information and translations of chemical oxygen demand in the most comprehensive dictionary definitions resource on the web. Chemical oxygen demand does not differentiate between biologically available and inert organic matter, and it is a measure of the total quantity of oxygen required to oxidize all organic material into carbon dioxide and water. Simultaneous determination of chemical oxygen demand cod.
Laboratory experiments are conducted for investigating the effect of treatment time, adsorbent dose, ph of the media, initial cod concentration, agitation speed and particle size of. The potential of fly ash, brick kiln ash and commercial activated carbon is determined for the reduction of chemical oxygen demand cod from domestic wastewater. Chemical oxygen demand test uses a strong chemical oxidant in an acid solution and heat to oxidize organic carbon to co2 and h2o. The quantity of oxidant consumed is expressed in terms of its oxygen equivalence. Jan, 2017 chemical oxygen demand indicates the amount of oxygen required to oxidize all soluble and particulate organic substances in water under specific conditions. Most applications of cod determine the amount of organic pollutants found in surface water e. While the bod test is performed by using a population of bacteria and other microorganisms to attempt to duplicate what would happen in a natural stream over a period of five days. Biochemical oxygen demand measures the quantity of oxygen consumed by microorganisms during the decomposition of organic matter. 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.
In environmental chemistry, the chemical oxygen demand is an indicative measure of the amount of oxygen that can be consumed by reactions in a measured solution. Chemical oxygen demand thermo orion method codl00 and codh00 revision 5, 03252005 accepted by u. Higher cod levels mean a greater amount of oxidizable organic material in the sample, which will reduce dissolved oxygen do levels. The level of concern is a concentration at which a storm water discharge could potentially impair, or contribute to impairing, water quality or affect human health from ingestion of water of fish. Pdf determination of chemical oxygen demand cod using an. Because oxygen demand is not a pollutant, it poses no direct threat to fish or other life. Biochemical oxygen demand and chemical oxygen demand. Organic matter is oxidized into carbon dioxide and water in an acidic condition. 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. The cod is defined as the number of oxygen equivalents consumed in the oxidation of organic compounds by strong oxidizing agents, such as dichromates and permanganates, and is indicative of the amount of organic pollutants. In essence a cod test determines the amount of carbon based materials by measuring the amount of oxygen the sample will react with. The interference from nitrogenous demand can now be prevented by an inhibitory chemical.
Rapid determination of the chemical oxygen demand of water. Chemical oxygen demand cod vs biological oxygen demand bod. It is most commonly used to measure the amounts of organic compounds in surface water, such as rivers and lakes, and wastewater. In recent years, increasing attention has been devoted to the removal of organic contaminants from wastewater. The results are expressed in terms of oxygen so that they can be compared directly to the results of biochemical oxygen demand bod testing.
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. Special pages permanent link page information wikidata item cite this page. The importance of biochemical oxygen demand bod aqualytic. A chemical oxygen demand cod test is a test that is used to measure the organic compounds in water. Chemical oxygen demand cod reagents reagecons product offering includes reagents for the two accepted methods for measuring cod at concentrations less than 400mgl. It binds the chlorides in the sample which reduces interferences. Cod measures the amount of oxygen consumed by contaminants in a solution of boiling potassium dichromate. 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. Chemical oxygen demand cod in wastewater i real tech water. Chemical oxygen demand cod is a measure of the capacity of water to consume oxygen during the decomposition of organic matter and the oxidation of inorganic chemicals such as ammonia and nitrite. Bodn biochemical oxygen demand after n days is defined in detail in german standard.