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 an overview sciencedirect topics. Cod measures the amount of oxygen consumed by contaminants in a solution of boiling potassium dichromate. Determination of chemical oxygen demand of water hard and. The test is performed by adding the oxidizing solution to a sample, boiling the mixture. The results are expressed in terms of oxygen so that they can be compared directly to the results of biochemical oxygen demand bod testing. Definition of chemical oxygen demand in the dictionary. Biochemical oxygen demand definition of biochemical. 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.
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. The quantity of oxidant consumed is expressed in terms of its oxygen equivalence. Because, biodegradable and nonbiodegradable substances are includes in cod values. 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. A cod test can be used to easily quantify the amount of organics 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.
By means of a funnel, transfer the measurement solution into the graduated measuring flask. A measure of the oxygen equivalent of the organic matter. 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. Where the concentration is greater than 400mgl, dilute the sample. 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. 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. 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 used as a discharge standard parameter in wastewater treatment plant design, environmental modelling and many other applications. Chemical oxygen demand cod in wastewater i real tech water. 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. The determination of chemical oxygen demand in waters and. Because of its unique chemical properties, the dichromate ion cr2o7. Water for cod chemical oxygen demand application water.
Bod measures the amount of oxygen required or consumed for. 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 importance of biochemical oxygen demand bod aqualytic. 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. Determination of biochemical oxygen demand bod omnilab. Nearinfrared spectrometry, wastewater, biological oxygen demand, chemical oxygen demand. Expressed as parts per million, the higher the cod of the sample. Chemical oxygen demand cod is a measure of the ability of chemical reactions to oxidize matter in an aqueous system. 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. Typically this measurement is used to monitor and control oxygenconsuming pollutants, both inorganic and organic, in domestic and industrial wastewaters. 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. Finding excessive levels of one or more of these parameters can serve as an early warning of potential pollution problems. Chemical oxygen demand measure of oxygen equivalent of the organic matter content of the sample that is susceptible to oxidation by a strong chemical. 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.
There are three widelyused methods of measuring oxygen demand. Jan, 2017 chemical oxygen demand indicates the amount of oxygen required to oxidize all soluble and particulate organic substances in water under specific conditions. The interference from nitrogenous demand can now be prevented by an inhibitory chemical. In recent years, increasing attention has been devoted to the removal of organic contaminants from wastewater. Most applications of cod determine the amount of organic pollutants found in surface water e. 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. 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. If the value exceeds 700 mgl, the water sample is diluted.
Simultaneous determination of chemical oxygen demand. 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. 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 testing is also used to determine the amount of inorganic chemicals in a sample. The mercury in the cod vials is derived from mercuric sulfate. The benchmarks are the pollutant concentrations above which epa determined represent a level of concern. The chemical oxygen demand cod is a measure of water and wastewater quality. Benchmark limits developed by epa the benchmarks are the. With water pollution becoming a serious issue, water quality assessment and pollutant control have become global imperatives 1,2.
This test is based on the fact that a strong oxidizing agent, under acidic conditions, can fully oxidize almost any organic compound to. Biological oxygen demand definition is biochemical oxygen demand. The standard method for indirect measurement of the amount of pollution that cannot be oxidized biologically in a sample. 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. Method specified is applicable to water with a value between 30 mgl and 700 mgl. Special pages permanent link page information wikidata item cite this page. The bod value is most commonly expressed in milligrams of oxygen consumed per litre of sample during 5 days. View chemical oxygen demand research papers on academia. Other than that, they are really the identical process. Biochemical oxygen demand definition and meaning collins.
Biological oxygen demand definition of biological oxygen. 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. Information and translations of chemical oxygen demand in the most comprehensive dictionary definitions resource on the web. A chemical oxygen demand cod test is a test that is used to measure the organic compounds in water. Why are the vials without mercury not epa approved. Chemical oxygen demand cod vs biological oxygen demand bod. 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. Biochemical oxygen demand bod is the amount of dissolved oxygen needed i. It is a significant parameter to determinate water characteristic. Pdf determination of chemical oxygen demand cod using. 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. 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. Epa on march 31, 2005 for wastewater compliance monitoring.
It can, however, pose an indirect threat to living organisms by reducing the level of dissolved oxygen. Pdf determination of chemical oxygen demand cod using an. The degree to which the test results approach the theoretical. Definition what does chemical oxygen demand cod mean. Chemical oxygen demand thermo orion method codl00 and codh00 revision 5, 03252005 accepted by u. 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. Determination of chemical oxygen demand of water hard. Estimation of chemical oxygen demand in wastewater using uv. Biochemical oxygen demand bod and concentration of ammonium in rivers. Chemical oxygen demand titrimetric, high level for saline waters analyte.
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. Simultaneous determination of chemical oxygen demand cod. All organic compounds may convert into carbon dioxide, water and ammonia. This oxygen transaction is the source of the tests name, chemical oxygen demand. Because oxygen demand is not a pollutant, it poses no direct threat to fish or other life. Chemical oxygen demand testing is typically performed using a strong oxidizing chemical. The chemical oxygen demand cod is a parameter used widely to determine the amounts of. Jun 18, 20 biochemical oxygen demand measures the quantity of oxygen consumed by microorganisms during the decomposition of organic matter.
Biochemical oxygen demand measures the quantity of oxygen consumed by microorganisms during the decomposition of organic matter. Chemical oxygen demand cod vs biological oxygen demand. The most common application of cod is in quantifying the amount of oxidizable pollutants found in surface water or wastewater. Organic matter is oxidized into carbon dioxide and water in an acidic condition. The standard method for indirect measurement of the amount of pollution that cannot be oxidized biologically in a sample of water. 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. Measurements that include nitrogenous demand generally are not useful for assessing the oxygen demand associated with organic material. 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. Biological oxygen demand bod5 is the amount of oxygen.
The carbohydrates cellulose, starch, sugars, proteins, petroleum hydrocarbons and other materials that comprise organic matter get into water from natural sources and from pollution. Chemical oxygen demand is the amount of oxygen needed to oxidize the organic matter present in water. Higher cod levels mean a greater amount of oxidizable organic material in the sample, which will reduce dissolved oxygen do levels. The biochemical oxygen demand bod determination is an empirical test. In essence a cod test determines the amount of carbon based materials by measuring the amount of oxygen the sample will react with.
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. Cod measurements are commonly made on samples of waste waters or of natural waters contaminated by domestic or industrial wastes. Chemical oxygen demand test uses a strong chemical oxidant in an acid solution and heat to oxidize organic carbon to co2 and h2o. Chemical oxygen demand testing is a useful measure of water quality. 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. Chloride interference is an important problem of cod measurement for wastewaters containing low organic matter and high chloride concentrations. Chemical oxygen demand cod is the amount of oxygen consumed by the organic compounds and inorganic matter which were oxidized in water. Chemical oxygen demand cod reduction in domestic wastewater. 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. 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 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. Rapid determination of the chemical oxygen demand of water. Estimation of chemical oxygen demand in wastewater using. The cod test is often used to monitor water treatment plant efficiency. It binds the chlorides in the sample which reduces interferences. Only vials that contain mercuric sulfate are epa approved to ensure this interferent does not affect the sample results. Chemical oxygen demand cod is the amount of oxygen necessary to oxidize all of the organic carbon completely to co2 and h2o.
The term also refers to a chemical procedure for determining this amount. Pdf study of chemical oxygen demand cod in relation to. Jun 06, 2014 the chemical oxygen demand cod is a parameter used widely to determine the amounts of organic pollutants in wastewater. 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. Biochemical oxygen demand bod and chemical oxygen demand pdf. Study of chemical oxygen demand cod in relation to biochemical oxygen demand bod in tigris river at missan governorate. Biochemical oxygen demand and chemical oxygen demand. The chemical oxygen demand cod test is commonly used to indirectly measure the amount of organic compounds in water. Chemical oxigen demand 11 of 8 interpretation of results the cod of the given sample of water 288 mgl. Bodn biochemical oxygen demand after n days is defined in detail in german standard. Worldwide, the standard methods for the determination of the important wastewater parameter chemical oxygen demand cod are still based on the. Biochemical oxygen demand definition of biochemical oxygen.