Chemical oxygen demand (COD) is used to determine the quantity of pollution in water after wastewater treatment. The higher value of chemical oxygen demand indicates the higher organic pollution in the water sample. Only chemically digest able matter can be determined by the COD test.
What is the principle of chemical oxygen demand?
The principle behind the COD testing method is that, under acidic conditions, a strong oxidising agent will oxidise almost any organic compound to carbon dioxide. COD analysis will measure the equivalent amount of oxygen that is required to chemically oxidise organic compounds in water.
What is chemical oxygen demand COD test?
Chemical Oxygen Demand (COD) is a test that measures the amount of oxygen required to chemically oxidize the organic material and inorganic nutrients, such as Ammonia or Nitrate, present in water.
What is chemical oxygen demand in wastewater?
The chemical oxygen demand (COD) is a measure of water and wastewater quality. The COD test is often used to monitor water treatment plant efficiency. 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.
What is chemical oxygen demand how is it determined?
COD is an indirect measure of the total organic matter widely used for wastewater monitoring, design and operation of STPs. It consists of the amount of oxygen required for the organic matter to be oxidized by a chemical oxidant (usually potassium dichromate in acid medium). The sample is digested for 2 h at 150°C.
How is COD determined in wastewater?
What test methods are typically used to determine COD at water and wastewater laboratories? The most common test method is the colorimetric analysis after oxidizing the COD with acid and using indicator compounds, such as hexavalent dichromate.
What are the two methods of determining the COD value of a water sample?
There are two methods available for COD determination namely open reflux and closed reflux.
Why is it important to determine COD in wastewater treatment?
In wastewater treatment, the Chemical Oxygen Demand (COD) is an important measurement for the amount of oxygen that is required to break down pollutants (organic substances) in water. The chemical oxygen demand can be measured using different methods, direct or indirect.
What is COD process?
Chemical Oxygen Demand (COD) analysis is a measurement of the oxygen-depletion capacity of a water sample contaminated with organic waste matter. Specifically, it measures the equivalent amount of oxygen required to chemically oxidize organic compounds in water.
What are the steps involved in COD test?
Method procedure
- Collect your sample in the appropriate size container and preserve with the appropriate volume of sulfuric acid.
- Properly label enough prepared COD vials (without mercury for non-regulatory samples) for all samples and standards to be digested.
- Turn on your COD reactor and ensure it is set to 150°C.
Why do we need to determine COD?
COD is useful in terms of water quality by providing a metric to determine the effect an effluent will have on the receiving body, much like biochemical oxygen demand (BOD).
How can you determine chemical oxygen demand COD Spectrophotometrically?
The COD can be easily determined using a spectroscopy method based on the oxidation of the organic matter by potassium dichromate (K 2 Cr 2 O 7 ), which is converted to potassium chromate (K 2 CrO 4 ) in the presence of mercury sulfate (HgSO 4 ) and silver sulfate (AgSO 4 ).
What is the importance of determining COD and BOD?
Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) are two of the most important parameters to characterise (measure the degree of pollution) of wastewater. BOD, the biological demand for oxygen a source of water has, is the amount of oxygen used by microorganisms to break down organic substances.
How do you prepare chemical oxygen demand?
Dissolve 9.8 g ferrous ammonium sulfate in a solution of 100 ml of distilled water and 20 ml concentrated Sulfuric acid. Cool the solution and make up the solution to 1000 ml of distilled water. Standardize the solution to determine the actual concentration to calculate the chemical oxygen demand.
How do you measure COD in water?
There is a formula for calculating COD. Consider the formula for COD calculation: (a – b) X C X 8,000 / the volume of the sample in mL. Let “a” represent the titrant used for your sample expressed in mL. Let “b” represent the titrant used for your blank sample in mL.
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