How to detect COD content in water quality

When it comes to COD water quality detectors in daily life, many people believe that this parameter has little impact on water quality, so the instrument is not very useful. But we want to tell everyone that this idea is wrong, because if the chemical oxygen demand is too high, it can lead to the death of aquatic organisms, and after they die, they produce oxygen due to lack of oxygen. Some toxic substances can affect the overall water quality. Therefore, understanding the COD parameters in daily life is very important. Below, the editor will introduce the specific detection methods for COD in water quality.

Specific detection methods for COD in water quality

COD can be measured for organic matter using chemical oxidants. It is crucial to use oxidants strong enough to react with almost all organic compounds in the sample. In history, potassium permanganate has played this role, but its ability to oxidize all organic matter has been found to be inconsistent in various waste samples.

Most current COD tests use potassium dichromate as an oxidant. Potassium dichromate is a hexavalent chromium salt with bright colors and is a strong oxidant. Dichromate can oxidize 95-99.9% of organic matter. Once dichromate oxidizes a substance, it will transform into trivalent chromium, appearing dark green.

The sample is dissolved by heating with a certain amount of oxidant and sulfuric acid at 150 ℃. Usually containing metal salts to suppress any interference and catalyze digestion. Digestion usually takes two hours to complete.

There must be an excess of oxidants during the digestion process; This ensures complete oxidation of the sample. Therefore, it is important to determine the amount of excess oxidant. The two most commonly used methods are titration and colorimetry.

Which water quality COD detection method is most suitable for me?

Although both methods have been tested by time, they have their own advantages and disadvantages.

The equipment required for titration is relatively small, as the devices you need are burettes, heating blocks, and digestion bottles. However, this process requires more labor. Automatic titrators can reduce the required amount of user input and can be used for other applications in wastewater.

Although colorimetric methods require a spectrophotometer or photometer, as most manufacturers offer it, it provides convenient pre mixed reagents, so all you need to do is run your sample with digestion and minimal contact.

Colorimetry also makes measurement easier, as analysts need to digest the sample and let the water quality testing equipment complete its work. Due to these reasons, colorimetric method is the most commonly used method for measuring COD.

Generally, COD detection mainly uses instruments, such as online monitoring devices, portable detectors, and laboratory measuring instruments, which can accurately measure the COD content in water samples. If the requirements are not high, COD rapid detection reagents can also be used.