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This oxidation is catalyzed by silver sulfate. The catalyst is required, Primarily to oxidize very low molecular weight fatty acids. The oxidation with the acidified dichromate may be represented by the subsequent equation:
COD contrasts with biochemical oxygen demand (BOD), which relies on the usage of microorganisms to stop working the natural content within the sample by aerobic respiration around an incubation period of time (ordinarily five days).
Discharge permits may stipulate a specific optimum concentration for BOD or COD, or maybe a per cent elimination. Some crops require achieving just as much as ninety% elimination of oxygen demand.
Presently, most COD tests use potassium dichromate since the oxidant. Potassium dichromate is a hexavalent chromium salt that is certainly vivid orange in coloration and is extremely sturdy.
It's not advisable to measure the vials right before allowing them great to place temperature. The measurement might be inaccurate, and also a scorching reagent vial could injury the digital instrument.
The existence of toxins together with other unfavorable situations for The expansion of microorganisms are unable to affect the COD values.
The dichromate COD reagent is often marketed within a sealed vial. Sample is added to your vial, along with the response get more info happens all through a digestion where the sample is heated for 2 hours at 150oC.
Soon after dilution, the resulting difference between the Original and closing DO looking through basically needs to be multiplied through the dilution element to determine the final BOD final result.
The important stage is always that upon getting proven an average COD:BOD ratio for the wastewater stream, then the somewhat basic and rapid COD test may be used to forecast BOD with relative dependability.
It entails check here the oxidation of organic and natural and inorganic carbon compounds present in the h2o sample at large temperatures.
Because of the higher than, it is necessary to test the various choice strategies, at the least for COD and BOD, in different regions like Charge–advantage, validation, efficacy and sensitivity While using the aim of proposing just one as a substitute with the reference strategies.
To evaluate COD, the h2o sample is placed inside of a closed container and subjected to your potent oxidant, for instance potassium dichromate and sulfuric acid, for the specified length and temperature.
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