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COD: Chemical Oxygen Demand

دسته : (WATER آّب) توسط روح الله افشارپور در ۲۹-۰۷-۱۳۹۵

For today I thought it is good to talk about a simple calculation that you might need during problems related to water treatment section. So we are going to learn how to calculate COD. But wait a second, what is COD, you might ask!

COD stands for Chemical Oxygen Demand. Ok, ok don’t panic I will explain a bit more.

first we should know that creatures like fish need Oxygen just like us to live and the amount of Oxygen in water like river is called DO (dissolved Oxygen) and when this DO gets lower and lower these poor creatures die. Ok, what does it have to do with COD. Well, COD represents the amount of Oxygen needed for oxidization of stuff in water like organic matter.

So if we want to know about these things we need to be able to estimate the COD for each compound, for example we will do it for Glucose (C6H12O6). To calculate that we need to know about the reaction:


To do the calculation we need to know how much Oxygen is needed and as we can see from the balanced reaction for 1 mol Glucose ,6 mol Oxygen is consumed so the COD is a ratio between them and we need the atomic mass of each element which is equivalent to the number of protons and neutrons in the atom and then as it is shown in orange box and blue box the atomic mass of Oxygen and Glucose are calculated and then the COD is determined 1.07 gram cod per gram Glucose. 

I hope you could learn it, wanna know if u learned? So as a practice, determine COD for Acetic acid (C2H4O2) and post it below.

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