Regarding the dilution of COD
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There is currently 36 cubic meters of wastewater with a COD concentration of 3000 mg/l. To reduce this COD concentration to 500 mg/l, how much clean water is needed for dilution (assuming the COD level in clean water is 0)? Is there any formula related to COD dilution?
X = (3000*36/500) - 36 = 180 tons
X = (3000*36/500) - 36 = 180 tons
It is not allowed to dilute wastewater with high COD concentrations until it meets the standards.
After dilution, it’s not discharged outside, right? In that case, the total COD amount remains unchanged. Isn’t it necessary to reduce its concentration before sending it to the wastewater treatment plant?
For some COD values, it is possible to reduce them by dilution, and there is a strict mathematical relationship between the reduction process and the dilution ratio. However, for some organic substances, since the digestion process does not reach an ideal state, after diluting the water sample, there is no clear mathematical relationship between its COD value and the dilution factor. The value obtained from measurements after dilution, when multiplied by the dilution factor, turns out to be much higher than the original COD value; this is because as the concentration of the components contributing to COD decreases, the digestion rate increases to a certain extent.
Another situation is the interference of chloride ions on COD measurement; when chloride ions are present, the COD value after dilution will be lower than the calculated value.