Final answer:
Chemical Oxygen Demand (COD) is used to quantify the amount of oxygen needed to oxidize all organic material in a water sample to CO2 and H2O. It is critical for monitoring water quality in natural and wastewater systems, and often overestimates the true oxygen demand since it does not distinguish between biologically decomposable and non-decomposable substances.
Step-by-step explanation:
Chemical Oxygen Demand (COD) is an analytical measurement used to determine the amount of oxygen required to oxidize the organic matter in water. This measurement is crucial for assessing the water quality of natural waters and wastewaters. COD estimates the quantity of oxygen needed to transform all the organic material in a sample into carbon dioxide (CO₂) and water (H₂O).
Particularly in the context of managing industrial wastewater treatment, COD serves as an indicator of the volume of organic-rich wastes released into municipal sewer systems or natural environments. The process involves refluxing a sample with an excess of potassium dichromate (K₂Cr₂O₇) in acidic conditions, catalyzed by silver sulfate (Ag₂SO₄) and with the addition of mercuric sulfate (HgSO₄) to combat interference from chlorides.
After the reflux, the excess dichromate is titrated to calculate the COD value. It's important to note that COD measurements typically overestimate the actual biodegradable oxygen demand, as it does not differentiate between biologically decomposable and non-decomposable organic matter.