What is the difference between BOD and COD? 【Basic Knowledge】

5 days for measurement? Or a few hours? Explaining the difference between BOD and COD!

■What do BOD and COD mean? Both are indicators that show the degree of water pollution. BOD stands for Biochemical Oxygen Demand, and COD stands for Chemical Oxygen Demand. A higher value indicates more severe water pollution, and they are important as regulatory items for industrial wastewater. ■How do the measurement methods differ? BOD measures the amount of oxygen consumed by microorganisms to decompose organic matter in water over a period of 5 days at 20°C in the dark. On the other hand, COD chemically decomposes organic matter using an oxidizing agent (potassium permanganate) and determines the amount of oxidizing agent consumed, allowing for measurement in a short time frame of about 30 minutes to 2 hours. ■Why use two different indicators? In rivers, where there is water flow and self-purification by microorganisms occurs, BOD is used. In lakes and marine areas, where water stagnates and organic matter that is difficult for microorganisms to decompose needs to be evaluated, COD is used as a standard item for environmental criteria. The fact that BOD takes 5 days to measure, while COD provides results in a short time, also contributes to the practical differentiation in their use. Please feel free to consult us first.

Water quality testingWastewater/wastewater treatment equipmentDissolved Oxygen Meter