Chemical Oxygen Demand Calculator

Chemical oxygen demand (COD) measures the amount of oxygen required to chemically oxidize organic matter in water. It's an important parameter for assessing water quality and pollution levels in wastewater treatment.

COD is determined through a standardized titration method using potassium dichromate and ferrous ammonium sulfate (FAS). The sample is heated with dichromate, then titrated with FAS to measure oxygen consumption.

COD indicates the level of organic pollution in water. Higher COD values suggest more organic matter present, which can deplete dissolved oxygen and harm aquatic life when discharged into water bodies.

BOD (Biochemical Oxygen Demand) measures oxygen consumed by biological processes over 5 days, while COD measures total oxygen required for chemical oxidation. COD is typically higher and faster to determine than BOD.

For drinking water, COD should be less than 3 mg/L. Industrial wastewater typically ranges from 200-2000 mg/L, while domestic wastewater usually has COD values between 250-800 mg/L.

COD is measured using the closed reflux method with potassium dichromate. The sample is digested at high temperature, then the remaining dichromate is titrated with FAS to calculate oxygen consumption.

Normality of the FAS solution is crucial for accurate COD calculation as it determines the exact amount of reducing agent available. The normality must be precisely known and standardized before use.

COD results can be affected by sample volume accuracy, FAS normality precision, temperature during digestion, presence of chlorides, and proper blank preparation. Following standard procedures ensures reliable results.