Chemical Oxygen Demand Calculator

Chemical Oxygen Demand (COD) measures how much oxygen is needed to break down organic pollutants in water — a key indicator of water and wastewater quality. Enter your FAS Used for Sample, FAS Used for Blank, Normality of FAS, and Volume of Sample into the Chemical Oxygen Demand Calculator to get the COD value in mg/L. Secondary outputs include Oxygen Consumed and the FAS Difference between blank and sample titrations.

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Results

Chemical Oxygen Demand (COD)

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Oxygen Consumed

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FAS Difference

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Frequently Asked Questions

What is chemical oxygen demand (COD)?

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.

How can I determine chemical oxygen demand?

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.

What does chemical oxygen demand indicate?

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.

What is the difference between BOD and COD?

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.

What is a good COD level for drinking water?

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.

How is COD measured in the laboratory?

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.

Why is normality important in COD calculation?

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.

What factors can affect COD results?

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.