Chemical Oxygen Demand (COD)

Introduction: The Essence of Chemical Oxygen Demand (COD)

Water quality is a cornerstone of environmental health, and Chemical Oxygen Demand (COD) stands as a vital metric in assessing pollution levels in aquatic systems. COD not only reflects the organic load in water but also serves as a key indicator of industrial and municipal wastewater treatment efficiency.

“Quality is never an accident; it is always the result of intelligent effort.” — John Ruskin

Definition and Importance of COD

COD measures the oxygen required to chemically oxidize organic and inorganic matter in water, expressed in milligrams of oxygen per liter (mg/L). Its significance extends beyond mere numbers, acting as a safeguard for both ecosystems and human health. According to the World Health Organization (WHO), untreated wastewater contributes to millions of preventable deaths annually, highlighting COD's role in mitigating waterborne diseases.

“The science of today is the technology of tomorrow.” — Edward Teller

The Science Behind COD Measurement

Chemical Oxygen Demand is determined through a robust chemical oxidation process. Potassium dichromate (K₂Cr₂O₇) in acidic conditions oxidizes contaminants, with silver sulfate acting as a catalyst. The process involves:

Sample Preparation: Mixing water with a dichromate solution.

Digestion: Heating the sample at 150°C for two hours.