What is BOD and why is it important in wastewater analysis?

BOD (Biochemical Oxygen Demand) measures the amount of oxygen consumed by microorganisms while decomposing organic matter in water over a specific period (typically 5 days at 20C - BOD5). It indicates the level of organic pollution in water. Higher BOD means more organic pollution and greater oxygen depletion in receiving water bodies. Typical domestic sewage has BOD of 150-300 mg/L.