What is BOD and COD?
Biochemical oxygen demand (BOD) and chemical oxygen demand (COD) measure how much oxygen the organic matter in wastewater would consume, biologically and chemically. They are the main measures of effluent strength.
Who tests BOD and COD
Any plant that discharges process wastewater, including dairies, food and beverage plants, distilleries and textile units, reports both to its pollution regulator. ETP and STP operators also use them daily to judge whether the biological stage is coping with its load.
Test methods and limits in India
BOD is a biological test. In India it is measured over 3 days at 27 degrees Celsius, which replaced the older 5 day test at 20 degrees Celsius through a 1996 amendment to the Environment (Protection) Rules, 1986. COD uses a strong chemical oxidant and returns a result within hours.
Schedule VI of those rules sets general BOD limits of 30 mg per liter for inland surface water, 350 mg per liter for public sewers and 100 mg per liter for land irrigation or marine coastal discharge. COD is capped at 250 mg per liter for inland surface water and marine coastal areas. Sector standards can differ, and the consent issued by the state board is what binds a plant.
Where Aqueduct's water data meets BOD
Aqueduct does not run lab tests. Where an online analyzer exists, its readings sit on the water digital twin beside flow, and the STP block already shows BOD out in mg per liter. Multiplying concentration by metered flow turns a lab value into a load in kilograms per day, the figure that explains when the biological stage is overloaded.