Biochemical Oxygen Demand (BOD) Calculator
Accurately calculate BOD₅ for water quality analysis and wastewater monitoring.
The calculated BOD₅ is:
What is Biochemical Oxygen Demand (BOD)?
Biochemical Oxygen Demand, or BOD, is a critical environmental parameter used to measure the amount of dissolved oxygen consumed by microorganisms while decomposing organic matter in water at a specific temperature over a specific time period (usually 5 days at 20°C, known as BOD₅). It is a primary indicator of the organic quality of water and is widely used in wastewater treatment plant management and environmental health monitoring.
How to Use the BOD Calculator
To use this calculator, you need the results from a standard dilution test:
- Initial Dissolved Oxygen (D1): The DO level measured immediately after preparing the diluted sample.
- Final Dissolved Oxygen (D2): The DO level measured after the 5-day incubation period.
- Sample Volume: The actual amount of wastewater or sample added to the incubation bottle.
- Total Bottle Volume: The capacity of the BOD bottle, typically 300 mL.
The BOD Formula
The standard formula used for calculating the Biochemical Oxygen Demand in a dilution test is:
BOD (mg/L) = (D1 - D2) / P
Where P is the decimal volumetric fraction of the sample used (Sample Volume / Total Volume). If the sample is not diluted (P = 1), the BOD is simply the difference between the initial and final dissolved oxygen levels.
Frequently Asked Questions (FAQs)
Why is BOD measured for 5 days?
The 5-day period was originally chosen because it represented the longest flow time of a river in the UK from source to sea. It has since become the international standard for assessing organic pollution.
What does a high BOD value mean?
A high BOD value indicates a high concentration of biodegradable organic matter. This suggests that the water is polluted, which can lead to oxygen depletion in natural water bodies, potentially killing fish and other aquatic life.
What is the difference between BOD and COD?
While BOD measures the oxygen used by microbes to break down organic matter biologically, COD (Chemical Oxygen Demand) measures the oxygen required to chemically oxidize organic and inorganic matter. COD results are typically higher and faster to obtain (hours vs. days).