Enter initial/final dissolved oxygen for the sample and blank, plus dilution factor, volume, and test duration — the BOD Calculator returns your BOD value, oxygen consumed, blank correction, and pollution level.
BOD Value
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Oxygen Consumed
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Blank Correction
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Pollution Level
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Biochemical Oxygen Demand (BOD) measures the amount of oxygen required by bacteria to decompose organic matter in water. It's a key indicator of water pollution and is essential for wastewater treatment monitoring.
BOD5 refers to the biochemical oxygen demand measured over 5 days at 20°C. This is the standard test duration used worldwide for water quality assessment and regulatory compliance.
Generally, BOD values below 3 mg/L indicate clean water, 3-5 mg/L is moderately polluted, 5-15 mg/L is heavily polluted, and above 15 mg/L indicates severe pollution requiring immediate treatment.
Dilution ensures there's enough dissolved oxygen in the sample bottle to support bacterial activity throughout the test period. Without proper dilution, oxygen would be depleted too quickly, giving inaccurate results.
The blank correction accounts for oxygen consumption by bacteria naturally present in the dilution water. This ensures the measured BOD reflects only the oxygen demand from the sample itself.
Temperature, pH, presence of toxic substances, bacterial seed quality, and proper sample handling all affect BOD accuracy. Tests must be conducted under standardized conditions at 20°C in darkness.
BOD helps operators monitor treatment efficiency, determine oxygen requirements for aeration systems, and ensure effluent meets discharge standards. It's also used to calculate organic loading rates.