A comparison of the graphical and standard methods for the determination of biochemical oxygen demand

The graphical and Standard Methods for the determination of biochemical oxygen demand (BOD) were compared. Average means ± standard deviation of 228 ± 28 mg/L and 199 ± 25 mg/L for the Standard Methods and graphical methods resulted when a primary standard was used. The graphical method showed no significant difference from the accepted Standard Methods procedural check value of 200 ± 37 mg/L. Analytical procedures, used for both methods were identical except for the separate seed correction step in the Standard Methods approach. The disagreement was eliminated by use of a seed correction derived from the graphical method. No significant difference between the results of the two methods occurred when effluent and raw wastewater samples were used. The seed correction discrepancy was minimal and lower dilution factors and less ammonia contribution from dilution water in the seeded low BOD samples and the higher BOD samples were unseeded wastewater samples.