A solid chemical oxygen demand (COD) method for determining biomass in waste waters

A method of biomass determination similar to volatile suspended solids (VSS) that used chemical oxygen demand (COD) as a detection method instead of gravimetric methods is described. The “solid COD” method has a strong correlation with VSS for biomass at different stages of growth on different wastewaters including municipal sewage and bleached kraft mill effluent. Soluble COD from the wastewaters did not interfere with the assay. However, non-biomass suspended solids in chemi-thermo-mechanical pulping effluent were found to have a different COD/VSS ratio and thus interfered with solid COD results. The ratio between COD and VSS for biomass was approx. 1.2–1.6 mg COD/mg VSS.