Measuring bacterial biomass-COD in wastewater containing particulate matter

The paper describes a method to determine bacterial biomass-COD in wastewater treatment systems in the presence of particulate matter. A quantitative measure of biomass-COD concentration could greatly enhance the accuracy and reliability of wastewater treatment models that rely on the component “biomass concentration”, which is usually expressed in terms of COD. Rarely is biomass-COD determined directly, despite the existence of microbiological methods for this measurement. Here, we have used a classic microbiological method, acridine orange stain direct counting (AODC), to count the number of bacteria. The average cell volume of wastewater bacteria was used to determine a conversion factor of 20 × 10−11 mg-COD/cell for calculating bacterial biomass-COD with a fast, reliable and simple method applied to wastewater samples in the presence of particulate substrate. Bacterial biomass-COD was measured in five different wastewater treatment systems and compared to the particulate COD.