Method development for measuring biodegradable organic carbon in reclaimed and treated wastewaters

Analyses that measure oxygen demand, such as biochemical oxygen demand (BOD) and chemical oxygen demand (COD) analyses, have long been used as indicators of contamination and wastewater treatment plant efficiency. They measure the tendency of pollutants to react with oxygen, which is generally a good indicator of the stability or level of treatment. Both parameters include reactions with organic as well as inorganic substances and suffer from a lack of precision and accuracy at low concentrations, which are becoming increasingly more important. Biodegradable dissolved organic carbon (BDOC) analysis is a relatively new procedure that has advantages over both BOD and COD analyses, including insensitivity to inorganic oxidations. A modified BDOC procedure was developed to characterize the performance of advanced treatment methods, such as those used in municipal water reclamation and secondary-treated wastewaters, where moderately low dissolved organic carbon concentrations (4 to 15 mg/L) are routinely encountered. The development of the modified BDOC procedure was based on a combination of the existing batch BDOC protocol and BOD techniques. Various aspects and incubation conditions were investigated to finalize the procedure. Nitrification does not interfere with the procedure. It is possible to simultaneously determine the soluble BOD (SBOD) under certain conditions. The procedure has reduced variability and increased precision as compared to BOD and COD analyses.