Biodegradable dissolved organic carbon (BDOC) for characterizing reclaimed and treated wastewaters: Method development and applications

Analyses that measure oxygen demand, such as biochemical oxygen demand (BOD) and chemical oxygen demand (COD), 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 usually a good indicator of water quality 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) is a relatively new procedure which 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 (DOC) concentrations (4 to 15 mg/L) are routinely encountered. The development of the modified BDOC procedure is based on a combination of a novel BDOC batch procedure utilized in drinking water treatment and the classical biochemical oxygen demand (BOD) technique used in wastewater treatment. The modified BDOC method was able to detect the increase in biodegradability of ozonated tertiary treated wastewater and to indicate secondary effluent quality. The procedure has reduced variability and increased precision as compared to BOD and COD. Employing a large volume of concentrated inoculum, such as mixed liquor suspended solids, the incubation time can be reduced from 28 days to 5 days and the simultaneous determinations of BDOC and soluble {dollar}rm BODsb5{dollar} are possible. With adequate further studies, the BDOC procedure using the concentrated inoculum can be proposed as a standard method.