Correlation between BOD5 and COD – biodegradability indicator of wastewaters

Abstract

Biochemical Oxygen Demand (BOD5) and Chemical Oxygen Demand (COD) are the most common parameters for the characterization of the organic matter content of water. Correlation between BOD5 and COD for different types of waters can provide relevant information about the nature of pollution, the content of organic matter, and its level of biodegradability. This correlation could also be used to assess the quality of effluent after the treatment processes, to improve the performance of wastewater treatment plants (WWTPs), and/or to monitor the quality of river water into which wastewater is discharged. The objective of this study was to assess the degree of biodegradability of different types of water (influents and effluents of 3 important municipal WWTPs of Romania, untreated wastewaters discharged by different economic units from Bucharest; effluents of 5 different hospitals and surface waters - natural receptors of the effluents discharged by the municipal treatment plants), based on the ratios of BOD5/COD. BOD5/COD ratio (also called Biodegradability Index) varied depending on the type of water investigated and should be periodically rechecked due to variations in climatic conditions, untreated industrial wastewater discharged into natural receptors, water supply characteristics, and water availability.

Keywords

• bod5/cod ratio
• biodegradability index
• wastewater