Wastewater COD biodegradability fractionated by simple physical–chemical analysis

•COD biodegradability fractions can be estimated from physical–chemical method.•Simple physical–chemical method can be an alternative to the respirometry method.•De-nitrification potential can be identified from physical–chemical method.

A simple physical–chemical method was developed as an alternative to the respirometry method for determining the wastewater COD fractions in terms of biodegradability. Wastewater was fractionated into soluble, colloidal, non-settleable and settleable particle components by the physical–chemical method. The COD biodegradability fractions including readily biodegradable COD, slowly biodegradable COD, inert soluble COD and inert particulate COD were determined from the respirometry and modeling method. A conversion matrix was derived that can be used for COD biodegradability fractions conversion from simple physical–chemical analysis. The denitrification experiment indicated that the physical–chemical conversion method can be a valuable tool for wastewater denitrification potential estimation.