Activated sludge model based COD fractionation in wastewater characterization

The successful application of activated sludge model (ASM) in wastewater treatment plant mainly depends on the correctness of wastewater fractionation. Based on three batch oxygen uptake rate (OUR) tests, a COD fractionation protocol and the corresponding Matlab program were developed to aid the standardization of COD fractionation in wastewater. COD fractionation results of two wastewater treatment plants (WWTP) in Shanghai show that COD in wastewater of the Quyang WWTP is composed of 8.1%±1.6% readily biodegradable COD (S_S), 6.3%±2.2% soluble inert COD (S_I), 45.5%±3.5% slowly biodegradable COD (X_S), 31.1%±2.1% particulate inert COD (X_I) and 9.0%±1.1% heterotrophic biomass (X_H), and those fractions in wastewater of the Bailonggang WWTP are 11.1%±2.2%, 9.9%±2.0%, 38.9%±10.7%, 23.3%±9.8% and 16.9%±1.8%, respectively. Compared to the Quyang WWTP, wastewater of the Bailonggang WWTP showed lower X_S and X_I contents in COD, but greatly higher X_H/COD value, indicating that long pipeline transportation could significantly influence the concentration of COD fractions.