Fractionation of soluble COD in wastewater based on batch respirometric method

A fractionation protocol of soluble COD (SCOD) was put forward by combining respirometric method with hydrolysis kinetics of soluble slowly biodegradable COD (S_H). SCOD fractionation results of two wastewater treatment plants (WWTP) in Shanghai show that the SCOD in sand basin effluents (typical domestic wastewater) of WWTP A is composed of 43.5%-58.6% SH. 21.8%-35.2% readily biodegradable COD (S_s) and 15.4%-30.9% soluble inert COD (S_I), and those SCOD fractions in sand basin effluents (combined sewers after long pipeline transportation) of WWTP B are 34.5%-45.2%, 29.3%-37.7% and 25.6%-31.2%, respectively. The linear regression results of respirometric tests data from nine samples demonstrate that the first-order kinetics can reliably describe hydrolysis process of S_H, and the kinetic constants of S_H from WWTP A and B are respectively 28.00-39.77 d ^-1 and 26.48-29.52 d^-1. Experimental results demonstrate that this protocol can achieve theoretical partition for the integration area of S_s, and also eliminate the effect of soluble microbial products on S, determination.