[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% S(H), 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(I) determination.