Distribution and degradation of organic matter with different molecular weight in an A2/O treatment system

Abstract

Organic matter (OM) fractions and their removal potentials in various stages of anaerobic–anoxic–oxic (A2/O) process were identified and evaluated. Molecular weight (MW) distribution of organic matter by continuous filtration method was used to characterize OM in influent and treated effluent. The results showed the MW of each reaction pool distributed in a U shape and ranged with particle size >0.45 μm and molecular weight <1 k accounted for a high proportion. These results suggested effluent organic matter <1 k of an anoxic pool, anaerobic pool, and an aerobic pool in the A2/O treatment systems significantly outnumbered the other stages. Meanwhile, influent organic matter within the range >0.45 μm, 10–30, 5–10, and <1 k was well removed while organic matter in the MW range of 30–100 and 1–3 k was used at a low rate during A2/O treatment. Denitrification required an external carbon source in 30 mg/L (calculated as methanol) for ensuring efficient process operation. Experimental approaches in this study can be applied to evaluate and diagnose the function of water treatment process.