General Fate Model for Microconstituents in an Activated Sludge System.

Nine lab-scale continuous flow porous-pot bioreactors operating at various solids retention times and hydraulic retention times were conducted to simulate activated sludge (AS) systems and to evaluate the biodegradation kinetic models for the fate of 17α-ethinylestradiol (EE2), bisphenol-A (BPA), and triclosan (TCS) at the µg/L range. Mathematical models were applied to describe the degradation mechanism of selected microconstituents (MCs) and pseudo second-order model were found to best fit the results when active MCs degraders (XC) were used (r2= 0.99). The result of XC estimation showed that SRT plays an important role in formation of the biomass capable of degrading selected MCs. It is also observed that the MCs degraders are naturally present in the AS system even at low SRTs; however, the concentration of XC is dependent on SRT. It is found that biodegradation studies should incorporate XC and not mixed liquor suspended solids concentration (MLSS) in their kinetic formulations.