kmax binh or kmax + bsti (gCOD(gVSStd)1) shows the substrate utilization rate at the highest rates of inhibition or acceleration. CLX had almost no effect on the microorganisms while ERY displayed the greatest toxic effect of the four antimicrobials. Kinh or Ksti expresses the antimicrobials concentration when the microbial activity is half of the maximum inhibition or acceleration. This indicates that the increase in inhibition or acceleration is related to the antimicrobials concentration. We find all the half maximum inhibition or acceleration occurring below 200 mg L1 and these low values of Kinh demonstrate the feasibility of microbial adaptation exposed to high concentrations of antimicrobials (Amin et al., 2006).