Mechanism and kinetics of bacteria-killing in a batch study in presence of Ag impregnated activated carbon

TL;DR

This study develops a mathematical model to understand bacteria-killing mechanisms in a batch reactor with silver-impregnated activated carbon, revealing contact killing dominance and complex Ag-bacteria interactions.

Contribution

It introduces a novel kinetic and thermodynamic model fitted with experimental data to elucidate bacteria-killing mechanisms involving silver-impregnated activated carbon.

Findings

Contact killing dominates over bulk-killing.

Ag-bacteria interaction is highly non-linear.

Surface Ag concentration controls bacteria-killing kinetics.

Abstract

A mathematical model based on classical species balance equation has been developed to explain the experimental observation on E.Coli cell-killing in a batch reactor and to extract information on cell-killing mechanism. Maximum likelihood optimization method has been used to obtain the best fit to the experimental data to extract ten unknown kinetic and thermodynamic parameters, which is otherwise practically impossible. Bacteria killing kinetics is found to be dominated by contact killing mechanism with approximately one order difference between contact-and bulk-killing kinetics. The order of Ag-bacteria interaction is highly non-linear and thus the interaction is highly complex in manner. Concentration of Ag on the outer surface of AC controls the kinetics of bacteria killing. Mechanism of release of Ag from the inner surface of pores does has minimal impact on the bacteria killing kinetics. Activity of silver seems to remain preserved after cell killing and the surface concentration of Ag used in the experiment is so high that bacteria killing kinetics is independent of whether Ag remains active or not.