Effect of Soil-Water Separation Technique on the Estimation of Bacterial Adsorption onto Soil

Adsorption is one of the most significant processes in dictating the fate of bacteria and viruses in soils. Knowledge of adsorption characteristics is, therefore, essential for the prediction of the migration path of such microorganisms. These characteristics include the adsorption capacity, soil-microorganism partitioning coefficient, the state of equilibrium and the applicable isotherm. The techniques used for the determination of those characteristics may have an effect on the outcome in terms of the parameters involved. In this study, laboratory batch experiments using a tracer bacterium, nalidixic acid resistant Escherichia coli (E.coli NAR), were carried out to study the effect of three soil-water separation techniques on determining the adsorption characteristics of bacteria onto soil. The techniques used are: centrifugation, sedimentation and filtration. The procedure involved measurements of biotracer concentration in the soil solution before and after the soil-water separation. The filtration technique was found to have the most pronounced effect on the adsorption of E.coli NAR onto soil. On the other hand, separating soil and water using the sedimentation technique gave the smallest amount of biotracer adsorption.