Transfer/Retention of Escherichia coli Cells from Exponential Phase in Acidic and Alkaline Percolating Water Through Sterilized/Unsterilized Sandy Soil

Introduction: Little is known about E. coli transfer and retention in acidic or alkaline water through sandy soils, and the role of sand sterilization. This study evaluated the transfer and retention of exponential-phase E. coli cells in acidic or alkaline water seeping through sterilized or unsterilized sand.Methods: Sterilized and unsterilized sand of three size ranges was poured into pipe fragments. Cells from the exponential phase were inoculated into sterile NaCl solution (۸.۵ g/L) contained in Erlenmeyer flasks (concentration ۷ × ۱۰۷ CFU/mL) at a given pH. Water percolation tests were then carried out by allowing bacteria‑contaminated water to fall above the sand column. Bacteriological analysis of the percolated water was subsequently performed.Results: Cell abundance in percolated water was lower than influent, with temporal variations depending on sand treatment and grain size. Smallest grains retained cells most efficiently. Few differences in retention efficiency occurred among sterilized sand sizes, but several differences occurred among unsterilized sizes. For pH ۵ percolates, cell abundances differed significantly from pH ۶, ۸, and ۹ (P < ۰.۰۵) for both sand types, but no differences were observed among pH > ۵.Conclusion: Cells are more retained in acidic influent than in alkaline influent, and also more retained through unsterilized sand grains than through sterilized sand. For a given pH value, the cell retention percentage increases relatively as sand grain size decreases.

کلیدواژه ها:

bacteria-contaminated water ، Acidic/alkaline pH ، Percolation ، sterilized/unsterilized sand ، cells transfer/retention ، percolated water