Significance of physicochemical factors in the transmission of Escherichia coli and chloride

Abstract

Background: Organic manures are the source of many pathogenic bacteria which could be dangerous for human health. Bacterial transmission and retention in soil is important for processes ranging from contaminant degradation during in situ bioremediation to transport of pathogenic bacteria into groundwater. Methods: The aim of this study was to evaluate the transport of Escherichia coli and chloride (Cl) in the soil saturation conditions, considering the importance of preferential flow using synthetic macrospores (different diameters of macrospores including 0, 1 and 2 cm) and HYDRUS-2D model. Also, the effect of different salinity levels of water (including electrical conductivity of 1, 2 and 4 dSm-1) on the transmission of E. coli was investigated. The preferential flow system was prepared and designed using two sand sizes including fine sand and coarse sands in the columns. Results: The results showed that the retention of E. coli increased with the ionic strength of the solution, while the effect of E. coli in the fine sand was greater than that of the coarse sand. This bacterial transfer behavior was well described by numerical simulations. The importance of preferential flow in bacterial transfer showed that it increases at higher ionic strength, even if overall transmission is reduced. Although the bacterial transmission is facilitated in salinity, the results of this study showed that with increase of ionic strength of the soil solution, the amount of bacterial purification was increased that could be effective in controlling groundwater contamination with saline water management. Conclusion: According to the results, with increase of ionic strength of the soil solution, the amount of bacterial purification was increased that could be effective in controlling groundwater contamination with saline water management, so that the least transition has taken place and the conditions for the use of unconventional water sources were also created, without the environmental problem of the risk of groundwater pollution.