The Distributions of Water and Bacteria in Soil from a Point Source Applying Sewage Effluents with Varying Concentrations of E. coli

摘要

The bacteria can be transmitted to soil and crops during irrigation of sewage effluents. The objective of this work was to investigate the transport of the typical bacteria, Escherichia coli, in a sandy soil under different drip irrigation schemes. A30° wedge-shaped plexiglass container was used to represent one twelfth of the complete cylinder. Three variables, including application rate, input concentration of E. coli, and volume applied, were considered and their effects are presented on a basisof a completely cylinder system. In the experiments, the apparent cylindrical application rate was varied 1.05 to 5.76 Uh, the apparent cylindrical applied volume from 4.8 to 12 L, and the input concentration of E. coli from 104 to 10s cfu/100mL. The designed concentration ofE. coli was obtained by diluting the constant concentration of penicillin resistance E. coli DH5a with sterile water. The moving of water front during water application was recorded and soil samples were collected at different locations from the point source as the designed water volume was applied. A plate count method was used to detect the concentration of E. coli for each sample. An extremely higher concentration of E. coli was observed in the proximity of the point source andthe concentration decreased greatly as the distance from the point source increased due to soil absorption and filtration. It was found that the amount of E. coli concentrated in the soil volume of 10 cm from the point source accounted for more than 70%of the E. coli in the total wetted volume. Moreover, the E. coli can hardly be detected within 10 cm from the wetting front.