KWRRI Research Reports


Effects of soil type, flow rate, antecedent soil moisture and other factors on transport of E. coli through soils was measured on disturbed and intact columns 20 cm in diameter by 25 to 30 cm in depth. Added E. coli were distinguished from indigenous microbes using an antibiotic resistance marker. Transport of Cl- and 3H2O was also measured. Up to 96 percent of the bacteria irrigated onto the surface of intact columns were recovered in the effluent. Soil structure appeared to be related to the extent of transport. Columns prepared from mixed, repacked soil were much more effective bacterial filters than the intact soils. As rate of water input increased, the fraction of E. coli recovered in the effluent increased. We concluded that flow through soil macropores, which by-passes the adsorptive or retentive capacities of the soil matrix, is conclusion was supported by the behavior of a common phenomenon. This conclusion was supported by the behavior of Cl- and 3H2O.

In waste disposal systems dependent on purification in the soil profile, this could significantly increase the probability of groundwater contamination by microbes. The effects of native soil structure (macropores) must be considered in the evaluation of these purification systems.

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The work upon which this report is based was supported in part by funds provided by the United States Department of the Interior, Washington, D.C., as authorized by the Water Research and Development Act of 1978. Public Law 95-467.