Assessing the Suitability of Soils With Macropores for Subsurface Liquid Waste Disposal

Publisher Website
Google Scholar
Abstract
The capacity of soils to accept and purify liquid waste can be manipulated by using different application regimes. The associated transient soil physical conditions, which govern purification processes, were measured experimentally in soil columns and in situ, and were predicted by simulation in three soils of which two had macropores.Measurements of pressure heads, outflow rates, and breakthrough curves were made following intermittent liquid applications of 2 cm d−1. Rapid breakthrough and short‐circuiting, which were observed in the soils with the macropores, could be reduced by adding a light crust.Predictions involved computer simulation of pressure heads during infiltration and redistribution, and of outflow rates in the columns. Good agreement was found between measured and calculated values, but only when the model for soils with macropores was modified to include a subprogram for macropore flow. Simulation required hydraulic conductivity (K) at and near saturation, which was obtained with a modified crust test procedure.Use of the simulation program allows the prediction of soil physical conditions for a range of application rates in terms of ponding times and drainage rates, which affect purification and clogging. Measurement of breakthrough curves yields travel times as a function of application rates. Optimal application rates can be estimated by considering these two types of data, as is illustrated with an example. This approach is preferred over the current procedure using a single hydraulic parameter.

This publication has 1 reference indexed in Scilit: