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

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.

Revisiting Vereecken Pedotransfer Functions: Introducing a Closed‐Form Hydraulic Model

“…Soil water content was determined at fi ve matrix suctions below 100 cm using a sand-box apparatus and at higher suctions with low-and high-pressure chambers. For the HCC, two diff erent methods were used: the crust method (Bouma et al, 1983) for the wet range and the hot air method (Arya et al, 1975) for the dry range. Part of the raw data could not be retrieved so that the fi nal data set contained only 136 HCC and 166 MRC.…”

Changes in physical properties of young and old volcanic surface soils in Costa Rica after clearing of tropical rain forest

“…This in-situ field test has been discussed comprehensively in other papers (Bouma et al, 1983;Klute, 1986;Spaans et al, 1989). Only a brief discussion is therefore presented here.…”

Determining Soil Hydraulic Properties

“…• Crust method : The crust method (Bouma et al, 1983) determines hydraulic conductivity, K(h), by measuring the water flux density into an unsaturated soil sample. Unsaturated conditions are obtained by supplying water through a crust made of sand and special cement with a lower hydraulic conductivity than the soil sample.…”