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A sustainability framework for land disposal systems involving highly saline industrial effluent

H. Bing So, Neal W. Menzies, K. Yatapanage, G. Kirchhof, Ross C. Bigwood, C. McDonald and Peter M. Kopittke

School of Land and Food Sciences, The University of Queensland, St Lucia, QLD 4072, Australia. E-mail: h.so@uq.edu.au

Abstract

The sustainability of a system for the land disposal of saline waste is fundamentally dependent on whether salt concentrations in the soil can be maintained at levels that allow adequate plant growth to remove water, salt or other solutes. Hence a suitably high leaching fraction is required to limit salt accumulation. If other potentially harmful solutes are present, the excessive amount of water application may give rise to other environmental problems of excessive solute accumulation or discharge. However, the application of salt as NaCl will increase the exchangeable sodium percentage (ESP) of the soil which could reduce the soil’s infiltration rates to levels where the required leaching fraction may not be achievable.

Experience derived from an investigation of a land disposal site for highly saline industrial effluent at Beaudesert, Queensland suggests that soils from undisturbed pasture sites are sufficiently stable to counteract the detrimental effect of high ESP. This finding is in sharp contrast to our current knowledge of the behaviour of disturbed (cultivated) sodic soils.

Relevant information on the relationship between the effluent sodium adsorption ratio (SAR), ESP and the infiltration rate of soils from the land disposal site is presented and the implication to the sustainability of the land disposal system discussed. The principal considerations necessary for the development of guidelines for the sustainable disposal of saline effluent are presented.

Key Words

Saline land disposal, irrigation, ESP, SAR, Infiltration rates.

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