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Soil osmotic potential and its effect on vapor flow from a pervaporative irrigation membrane

Todman, L. C. ORCID:, Chhang, A., Riordan, H. J., Brooks, D., Butler, A. P. and Templeton, M. R. (2018) Soil osmotic potential and its effect on vapor flow from a pervaporative irrigation membrane. Journal of Environmental Engineering-Asce, 144 (7). 04018048. ISSN 0733-9372

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To link to this item DOI: 10.1061/(ASCE)EE.1943-7870.0001379


Pervaporative irrigation is a membrane technology that can be used for desalination and subsurface irrigation simultaneously. To irrigate, the tube-shaped polymer membrane is buried in soil and filled with water. Due to the membrane transport process, water enters the soil in vapor phase, drawn across the membrane when the relative humidity in the air-filled pores is low. Soils are typically humid environments, however, the presence of hygroscopic compounds such as fertilisers decreases the humidity. For example, at 20oC the humidity in air in equilibrium above a saturated ammonium nitrate solution is 63%. Here, experiments showed that the presence of fertilisers in sand increased the water flux across the membrane by an order of magnitude. An expression for vapor sorption into sand containing different hygroscopic compounds was developed and combined with a model of vapor and liquid flow in soil. The success of the model in simulating experimental results suggests that the proposed mechanism, adsorption of moisture from the vapor phase by hygroscopic compounds, explains the observed increase in the flux from the irrigation system.

Item Type:Article
Divisions:Life Sciences > School of Agriculture, Policy and Development > Department of Sustainable Land Management > Centre for Agri-environmental Research (CAER)
ID Code:74569
Publisher:American Society of Civil Engineers


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