Phosphorus removal from wastewater applied to land

J. C. Ryden and P. F. Pratt

Hilgardia, 1980, vol. 48, issue 1

Abstract: Low concentrations of phosphorus (P) are desired in surface waters to minimize production of organic materials which cause problems in water use. The low P concentrations characteristic of the soil solution suggest that soils represent an appreciable sink for P in wastewaters applied to land. The mechanisms responsible for maintaining low (usually less than 0.5 mg P 1-1 soil-solution P concentrations and for control of the chemical mobility of P in the soil profile appear in most cases, to involve a sorption reaction at soil surfaces with a hydrous oxide structure. Recent work has led to an interpretation of P sorption by soils which has direct relevance to an understanding of P removal from wastewater applied to land. Crops harvested at wastewater treatment sites, also represent a sink for added P. Phosphorus removal of 10% of that applied is typical, but 30 to 40% of the P applied at a rate of 200 to 300 kg P ha-1 yr-1 may be removed by harvested forage crops. Schemes of wastewater application to land involve either infiltration and percolation of the wastewater through the soil profile or overland flow. Most complete P removal is generally observed in infiltration-percolation schemes which permit maximum contact between wastewater and soil, and particularly if wastewater is applied to give a P input comparable to that under normal agricultural practice. Several mathematical models have been developed to predict P movement through a soil profile, but the P sorption data required are dificult to obtain. A simple mass-balance model is proposed, the P sorption parameters of which are easily measured, are independent of soil type, and can be adjusted to account for the kinetics of P sorption, thereby providing an estimate of the longevity of a treatment site for P removal.

Keywords: Resource/Energy; Economics; and; Policy (search for similar items in EconPapers)
Date: 1980
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