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Removing soluble phosphorus in irrigation return flows with alum additions

Leytem, A.B. and Bjorneberg, D.L. (2005) Removing soluble phosphorus in irrigation return flows with alum additions. Journal of Soil and Water Conservation. 60(4):200-208.

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ABSTRACT: Phosphorus (P) losses from irrigated cropland transferred to surface waters via
irrigation return flows, can impair regional water quality. Best management practices to reduce
soil erosion on fields and sediment concentration in return flows do little to reduce soluble P
concentrations, which can exceed total maximum daily load (TMDL) limits for total P. Laboratory
and field tests were conducted to evaluate the effect of alum on soluble P concentration in return
flow water from an irrigation tract in southern Idaho. The laboratory study used two water
sources (tap and irrigation), three sediment concentrations (0, 100 and 1000 mg L-1), two added
P concentrations (0 and 1 mg L-1), and five alum concentrations (0, 5, 10, 20 and 40 mg L-1). Field
tests were conducted at sediment ponds on two irrigation drains with 20 to 500 mg L-1 sediment
and 0.09 to 0.19 mg L-1 dissolved P in inflow water. Regression analysis of laboratory data
showed a 53 percent reduction in soluble P concentration with 20 mg L-1 alum, which was similar
to field data. Applying 40 mg L-1 alum to irrigation water reduced soluble P concentrations up to
98 percent in the field. Achieving 50 percent soluble P reduction would cost about $0.007 m-3
($8.25 per ac ft) at the current alum cost of $0.33 kg-1 ($0.15 lb-1). Although alum effectively
reduced soluble P in irrigation return flow, the cost of applying alum may be too high for routine
use in many irrigation districts.

Item Type: Article
NWISRL Publication Number: 1335
Subjects: Water
Soil > Chemistry > Phosphorous
Water > Water quality
Depositing User: Users 6 not found.
Date Deposited: 18 Mar 2010 21:56
Last Modified: 14 Oct 2016 14:41
Item ID: 1358