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ARS Home » Pacific West Area » Kimberly, Idaho » Northwest Irrigation and Soils Research » Research » Publications at this Location » Publication #60251
Title: ESTIMATING POLYACRYLAMIDE CONCENTRATION IN IRRIGATION WATER

Author
item Lentz, Rodrick
item Sojka, Robert
item Foerster, James

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Some farm managers in the Western U.S. are controlling irrigation- induced erosion by amending irrigation furrow inflows with water- soluble, anionic polyacrylamide (PAM) at low concentrations (0-10 mg/L). Current research seeks to determine the fate of PAM, once added to furrow water streams. We developed and tested an instrumented flocculation test for determining PAM concentration in irrigation- water. The procedure adds a standard clay mineral to a PAM-amended water sample, which is agitated, then placed in a spectrophotometer. Flocculation and settling in the suspension as function of transmitted light is monitored over time. PAM concentration was correlated with settling-related transmittance changes. The procedure can detect as little as 0.1 mg/L PAM dissolved in irrigation water. Accuracy of the test ranges from 0.06 to 0.11 mg/L for 0-2.5 mg/L PAM and 0.39 to 0.86 mg/L for 2.5-10.0 mg/L PAM. Independent operator error was well within the recommended accuracy. The CSI test provides a relatively simple, rapid, and accurate method for determining polyacrylamide in surface waters. The CSI test will not only be applicable to irrigated agriculture and agricultural research, but potentially may provide a useful tool for other industries, such as, wastewater treatment, mining, paper-making, and/or oil field uses.

Technical Abstract: Some farm managers in the Western U.S. are controlling irrigation- induced erosion by amending irrigation furrow inflows with water- soluble, anionic polyacrylamide (PAM) at low concentrations (0-10 mg/L). We developed and tested an instrumented flocculation test for quantitativel determining PAM concentration in irrigation-water. The procedure adds a kaolinite mineral standard to a PAM-amended water sample, which is agitate then placed in a spectrophotometer. Flocculation and settling in the suspension as function of transmitted light is monitored over time. PAM concentration was correlated with settling-related transmittance changes. parameter, the time needed to initiate suspension clearing (clarity- shift inflection, CSI), was highly correlated (r=0.91-0.98). The CSI parameter is used as the procedure endpoint. The procedure is particularly sensitive to variations in the amount of kaolinite added, sample volume, and sample water characteristics such as salinity, temperature, and original sediment concentration in the sampled furrow- water. The sediment effect on CSI was attributed to sediment-induced increase in the sample's dissolved organic carbon concentration. The procedure can detect as little as 0.1 mg/L PAM dissolved in irrigation water, although in samples containing > 4 ml volume settled sediment, the PAM detection limit is approximately 0.25 mg/L. Precision ranges from 0.06 to 0.11 mg/L for 0-2.5 mg/L PAM and 0.39 to 0.86 mg/L for 2.5-10.0 mg/L PAM. Independent operator error was well within the recommended accuracy. The CSI test provides a simple, rapid, and accurate method of determining polyacrylamide in surface waters.