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Thesis (M.S.)—University of Nebraska—Lincoln, 1969. Department of Agricultural Engineering.


Copyright 1969, the author. Used by permission.


Runoff from beef cattle feedlots is one source of potential water pollution. Two alternatives are available to prevent feedlot runoff from polluting streams; the water can be spread on agricultural land as irrigation water, or it can be treated before it is released to the streams.

Zeta potentials on colloidal solids in feedlot water samples were investigated as one method of treatment control.To study the problem in the laboratory, samples of the feedlot surface material were obtained.The samples were mixed and frozen until used. All determinations were made using commercially available equipment in a temperature controlled room held at 70˚ F ± 1˚ F.

A statistical model was developed to define quadratic equations for three variables. Multiple regression analyses resulted in three quadratic equations to define three separate relationships.

Zeta potentials were found to average -29.5 millivolts on untreated samples. The potentials varied with pH and solids concentration according to theory.

Two different chemical treatments were tested to control the zeta potentials on the colloids. Alum effectively reduced the zeta potentials.The dosage required was high, and depended on solids concentration.As the solids concentration was reduced, lower dosages could be used to obtain similar charge reductions.

One organic polyelectrolyte was tested.It was more effective than alum in reducing the charges.The dosage of polyelectrolyte required depended on solids concentration as alum did.

The more important conclusions deduced from this study of suspended solids from a beef cattle feedlot surface were: 1) The zeta potentials of the solids were negative and varied with pH and sample dilutions.2) Particle zeta potentials could be controlled by chemical treatments.3) High chemical dosages were required to reduce the zeta potentials to near the isoelectric point.4) Quadratic equations could be written to accurately define the relationships between zeta potentials, solids concentrations, and pH; and zeta potentials, chemical dosages, and solids concentrations.

Advisor: Donald M. Edwards