Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Civil Engineering

First Advisor

Dwayne A. Rollag


The city of Yankton, South Dakota draws its drinking water supply from the Missouri River. The water contains organic matter which may form trihalomethanes upon chlorination, and produce tastes, odors, increased chlorine demand, and reduced flocculation efficiency. In this research ozone was applied to raw water through use of a pilot plant to determine the effects of ozonation on organics, chlorine demand, and flocculation. Ancillary studies were conducted to find surrogate parameters for total organic carbon. Following a preliminary study based on trihalomethane reduction, ozone dosages of 0, 2, 4, and 8 mg/1 were applied to the raw water at contact times of 10, 15, and 20 minutes. The ability of ozone to reduce organics was determined by measuring total organic carbon and chemical oxygen demand. Tota1 organic carbon and chemica1 oxygen demand were also determined on the settled jar test samples. Jar tests were also used in the flocculation research. Chemicals used at the Yankton Plant were added to both raw and ozonated water samples used in the jar test procedure. The settled samples were then measured for turbidity which was assumed to be a direct function of flocculation efficiency. Chlorine demand tests were performed on raw water, ozonated raw water, and settled jar test samples. Samples were chlorinated, and after a sufficient contact time the chlorine demand of the samples was determined. The various surrogate parameters for total organic carbon that were tested were chemical oxygen demand, apparent color, true color, raw ultraviolet absorbance, and filtered ultraviolet absorbance. Ozonation resulted in a reduction in the organic content of the· raw samples, but did not change the organic content of the jar test samples. Ozonation did reduce the chlorine demand of the raw samples, but had a variable effect on the chlorine demand of the jar test samples. In the flocculation studies, aeration resulted in an increased flocculation efficiency, whereas ozonation resulted in a decreased flocculation efficiency. This was a probable explanation for the variability of the organics and chlorine demand data. In the study involving surrogate parameters for total organic carbon, no acceptable surrogate parameter for total organic carbon was found.

Library of Congress Subject Headings

Water -- Purification -- Ozonation
Water -- Purification -- Flocculaton
Water -- Purification -- Chlorination
Water -- Purification -- Organic compounds removal
Yankton (S.D.) -- Water-supply



Number of Pages



South Dakota State University