Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Civil Engineering


Numerous researchers have shown that THMs are essentially absent in natural waters but are nearly always present in chlorinated water supplies. Furthermore, it is generally agreed that THMs are formed by the reaction of chlorine with organic precursors, particularly humic substances, in the water. Thus, since surface waters typically are higher in organics, surface water supplies are usually higher in halogenated organics. The factors controlling production of THMs during potable water treatment have been investigated for a number of water supplies. Water parameters such as temperature, total organic carbon (TOC) content, pH, color, chlorine demand, turbidity, and water type (surface water or groundwater) have been shown to affect THM production. Because the analysis for THMs is a time-consuming and relatively expensive gas chromatographic procedure, a simple, rapid surrogate measurement that. would predict THM concentration with reasonable accuracy would seem desirable. Chlorine reacts with organic precursors in the water to form THMs, therefore a test that would measure these precursor concentrations in the raw water would be useful for anticipating finished water THMs. Through the use of these measurements, parameters influencing THM production most could be identified. If a suitable surrogate parameter could be found, it would be useful in routine water quality monitoring process control even though it may be of insufficient accuracy for evaluating compliance with EPA guidelines. The City of Yankton, South Dakota, draws its drinking water supply from the Missouri River. The raw water contains organic matter which may cause THMs upon chlorination, tastes, odors, increased chlorine demand, and reduced flocculation efficiency. Investigations were conducted to determine the abi1ity of ozone to reduce the formation of trihalomethanes. Raw water and raw water samples ozonated at contact times of 5, 10 and 15 minutes were chlorinated and analyzed for THMs at various times after chlorination. Jar tests were also used to determine the effect of coagulation on THM formation for both raw and ozonated raw water. Following chemical additions, stirring, and settling, the water samples were chlorinated and after various reaction times, the THM concentration was determined. Another objective involved the evaluation of ozone pilot plant data to seek out passib1e surrogate parameters for THMs. Data for both Yankton and Huron and were used for this investigation. The various parameters investigated were chemical oxygen demand (COD), true color, apparent color, raw ultraviolet (UV) absorbance, filtered UV absorbance, and TOC.

Library of Congress Subject Headings

Water -- Purification -- Ozonization


Yankton (S.D) -- Water-supply

Huron (S.D.) -- Water-supply

South Dakota State University Theses



Number of Pages



South Dakota State University