Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Civil Engineering


In recent years, State and Federal governments have developed water pollution control legislation in response to the public's growing concern for conservation of water resources. This legislation has been enacted to obtain the highest water quality that will provide maximum benefit to the people. Water quality standards for the surface waters of South Dakota have been developed based on the beneficial uses of these sur face waters. Included in these standards are bacterial requirements for streams. The establishing of the bacterial standards has increased the need for disinfection processes in wastewater treatment plants. Although several agents may be employed to accomplish disinfection of wastewater, chlorine is most commonly used. Chlorine is potent, easily applied and measured, and economical to use. However, some plants utilizing chlorination have had difficulty controlling effluent bacterial quality. This is primarily due to poorly conceived designs of wastewater chlorination systems, or improper operation of existing facilities. Despite the problems, chlorination is the most prominent means of wastewater disinfection. Upon notification by the South Dakota Department of Health that wastewater disinfection would be required, the City of Sioux Falls decided upon chlorination to meet these requirements. The Sioux Falls Wastewater Treatment Plant is divided into two sections, the industrial section and the combined domestic -industrial section. The industrial flow enters the plant in a line separate from the domestic flow and passes through primary sedimentation tanks and roughing filters. From the filters, part of the flow is settled and recycled to the influent of the trickling filters. The remainder of the industrial flow is clarified and brought back to the head of the plant where it mixes with the domestic flow. The combined domestic. and industrial flow is then subjected to the activated sludge process. The treated wastewater is then discharged to the Big Sioux River. Plant personnel were unfamiliar with the theory of chlorination. The chlorinators were set manually in order to obtain a combined chlorine residual at the effluent of the chlorine contact tank. This was believed to provide adequate disinfection. After measuring· residuals for a period of time, a "rule of thumb" procedure was developed for setting the chlorine dosage. The pounds-per- day setting on the chlorinators was calculated by taking the total flow into the plant, dividing it by three, and multiplying this result by one hundred.

Library of Congress Subject Headings

Water -- Purification

Sewage disposal -- South Dakota -- Sioux Falls

South Dakota State University Theses



Number of Pages



South Dakota State University