Document Type

Thesis - University Access Only

Award Date

2010

Degree Name

Master of Science (MS)

Department / School

Civil and Environmental Engineering

Abstract

Chloramines are becoming a popular choice for secondary disinfectants to control the formation of disinfection by-products in water distribution systems. As water treatment plants convert to chloramines, opportunities for blending waters disinfected with free chlorine and chloramine occur. The Mni Wiconi Water System in South Dakota is facing this issue. A core line has been constructed to carry chloraminated water from the Mni Wiconi water treatment plant to serve sponsor rural water systems. Chlorinated wells also provide water to three of the sponsor water systems. The primary objective of this project was to evaluate alternatives for potential blends of chlorinated sponsor system water with chloraminated core line water to serve the Mni Wiconi System. Existing water quality data generated by monitoring in distribution systems (Mni Wiconi core line as well as sponsor systems) was compiled and interpreted with particular emphasis on disinfectant residual and disinfection by-product concentrations. The fate of chlorine residuals and formation of disinfection by-products resulting from mixing Mni Wiconi core line water with source waters from the individual sponsor systems was determined in experimental tests. The test results revealed that the core line water chloramine decomposed to ammonia in sufficient quantities to recreate a chloramine residual as chlorinated sponsor water was blended with the core line water. Breakpoint chlorination of the core line water created TTHMs and HAAs above the USEP A regulation MCLs. As long as the blending is controlled so the free chlorine to ammonia ratio is less than 5: 1, a chloramine residual will remain. At higher ratios, the chlorine residual was depleted and breakpoint chlorination occurred. If the two source waters (chlorinated source and chloraminated source) are kept separate, both sources will be able to serve the Mni Wiconi System, and there will be no problems with breakpoint chlorination or residual depletion. In areas where the sponsor system is achieving chloramination of their water, the water can be directly blended with the core line water. In locations where the sponsor chlorinated water is blended with the chloraminated water, the blend ratio must be closely controlled to prevent breakpoint chlorination.

Library of Congress Subject Headings

Mni Wiconi Rural Water Supply Project (U.S.)

Water -- Purification -- Chlorination -- South Dakota

Water -- Purification -- Chloramination -- South Dakota

Water -- Purification -- Disinfection -- By-products

Format

application/pdf

Number of Pages

181

Publisher

South Dakota State University

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