Document Type

Thesis - Open Access

Award Date

1983

Degree Name

Master of Science (MS)

Department

Civil Engineering

Abstract

Groundwaters often contain considerable amounts of carbon dioxide and under anaerobic conditions, the ferric and manganic compounds are reduced by the slightly acidic water to their soluble ferrous and manganous states, and solution occurs without difficulty. The development of anaerobic conditions is essential for appreciable amounts of iron and manganese to gain entrance to a water supply. For this reason, groundwaters usually contain much higher concentrations of iron and manganese than do surface waters. An oxidation process is the best method for removing soluble iron and manganese. During an oxidation process, the soluble ferrous (Fe+2) and manganous (Mn+2) compounds will be converted to ferric (Fe+3) and manganic (Mn+4) precipitates (Fe(OH)J) and Mn02. such as ferric hydroxide Humans suffer no known harmful effects from drinking waters containing iron and manganese. However, for economic and aesthetic reasons, the 1962 water quality standards established by the United States Public Health Service (USPHS) recommended maximum iron and manganese concentrations of 0.3 and 0.05 mg/1 respectively. Furthermore, the goal of the American Water Works Association (AWWA) is to maintain level s of iron and manganese below 0.05 and 0.01 mg/1 respectively. Iron and manganese concentrations in excess of the USPHS limits are objectionable for the following reasons: 1. The precipitation of iron and manganese alters the appearance of water, turning it a yellow-brown to black. 2. Iron and manganese precipitates cause black and brown stains on laundry and porcelain plumbing fixtures. 3. Clonothrix and Crenothrix, which are commonly called iron bacter1a, use iron and manganese in their metabolism. If small amounts (0.1 mg/1) of iron and manganese are allowed to enter the distribution sys tern, these forms of 1ife may thrive and cause slimes which will, in turn, reduce the effective area of distribution pipes, clog meters, and obstruct valves. 4. When the bacterial growths die off and decay, taste and odor problems occur. 5. Increased flow rates frequently resuspend iron and manganese deposits, resulting in high turbidites. 6. Iron- and manganese-bearing waters may impart a disagreeable color or taste to beverages as well as forming a dark deposit on vegetables during cooking. 7. Water containing iron and manganese is unsuitable for many industrial processes including paper manufacturing, dyeing, bleaching, and film developing. 8. Iron and manganese themselves, in concentrations greater than a few milligrams per liter, will impart a metallic or bitter taste to the water. The city of Sioux Falls, South Dakota obtains its water supply from the Big Sioux aquifer below and adjacent to the Big Sioux River north of Sioux Falls. While there are two surface supply intakes on the diversion canal, the city mainly depends on a field of 34 wells to provide the water needed. Because the raw water generally has iron concentrations in the range of 3.0 to 6.0 mg/1 and manganese concentrations in the range of 2.0 to 2.6 mg/1, the treatment process is designed primarily to remove iron and manganese. The city presently employs prechlorination, lime softening, flocculation, recarbonation, chlorination, fluoridation, and filtration. Iron and manganese levels in the finished water comply with the USPHS recommended standards. The purpose of this study was to determine the. feasibility of using ozonation followed by filtration to remove iron and manganese. A small scale pilot plant was utilized to generate and expose the ozone to the raw water. The filter media and filtering rates employed during the pilot studies were identical to those used at the Sioux Falls Water Treatment Plant.

Library of Congress Subject Headings

Water -- Purification -- Ozonation

Iron

Manganese

South Dakota State University Theses

Format

application/pdf

Number of Pages

105

Publisher

South Dakota State University

Share

COinS