Masters Theses

Paul D. Ewing

Date of Award

12-1988

Degree Type

Thesis

Degree Name

Master of Science

Major

Environmental Engineering

Major Professor

R. Bruce Robinson

Committee Members

Gregory Reed, Dennis Weeter

Abstract

Operating characteristics in iron and manganese sequestration are poorly understood. Most of the knowledge is laboratory based and needs to be expanded to the field. The primary objective of this study is to (1) develop detailed, quantitative documentation of effectiveness of sequestering in actual systems, (2) compare previous results and conclusions reported in the literature review with field findings, and (3) optimize the sodium silicate-chlorine method for iron control in the presence of calcium. Secondary objectives are to determine the effects on sequestering by water heaters and by neutral pH.

Data were collected both from the laboratory and the field. Laboratory results were obtained by treating a deaerated model groundwater containing 2 ppm of ferrous iron with sodium silicate and sodium hypochlorite. Tests were run over a five day period recording the filterable iron, total iron, tiurbidity, and pH for the various dosages involved. Field results were obtained by collecting samples at various points at each location and recording the data after the samples were brought back to the lab.

Both field and laboratory results show that stabilization is only temporal, that calcium reduces the length of stabilization, that an increase in the silica dosage increases the length of treatment in the presence of calcium, that long lag times between the silicate and chlorine dosages are not efficient to treatment, that stabilization breaks down faster at elevated temperatures, that no treatment is more favorable in manganese stabilization, and that objective, scientific field studies are able to characterize and quantify the success of sequestration at field sites. Other conclusions are that 0.45 μm filter results correlated slightly better with actual field practices than the 0.1 μm filter results, that better treatment at high pH are conflicting with previous studies where low pH was more favorable, and that previous results of laboratory studies have been shown to closely model field conditions.

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