Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Civil Engineering

First Advisor

Dwayne A. Rollag


The objectives of the investigation were: 1.) to determine the validity of the Caldwell-Lawrence diagrams in predicting alkalinity, calcium, and pH values at various levels of lime addition of the softening process. 2.) to determine the practical application of the diagram for plant operators in daily operations and design engineers for design calculations. Throughout the investigation, primary consideration was given to the practical aspects of water treatment in terms of water sampled, methodology, and.statistical analysis of test results. Construction of the Caldwell-Lawrence diagrams is based on chemical equilibrium between the carbonic species and calcium and magnesium in water. The theory is well documented in the literature and is the very backbone of equilibrium chemistry. It was the practical applications of these equilibrium equations that were investigated. If the methods of chemical determination by Caldwell-Lawrence are adversely affected by local conditions and the routine problems encountered in daily plant operations, the benefit for both operators and design engineers would be greatly reduced.

Library of Congress Subject Headings

Water quality


Includes bibliographical references



Number of Pages



South Dakota State University