Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Civil Engineering

First Advisor

Dr. Lyle Johnson


Anaerobic digestion is a method of sludge stabilization commonly used by municipalities on wastewater sludges. The process takes place in a-sealed vessel in the absence of free molecular oxygen and biologically converts a portion of the organic material to primarily methane and carbon dioxide gas. The methane, which is the major component of natural gas, may be used as a source of energy for the treatment plant. The wastewater treatment facility utilized in this study was located in Sioux Falls, South Dakota. This facility uses the methane produced in the anaerobic sludge digestion process to heat the digesters as well as to power generators to provide supplemental electrical power to the treatment plant. Any excess gas produced is compressed and stored on site in a gas sphere for later use. This study will investigate the possibility of adding whey and initial vat wash down water directly to the anaerobic digesters to produce additional gas while reducing the organic loading to the treatment plant. Whey, which is a by-product from cheese making, is produced in large quantities along with the cheese. The whey is a green-yellow liquid, approximately 90 percent water, and has a high organic content. Currently Land-O-Lakes Dairy in Sioux Falls is discharging the whey it produces directly to the City's sanitary sewer system. The whey adds an additional pollutional load to the wastewater treatment plant and thus results in an increased solids production in the secondary and tertiary portions of the treatment process. The City of Sioux Falls bases its sewer use Charge for its industrial users on the organic loading and wastewater flow. Discharging of the whey and initial wash water to the sanitary sewer system imparts- a relatively high sewer use charge on the dairy. Addition of the whey and initial wash water directly to the anaerobic digesters was investigated due to the possibility of a number of benefits: 1) the organic loading to the aerobic portion of the wastewater treatment plant would be reduced thus lowering the oxygen requirement and the associated power costs, 2) a reduction in the amount of biological sludge generated, 3) production of additional methane which may be used as a source of energy for the treatment facility and 4) reduction of the sewer use charges imparted on Land-O-Lakes. Because of lack of available information on anaerobic codigestion of whey and municipal sewage sludge a research project was conducted to determine the treatability and the effect that the addition of whey would have on the operation of the anaerobic digestion process.

Library of Congress Subject Headings

Sewage sludge digestion

Factory and trade waste


South Dakota State University Theses



Number of Pages



South Dakota State University