Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Civil Engineering


The history of anaerobic sludge digestion has shown an ever increasing body of knowledge concerning the causes and operation of anaerobic organic wastes. Two of the earliest methods used in he anaerobic treatment of organicwastes were cesspools and septic tanks. The theory of the design of these units was based upon retaining the waste material and allowing it to undergo bacterial decomposition. An improvement in the anaerobic treatment process was made with the advent of the Imhoff tank. In this unit the sedimentation and digestion portions were separated so that the sludge digestion unit was not in contact with the incoming sewage. Imhoff tanks flowed the design criteria of providing enough volume to hold the sludge until it was decomposed or until it was discharged. The above processes were operated at the temperature established by the incoming waste material and the environmental conditions. It was observed that the waste was broken down faster in the summer than in the winter. Based on this knowledge many studies were undertaken to determine the optimum temperatures for the degredation of organic material under anaerobic conditions. The vast majority of these investigations wee in the mesophilic and thermophilic temperature ranges. This is understandable because ir is at these higher temperatures that the faster reduction of organic waste is accomplished. Some study is needed, however, to determine the rate of solids reduction in the cryophilic (below 10°C) and temperate (10°-28°C) zones. The animal waste lagoons in northern climate utilizes anaerobic processes in the stabilization of their organic waste material. The design criteria for those units gives little consideration to the solids reduction occurring in the bottom sludge layer of the lagoon. The seasonal and daily variation in air temperature made the problem of evaluating solids reduction even more acute. The variation in temperature of the lower sludge layers of an animal waste laggon does not have the extreme variation of the air temperature. The objective of this laboratory investigation was to study the anaerobic reduction of organic fecal material at temperature approximating those found in the sludge layers of animal waste lagoons in northern climates. These ambient temperatures are generally less than 25°C and in most cases are those temperatures that prevail for the ground water at the lagoon location.

Library of Congress Subject Headings

Refuse and refuse disposal
Sewage disposal
Anaerobic bacteria




South Dakota State University