Sewage Decomposition in Acid Mine
Drainage Water
H. A. Wilson, Professor of Bacteriology
Jack L. Hipke, Graduate Student
Thomas O. Rogers, Graduate Student
Department of Plant Pathology, Bacteriology, and Entomology
West Virginia University
Morgantown, West Virginia
The normal problems of sewage decomposition are compounded when sewage
enters an acid mine water polluted stream. The acid mine water itself is a pollution problem of great magnitude which, at present, seems to have no economical solution.
The bacteria active in sewage stabilization under normal conditions are inhibited or even killed in the strongly acid conditions in streams polluted with
much acid mine drainage. Carpenter and Hemdon (1) reported a tremendous
reduction in bacteria present in sewage after a two-hr period of contact with acid
mine water. Joseph and Shay (2) found a great reduction in total numbers of bacteria where acid mine water entered a sewage polluted stream.
Chubb and Merkel (3) reported that the dissolved oxygen in the Schuykill
River, with a pH of 4.3, gradually increased until the river received waters from
a tributary that flowed through a limestone region and raised the pH above 7.0.
They believed that the increase of dissolved oxygen indicated organic stability at
low pH and that decomposition began again, as indicated by a decrease in dissolved oxygen, when the pH returned to near neutral and sewage decomposers
were re-established in the water.
Ruchoft et al (4) followed the decomposition of sewage at pH values similar
to those found in sewage polluted, acid mine water streams. They suggested that
the biological self-purification process that occurs in acid sewage at pH values of
2.0 to 3.0 was largely the result of biochemical oxidation carried on by a limited
number of biological species. It has been stated that decomposition of sewage in
such strongly acid environments depends upon "select specific individuals ...
most fit to survive" (5) in the environment. The lower pH limit for most bacteria
is pH 4.5 to 5.0 (6). Porter (7) gives the minimum pH for 43 species of bacteria;
only six of these had a minimum pH for growth of 4.0 or below and eight between
4.0 and 4.5.
Normally, any discussion of sewage decomposition infers that most of the
activity is in the domain of bacteria. However, several species of filamentous
fungi commonly isolated from sewage polluted streams were active in sewage decomposition, especially at low pH levels (8). Yeasts have also been isolated from
sewage polluted streams (9) and sewage-acid mine water streams (10), but little
is known of their actual role in sewage decomposition.
This paper reports some of the results obtained from an investigation to learn
more about the mode and rate of sewage decomposition in acid mine water and
the microorganisms involved.
- 272