Kelly Ball

Publication Date


Advisor(s) - Committee Chair

Larry Elliott, Scott Ford, Martin Houston

Degree Program

Department of Biology

Degree Type

Master of Science


Because of the potential health hazards associated with the use of sludge for agricultural purposes, Dudley et al (1980) published a scheme for the routine analysis of bacteria in municipal sewage sludge. In this study, the Dudley et al scheme (1980) was modified by updating some of the procedures. Aerobically digested sludge generated by the Bowling Green Wastewater Treatment Plant, Bowling Green, Kentucky, was analyzed using the modified scheme. Sludge samples were collected once every two months over a one-year period from October 1989 to August 1990.

Egg yolk-free tryptose sulfite cycloserine agar in conjunction with the revewrse CAMP test was used to assay for Clostridium perfringens. This procedure improved the one proposed by Dudley et al. (1980) by achieving a higher confirmation rate, reducing testing time, allowing for easier interpretation of results, and increasing accuracy.

Selective and differential media by Rippey and Cabelli (1979) were added to the scheme to isolate Aeromonas, Aeroomonas hydrophila and Aeromonas caviae were successfully isolated wand were identified using the system by Cunliffe and Adcock (1989) for speciating aeromonads.

Baird-Parker medium was compared to mannitol salt agar for effectiveness in isolating Staphylococcus from sludge. Statistical analysis showed Baird-Parker medium to be significantly more effective than mannitol salt agar. However, neither agar reduced background flora to acceptable levels. Staphylococcus isolates were subject to species identification by the API Staph Ident system (Analytab Products, Plainview, New York). Staphylococcus xylosus, Staphylococcus haemolyticus, and Staphylococcus epidermidis were found to be present in the sludge.

A procedure by Ottolenghi and Hamparian (1987) was employed to isolate Salmonella in sludge. No salmonellae were isolated over the one year period.

Over the year-long study, bacterial numbers, with the exception of Clostridium perfringens and the total aerobic count, fluctuated with variations in the aerobic digester temperature. Numbers decreased as temperature increased. Clostridium perfringens counts were the most consistent throughout the year and exceeded fecal coliform and fecal streptococci counts in five of the six samplings.


Agriculture | Bacteriology | Biology | Environmental Microbiology and Microbial Ecology | Life Sciences | Microbiology