Two approaches for the examination of microbially-caused degradation of water quality within water distribution systems were considered: the results of a questionnaire were analyzed and a sampling technique utilizing a concentrator was evaluated. A questionnaire, completed by water treatment plant operators in Virginia, was analyzed to ascertain what complaints regarding water quality were being received and what the causes of the complaints were. The most frequently reported complaints were those of taste and odor. Although they were not the sole factor, it appears nuisance bacteria were causative agents in degradation problems related to turbidity and red water. The Pellicon cassette system concentrator was evaluated for use during sampling in water distribution systems. The evaluation included determining the range of percent recovery in the retentate to be expected and the factors affecting this recovery. Thirty to sixty percent recovery of bacteria (Pseudomonas cepacia or Escherichia coli) in the retentate can be expected. The percent reduction in volume was the system parameter which most affected the percent recovery. / Master of Science