Degree Name

Master of Science (MS)

Semester of Degree Completion

1978

Thesis Director

William A. Weiler

Abstract

The survival of fecal coliforms, fecal streptococci, and heterotrophs after exposure to chlorine were compared in receiving waters of the Mattoon and Charleston, Illinois waste treatment facilities employing membrane filter techniques and Standard Plate Counts. Water samples were taken from receiving waters upstream from the treatment plant, from secondary effluent and chlorinated secondary effluent within the plant, and from downstream receiving waters. Stream flow contribution and plant effluent contribution required the calculation of dilution factors to determine expected numbers of the various microflora found downstream assuming no residual chlorine effect. Total chlorine concentration was measured by amperometric titration at the plant outfall and downstream approximately one quarter mile from the treatment plant. Fecal coliform-fecal streptococcus ratios were used to determine predominant sources of contamination from upstream and downstream receiving waters. Results showed that fecal coliforms were more susceptible to the effects of chlorine than fecal streptococci or heterotrophs. During periods of storm water flow the effects of chlorination were nullified (apparent survival greater than 100%). This increase was due to excessive dilution of chlorine by surface run-off, increased chlorine demand of the receiving water, and/or contribution of microorganisms by run-off from adjacent areas. It was concluded that the residual chlorine downstream (0.0-0.29mg/l) in the receiving water had a prolonged effect on plant contributed microorganisms and normal stream microflora. In general fecal coliforms were more sensitive to chlorine than fecal streptococci or heterotrophs. The feasibility of this method for the examination of the effects of residual chlorine on selected microflora is valid yet the methods of sewage treatment and the physiognomy of receiving bodies of water must be closely examined.

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