The densities of filamentous fungal colonies, together with physicochemical and bacteriological parameters, were assessed in a chlorinated and unchlorinated drinking water distribution system at eight separate times over a period of 1 year. Filamentous fungal colonies were enumerated by membrane filtration on Czapek-Dox agar. The mean number of filamentous fungal colony-forming units per 100 mL of drinking water was 18 in the unchlorinated and 34 in the chlorinated system. The majority of filamentous fungi isolated wee saprophytic Deuteromycotina. The four most frequently occurring genera were Penicillium, Sporocybe, Acremonium, and Paecilomyces. In the chlorinated system, only physicochemical parameters correlated with observed fungal frequencies, whereas in the unchlorinated system, none of the parameters exhibited significant correlations with fungal numbers.

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Tetrachloroethylene has been detected in concentrations ranging from a few micrograms per litre to several milligrams per litre in dead ends of water distribution systems made of vinyl‐toluene‐lined asbestos–cement pipe. About 1600 km (1000 mi) of this lined pipe is being used, primarily in New England. Tetrachloroethylene concentrations can be lessened by flushing and installing continuous bleeders, two of the solutions being suggested to correct this organics problem, which resulted from steps to control corrosion of asbestos–cement pipe. Physicochemical and microbiological analyses were performed on influent and effluent samples taken from Garvey Reservoir (Los Angeles County, Calif.). Data collected on particle counts and size distributions, total plate count, coliform bacteria, algal counts, chlorophyll, turbidity, copper, and iron were analyzed with a computerized statistical package. The quality of the influent was degraded through biological activity in the reservoir to produce a lower‐quality effluent. Results indicated that algae were associated with increased turbidity and particulate levels and might enhance or support bacterial activity, including physical protection of bacteria against the effects of chlorination.