This study defined major factors influencing the survival of the bacterial indicators, fecal coliforms (FC) and fecal streptococci (FS), in separate storm drain sediments during dry weather periods. FC and FS abilities to survive were determined by field sampling and experimental treatments of laboratory stream models. The effects of interspecific competition, antagonism, and predation on FC and FS survivals were determined using recirculating models that contained either untreated drain water and sediment, cycloheximide-treated drain sediment, or autoclaved drain water and sediment seeded with drain isolates of FC and FS. Storm drain sediment FC and FS counts were stable at 105/100 ml during dry weather (4-6 days), with little or no bacterial supplementation from the water (10~-102/100 ml). Untreated (control) model FC and FS populations stabilized at 103/100 ml for 7-9 days. In cyctoheximide-treated models, FS and FC survived at 104 and 10~/100ml, respectively. In autoclaved-seeded models, FS and FC initial counts of 104/100ml increased to and stabilized at 107-109/100ml. Separate storm drain sediments serve as reservoirs of high concentrations of FC and FS during warm, dry weather periods. FC exhibited some ability to multiply in drain sediment. Native microfloral competition/antagonism (including bacterial predation) and protozoan predation are major biotic factors influencing FC and FS survivals. During warm, dry weather periods, abiotic factors were generally stable and had minimal affects on FC and FS survivals.

Fecal colitbrm (FC) disappearance studies were conducted in Ford Lake during the summer of 1979. Ford Lake, an artificial impoundment at the lower end of the Huron River drainage basin belov, ~ Ypsilanti, Michigan, receives all upstream flow (2072 km: of drainage). During dry weather an overall daytime FC disappearance rate of 0.4 (h-t) (K base e) was measured using dye tracer for timed collection. assuming a first order equation of the Chick type. Sedimentation was demonstrated as important in the overall FC disappearance in the upper end of the lake. Rooftop studies showed light level to affect daytime disappearance. Two types of wet weather conditions were documented: (1) where a substantial increase in flow occurred due to an isolated upriver storm; and (2) as a result of two different storm events in the Ford Lake area itself. In both cases, Ford Lake was effective in substantially reducing the large FC contribution.

Michigan area affects the bacterial indicator organism quality of the Huron River. Investigations during the 1985 summer period involved sampling during dry and wet periods with parallel determination on each sample for fecal coliforms, fecal streptococci, E. coli and enterococci. Wet weather bacterial indicator densities were statistically significantly higher than dry weather levels, and downstream densities were statistically significantly higher than upstream densities. The FC/FS (fecal coliforms/fecal streptococci) ratios for the storm drains were low and suggestive of more animal than human sources. The geometric mean EC/FC (E, coli/fecal coliforms) ratios were in the range of 0.82-1.34, well above the ratio of 0.63 calculated using the U.S. EPA recommended level for E. coil of 126/100 ml to the presently accepted level for fecal coliforms of 200/100 ml. If the intent is to maintain the currently accepted illness rate, additional results from other areas are necessary to refine the E. coil and enterococci levels for water quality standard development purposes. In general, physical-chemical observations reflected the source of the sample.

The occurrence of animal viruses in the aerosol emissions of wastewater treatment facilities was evaluated by direct assay and by the use of coliforms and coliphages as indicator organisms. Coliforms and coliphages were compared and evaluated with regard to their suitability as indicators of airborne animal viral contamination from wastewater treatment facilities. Two plants, one with treatment by activated sludge and the other by trickling filtration, were studied. Field air sampling procedures used large-volume air samplers, with recirculation devices, and Andersen samplers. Airborne viruses were enumerated by a most probable number (MPN) procedure. Partially treated liquid sewage contained about 1.0x 102 pfu 1-~ of animal viruses assayed on Buffalo Green IVlonkey (BGM) cells, 3.6 x 105 and 5.0 x 105 pfu It of coliphages, depending upon the E. coli host strain used for assay, and 2.0 x 10 9 colonies 1-~ of coliform bacteria. No airborne animal viruses were recovered, airborne coliphage levels averaged 2.3 x 10-t and 3.0 x 10-t MPNm-3, coliforms from aerosol emissions were 2.1 x 102 colonies m-3. Ratios of coliphages to animal viruses indicate that wastewater treatment plants may be continuous sources of low level concentrations of animal virus aerosols. Evidence shows coliforms to be much less stable than coliphages in the airborne state. Coliphages may be a more acceptable indicator of airborne animal viral contamination than coliforms.

Abstract--Survival of calf rotavirus and reovirus under controlled laboratory conditions in microorganism-free, distilled and wastewater at 8 and 26°C was examined by periodic measurement of cytopathic effects (CPE) and indirect fluorescent antibody (IFA) assays. Five samples of both water-types were collected and inoculated with the two viruses. Three samples of each type of water were divided into two bottles, one per virus, for incubation at 8°C. Two samples were used at 26°C, one per trial. In the absence of light and shaking at 26°C, 7 13 days were required for a loss of 90~o infectivity for rotavirus and reovirus, while at 8°C, averages were 80 days for rotavirus and 260 days for reovirus. Virus infectivity remained for more than 30 days at 26°C and 400 days at 8°C. Rates of decline were 10-100 times greater at 26 than at 8°C, but at both temperatures, the MPN log10 rate of decline of infectivity was linear.