| To assess the microbiological water quality and determine the effects of on-site disposal systems (OSDS) on the adjacent groundwater and surface waters, 296 groundwater (GW) samples and 18 near-shore surface waters were collected from OSDS and control sites adjacent to Crane Creek, Florida, from June 2002 to May 2003. Fecal indicators measured were total coliform (TC), fecal coliform (FC), fecal streptococci (FS), and enterococci (ENT). Also, concentration of somatic (SOM) and F-male coliphages, and Vibrio (VIB) were determined. Salinity (S), temperature (T), dissolved oxygen (DO), pH, turbidity (Tur), and rainfall were measured to compare them with the presence of microorganisms in the samples. Groundwater seepage rates into Crane Creek were determined to estimate loading rate to the Creek. Fecal contamination of both groundwater and Crane Creek surface waters was evident, with concentrations of fecal indicators two-fold to nine-fold higher in surface water than groundwater. Groundwater contamination appeared to be most related with animal sources, as FS was the most frequent bacteria isolated (78%), and low FC:FS ratios (<0.7) were found at most locations. In sites having septic tanks (OSDS), higher concentrations and frequency of fecal indicators, especially FC, were found in transects near the septic tanks and drainfield. Higher FC:FS ratios were found in these locations, indicating human contamination. A statistically significant (p < 0.05) difference between FS means was found between sites. Higher concentrations of bacterial indicators in groundwater were found during June through September and also during March, exhibiting significant (p < 0.05) correlation with the rain and turbidity. In contrast, in surface water, higher concentrations were found during the dry season, indicating higher increases due to evaporation than to runoff or groundwater influence. The presence of Vibrio showed seasonal variations with highest concentrations occurring during November, December and March to May. A negative correlation (r = -0.76; p < 0.05) was found between bacteriophages and temperature in surface water, and is associated with inactivation of viruses. In general, no significant (p < 0.05) correlations were found between bacterial indicators and bacteriophages. Significant difference (p < 0.01) between concentration of microorganisms in piezometer and pushpoint was found, with higher values using the piezometer sampler, this may be related to the larger capture zone of the piezometer sampler. |
