presence of microbial indicators in reid park wetlands jepson sutton scott stine swes 574
Post on 22-Dec-2015
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Purpose
• Determine the effect of water flow rate on microbial indicator concentration– Stagnant Pond, Turbulent Pond, and Waterfall
• Determine the effect of aquatic plants on microbial indicator concentrations– Open water vs. Planted area
• Presence/Effect of chlorination and pH• Compare presence of coliforms and enterococci
Experimental Problems
• It was determined that the ponds contained a shading dye that eliminated all plant growth.
Methods
• Collect samples from three varied areas of constructed wetlands at Reid Park– Located at 22nd Street and Country Club
• Use Colilert and Enterolert (IDEXX) to determine indicator concentrations
Total Coliforms
• Includes Escherichia, Citrobacter, Enterobacter, and Klebsiella
• Used as a standard for assessing fecal contamination of recreational and drinking water.
• Problems in accuracy due to ability to replicate in environment.
• Colilert positive=Yellow well
Fecal Coliforms
• Includes Escherichia and Klebsiella
• Definitive indication of fecal contamination
• Unable to replicate in the environment
• Colilert can enumerate E. coli concentrations
• Colilert positive=fluoresce under UV lamp
Colilert (IDEXX)
• Defined substrate technology (DST) simultaneous detection of total coliforms and E. coli
• Contains specific indicator nutrients: ortho-nitrophenyl-beta-D-galactopyranoside (ONPG) and 4-methyl-umbellifery-beta-D-glucuronide(MUG)
Colilert (IDEXX)
• Total coliforms react with ONPG to form yellow color.
• E. coli react with MUG to form fluorescent color
• Can detect low levels of total coliforms and E. coli (1CFU/100ml)
Fecal Streptococci Indicators
• Fecal Streptococci have advantages over coliform indicators:– they rarely multiply in water– they are more resistant to environmental stress
and chlorination– they generally persist longer in the environment
Enterococci
• Members of Lancefield Group D of Streptoccocus (fecal streptococci subgroup)
• “Enterococci” - normal colonist of the human large intestine
• Streptococcus often given as genus of this group in water industry
Enterococci
• Includes Enterococcus species faecalis, faecium, avium, and durans
• E. faecalis:– infects elderly patients undergoing surgery
• urinary tract, wounds, blood, appendix, intestinal structures
– emerging nosocomal opportunist due to:• rising incidence of multi-drug-resistant strains
• ease of person to person transfer
Enterococci
• Have been suggested as indicators of:– presence of enteric viruses in environment
• biosolids and seawater
– risk of gastroenteritis for recreational bathers
Enterolert (IDEXX)
• Uses a nutrient-indicator to detect enterococci– fluoresces when metabolized by enterococci
• Compared to standard membrane filtration (MF) method:– 50% fewer false positives– 95% fewer false negatives
FC/FS Ratio
• >4.0 = contamination of human origin
• <0.7 = contamination of animal origin
• Pond 1: FC/FS = 5
• Pond 2 : FC/FS = 15
• Waterfall : FC/FS = 0.8
Discussion
• Probable pathogen removal factors– temperature, natural die-off, sedimentation
• sedimentation most significant
• Studies have shown slower flow rates allow more settling of microorganisms– Pond 1 would be expected to have lowest
numbers
Discussion
• The highest amount of contamination in all categories occurred in Pond 2– Area where ducks gather
• Total coliforms were present in the largest amounts in all samples– Total coliforms broadest of groups assayed
• Presence of microorganisms could vary over time
Discussion
• Pond 1 and Pond 2 have similar distributions in all categories
• Waterfall does not follow the trend– Total coliforms higher compared to other
samples
• Why?– Turbulence– Cycling of water
Discussion
• FC/FS Ratio suggests:– Pond 1 and Pond 2 contamination is of human
origin
– Waterfall contamination is predominantly of animal origin
Discussion
• Values used to calculate ratio are not completely representative of FC and FS– E. coli is not only member of FC group– Enterococci is only a subgroup of FS
• Ratio only valid for recent (24 hrs) fecal pollution
• Validity of ratio has been questioned