Effects of Sample Holding Time on Concentrations of Microorganisms in Water Samples

• Published in: Water environment research Vol. 76; no. 1; pp. 67 - 72
• Main Authors: Selvakumar, Ariamalar, Borst, Michael, Boner, Mark, Mallon, Phil
• Format: Journal Article
• Language: English
• Published: Alexandria, VA Water Environment Federation 01.01.2004; Blackwell Publishing Ltd
• Subjects: Applied sciences; Continental surface waters; Enterobacteriaceae - isolation & purification; Enterococcus; Environmental agencies; Environmental Monitoring; Escherichia coli; Exact sciences and technology; Fecal coliforms; Freshwater; General purification processes; HOLDING TIME; INDICATOR ORGANISMS; Microorganisms; Natural water pollution; PATHOGENS; Pollution; Pseudomonas aeruginosa; Pseudomonas aeruginosa - isolation & purification; Reproducibility of Results; Research Papers; SANITARY WASTEWATER; Specimen Handling; Staphylococcus aureus; Staphylococcus aureus - isolation & purification; STORMWATER; Streptococcus; Time Factors; Wastewater; Wastewaters; Water Microbiology; Water pollution; Water quality; Water samples; Water treatment and pollution; WATERSHED; Watersheds; Pseudomonadales; Statistical analysis; Microbiology; Escherichia coli; Coliforms; Pseudomonas; Indicator; Waste water; Membrane separation; Pathogenic; Watershed; Membrane filtration; Bacteria; Pseudomonadaceae; Sample conservation; Storm water; Time analysis; Biological contamination; Enterobacteriaceae; Field study
• ISSN: 1061-4303; 1554-7531
• DOI: 10.2175/106143004X141591

This research investigated the effects of extending the holding time of samples for microbial analysis beyond the standard of 24 hours for purposes such as watershed characterization. Experiments were conducted with both sanitary wastewater and stormwater samples. The refrigerated samples (4 °C) were held for up to 9 days before being analyzed for two pathogens (Pseudomonas aeruginosa and Staphylococcus aureus) and five indicator organisms (total coliform, fecal coliform, fecal streptococcus, enterococcus, and Escherichia coli) by membrane filtration. The concentrations (as colony-forming units per 100 mL) were normalized by${\rm log}_{10}$transformation and used in subsequent statistical analysis testing for significant differences. The results suggested that the concentrations of microorganisms in water samples analyzed on days 1 and 2 did not vary significantly in 8 of 13 analyses. The results of a field study concluded that the concentration of fecal coliform did not change significantly between 7 hours holding time and greater than 24 hours holding time for fecal coliform.