New articles in Water Research

[Muruleedhara Byappanahali <byappan@usgs.gov>]

Water
Research 
Volume
41, Issue 1 , January 2007, Pages
3-10 

Quantitative evaluation of bacteria released by bathers
in a marine water

Samir M. Elmir^{a, b, c}, Mary E. Wright^{a, b}, Amir Abdelzaher^{a, b}, Helena M. Solo-Gabriele^{a, b, ,} , Lora E. Fleming^a, Gary Miller^c, Michael Rybolowik^c, Meng-Ta Peter Shih^d, Segaran P. Pillai^d, Jennifer A. Cooper^d and Elesi A. Quaye<sup>d

a</sup>NSF-NIEHS Oceans and Human Health Center, University of Miami, Rosenstiel School for Marine and Atmospheric Sciences,1801 NW 9 Avenue, Suite 200 (R-669), Miami, Florida 33136, USA
^bDepartment of Civil, Architectural, and Environmental, Engineering, University of Miami, P.O. Box 248294, Coral Gables, Florida, 33124-0630, USA
^cMiami-Dade County Health Department, 1725 NW 167 Street Miami, Florida 33056, USA
^dFlorida Department of Health, Bureau of Laboratories-Miami, 1350 NW 14 Street, Miami, Florida, USA

Received 17 July 2006;  revised 24 September 2006;  accepted 2 October 2006.  Available online 17 November 2006.

Abstract

Enterococci, a common fecal indicator, and Staphylococcus aureus, a common skin pathogen, can be shed by bathers affecting the quality of recreational waters and resulting in possible human health impacts. Due to limited information available concerning human shedding of these microbes, this study focused on estimating the amounts of enterococci and S. aureus shed by bathers directly off their skin and indirectly via sand adhered to skin. Two sets of experiments were conducted at a marine beach located in Miami-Dade County, Florida. The first study, referred to as the “large pool” study, involved 10 volunteers who immersed their bodies in 4700 L during four 15 min cycles with exposure to beach sand in cycles 3 and 4. The “small pool” study involved 10 volunteers who were exposed to beach sand for 30 min before they individually entered a small tub. After each individual was rinsed with off-shore marine water, sand and rinse water were collected and analyzed for enterococci. Results from the “large pool” study showed that bathers shed concentrations of enterococci and S. aureus on the order of 6×10⁵ and 6×10⁶ colony forming units (CFU) per person in the first 15 min exposure period, respectively. Significant reductions in the bacteria shed per bather (50% reductions for S. aureus and 40% for enterococci) were observed in the subsequent bathing cycles. The “small pool” study results indicated that the enterococci contribution from sand adhered to skin was small (about 2% of the total) in comparison with the amount shed directly from the bodies of the volunteers. Results indicated that bathers transport significant amounts of enterococci and S. aureus to the water column, and thus human microbial bathing load should be considered as a non-point source when designing recreational water quality models.

Keywords: Recreational water; Bacteria indicators; Enterococci; Staphylococcus aureus; Bathers; Sediments; Beach sand; Non-point pollution sources; Water quality models

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Water Research
Volume 41, Issue 1 , January 2007, Pages 235-243

Effects of sonication on bacteria viability in wastewater treatment plants evaluated by flow cytometry—Fecal indicators, wastewater and activated sludge

Paola Foladori^{a, ,} , Bruni Laura^b, Andreottola Gianni^a and Ziglio Giuliano<sup>a

a</sup>Department of Civil and Environmental Engineering, University of Trento, Via Mesiano, 77, 38050 Trento, Italy
^bSOIS Biological and Chemical Laboratories, Autonomous Province of Trento, via Pozzo, 6, 38100 Trento, Italy

Received 26 January 2006;  revised 7 July 2006;  accepted 21 August 2006.  Available online 18 October 2006.

Abstract

The application of sonication to wastewater or sludge contributes to the dispersion of aggregates, the solubilisation of particulate matter with an increase in its biodegradability, the damage of microorganisms due to the loss of cellular membrane integrity. This research is aimed at investigating the effects of sonication at 20 kHz frequency on viability of microorganisms present in raw wastewater and activated sludge taken from a municipal wastewater treatment plant, as well as pure strains of Escherichia coli and E. faecalis. Flow cytometry was applied for the identification and quantification of viable and dead bacteria free in the bulk liquid, after the fluorescent staining of cellular nucleic acids. The main results showed that: (i) cells of E. coli were highly sensitive to sonication, even at low specific ultrasonic energy (E_s), and disintegration of a large amount of cells was observed; (ii) on the contrary E. faecalis were more resistant than E. coli, even if high levels of E_s were applied; (iii) bacteria in raw wastewater exhibited a dynamic of viable and dead bacteria similar to E. coli; (iv) in activated sludge samples, low levels of E_s produced a prevalent disaggregation of flocs releasing single cells in the bulk liquid, while disruption of bacteria was induced only by very high levels of E_s.

Keywords: Sonication; Bacteria viability; Cellular membrane integrity; Flow cytometry;

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Murulee Byappanahalli, Ph. D.
Research Microbiologist
U.S. Geological Survey, Great Lakes Science Center
Lake Michigan Ecological Research Station,
1100 N. Mineral Springs Road
Porter, Indiana 46304
Phone: (219) 926-8336 ext. 421
Fax:      (219) 929-5792
E-mail: byappan@usgs.gov