Pilot- and bench-scale testing of faecal indicator bacteria survival in marine beach sand near point sources

Abstract

Aim Factors affecting faecal indicator bacteria (FIB) and pathogen survival/persistence in sand remain largely unstudied. This work elucidates how biological and physical factors affect die-off in beach sand following sewage spills. Methods and Results Solar disinfection with mechanical mixing was pilot-tested as a disinfection procedure after a large sewage spill in Los Angeles. Effects of solar exposure, mechanical mixing, predation and/or competition, season, and moisture were tested at bench scale. First-order decay constants for Escherichia coli ranged between −0·23 and −·102 per day, and for enterococci between −0·5 and −1·0 per day. Desiccation was a dominant factor for E. coli but not enterococci inactivation. Effects of season were investigated through a comparison of experimental results from winter, spring, and fall. Conclusions Moisture was the dominant factor controlling E. coli inactivation kinetics. Initial microbial community and sand temperature were also important factors. Mechanical mixing, common in beach grooming, did not consistently reduce bacterial levels. Significance and Impact of the Study Inactivation rates are mainly dependent on moisture and high sand temperature. Chlorination was an effective disinfection treatment in sand microcosms inoculated with raw influent.

Public Health Risks of Multiple-Drug-Resistant Enterococcus spp. in Southeast Asia

“…Enterococci are well adapted for living in biofilms, where adhesion to extracellular matrix proteins of the human gut is the first step in colonization and infection (15,16). The ability to form biofilms is a critical factor in causing endodontic and urinary tract infections, as well as endocarditis.…”

Routine screening of harmful microorganisms in beach sands: Implications to public health

“…Our belief is that potential public health issues concerning both sand and water quality of beaches should be taken into account in future policy decisions. In the event that beach sand is to be remediated, the use of chlorine (Mika et al, 2009) and iodine (Sabino et al, 2011) may be warranted.…”

Relationship between Enterococcal Levels and Sediment Biofilms at Recreational Beaches in South Florida

“…The validity of these closings is based on the positive correlation of FIB in the water column to both human pathogens (31,41) and swimmer illness (68), which has been well established for sewage sources. However, the detection of high levels of FIB in beach sands (3,4,15,19,21,24,26,28,39) has called into question these monitoring efforts and initiated a number of studies aimed at understanding FIB persistence and growth in sand (10,32,37,48,55,69,70,71) and/or their possible relation to pathogen presence (1,61). Recent reports have shown a positive relationship between sand contact activities and enteric illness as a function of concentrations of fecal microbial pollution in beach sand (33,34).…”

“…Once seeded into beach sand, these bacteria are able to persist (3,4,14,15,18,21,32,37,48,71). The persistence and growth of FIB have been investigated extensively to better understand contamination at recreational beaches (10,12,14,15,32,48,55,65,68,69,70,71), identifying important growth requirements in microcosms such as moisture content, temperature, and lack of predators. However, no set of factors can consistently account for the variation and patchy distribution of indicator levels in the natural beach environment.…”

“…In doing so, EPS provide protection from the significant physical and biological challenges of the shoreline environment, including frequent fluctuations in temperature, ion concentration, desiccation, UV radiation, predation, and wave action (12,16,17,64). Human intestinal bacteria, like enterococci, are well adapted for living in biofilms where adhesion to extracellular matrix proteins of the human gut is the first step in colonization and infection (48,49,50).…”