Sunlight Inactivation of Fecal Indicator Bacteria and Bacteriophages from Waste Stabilization Pond Effluent in Fresh and Saline Waters

Abstract

Sunlight inactivation in fresh (river) water of fecal coliforms, enterococci, Escherichia coli, somatic coliphages, and F-RNA phages from waste stabilization pond (WSP) effluent was compared. Ten experiments were conducted outdoors in 300-liter chambers, held at 14°C (mean river water temperature). Sunlight inactivation (k S ) rates, as a function of cumulative global solar radiation (insolation), were all more than 10 times higher than the corresponding dark inactivation (k D ) rates in enclosed (control) chambers. The overall k S ranking (from greatest to least inactivation) was as follows: enterococci > fecal coliforms > E. coli > somatic coliphages > F-RNA phages. In winter, fecal coliform and enterococci inactivation rates were similar but, in summer, enterococci were inactivated far more rapidly. In four experiments that included freshwater-raw sewage mixtures, enterococci survived longer than fecal coliforms (a pattern opposite to that observed with the WSP effluent), but there was little difference in phage inactivation between effluents. In two experiments which included simulated estuarine water and seawater, sunlight inactivation of all of the indicators increased with increasing salinity. Inactivation rates in freshwater, as seen under different optical filters, decreased with the increase in the spectral cutoff (50% light transmission) wavelength. The enterococci and F-RNA phages were inactivated by a wide range of wavelengths, suggesting photooxidative damage. Inactivation of fecal coliforms and somatic coliphages was mainly by shorter (UV-B) wavelengths, a result consistent with photobiological damage. Fecal coliform repair mechanisms appear to be activated in WSPs, and the surviving cells exhibit greater sunlight resistance in natural waters than those from raw sewage. In contrast, enterococci appear to suffer photooxidative damage in WSPs, rendering them susceptible to further photooxidative damage after discharge. This suggests that they are unsuitable as indicators of WSP effluent discharges to natural waters. Although somatic coliphages are more sunlight resistant than the other indicators in seawater, F-RNA phages are the most resistant in freshwater, where they may thus better represent enteric virus survival.

Staphylococcus aureus Strain Newman Photoinactivation and Cellular Response to Sunlight Exposure

“…A number of studies have therefore investigated bacterial photoinactivation in the context of environmental water quality (1)(2)(3)(4)(5)(6)(7), with further studies also focusing on photoinactivation in drinking water treatment (8)(9)(10)(11), photodynamic therapy (12)(13)(14)(15), and wastewater treatment (16)(17)(18)(19)(20). Bacteria can be inactivated by sunlight by direct and indirect mechanisms.…”

Densidade de Enterococcus sp em águas recreacionais e areias de praias do município de São Vicente-SP, Brasil e sua relação com parâmetros abióticos

“…Durante a maré baixa, todos os corpos de água, inclusive aqueles que recebem carga orgânica, têm uma maior vazão, sendo despejados na água do mar. Além disso, a sobrevivência de microrganismos patógenos na água do mar diminui com o aumento da salinidade 14,15 , o que explica a correlação negativa entre a salinidade e as densidades bacterianas na água obtida no presente estudo.…”

Constructed Wetlands

“…Different pathogen types are also not necessarily removed at the same rate by a similar mechanism. For example, it was stated in the Waste Stabilization Pond chapter that viruses are generally more resistant than bacteria to removal from sunlight mediated reactions (Davies-Colley et al, 2005a;Sinton et al, 2002) and differences in their structural and genetic composition impacts the rate of removal (Silverman et al 2013;Mattle et al 2014;Kohn et al 2016).…”

“…A free surface flow constructed wetland which has some open areas without vegetation (e.g., zone 2 in Figure 8 and the front part of the experimental wetland in Figure 4b) can allow for pathogen exposure to sunlight. UV-B (280 -320 nm), UV-A (320-400 nm) and photosynthetically active radiation (PAR > 400 nm) of the solar spectrum are known to be responsible for inactivating indicator microorganisms (Muela et al, 2000;Sinton et al, 2002;Kadir and Nelson, 2014;Silverman and Nelson, 2016). The dominating bactericidal portion of the solar spectrum is the UV-B radiation which causes direct (photo-biological) DNA damage (Jagger, 1985).…”