Use of reflectors to enhance the synergistic effects of solar heating and solar wavelengths to disinfect drinking water sources

Abstract

Aluminum reflectors were added to solar units designed to inactivate faecal microorganisms (faecal coliform, E. coli, enterococci, FRNA coliphage, C. perfringens) in stream water and diluted sewage by the two mechanisms (solar heat, solar UV) known to inactivate microorganisms. During sunny conditions, solar units with and without reflectors inactivated E. coli to <1 CFU/100 ml to meet drinking water standards. Solar units with reflectors disinfected the water sooner by increasing the water temperature by 8-10°C to 64-75°C. However, FRNA coliphages were still detected in these samples, indicating that this treatment may not inactivate pathogenic human enteric viruses. During cloudy conditions, reflectors only increased the water temperature by 3-4°C to a maximum of 43–49°C and E. coli was not completely inactivated. Under sunny and cloudy conditions, the UV wavelengths of sunlight worked synergistically with increasing water temperatures and were able to disinfect microorganisms at temperatures (45-56°C), which were not effective in inactivating microorganisms. Relative resistance to the solar disinfecting effects were C. perfringens > FRNA coliphages > enterococci > E. coli > faecal coliform.

Effect of soaking and gaseous treatment on GABA content in germinated brown rice

“…In general, Bacillus and molds such as Aspergillus are widely distributed in stored grain (Tsuruta, Ikekawa, & Saito, 1984). Although they die when treated at over 80°C for 10 min (Rijal & Fujioka, 2003), it is possible that bacterial spores survive. High-pressure treatment reduced the viable bacterial count in brown rice, but number of bacterial spores subsequently increased (Kinefuchi et al, 1999a(Kinefuchi et al, , 1999b.…”

Speeding up solar disinfection (SODIS): effects of hydrogen peroxide, temperature, pH, and copper plus ascorbate on the photoinactivation of E. coli

“…Several groups have already described modifications to accelerate SODIS. Sunlight exposure combined with water temperatures of 45-508C resulted in rapid, synergistic inactivation, (Wegelin et al 1994;Sommer et al 1997;McGuigan et al 1998) leading to the use of reflectors (Kehoe et al 2001;Rijal & Fujioka 2003;Mani et al 2006), bottles with the bottoms painted black (Sommer et al 1997), and thermoregulated reactors (Sommer et al 1997) to accelerate the process. Several groups have used TiO 2 as a suspended catalyst or coated onto a support to accelerate the photoinactivation of bacteria, (Ireland et al 1993;Dunlop et al 2002;Salih 2002;Rincon & Pulgarin 2004, 2006 while others have proposed the use of photosensitizers such as methylene blue in SODIS (Acher & Juven 1977;Wegelin et al 1994).…”

Drinking Water Disinfection by Solar Radiation

“…Periodic agitation, using foil to increase reflection rate, adding non-transmissive backing to the container, circulation of water on a black surface in a closed enclosure that passes UVA radiation, using a solar collector connected to a double glass enclosure, and painting the half of the bottle's black to increase the achievable temperatures are main examples of these enhancement applications [22,35,39,67,71,82].…”

“…It is understood from results of previous studies, these methods help to improve or enhance the traditional solar disinfection process [22,35,39,67,82] since over 6 log E.coli inactivation can be achieved by using these ways [39,71].…”