Microbiological Decontamination of Water: Improving the Solar Disinfection Technique (SODIS) with the Use of Nontoxic Vital Dye Methylene Blue

Abstract

Rational use of water is a major challenge for governments and global organizations, with easy and inexpensive interventions being sought by communities that are not supplied with drinking water. In this context, solar disinfection (SODIS) has shown great efficiency for water disinfection. To speed up the process and improve inactivation, we studied the effects of methylene blue (MB) as a photodynamic agent because of its ability to absorb visible light (red wavelength) and generate singlet oxygen as a reactive species, thereby inactivating bacteria and viruses present in water. In this study, samples of clean mineral water were artificially contaminated with Gram-positive (Staphylococcus epidermidis or Deinococcus radiodurans) or with Gram-negative strains (Escherichia coli or Salmonella typhimurium) and exposed to traditional SODIS or to MB-SODIS. A lethal synergistic effect was observed when cultures were illuminated in the presence of MB. The obtained results indicate that bacterial inactivation can be achieved in a much shorter time when using MB associated with SODIS treatment. Therefore, this technique was able to provide safe water for consumption through the inactivation of microorganisms in general, including pathogens and some strains resistant to the traditional SODIS procedure, thus allowing its use in areas usually less exposed to sunlight.

The role of the light source in antimicrobial photodynamic therapy

“…The most common light sources reported for MB-mediated APDT were lasers (48.5%), LEDs (32%), and lamps (13%). The other light sources category (6.5% in total) includes so-called non-coherent light sources (name taken from publication methodologies), solar radiation, 454–456 optical parametric oscillator (OPO), 457 hand-held photopolymerizer (HHP), 459 endoscopy system, 458 superluminescent diodes (SLED or SLD) 460 and organic light-emitting diodes OLEDs 125,128,129 (Fig. 9).…”

Improvement of dyes removal from aqueous solution by Nanosized cobalt ferrite treated with humic acid during coprecipitation

“…Dyes, such as malachite green, remazole-red (RR), methyl orange, crystal violet and methylene blue (MB) are the most common effluents discharged directly to water resources. MB and RR are being used in several applications including textile and paper industries [1,2]. MB has some medical uses for many therapeutic and diagnostic procedures [1][2][3].…”

“…MB and RR are being used in several applications including textile and paper industries [1,2]. MB has some medical uses for many therapeutic and diagnostic procedures [1][2][3]. However, MB and RR are a carcinogenic, non-degradable materials and causes serious environmental problems against aquatic animals, plants and human beings [4].…”

Disinfection and antimicrobial processes

“…The effects of methylene blue were studied by Cardoso‐Rurr et al (2019) as a photodynamic agent to improve the inactivation of the solar disinfection process. The enhanced process is supposed to absorb the red wavelength of the visible light and generate singlet oxygen as reactive species.…”

“…The enhanced process is supposed to absorb the red wavelength of the visible light and generate singlet oxygen as reactive species. The results indicated that the synergistic extermination effect of the photosensitized methylene blue solar disinfection process inactivated gram‐positive ( Staphylococcus epidermidis or Deinococcus radiodurans ) in addition to the gram‐negative strains ( Escherichia coli or Salmonella typhimurium ) which were spiked in clean mineral water (Cardoso‐Rurr et al, 2019).…”