Beyond the Pipeline: Assessing the Efficiency Limits of Advanced Technologies for Solar Water Disinfection

Abstract

This critical review analyzes and compares the efficiency of select technologies that harness solar energy for point-of-use water disinfection, including photocatalysts, photosensitizing chromophores, UVC light-emitting diodes, and visible-to-UVC upconversion phosphors. The volume rate of water that each material can treat to achieve 99% inactivation of model microorganisms, given the same sunlight exposure, was estimated on the basis of literature data and theoretical predictions, in the context of both currently reported efficiencies and theoretical thermodynamic maximum efficiencies. Each material is further critiqued in terms of the spectral match with sunlight, quantum efficiency, and the relative strength of the resulting disinfecting agent such as hydroxyl radicals, singlet oxygen, and UVC radiation. This review emphasizes critical needs for disinfection strategies that can efficiently inactivate more than one type of microorganism. In addition, the approach described herein can guide future research in efforts to identify more efficient materials and technologies for capturing sunlight for water disinfection.

Sunlight-mediated inactivation of health-relevant microorganisms in water: a review of mechanisms and modeling approaches

“…264 Organic sensitizers include avins and psoralens (furocoumarins). Riboavin has been shown to accelerate the rates with which various viral, bacterial, and protozoan pathogens can be inactivated during exposure to simulated sunlight, 186,265 presumably due to interactions of the pathogens with either 1 O 2 or the excited triplet-state of the riboavin itself.…”

Ozone and Photocatalytic Processes for Pathogens Removal from Water: A Review

“…Six hours of exposure of unsafe drinking water to the sun in plastic PET bottles results in an inactivation of enteric pathogens (bacteria, protozoa, and viruses) of several orders of magnitude [104][105][106][107]. It is reported [108] that, under clear 1.5 atmospheric mass conditions, SODIS is predicted to treat up to 0.057 L/m 2 s, leading to 2-log inactivation of E. coli, 0.0016 L/m 2 s for C. parvum, and 0.022 L/m 2 s for MS2.…”

Challenges and opportunities at the nexus of energy, water, and food: A perspective from the southwest United States

“…Traditional water purification technologies, and even some of the more advanced membrane separation technologies, may not fully remove micropollutants to levels that are acceptable for human consumption or for use in industrial and agricultural processes that require high water purities. [119][120][121][122][123][124] Micropollutants include low molecular weight, low polarity pharmaceuticals, personal care products, industrial compounds, pesticides, hormones, and low molecular weight surfactants used in energy extraction. Their identities and concentrations vary substantially depending upon the water source.…”

“…Several different AOPs have been developed over the last 20 years using extremely oxidizing reactants and are designed to degrade both residual pathogenic microorganisms and micropollutants. 70,[119][120][121][122][123][124][125][126] The desired outcome is degradation of the contaminant to a product which can be easily removed, and for which there are no health consequences. The less desired outcome, which may arise as new chemically stable micropollutants emerge in our water systems, is the difficult-to-remove degradation products, which have risks to health and safety, are created.…”