Query: Photocatalytic Enhancement for Solar Disinfection of Water

Candidate papers:

abstract: It is estimated that 884 million people lack access to improved water supplies. Many more are forced to rely on supplies that are microbiologically unsafe, resulting in a higher risk of waterborne diseases, including typhoid, hepatitis, polio, and cholera. Due to poor sanitation and lack of clean drinking water, there are around 4 billion cases of diarrhea each year resulting in 2.2 million deaths, most of these are children under five. While conventional interventions to improve water supplies are effective, there is increasing interest in household based interventions to produce safe drinking water at an affordable cost for developing regions. Solar disinfection (SODIS) is a simple and low cost technique used to disinfect drinking water, where water is placed in transparent containers and exposed to sunlight for 6 hours. There are a number of parameters which affect the efficacy of SODIS, including the solar irradiance, the quality of the water, and the nature of the contamination. One approach to SODIS enhancement is the use of semiconductor photocatalysis to produce highly reactive species that can destroy organic pollutants and inactivate water pathogens. This paper presents a critical review concerning semiconductor photocatalysis as a potential enhancement technology for solar disinfection of water.
author_names: John Anthony Byrne

Pilar Fernandez-Ibanez

Patrick Stuart Morris Dunlop

Dheaya Alrousan

Jeremy William John Hamilton
title: Photocatalytic Enhancement for Solar Disinfection of Water: A Review
year: 2011

author_names: Anvith Deeconda
title: The Effect Of Different Photocatalytic Semiconductors On The Enhancement Of PET Solar Disinfection Of E. coli contaminated Water Sources
year: 2015

abstract: .v Chapter 1: Introduction. 1 Chapter 2: Synthesis and Characterization of MoS2 TiO2 Complex..6 Synthesis..6 Characterization..8 XRD results..8 UV Vis results..15 Fourier transform infrared spectroscopy (FTIR) results..18 SEM results..22 Chapter 3: Testing the Effectiveness of MoS2 TiO2 in Water Disinfection..30 Background..30 Experimental setup..30 Preparation of nanomaterial inserts..32 Preparation of E. coli broth suspension..33 Preparation of agar plates with medium..33 Culturing of E. coli..34 Colony count through serial dilution..37 Experimental procedure: testing disinfection properties of the nanomaterials..38 Results and Discussion..40 Experiment 1: Pure TiO2 disinfection properties..40 Experiment 2: 1.5% MoS2 98.5% TiO2 disinfection properties..41 Experiment 3: 5% MoS2 95% TiO2 disinfection properties..42 Experiment 4: 10% MoS2 90% TiO2 disinfection properties..44 Experiment 5: No insert disinfection properties..45 Discussion..47 Chapter 4: Conclusions. 50 Chapter 5: References Cited. 51 Appendix A..55
author_names: Timothy McColgan
title: MoS2 Doped TiO2 Nanomaterial and the Enhancement of Photocatalytic Properties for Solar Disinfection
year: 2018

abstract: Abstract Interest has grown in the modification of titanium dioxide with graphene to improve the photocatalytic behaviour. In this work, titanium dioxide reduced graphene oxide (TiO2 RGO) composites were synthesised by the photocatalytic reduction of exfoliated graphene oxide (GO) by TiO2 (Evonik P25) under UV irradiation in the presence of methanol as a hole acceptor. The composite materials were characterised using high resolution transmission electron microscopy (HRTEM) X ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Raman and XPS analysis provided evidence that GO was converted to RGO by photocatalytic reduction. The TiO2 RGO composites were compared to TiO2 in suspension reactors for the disinfection of water contaminated with Escherichia coli and Fusarium solani spores under real sunlight. Very rapid water disinfection was observed with both E. coli and F. solani spores. An enhancement in the rate of inactivation of E. coli was observed with the TiO2 RGO composite compared to P25 alone. The rate of inactivation of F. solani spores was similar for both the TiO2 RGO and P25. When the major part of the solar UVA was cut off (l 380 nm) using a methacrylate screen, there was a marked increase in the time required for inactivation of E. coli with P25 but no change in the inactivation rate for the TiO2 RGO. There is evidence of singlet oxygen production with visible light excitation of the TiO2 RGO composites which would lead to E. coli inactivation.
author_names: Pilar Fernandez-Ibanez

Maria Inmaculada Polo-Lopez

Sixto Malato

Shikha Wadhwa

Jeremy William John Hamilton

P S M Dunlop

Raechelle A D'Sa

Erin Magee

Kevin E O'Shea

Dionysios D Dionysiou

John Anthony Byrne
title: Solar photocatalytic disinfection of water using titanium dioxide graphene composites
year: 2015

abstract: The solar water disinfection method (SODIS) was modified by the addition of a photocatalytic layer of titania on the interior surface of polyethylene terephthalate (PET) and acrylic bottles. Titania was solvent deposited on the interior of commercially available PET bottles, as well as bottles that were constructed from acrylic. Uncoated and titania coated acrylic bottles removed 3,000,000 5,000,000 colony forming units per milliliter of K12 E. coli from 670 mL of contaminated water in 40 min of solar irradiance. After five hours of sunlight exposure, the concentration of 10 ppm methyl orange (a representative organic water contaminant) was reduced by 61% using the titania coated acrylic bottles. The concentration of 87 ppb microcystin LR (a representative algal toxin) was reduced by 70% after 7 hours of sunlight exposure in the titania coated acrylic bottles. Acrylic is an effective alternative to PET for use in the SODIS method due to its greater UV transparency. The addition of titania to PET and acrylic bottles confers the ability to remove chemical contaminants in addition to inactivating microbiological contaminants.
author_names: Jonathan M Carey

T M Perez

E G Arsiaga

Lucas Loetscher

Joel E Boyd
title: The photocatalytic enhancement of acrylic and PET solar water disinfection (SODIS) bottles.
venue: Water science and technology a journal of the International Association on Water Pollution Research
year: 2011

abstract: Abstract This study presents a simple method of titanium dioxide modification by carbon. Monosaccharide (fructose) was used as the carbon source. The pressure modification using fructose caused enhancement of antibacterial efficiency. It was found that prepared photocatalysts were capable of total Escherichia coli and Staphylococcus epidermidis inactivation under the UV A and artificial solar light, which was attributed to the changes of the surface characteristics, i.e. zeta potential. The best results were observed for the TiO2 F 1% 100 photocatalyst, containing 0.51 wt% of carbon with less negative zeta potential 18.08 mV) The two stage photocatalytic mechanism of bacteria destruction by OH radicals was found. Obtained data suggest that fructose modified photocatalysts may be useful in the development of alternative water disinfectants.
author_names: Paulina Rokicka-Konieczna

Agata Markowska-Szczupak

Ewelina Kusiak-Nejman

Antoni W Morawski
title: Photocatalytic water disinfection under the artificial solar light by fructose modified TiO2
venue: Chemical Engineering Journal
year: 2019

abstract: Abstract It is estimated that 780 million people lack access to improved water supplies and many more are forced to rely on sources that are microbiologically unsafe. While piped in water supplies are the ultimate goal for the provision of water in developing countries, low cost point of use disinfection treatments could help to significantly reduce the incidence of water borne disease. Solar disinfection of water (SODIS) is a simple method of treating water where the UV and thermal energy of the sun act to inactivate pathogenic microorganisms in water; however, the recommended protocol is 6 h under direct sunlight, the efficiency depends on environmental factors, and some pathogens are more resistant to solar disinfection. The use of compound parabolic collectors (CPC) and immobilised titanium dioxide for photocatalysis were investigated as enhancement technologies for solar disinfection. The reactors consisted of borosilicate glass tubes (1.5 m in length) as either single tubes of diameter 50 mm or two concentric tubes (inner tube of diameter 32 mm) with and without CPC. For solar photocatalytic disinfection (SPC DIS) the inside wall of the 50 mm tube was dip coated with TiO 2 (TiO 2 Evonik P25 and/or the outside wall of the 32 mm tube. SPC DIS and SODIS were tested under flow conditions using different reactor configurations under real sun conditions. E. coli was used as the model microorganism for the disinfection studies in 0.9% saline solution and the total volume in each experiment was 7 L. It was found that the use of CPCs improved the SODIS and SPC DIS efficiency. The disinfection kinetics were observed to follow a log linear with shoulder and/or tailing model. The kinetic parameters were determined using the UVA dose as the independent variable and the configurations were compared for E. coli inactivation efficiency based on the log of the residual concentration (Log N res and the first order rate constant k Three reactor configurations showed a residual bacterial count below the detection limit and they were compared based upon the first order rate constant. The concentric tube arrangement (a tube within a tube) with CPC was the most effective configuration. The following order was found for k where coated refers to TiO 2 coating and the equals sign indicates no significant difference; uncoated external coated internal double coated tube uncoated double tube. It is known that E. coli is inactivated by SODIS and it may be a 'soft' target for comparing the effectiveness of SODIS vs SPC DIS. Nevertheless, photocatalysis presents advantages in terms of the non recovery of inactivated organisms and the inactivation of SODIS resistance organisms.
author_names: Dheaya Alrousan

Maria Inmaculada Polo-Lopez

P S M Dunlop

Pilar Fernandez-Ibanez

John Anthony Byrne
title: Solar photocatalytic disinfection of water with immobilised titanium dioxide in re circulating flow CPC reactors
year: 2012

abstract: Solar water disinfection (SODIS) is an effective, simple, household level, point of use technology suitable for application in developing countries. Contaminated water is placed in a plastic container (typically a 2L PET bottle) and exposed to sunlight for at least 6 hours. Laboratory and field trials have demonstrated SODIS to effective against a wide range of waterborne pathogens with health impact assessments demonstrating significant benefits from consumption of SODIS treated water. Photocatalytic (PC) enhancement of the SODIS process could provide larger volumes of safe drinking water and reduce the sunlight exposure time. Pilot scale, modular PC SODIS reactors were designed and constructed from low cost materials and tested, under real sunlight the south of Spain, for their efficiency to disinfect water containing ~1 x10 6 Escherichia coil cells/mL. The inclusion of an immobilised nanostructured titanium dioxide coating within 1.25 L static batch and 7 L re circulating reactors accelerated the rate of disinfection with 6 log kill observed in 3 hours. Complete disinfection was not observed in re circulating SODIS reactors. Photocatalytic enhancement was observed during full sun and cloudy weather conditions.
author_names: P S M Dunlop

Dheaya Alrousan

Maria Inmaculada Polo-Lopez

Pilar Fernandez-Ibanez

John Anthony Byrne
title: Photocatalytic enhancement of solar water disinfection for application in developing regions
year: 2009

abstract: Abstract The enhancement of current technologies used to treat polluted water is one of the most important challenges in water research. The application of physico chemical treatments could reduce the load of chemical and biological pollutants present in WW reducing the pressure over water requirements, allowing the reclaim of the treated water. Advanced Oxidation Processes (AOPs) and, in particular, photocatalysis using titanium dioxide (TiO 2 have shown a great potential for chemicals removal as well as for pathogens reduction in water. Moreover, the use of solar Compound Parabolic Collectors (CPC) reactors has been also shown to be very effective for water treatment purpose by solar photocatalysis. Nevertheless, the effects of some key parameters in photocatalytic disinfection have not been already investigated at pilot scale in solar reactors; like dissolved oxygen concentration, water temperature, water matrix composition and the type of microorganism. The roles of these parameters in photocatalytic processes are individually known for chemicals degradation, but their relative significance in water photocatalytic disinfection has been never studied at pilot scale. The aim of this work was to investigate the influence of these parameters on the disinfection efficiency using a solar 60 L CPC reactor with suspended TiO 2 (100 mg/L) The following variables were experimentally evaluated: injection of air in the reactor (160 L/h) different controlled temperatures (15, 25, 35 and 45 degC) two very different models of water pathogen, Escherichia coli (model of fecal water contamination) and Fusarium solani spores (a highly phytopathogenic fungus) and the chemical composition of the water comparing urban WW effluents (UWWE) and simulated urban WW effluent (SUWWE) The increase of water temperature (from 15 to 45 degC) had a benefit on the disinfection rate for both pathogens in all the experimental conditions evaluated. The air injection led to an important enhancement on the inactivation efficiency, which was stronger for F. solani spores, the most resistant microorganisms to TiO 2 photocatalysis. The composition of the water matrix significantly affected the efficiency of the photocatalytic treatment, showing a better inactivation rate in SUWWE than for UWWE.
author_names: Irene Garcia-Fernandez

I Fernandez-Calderero

Maria Inmaculada Polo-Lopez

Pilar Fernandez-Ibanez
title: Disinfection of urban effluents using solar TiO2 photocatalysis: A study of significance of dissolved oxygen, temperature, type of microorganism and water matrix
year: 2015

abstract: The objective of this work was to assess the effectiveness of using near UV light to disinfect water supplies for potential applications in developing countries. A pilot scale photoreactor comprised of non tracking compound parabolic collectors installed at Plataforma Solar de Almeria was examined and a comparison of disinfection efficiency using E. coli K 12 was carried out with a reactor configuration of 3 and 1 m2 illuminated area. Tests were also carried out using suspensions of titanium dioxide (TiO2) at concentrations ranging from 0 to 9 mg/l. The removal of E. coli K 12 from initial concentrations of 1 x 105 CFU/ml to below the limit of detection was achieved both with and without the use of TiO2. Levels of inactivation in 35 l of inoculated water of up to 4 log removal were achieved in under 30 min. The addition of TiO2 created an enhancement to the process only at the 3 mg/l dose. However, the results have also suggested the possibility that another disinfection mechanism, possibly governed by the frequency of intermittent UV light exposure, was regulating the overall inactivation kinetics of the trials.
author_names: O A McLoughlin

Pilar Fernandez Ibanez

Wolfgang Gernjak

Sixto Malato Rodriguez

Laurence W Gill
title: Photocatalytic disinfection of water using low cost compound parabolic collectors
year: 2004