Final Report: Enhanced Photocatalytic Solar Disinfection of Water as Effective Intervention Against Waterborne Diarrheal Diseases in Developing CountriesEPA Grant Number: SU833942
Title: Enhanced Photocatalytic Solar Disinfection of Water as Effective Intervention Against Waterborne Diarrheal Diseases in Developing Countries
Investigators: Dionysiou, Dionysios D. , Pelaez, Miguel A , Bandala, Erick R. , Castillo, Jordana , Dunlop, Patrick
Institution: University of Cincinnati , NIBEC, School of Electrical and Mechanical Engineering , Universidad de Las Américas-Puebla
EPA Project Officer: Page, Angela
Project Period: August 15, 2008 through August 14, 2009
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2008) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Materials & Chemicals , P3 Challenge Area - Water , P3 Awards , Sustainability
Solar water disinfection (SODIS) is a simple, environmentally friendly and low cost point-of-use treatment technology for drinking water purification. However, bacterial re-growth after short storage (24 h) of SODIS treated water has been observed. Seeking for improvements of SODIS performance, reduction of irradiation time and avoidance of bacteria regrowth, solar based-Advanced Oxidation Technologies (AOTs), such as solar TiO2 photocatalysis, are promising enhancements to SODIS. Unfortunately, one of the main problems with the use of conventional TiO2 for solar applications is its limited capability to absorb only the radiation in the UV range, which is only about 5-8% of the total solar radiation. In this study, we employed novel nanotechnological procedures to synthesize visible light activated nonmetaldoped TiO2 (i.e., nitrogen-doped TiO2) with high surface area and immobilized on appropriate support materials that were used in novel photocatalytic reactors for water purification in rural zones in Mexico as a case study. In combination with visible light activated TiO2, we also propose to incorporate in our process the V trough solar collector which has never been applied to solar photocatalytic processes in the past, but has much simpler geometry and demonstrated in preliminary results performance comparable to other types of solar collectors. Because of its simpler geometry, the V trough solar collector is much less expensive and is attractive to applications is developing countries. This overall process for water purification was denominated “Enhanced Photocatalytic Solar Disinfection” (ENPHOSODIS).
A complete inactivation of the bacteria was achieved when using ENPHOSODIS under solar and visible light at three different NF-TiO2 catalyst concentrations. Under dark conditions, no difference in the bacteria count was observed and no inactivation of E. coli was observed when employing visible light only. pH was an important influence on the bacteria resistence to solar radiation. E. coli was able to survive for longer radiation periods at pH 7 and 7.5 than at lower or higher pH values (i.e., 6, 6.5 and 8). An azo dye, acid orange 24 (AO24), was explored for the development of a UV dosimetric indicator for disinfection. Complete color removal was found to be equivalent to that when water submitted to ENPHOSODIS treatment, under the proposed conditions, will get enough energy to deactivate completely the viable helminth eggs present. Different configurations of immobilized TiO2 photocatalytic reactors were tested under real sun conditions. Experiments under full sun and cloudy conditions showed that these photoreactors are capable of disinfection with an optimum configuration of internal and external coationg along with a compound parabolic collector.
Photocatalytic enhanced solar disinfection using NF-TiO2 was responsible for complete inactivation of E. coli in those reactors exposed to both solar and visible light radiation. The presence of NF-TiO2 enhanced the disinfection rate efficiency of E.coli when compared to those experiments where no photocatalyst was used. Practical application of dye solutions as dosimetric indicator appears as very useful for determining the solar radiation dose necessary for waterborne pathogen deactivation.
Proposed Phase II Objectives and Strategies:
Large scale testing of immobilized NF-TiO2 in model “real water” using real sunlight and CPC’s. Use a more disinfection resistant organisms rather than E. coli under experimental and “real water” conditions. Test the efficiency of system using a real drinking water source in rural location in Mexico.
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||Bandala ER, Gonzalez L, de la Hoz F, Pelaez MA, Dionysiou DD, Dunlop PSM, Byrne JA, Sanchez JL. Application of azo dyes as dosimetric indicators for enhanced photocatalytic solar disinfection (ENPHOSODIS). Journal of Photochemistry and Photobiology A: Chemistry 2011;218(2-3):185-191.||