DSD Research & Development Forum 2018 1. Introduction 1.1 Pathogens in sewage Novel Photocatalytic Disinfection of Sewage with • Bacteria and virus • Waterborne disease Visible-light-driven Magnetic Photocatalysts • E. coli as indicator organisms Irene M. C. Lo, PhD, JP 1.2 Sewage disinfection F.HKIE, F.ASCE, F.HKIQEP, M.EASA • Remove and inactivate/kill pathogenic microorganisms to the level in compliance with the Microorganisms in water Chair Professor of Civil and Environmental Engineering causing disease discharge standards Director of Environmental Engineering Program • Prevent diseases from spreading and Source: Academician, European Academy of Sciences and Arts http://www.freedrinkingwater.com/images safeguard human health -new/education-page/image/water- contaminants.jpg Smart City · Innovative Wastewater Management Hong Kong University of Hong Kong University of 2 5 December 2018 Science and Technology Science and Technology 1.3 Conventional disinfection technologies 1.4 Photocatalytic disinfection Chlorination UV disinfection Solar light ： UV disinfection system abundant, free and renewable energy on earth Picture from Xylem https://www.xylem.com/ O 2 • Chemical-intensive process • UV lamps: expensive; aging; fouling Excitation e - e - . O 2 - bacteria hv>Eg • Disinfection byproducts (DBPs): • Energy-intensive process Inactivation . OH h + h + Damage to • cancer causing compounds Bacteria regrowth cell structure H 2 O Photocatalyst Ref: Chlorination Disinfection Fact Sheet, Ref.: UV Disinfection Fact Sheet, Environmental Technology Initiative (1998) Environmental Technology Initiative (1998 ) Hong Kong University of Hong Kong University of 3 Science and Technology Science and Technology
2. Modified Titanium Dioxide (TiO 2 )-based 3. Advantages of our magnetic photocatalysts Magnetic Photocatalyst 2.1 TiO 2 photocatalyst (I) No toxic DBP formation and bacteria regrowth/reactivate Advantages: Low cost, nontoxicity, and good chemical stability TiO 2 Drawbacks: (II) Economical and environmental friendly process Large bandgap of 3.2 eV and limited absorption of visible light; - No extra treatment process (i.e., replacing chlorination or UV Separation difficulty of fine size of photocatalyst from water; disinfection by photocatalysis) Recombination of photo-electrons and holes - Solar energy driven (i.e., visible light driven) Engineering methods to modify TiO 2 - Reusable photocatalysts with magnetic property Co-doping with ions (III) Photocatalytic disinfection with additional degradation of Magnetic TiO 2 @ Visible light-driven TiO 2 - Fe 3 O 4 @SiO 2 EDs/PPCPs Fe 3 O 4 @SiO 2 based magnetic photocatalyst Hong Kong University of Hong Kong University of 5 Science and Technology Science and Technology 5. Results 4. Methodology Batch reactor with visible-light CFL (1) Ag/Fe,N-TiO 2 /Fe 3 O 4 @SiO 2 Magnetic Photocatalyst - photocatalytic performance using synthetic wastewater and visible-light lamp - bacteria regrowth - magnetic separation efficiency - reusability of magnetic photocatalytic - photocatalytic performance in real sewage (2) rGO-Fe/N-TiO 2 /Fe 3 O 4 @SiO 2 Magnetic Photocatalyst - photocatalytic disinfection using solar simulator and real sewage - Prototype photocatalytic reactor with magnetic separator Visible-light-emitting compact fluorescent lamps system Hong Kong University of Hong Kong University of 7 8 Science and Technology Science and Technology
Investigation of the changes of bacterial Ag/Fe,N-TiO 2 /Fe 3 O 4 @SiO 2 Magnetic Photocatalyst membrane structure Performance of TiO 2 -based photocatalyst ( AgFeNTFS) Simultaneous photocatalytic degradation of 4',6-diamidino-2-phenylindole (DAPI) and propidium iodide (PI) Photocatalytic disinfection of E. coli bisphenol A ( BPA) and disinfection of E. coli dyes were employed to stain the DNA of bacteria. Live cells Photocatalyst (Ag/Fe,N-TiO 2 /Fe 3 O 4 @SiO 2 ) DAPI PI Dead cells Dead cells Photocatalyst 1 g/L Photocatalyst 1 g/L 10 6 CFU/mL 10 6 CFU/mL E. coli E. coli 330 W/m 2 Penetrate into the Penetrate only into the Visible light BPA 2 mg/L Water matrix 0.9 wt% NaCl solution 330 W/m 2 Visible light integrated and damaged cell damaged cell membrane Water matrix 0.9 wt% NaCl solution Complete disinfection in 120 membrane (blue fluorescence) (red fluorescence) Complete disinfection in 120 min and min. 90% degradation of BPA in 120 min Hong Kong University of Hong Kong University of 9 10 Science and Technology Science and Technology Fluorescence microscope images of bacteria Magnetic Separation of Photocatalyst 2.4 Magnetic property of AgFeNTFS photocatalyst Blue fluorescence Red fluorescence Magnetic separation Vibrating sample Separation from efficiency of 120 min. 0 min. magnetometer treated water photocatalyst by a (VSM) analysis magnet TiO 2 -based magnetic 99% magnetic separation Saturation magnetization photocatalyst in water efficiency in 5 min = 5.82 emu/g • Cell membranes were damaged in photocatalytic process indicating bacteria inactivation. No regrowth of bacteria after 2 days. Hong Kong University of Hong Kong University of 11 12 Science and Technology Science and Technology
Simultaneously photocatalaytic disinfection and degradation in sewage obtained from Sai Kung STW 2.5 Reusability for photocatalytic disinfection Photocatalytic disinfection Photocatalytic degradation of BPA AgFeNTFS in sewage in sewage In 3 cycles, the photocatalytic disinfection performance of recycled photocatalyst remained the same as that of the initial one . ( AgFeNTFS) Good reusability for ( AgFeNTFS) photocatalytic disinfection • 100% photocatalytic disinfection (3.7 log of bacteria disinfected) in 210 min. Reusability of photocatalyst for photocatalytic disinfection • Only 1.5 log of disinfection in 60 min. after magnetic separation from treated synthetic water • 100% of BPA was photocatalytic degraded from sewage in 300 min. Hong Kong University of Hong Kong University of 13 Science and Technology Science and Technology Redesign the photocatalysts: rGO-FeNTFS Photocatalytic disinfection in real sewage Batch reactor using solar simulator Reaction Fan flask Solar simulator The FeNTFS photocatalyst can only inactivate 1.5-log E.coli Stirrer reduction in 60 min. The new rGO-FeNTFS can effectively Irradiance spectrum of authentic sunlight (1pm, 11 th July 2018 at HKUST) and light inactivate E. coli cells, achieving about 3.0-log of reduction in 60 irradiance spectrum of the reaction flask Setup for the photocatalytic disinfection position under solar simulator by rGO-FeNTSF under solar simulator Integrated irradiance=8 × 10 4 W/m 2 min in synthetic saline solution under CFL reactor. 15 Hong Kong University of Hong Kong University of 16 Science and Technology Science and Technology
Sewage samples collected from Sewage samples collected from Sai Kung STW before disinfection Ngong Ping STW before disinfection E.coli =80000 CFU/100 mL E.coli = 51000 CFU/100 mL Sai Kung STW Ngong Ping STW (secondary treatment, low-saline sewage) (tertiary treatment, low-saline sewage) Source: https://www.dsd.gov.hk Source: https://www.dsd.gov.hk Hong Kong University of Hong Kong University of 17 18 Science and Technology Science and Technology Magnetic separation Unit: patent in HK & China in 2015 Photocatalytic performance in Sai Kung and Ngong Ping sewage Prototype photocatalytic reactor integrated with a magnetic separation unit Light source Sai Kung (3 g/L of dosage) Ngong Ping (1 g/L dosage) (90 min) E. coli Time to meet (90 min) E. coli Time to meet reduction discharge standard reduction discharge standard Photocatalytic reactor Solar simulator with filter 1.9-log 90 min 1.2-log 60 min (only visible-light) Electromagnetic system Magnetic separation unit Solar simulator without filter 3.1-log 60 min 2.0-log 30 min (full spectrum) Hong Kong University of Hong Kong University of 19 20 Science and Technology Science and Technology
Acknowledgement Research group on photocatalysis study The financial support from General Research Fund, TiO 2 -based photocatalytic g-C 3 N 4 /La-based HKSAR and the upcoming financial support for this g-C 3 N 4 /based photocatalytic disinfection and photocatalytic photocatalytic removal of disinfection R&D project from DSD, HKSAR are appreciated. removal of EDs phosphate BiOX-based photocatalytic removal of PPCPs Simultaneous photocatalytic removal of Piezophotocatalysis for removal of PPCPs HKUST PPCPs and hydrogen evolution Hong Kong University of Hong Kong University of Science and Technology Science and Technology
Recommend
More recommend
