Electron Beam Treatment for Potable Water Reuse: Removal of Bromate and Perfluorooctanoic Acid

Transcription

1 Electron Beam Treatment for Potable Water Reuse: Removal of Bromate and Perfluorooctanoic Acid B. Batchelor, S.D. Pillai, L. Wang and V.S. Botlaguduru National Center for Electron Beam Research An IAEA Collaborating Center for Electron Beam Technology Texas A&M University, USA

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3 Water is a Precious Commodity

4 Abbreviated Contaminant List of Concern in Texas Reclaimed Water (TWDB, 2015) Chemical Contaminants Disinfection by products (bromoform, bromate, chloroform, trihalomethanes) Household products and food additives (Bisphenol A, Perflurooctanoic acid, Perfluorooctane sulfonate) Estrogenic compounds (17β-estradiol) Microbial Contaminants Cryptosporidium oocysts Giardia cysts Enteric viruses, Norovirus Total coliforms, E.coli Bacterial pathogens

5 What and Why Bromate? Formation Bromate is a disinfection by-product, primarily formed when ozonating bromide-containing waters a) Molecular ozone mechanism b) Hydroxide radical mechanism

6 What and Why Bromate? Health Impact & Regulation a) Renal cell cancer b) Classified as a substance possibly carcinogenic to humans by International Agency for Research on Cancer (IARC) c) Maximum contaminant level: 10 μg/l

7 Experimental System Synthetic waste water to simulate reclaimed water Revere osmosis water ph mg CaCO 3 /L alkalinity 50 µg/l Dissolved organic carbon (from fulvic acid) Fulvic acid chosen since mol weight < 1000 Daltons used as surrogate for NOM

8 Experimental System Samples prepared under anaerobic system Sample volumes ~ 30 ml Sealed bags to maintain anaerobic conditions Analytical technique BrO 3- and Br - and F - measured using ion chromatography

9 Effect of Nitrate on Bromate Removal 20 mg/l 10 mg/l 5 mg/l

10 Scavenging Model for Effect of Nitrate on Bromate Dose Constant

11 Effect of Alkalinity on Bromate Dose Constant

12 Effect of ph on Bromate Dose Constant ph 5.0 ph 7.3 ph 9.0

13 Effect of Dissolved Oxygen on Bromate Removal With dissolved oxygen Without dissolved oxygen

14 Perfluorinated Chemicals (PFCs) Perfluorooctanoic acid -PFOA: C 7 F 15 CO 2 - Perfluorooctane sulfonate PFOS C 8 F 17 SO 3 - Widely used in consumer products (carpets and fabrics) Widely used in fire fighting foams

15 PFOS & PFOA

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17 Perfluorinated Chemicals (PFCs) Extremely mobile in aquifers Contaminating drinking water wells PFOA and PFOS are extremely stable C-F bond ~ kcal/mole) PFOA and PFOS have entered the food chain Breast milk, blood, umbilical cord blood, wildlife US EPA health advisory threshold : 70 ng/l

18 Remediation Technologies Attempted In situ chemical oxidation Bio-augmentation using vault proteins PFC-coagulant Photochemical approaches Electro microfiltration Sonochemical decomposition Cobalt-60 irradiation

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20 Effect of Nitrate on PFOA Defluorination 20 mg/l NO 3- (mg/l) Defluorination(%) mg/l 20 93

21 Effect of Alkalinity on PFOA Defluorination 100 mg/l Alk (mg/l) Defluorination(%) mg/l

22 Effect of Fulvic Acid on PFOA Defluorination 0 μg/l FA(μg /L) Defluorinati on(%) μg/l

23 Effect of Dissolved Oxygen on PFOA Defluorination Without dissolved oygen With dissolved oxygen

24 % Light loss (-) or gain (+) ebeam eliminates toxicity of wastewater effluent based on V.fischeri test Toxicity of ebeam processed effluents Dose (kgy)

25 Take-Home Messages for ebeam-based Degradation of Chemical Contaminants # 1 Electron beam (ebeam) irradiation has been tested to remove bromate and peflurooctanoic acid (PFOA) in synthetic wastewater effluent simulating potable water reuse # 2 A simple model has been developed for bromate degradation, and a pseudo onecomponent model has been developed for PFOA defluorination # 3 ebeam treatment is a viable option to treat reclaimed water if dissolved oxygen levels are controlled and nitrate levels can be modulated # 4 Transportable ebeam systems are needed to address contaminated groundwater situations

26 Suresh D. Pillai ebeam-tamu.org