Advanced Oxidation Processes: Treatment of 1,4-Dioxane and VOCs for Potable Water Applications

Transcription

1 Advanced Oxidation Processes: Treatment of 1,4-Dioxane and VOCs for Potable Water Applications H2M architects + engineers Sujata Pal-Frank, Project Engineer John R. Collins, P.E. Senior Project Engineer

2 Outline Project Background 1,4-Dioxane Advanced Oxidation Processes (AOPs) Water Quality Considerations Pilot Study & Results

3 Project Background Potable water supply well Water Quality: Tetrachloroethylene 1,1,1 Trichloroethane 1,4-Dioxane Trichloroethylene 1,1-Dichloroethane cis 1,2-Dichloroethylene Freon 10 & 12 Wellhead Treatments Considered: AST GAC AOP 3 water suppliers Max: 4.4 mg/l 13 water suppliers Max: 33 mg/l

4 1,4-Dioxane Stabilizer for chlorinated solvents Wastewater discharge, spills, leaks Common household products 2,000 ug/l to 300,000 ug/l Manufactured Food Additives Probable Human Carcinogen (Group B2) Persistent in the environment Highly soluble

5 1,4-Dioxane Regulations EPA Contaminant Candidate List (CCL3) Indicates potential for regulation under SDWA EPA IRIS: 0.35 mg/l in drinking water NYS UOC MCL: 50 mg/l UCMR3: 70% of NYSMCL on Long Island

6 Treatment Options Considered Air Stripping Low volatility in water Granular Activated Carbon Hydrophilic Advanced Oxidation Processes (AOPs)

7 Advanced Oxidation Processes Removal of organic materials from water by oxidation using hydroxyl radicals Characteristics Strong oxidant Highly reactive Production Methods: Ozone + Hydrogen Peroxide UV + Titanium Dioxide UV + Hydrogen Peroxide UV + Chlorine Oxidation Species Oxidation Power [V] Fluorine 3.03 Hydroxyl Radical 2.80 Atomic Oxygen 2.42 Positively charged TiO Ozone 2.07 Hydrogen Peroxide 1.77 Permanganate 1.67 Hypochlorous Acid 1.49 Chlorine 1.36 Iodine 0.54

8 Advanced Oxidation Processes Three Steps 1. Form Oxidant 2. Attack target compound 3. Mineralization

9 Oxidation

10 Oxidation

11 Water Quality Considerations ph & Photolysis Hypochlorous Acid v Hypochlorite Ions HOCI & OCI- HOCI OCI -

12 Water Quality Considerations ph & Alkalinity - Scavengers Carbonates (CO 3 2- ) ph > 9 Bicarbonates (CO 3 - ) ph 7-8 Carbonic Acid (H 2 CO 3 ) ph < 6 TOC Scavengers Nitrate & Nitrite - Scavengers Turbidity & TSS UV Transmittance (%UVT)

13 Pilot Study Partner: Calgon Carbon Corporation Study: UV Oxidation with Chlorine (Calcium Hypochlorite) to confirm removal efficiency of: 1,4 Dioxane & VOCs Estimated requirements for full scale system

14 Sample Raw Water Quality ph Slightly elevated for complete hypochlorous acid (6.11 vs 5) Slightly elevated alkalinity (Total Alkalinity: 6 to 7 vs <6) TOC : Less than 1 mg/l Nitrate & Nitrite: Nitrite <0.25 mg/l, typical Turbidity & TSS: Low as indicated by high UVT

15 Pilot Unit Batch Design Test Pilot Unit: 1 kw high intensity MP mercury vapor lamp MP lamps give more light in 200 nm 260 nm 10 gallon cylindrical stainless steel reactor Air actuated transmittance controller (quartz cleaner) Mixer - Chlorine Steel shutter UV Dosage

16 Pilot Procedure 1. Add 30 liters of water sample to unit 2. Ignite UV lamp with shutter closed 3. Dose water with chlorine and mix 4. Open shutter for fixed period of time (UV Dose) 5. Close shutter, take sample, increase UV Dose 6. Repeat steps 4 and 5 When residual chlorine measured <0.5, ppm additional chlorine was added for a target ~1 ppm residual

17 Test Results Run 1 Sample No. UV Dose (kwh/1,000 gal) ph Chlorine (ppm) 1,4-Dioxane (ppb) Raw <0.07 Chlorine <0.07

18 Test Results Run 2 Sample No. UV Dose (kwh/1,000 gal) ph Chlorine (ppm) 1,4-Dioxane (ppb) Raw <0.07 Chlorine <0.07

19 Test Results 1,4-Dioxane Test Run ph Initial Chlorine Concentration [ppm] Max UV Dose (kwh/1,000gal)

20 Test Results Compound 1-0 ppb 1-5 ppb 2-0 ppb 2-5 ppb 1,1-DCE 8.36 < <0.50 Cis 1,2-DCE 8.13 < <0.50 PCE 3.21 < <0.50 TCE 11.7 < <0.50 Benzene 0.69 < <0.50 1,1,1-TCA ,1-DCA Carbon Tetrachloride 1.69 < Bromodichloromethane <0.50 <0.50 < Chloroform <0.50 <0.50 <

21 Test Results Organic Molecule Rate Constant [mol/l-sec] Chlorinated alkenes 10 9 to Phenols 10 9 to N-containing organics 10 8 to Aromatics 10 8 to Ketones 10 9 to Alcohols 10 8 to 10 9 Alkanes 10 6 to 10 9

22 Full Scale Operation 1,400 2,200 hrs Two Calgon Sentinel TM Reactors Nine 10 kw lamps

23 Capital Cost Considerations Process Treatment Well Rehabilitation AOP Reactor - $200,000/reactor Chlorine Bulk Storage System - $80,000 AST GAC Buildings/Structure Electrical MCC, Telemetry, Security Primary Service Site Work

24 O&M Cost Considerations Electrical Loads Building & Heating Demands (3 systems) GAC Replacement Costs Monitoring & Laboratory Costs Chemical Costs Chlorine Oxidation Chlorine Disinfection Sodium Hydroxide ph Adjustment

25 Considerations/Concerns Incomplete reactions Formation of unknown compounds Raw Water Quality Considerations Cost

26 Acknowledgements Calgon Carbon Corporation

27 Thank You