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TRANSCRIPT
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
Outline • Project Background
• 1,4-Dioxane
• Advanced Oxidation Processes (AOPs)
• Water Quality Considerations
• Pilot Study & Results
Project Background • Potable water supply well
• Water Quality:
• Wellhead Treatments Considered: • AST
• GAC
• AOP
13 water suppliers Max: 33 mg/L
3 water suppliers Max: 4.4 mg/L
Tetrachloroethylene 1,1,1 Trichloroethane 1,4-Dioxane
Trichloroethylene 1,1-Dichloroethane
cis 1,2-Dichloroethylene Freon 10 & 12
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
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
Treatment Options Considered • Air Stripping
• Low volatility in water
• Granular Activated Carbon • Hydrophilic
• Advanced Oxidation Processes (AOPs)
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 TiO2
2.35
Ozone 2.07
Hydrogen Peroxide 1.77
Permanganate 1.67
Hypochlorous Acid 1.49
Chlorine 1.36
Iodine 0.54
Advanced Oxidation Processes Three Steps
1. Form Oxidant
2. Attack target compound
3. Mineralization
Oxidation
Oxidation
Water Quality Considerations • pH & Photolysis
• Hypochlorous Acid v Hypochlorite Ions
HOCI & OCI-
OCI - HOCI
Water Quality Considerations • pH & Alkalinity - Scavengers
• Carbonates (CO32- ) pH > 9
• Bicarbonates (CO3- ) pH 7-8
• Carbonic Acid (H2CO3) pH < 6
• TOC – Scavengers
• Nitrate & Nitrite - Scavengers
• Turbidity & TSS – UV Transmittance (%UVT)
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
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
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
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
Test Results – Run 1
Sample No. UV Dose
(kWh/1,000gal)
pH Chlorine
(ppm) 1,4-Dioxane
(ppb)
Raw 0.00 5.82 0.00 37.0
1-0 0.00 6.19 3.80 37.0
1-1 0.60 6.62 2.66 11.0
1-2 1.19 6.12 1.82 2.40
1-3 2.38 6.09 0.60 0.12
1-4 4.76 6.18 0.00 <0.07
Chlorine 1.35
1-5 9.52 6.43 0.00 <0.07
Test Results – Run 2
Sample No. UV Dose
(kWh/1,000gal)
pH Chlorine
(ppm) 1,4-Dioxane
(ppb)
Raw 0.00 5.77 0.00 38.0
1-0 0.00 6.33 6.75 36.0
1-1 0.60 6.24 5.25 13.0
1-2 1.19 6.26 3.60 3.80
1-3 1.90 6.24 2.40 1.00
1-4 3.93 6.22 0.34 <0.07
Chlorine 1.90
1-5 7.14 6.32 0.00 <0.07
Test Results 1,4-Dioxane
Test Run pH
Initial Chlorine Concentration
[ppm]
Max UV Dose (kWh/1,000gal)
1 6.11 3.80 9.52
2 6.11 6.75 7.14
Test Results
Compound 1-0 ppb 1-5 ppb 2-0 ppb 2-5 ppb
1,1-DCE 8.36 <0.50 7.78 <0.50
Cis 1,2-DCE 8.13 <0.50 7.84 <0.50
PCE 3.21 <0.50 3.00 <0.50
TCE 11.7 <0.50 11.3 <0.50
Benzene 0.69 <0.50 0.69 <0.50
1,1,1-TCA 2.07 0.54 2.1 0.77
1,1-DCA 17.9 3.78 17.5 5.29
Carbon Tetrachloride 1.69 <0.50 1.59 0.56
Bromodichloromethane <0.50 <0.50 <0.50 0.72
Chloroform <0.50 <0.50 <0.50 0.55
Test Results
Organic Molecule
Rate Constant [mol/L-sec]
Chlorinated alkenes 109 to 1011
Phenols 109 to 1010
N-containing organics 108 to 1010
Aromatics 108 to 1010
Ketones 109 to 1010
Alcohols 108 to 109
Alkanes 106 to 109
Full Scale Operation
• 1,400 GPM @ 2,200 hrs
• Two Calgon SentinelTM Reactors
• Nine 10 kW lamps
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
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
Considerations/Concerns • Incomplete reactions
• Formation of unknown compounds
• Raw Water Quality Considerations
• Cost
Acknowledgements Calgon Carbon Corporation
Thank You