Treatment of 1,4-Dioxane and VOCs for Potable Water Applications - - PowerPoint PPT Presentation

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 (CO3

2- )

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/1,000 gal) 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/1,000 gal) 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