UV/Chlorine AOP for Potable Reuse: Lower Cost OptionKeel Robinson, North America Water Reuse Leader

June 15th, 2016

Water Reuse in TexasSan Marcos, TX

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Agenda

AOP 101

UV-AOP for Potable Reuse

UV-AOP Design Considerations

First Full-Scale UV/Cl2 AOP Design

AOP 101

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What is AOP?

Advanced oxidation processes (AOPs) are technologies that

generate hydroxyl radicals (OH●)

The goal of an AOP technology is to maximize the production of

hydroxyl radicals (OH●) to provide fast reaction kinetics to most

efficiently destroy specific contaminants at the lowest possible cost

Technology and/or Chemicals OH●

OrganicCompounds

OH●

H2O

IntermediateCompounds H2O

OH●

CO2

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Why Do We Need AOP?

Contaminant of Concern Typical Source Regulated?

1,4-Dioxane Solvent stabilizer, found in groundwater from past

industrial releases

Yes (some states)

NDMA Found in groundwater from past industrial releases,

or formed in wastewater plants

Yes (some states)

Atrazine Herbicide, found in surface water bodies from

agricultural runoff

Yes

MIB & Geosmin Taste & odor compounds found in drinking water

from algal blooms

No, but a nuisance to customers

Endocrine Disrupting Compounds

(EDCs)

Found in wastewater from human use No, but under consideration

Pharmaceutical and Personal Care

Products (PPCPs)

Found in wastewater from human use No, but under consideration

Industrial Micropollutants including

VOCs

Chlorinated Solvents, Petroleum Hydrocarbons, Fuel

Additives, Phenols

Yes

� Some compounds are not strippable, adsorbable, or biodegradable. Some of these compounds are

regulated (either at a federal level or state level) or are candidates for future regulations. AOP is often the

best solution to destroy these types of compounds of concern.

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Common AOP Technologies

Excellent for a majority of AOP applications due to highly

efficient generation of hydroxyl radicals

Ideal for NDMA, excellent for low concentrations of

contaminants in RO effluent

Ozone + Peroxide

UV + Peroxide

At low pH, chlorine reacts with UV to create hydroxyl and

chlorine radicals. In some cases, may be more cost-

effective and implementable than peroxide.

UV + Chlorine

� ALSO, “OZONE” AND “OZONE WITH BIOLOGICALLY ACTIVE FILTRATION” CAN BEHAVE AS AN EFFECTIVE AOP

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Typical AOP Applications (examples)

AOPAir

Stripper (optional)

Well From Contaminated

Aquifer

Groundwater Remediation/Wellhead Treatment (industrial micropollutants)

Granular Activated Carbon

(optional)

Disinfection

and AOP

FiltrationSedimentation

Drinking Water/Surface Water Treatment (taste & odor compounds)

AOPIndustrial

Wastewater Treatment

End of Pipe (industrial waste discharge, recalcitrant contaminants)

Potable Reuse (1,4-Dioxane, NDMA, CECs)

Reverse OsmosisMembrane

Filtration (MF, UF)Filtered

Secondary WW Effluent

AOP

UV-AOP for Potable Reuse

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Why Do We Need UV-AOP for Potable Reuse?

Regulations for Indirect Potable Reuse

• California Groundwater Recharge Regulations (Full Advanced Treatment)

o Section 60320.201 (Requires Reverse Osmosis and Oxidation Treatment Process)

o 0.5 log removal of 1,4-Dioxane as an AOP surrogate because it partially passes through RO and is recalcitrant

• Big Spring, TX (TCEQ case-by-case)

NDMA

• Commonly found in tertiary wastewater and partially passes through RO

• California Notification Level (10 ng/l)

• UV-based AOP more effective than O3-based AOP at NDMA removal

Multiple Barrier Treatment

• Treatment redundancy to protect environment and human health

• Low molecular weight compounds (NDMA, 1,4-Dioxane, and CECs) pass through RO

• UV-based AOP provides pathogen barrier with maximum disinfection credit

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Full Advanced Treatment Train

Indirect Potable Reuse (typical FAT)

Environmental

BufferUV AOP

Reverse

Osmosis

Membrane

Filtration

Secondary or

Tertiary

Effluent

� This treatment train is ideal for UV-based AOP because RO produces a high quality effluent � High UVT (>95%) reduces power demand of UV reactor

� Low DOC and alkalinity reduce scavengers, more efficient contaminant removal

� Other treatment trains are possible with oxidation processes such as Ozone or O3-BAF� Ozone-based processes are very effective at removing a majority of trace organic

contaminants (TOrCs)

� May be used as pretreatment to membranes and UV AOP

� May displace membranes and/or UV AOP

UV-AOP Design Considerations

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Importance of Treatability Testing

Bench-Scale Testing

• Quick and inexpensive, great screening and preliminary

design tool

• Snapshot-in-time, but useful if water sample is representative

of design conditions

• UV Collimated Beam Testing

• Dose-response curves

Pilot-Scale Testing

• Optimize process under a range of real-life conditions

• Optimize equipment sizing variables

• Scale-up tool for full-scale design and performance guarantee

• Demonstration-scale for operators

• Regulatory and public acceptance

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Dose-Response Curve

LOG reduction

(Pilot reactor)

Dose-response curve

(CBD-Test)

UV dose [J/m²]

Log r

educti

on

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Design and Operation of UV Reactor: Dose vs. EED

tIDose *=][*

][

60 gpm

kW

Q

PEED =

UV Dose Setpoint Electrical Energy Dose (EED) Setpoint

Independently measured and verified through Collimated

Beam Testing

Does not directly measure UV output of lamps

Provide a common design basis for all manufacturers Specific to a reactor type

Can be used to scale up Difficult to scale unless same reactor used for both pilot-

scale and full-scale

Ensures regulatory compliance when using validated

dose equation (PSS) and on-line sensors

Good parameter for comparing power efficiency of

different UV reactors and different operating conditions,

but not measuring output of lamps

Allows for energy savings by turning down power to

lamps when conditions change

May waste energy when conditions change

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Validate Performance With Collimated Beam Testing

RO

Permeate

Contaminant or

Surrogate Spiking

H2O2 or NaOCl

Pilot- or Full-Scale

UV Reactor

Collimated Beam

Testing Device

UV Dose and Log Removal Comparison

UV Dose may be calculated via Point Source Summation (PSS) Method

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Why PSS for AOP Applications?

• PSS equation developed through extensive validation testing of UV reactors by 3rd party consultant

• PSS, CFD, and RED are different methods for calculating the average UV dose

• PSS accounts for real-time sensor inputs such as flow rate, UVT, and UV intensity

Flow Rate (MGD)

UVT (%)

PSS(mJ/cm2)

CFD (mJ/cm2) RED(mJ/cm2)

12 96 920 902 942

K143 12-17 (with 12 600W lamps per row, 17 rows)

PSS calculation method is validated by CFD and RED

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UV Dose Control

PLC

S = UV intensity sensor reading (per row)

UVT = UV transmittance

Q = Flow Rate

INPUTS OUTPUTS

P = ballast power (same to each lamp)

Number of rows on

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CBT Dose vs. PSS Dose

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UV Dose mJ/cm2

LP UV/H2O2 AOP1,4-Dioxane Removal

CBT vs. Pilot-Scale UV Reactor5 ppm H2O2

PSS Dose from Pilot

Collimated Beam Dose

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Upscaling and Sizing with UV Dose

� The reactor data and PSS model are validated using CBT data ideally

generated in parallel on site

� The reactor UV dose is calculated in real-time based on the measured

flow rate, UVT, and UV intensity

� The dose-response curve is used for upscaling using the same PSS

approach with full-scale reactor

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UV/H2O2 AOP For Potable Reuse Has Been The Status Quo

• Has historically been the standard AOP technology for groundwater recharge/indirect potable reuse in California with multiple successful installations in operation today (e.g. Orange County, West Basin, WRD, Big Spring)

• Also used in drinking water for taste & odor and in groundwater remediation applications

• Hydrogen peroxide is relatively expensive and not readily used at WWTPs

• The photolysis of hydrogen peroxide is inefficient as only about 10% of the chemical is consumed in the UV AOP reaction; thus, incurring significant residual quenching costs

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Introducing UV/Cl2 AOP

• Recent academic research shows that UV/Cl2 AOP is effective at low pH�Watts, M. & Linden, K., 2007. Chlorine Photolysis and Subsequent OH Radical Production During UV Treatment of Chlorinated Water. Water Res., 41:13:2871

�Watts, M., Rosenfeldt, E,. & Linden, K., 2007. Comparative OH Radical Production Using UV-Cl2 and UV-H2O2 Processes. Jour Supply Water Res Technol - AQUA., 56:8:469

�Watts et al. 2012. Low pressure UV/Cl2 for advanced oxidation of taste and odor. Journal-AWWA

• Reverse osmosis for FAT produces a low pH permeate (~5.5)

• Sodium hypochlorite (chlorine) is readily used at most WWTPs

• Use of sodium hypochlorite may result in significant life cycle cost savings relative to hydrogen peroxide

• Residual chlorine may be desirable for additional pathogen credit and/or secondary disinfection

• First greenfield full-scale system under construction by City of Los Angeles

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UV/Cl2 AOP for Reuse – Chemistry Considerations

Chloramines and Breakpoint Reactions

� Residual chloramines may be present in RO

permeate prior to hypochlorite addition

pH and Chlorine Speciation

� Lower pH favors free chlorine in hypochlorous

acid form (slow hydroxyl radical scavenger)

� Higher pH shifts free chlorine to hypochlorite ion

form (rapid hydroxyl radical scavenger)

Disinfection by-product formation

� THMs/HAAs

� Chlorate

Target pH and free chlorine residual at inlet to UV reactor

Ref: Hach

Terminal Island Water Reclamation Plant

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LASAN TIWRP AWPF AOP Design

• 5 MGD to 12 MGD expansion, converting

chloramination to comply with groundwater

recharge regulations

• 18 month bench and pilot scale study

including O3/H2O2, UV/H2O2, and

UV/HOCl led by LASAN, Trussell

Technologies, and Carollo Engineers

• Selected UV/HOCl based on performance

and life cycle costs

• Awarded AOP system to Xylem/Wedeco,

startup expected in late 2016

First Ever UV/Cl2 AOP Full-Scale Design

AOP Design Basis:� 3 to 12 MGD

� TOC < 0.25 mg/l

� UVT >96%

� CA Groundwater Recharge Regulations

AOP Specifications:� 6-log virus credit

� 0.5 log 1,4-Dioxane removal

� <10 ppt NDMA in effluent

� UV dose = 920 mJ/cm2

� Free chlorine dose = 2-4 mg/l

UV Dose is the design and operational basis, not EED

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Wedeco MiPRO AOP Pilot System

� Containerized with climate control (HVAC), lighting, sink,

and refrigerator

� Fully automated with PLC and Operator Interface

� Remote Monitoring & Datalogging

� Can run operate in various modes of operation including

Ozone only, UV only, Ozone with Peroxide (AOP), UV

with Peroxide (AOP), and UV with Chlorine (AOP)

� State-of-the art instrumentation

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Terminal Island Treatability Testing Objectives

12 month pilot study to compare 6 different AOPs

� UV LP + H2O2

� UV LP + NaOCl

� UV MP + H2O2

� UV MP + NaOCl

� Ozone + H2O2

� H2O2 + Ozone

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Bench and Pilot Scale Results

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Investment Decision: Chemical Savings

• $3.3M in chemical savings over 20 years

• NaOCl already on-site

• Additional pathogen barrier/credit with Cl2 for FAT

� UV/Cl2 AOP selected

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Investment Decision: Real-Time Energy Savings

Q [gpm]

UVT [%]

UV Dose[mJ/cm2]

EED [kWh/1000gal]

Power Savings [%]

Log removal of 1,4-Dioxane

8333 98 920 0.194 28 >0.5

8333 97 920 0.230 14 >0.5

8333 96 920 0.268 0 >0.5

� UV Dose control reduces power usage

� Allows for variable power control to optimize power consumption and ensure regulatory compliance

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Wedeco Full-Scale UV Reactor

• Wedeco K143 Series LP UV Reactor

• Validated for 6-log virus removal

• 12 lamps per row

• 17 rows of lamps

• 1 UV intensity sensor per row

• 600W lamps

• 34:1 linear power turndown

• Low headloss

• Add more rows for linear expansion

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Acknowledgments on TIWRP Project

Roshanak Aflaki, Ph.D, P.E. ,

Plant Manager, Water Reclamation Division

Donald C. Tillman and Los Angeles-Glendale Water Reclamation Plant

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Thank You! Questions?

Keel Robinson

keel.robinson@xyleminc.com

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