UV-C LED and When Will it Be Primetime in Wastewater? RayEhrhardPE,BCEE

28February2018

OliverLawalGaryHunter,PE,BCEEENVSP

BACKGROUND

2

A Brief History of UV Technology Hardware

Invention of mercury arc lamp by Cooper-Hewitt

Küch & Retschinsky use quartz as transmitting

material19061901First full-scale UV disinfection

apparatus by Henri and coworkers in France1910

Water treatment systems installed by Wedeco and Berson1972

2000s

Patent issued to A. Landry for gravity flow ww system using PTFE

tubes1972

Large municipal systems common globally for DW & WW

UV Disinfection Today• Mercury-based vapor lamp systems are very common

• Traditional UV treatment benefits• Chemical free• No disinfection by-products• Effects a wide range of pathogens• Established validation history• Established regulatory frameworks

Limitations of Current UV Technology

Materials•Mercury•Quartz

Operation•Warm-up time•Limited on/off

cycles

Durability•Fragile quartz tube

Footprint•Low power density•Large ancillaries

Weight•Reactor•Electronics

Power•AC Mains Voltage

only

Temperature•100-600ͦ C impacts

process fluid

Wavelength Compromise•LP: 254nm•MP: 200-300nm

UVLEDTECHNOLOGY

LED Technology Consideration #1: CapEx

Substrate very small percentage of UV-C LED

Device Cost

Source: Internal AquiSense Data

Lens

LED chip

Submount

Sapphire

UV output

Active layer Electrode

Electrode

AIGaN

UV-C LED WaferLED Layers

UV- C LED Device

Outer Package

UV-C LEDs on track to become ultra-low cost as volumes increase = Efficiency becomes less critical

LED Technology Consideration #2: Efficiency

Commercial UV-LEDs Have Low Efficiency

Research grade UVC LEDs are already more efficient than some MP lamps

Reference: Medium Pressure UV Lamps

Haitz’s Law

“For every decade of development LED Optical Power increases 20x and

cost/lumen falls by 10x”

It’s early but… UV-C LED development so far consistent with Haitz’s law

Implication for 2026 is 1.4 Watt per LED at 0.1 $/mW

LED Technology Consideration #3: Reactor Design • Overall Disinfection Performance efficiency is dependent on two things

• Lamp Efficiency and Reactor Efficiency• Mercury lamps are 15-35% efficient so they can be pared with a moderately efficient reactor.• UV LEDs are less than 5% efficient so they must be paired with a highly efficient reactor.

• Target Treatment• Fouling• Lamp Replacement• Upstream Process• Downstream Process• Energy Usage• Controls• Reporting• Mean Time Between

Failure• ……

UV System Operating

Cost

LED Technology Consideration #4: Opex

Operating Cost à Lamp Replacement Interval

0

50

100

0 20 40 60 80LampOutpu

t[%]

Time[sec]

LampWarm-UpTime

UV-LED

-30

20

70

120

0 2000 4000 6000 8000 10000

LampOutpu

t[%]

Time[hrs]

LampAgingwithHighOn-OffCycling(over10/day)

UV-LED GasDischarge

Conventionalvs.LEDlampcomparisonfactors

include:

• On-OffCycling

• OperatingLife

• MeanTimeBetweenFailure(MTTF)

Operating Cost à Water Quality Factors

020406080100120

0 20 40 60 80

LampOutpu

t[%]

WaterTemperature[◦C]

LampOutputvs.WaterTemperature

UV-LEDGasDischarge

LampHeatandLightDirection– FoulingPotential

Conventionalvs.LEDlampcomparisonfactors

include:

• FoulingRate

• WaterTemperatureVariations

Operating Cost

Capital Cost

System Efficiency

Lamp Efficiency

Consider Holistic View4%best-in-classcommercial20%labdevicesNovelLEDreactorshaveshownhigherefficienciesthanconventionallampreactors

IfLEDsbecomeultra-lowcost,thenefficiencyhasalowerfactor

LEDshavespecificcharacteristicsthatcanlowerOperatingCost

InitialCostComparisonfor0.1mgd(EPRI2015)

$0

$500

$1,000

$1,500

$2,000

MPMercury LPHI

Mercury LPLIMercury UV-CLED

Capex- $/gpm

$0

$50

$100

$150

$200

$250

$300

$350

$400

MPMercury

LPHIMercury

LPLIMercury

UV-CLED

OPEX- $/gpm/yr

When Will UV-C LEDs be Suitable for Wastewater Treatment?

Pilot Study: Mill Creek Water Treatment Plant

• In operation since 1959• Treats 130 MGD, Max of 360 MGD• Discharge into Ohio River• Currently disinfects with chlorine only• UV considered but too land-locked to add

traditional LP or MP UV facility

Goals of Pilot Plant Study

• DetermineUV-DoseResponseofEffluentat254nmvs.285nm

• DetermineDisinfectionPerformanceofstandardPearlAqua™product

• Determinescale-uppotential(cost/footprint)forfullscaletreatmentwithUV-CLEDtechnology

• InvestigateInfluenceofWaterQualityParametersonDisinfectionPerformance

• Fouling

• WaterTemperature

Pilot Plant Set-up

EffluentPump EffluentInlet(fromtreatmentplant)

PearlAquaHousingCasePost-TreatmentSamplePoint

EffluentReturn(totreatmentplant)Pre-TreatmentSamplePoint

Pilot System Set-up

Inlet Outlet

MeasuredFlowRate: 18lpm (4.75gpm)MeasuredAverageUV-T: 65%TargetEffluent: FC200MPN/100ml

UV-C LED Pilot System Hardware• StandardPearlAqua

• Model:24G• ReplaceableLEDlampmodule• Mechanicalsafetyinterlock• RemoteStart/Stop• 2xDigitalOutputAlarms• AnalogueUVIntensityOutput• Activecooling• On-boarddatalogging

Equivalentto3.5WConventionalUVSystem

Dose Response DeterminationInstrumentationUsed• AquiSensePearlBeam• ILT1400Radiometer

Correlationto2016datafromBecketal.

0

1

2

3

4

5

6

27-Aug 28-Aug 29-Aug 30-Aug 31-Aug 1-Sep

LogE.coli

SampleDate

FecalColiform,MembraneFilter

Pre-UV Post-UV0

1

2

3

4

5

6

27-Aug 28-Aug 29-Aug 30-Aug 31-Aug 1-Sep

LogE.coli

SampleDate

ColilertSampling

Pre-UV Post-UV

Initial Disinfection Results

Precision issue on sample EquatestoREDapprox.10mJ/cm^2

Goals of Pilot Plant Study

InitialWorkCompleted

• DetermineUV-DoseResponseofEffluentat254nmvs.285nm

• DetermineDisinfectionPerformanceofstandardPearlAqua™product

NewWorkDetermined

• UVSystemOptimization

OngoingWork

• Determinescale-uppotential(cost/footprint)forfullscaletreatmentwithUV-CLEDtechnology

• InvestigateInfluenceofWaterQualityParametersonDisinfectionPerformance.e.g.Fouling,WaterTemp

2017 Pilot Systems

Source:TyphoonTreatment Source:MetaWater

• CapitalCost• LED– Cost&Performance• Reactor– Cost&Performance• Footprint– LEDPowerDensity

• OperatingCost• LampReplacementInterval• MeanTimeBetweenFailure• FoulingPotential

• LifecycleCost

UVSystemDesignFactors

Summary: Scale-up Potential