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

Transcription

1 UV-C LED and When Will it Be Primetime in Wastewater? 28 February 2018 Gary Hunter, PE, BCEE ENVSP Oliver Lawal Ray Ehrhard PE, BCEE

2 BACKGROUND 2

3 A Brief History of UV Technology Hardware 1901 Invention of mercury arc lamp by Cooper-Hewitt 1906 Küch & Retschinsky use quartz as transmitting material 1910 First full-scale UV disinfection apparatus by Henri and coworkers in France Patent issued to A. Landry for gravity flow ww system using PTFE 1972 tubes 1972 Water treatment systems installed by Wedeco and Berson 2000s Large municipal systems common globally for DW & WW

4 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

5 Limitations of Current UV Technology Mercury Quartz Materials Operation Warm-up time Limited on/off cycles Durability Fragile quartz tube Footprint Low power density Large ancillaries Weight Power Temperature Wavelength Compromise Reactor Electronics AC Mains Voltage only C impacts process fluid LP: 254nm MP: nm

6 UV LED TECHNOLOGY

7 LED Technology Consideration #1: CapEx UV-C LED Wafer LED Layers UV output Sapphire AIGaN UV- C LED Device Source: Internal AquiSense Data Active layer Electrode Lens Submount Substrate very small percentage of UV-C LED Device Cost Electrode LED chip UV-C LEDs on track to become ultra-low cost as volumes increase = Efficiency becomes less critical Outer Package

8 LED Technology Consideration #2: Efficiency Reference: Medium Pressure UV Lamps Commercial UV-LEDs Have Low Efficiency Research grade UVC LEDs are already more efficient than some MP lamps

9 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

10 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.

11 LED Technology Consideration #4: Opex UV System Operating Cost Target Treatment Fouling Lamp Replacement Upstream Process Downstream Process Energy Usage Controls Reporting Mean Time Between Failure

12 Operating Cost à Lamp Replacement Interval Conventional vs. LED lamp comparison factors include: On-Off Cycling Lamp Output [%] Lamp Warm-Up Time UV-LED80 Time [sec] Operating Life Mean Time Between Failure (MTTF) Lamp Output [%] Lamp Aging with High On-Off Cycling (over 10/day) UV-LED Gas Discharge Time [hrs]

13 Operating Cost à Water Quality Factors Conventional vs. LED lamp comparison factors include: Fouling Rate Lamp Heat and Light Direction Fouling Potential Water Temperature Variations Lamp Output [%] Lamp Output vs. Water Temperature UV-LED Gas Discharge Water Temperature [ C]

14 Consider Holistic View If LEDs become ultra-low cost, then efficiency has a lower factor Lamp Efficiency System Efficiency Capital Cost Operating Cost LEDs have specific characteristics that can lower Operating Cost 4% best-in-class commercial 20% lab devices Novel LED reactors have shown higher efficiencies than conventional lamp reactors

15 Initial Cost Comparison for 0.1 mgd (EPRI 2015) Capex - $/gpm OPEX - $/gpm/yr $2,000 $400 $1,500 $1,000 $350 $300 $250 $500 $200 $0 MP Mercury LPHI Mercury LPLI Mercury UV-C LED $150 $100 $50 $0 MP Mercury LPHI Mercury LPLI Mercury UV-C LED

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

17 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

18 Goals of Pilot Plant Study Determine UV-Dose Response of Effluent at 254nm vs. 285nm Determine Disinfection Performance of standard PearlAqua product Determine scale-up potential (cost/footprint) for full scale treatment with UV-C LED technology Investigate Influence of Water Quality Parameters on Disinfection Performance Fouling Water Temperature

19 Pilot Plant Set-up PearlAqua Housing Case Post-Treatment Sample Point Pre-Treatment Sample Point Effluent Return (to treatment plant) Effluent Pump Effluent Inlet (from treatment plant)

20 Pilot System Set-up Measured Flow Rate: 18 lpm (4.75 gpm) Measured Average UV-T: 65% Target Effluent: FC 200MPN/100ml Inlet Outlet

21 UV-C LED Pilot System Hardware Standard PearlAqua Model: 24G Replaceable LED lamp module Mechanical safety interlock Remote Start/Stop 2 x Digital Output Alarms Analogue UV Intensity Output Active cooling On-board data logging Equivalent to 3.5W Conventional UV System

22 Dose Response Determination Instrumentation Used AquiSense PearlBeam ILT1400 Radiometer Correlation to 2016 data from Beck et al.

23 Initial Disinfection Results 6 Colilert Sampling 6 Fecal Coliform, Membrane Filter Log E.coli 3 2 Log E.coli Pre-UV Post-UV 0 27-Aug 28-Aug 29-Aug 30-Aug 31-Aug 1-Sep Sample Date 1 Pre-UV Post-UV 0 27-Aug 28-Aug 29-Aug 30-Aug 31-Aug 1-Sep Sample Date Precision issue on sample Equates to RED approx. 10mJ/cm^2

24 Goals of Pilot Plant Study Initial Work Completed Determine UV-Dose Response of Effluent at 254nm vs. 285nm Determine Disinfection Performance of standard PearlAqua product New Work Determined UV System Optimization Ongoing Work Determine scale-up potential (cost/footprint) for full scale treatment with UV-C LED technology Investigate Influence of Water Quality Parameters on Disinfection Performance. e.g. Fouling, Water Temp

25 2017 Pilot Systems Source: Typhoon Treatment Source: MetaWater

26 Summary: Scale-up Potential UV System Design Factors Capital Cost LED Cost & Performance Reactor Cost & Performance Footprint LED Power Density Operating Cost Lamp Replacement Interval Mean Time Between Failure Fouling Potential Lifecycle Cost

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