Designing and Commissioning an Ultraviolet Light Disinfection ...

DESIGNING & COMMISSIONING AN ULTRAVIOLETLIGHT DISINFECTION SYSTEM TO MEET NWRIGUIDELINES AT WARDEN, WASHINGTON26 th Annual WateReuse SymposiumPhoenix, ArizonaSeptember 12, 2011Ken Alexander, P.E.Gray and Osborne, Inc.Vancouver, WA

AcknowledgmentsCOAUTHORS / TEST DESIGNERS• Bruno Ferran, Degremont Technologies• Dave VanCleve, P.E., Gray & Osborne• Jay Swift P.E., Gray & OsborneTEST TEAM• Susan Welland, Gray & Osborne• Steve Maddox & Donnie Edson, City of Warden• Mark Siegenthaler, WSU Water Research Center• TEK Construction

Presentation Outline• Background• UV Disinfection Design Standards for Reuse• Checkpoint Bioassay• Review and Acceptance of Checkpoint Bioassay

• Project DriversBackground• No surface water discharge availablea ab • Discharge to USBR canal not allowed• Year round agronomic management infeasible• Regulatory Issues with Groundwater Discharge• Groundwater degradation with existing facilities• Disinfection byproducts to groundwater• Previous Design of UV Disinfection for Reusewith Groundwater Recharge• Ephrata, WA• Royal City, WA

Water Reclamation Facilities Warden, WAWaterReclamationFacilityGroundwaterRechargeBasin 4Short TermStorage BasinUSBR CanalFlows Apr - OctGroundwaterRechargeBasins 1 - 3

Water Reclamation Facilities Warden, WASecondaryClarifiersFilter / UV RoomAnoxicBasinOxidationDitch

Warden, WashingtonUV

Warden, WashingtonWarden UV Disinfection SystemMaximum Month Average Flow 0.474 mgdMaximum Day Flow0.60 mgdPeak Hour Flow1.2 mgdUV Design Flow0.60 mgdUV Transmittance for Design Flow 55 %UV Lamp TypeLow PressureHigh IntensityLamp OrientationVerticalNumber of Banks Total 6Number of Redundant Banks 1Lamps Per Bank 40Total Lamps 240Channel Width (less baffle width) 4 ftChannel Depth6 ftChannel Length33.83 ftTotal Reactor Volume6,065 galReactor Water Depth5 ftEffective Reactor Volume5,054 galUV Model/ManufacturerAquaRay 40 HO

Warden, WashingtonWarden UV Disinfection System• Began Operation June 2009• Typically 2 Modules On• Daily Total Coliform (TC) Testsmet standards continuously:< 2.2 TC/100 mL 7 day median< 23 TC/100 mL single sample• Continuous UVT Monitoring> 65 % UVT nearly continuously

UV Disinfection Design StandardsDesign Requirement(Media Filtration)Ephrata and Royal City (1)(pre-2000)Warden (2)(after 2005)Microorganism Coliform Bacteria VirusMeasure of MicrobialInactivationTurbidity Entering UV Reactor< 2.2 total coliform/100 mL 7-daymedian< 23 total coliform/100 mL singlesample< 2 NTU monthly average< 5 NTU at all times< 2.2 total coliform/100 mL 7-daymedian5-log Virus Inactivation< 2 NTU 24-hour average< 5 NTU at all timesUV Dose at Maximum Day Flow 100 mJ/cm 2 100 mJ/cm 2UV Transmittance (UVT) 65 percent 55 percentContinuous UVT TransmittanceMonitoringField Verification of DesignNoComply with Coliform Density Criteriafor Reclaimed WaterYesCheckpoint Bioassay (3)(1) Class “A” Reclaimed Water Disinfection Standards for the State of Washington(2) May 2003 NWRI Guidelines for Drinking Water and Water Reuse(3) Although the 2003 NWRI Guidelines include velocity profiling instead of checkpoint bioassays for field verification, checkpointbioassays are the current de facto standard.

Checkpoint BioassayWarden WRF Checkpoint Bioassay – Target Test ConditionsFlow,No. Lamp LoadingRun Flow, % of UVT,Modules rate,ID mgd Design%On gpm/lampFlowA 0.07 5.8 % 55 2.0 0.61B 060 0.60 50.00 % 55 20 2.0 347 3.47C 0.86 71.2 % 55 3.0 3.73D 1.20 100 % 65 4.0 5.21Note: Low flow (0.07 mgd) set by influent pump station VFD

Checkpoint BioassayWRF Checkpoint Bioassay - Test Data SummaryMS-2 ModuleTest Power No.Avg. MS-2Test RunFlowRED Avg. MS-2UVT Draw ModulesREDDate ID(mgd)Stdev RED(%) (kW) ON(mJ/cm )(mJ/cm 2 ) (mJ/cm 2 )10-13-09 A 56.5 13.8 2.0 0.074 n/a n/a n/a10-13-09 B 56.6 20.8 3.0 0.60 134.3 2.13 44.810-12-09 C 56.1 27.9 4.0 0.87 122.3 3.24 30.610-12-09 D 65.5 23.7 3.4 1.19 103.1 1.60 30.3

Checkpoint Bioassay Test Flow Scheme

Checkpoint Bioassay Test SetupUV Reactor

Checkpoint Bioassay Test Setup

Checkpoint Bioassay Test ResultsRED = Reduction Equivalent Dose

Checkpoint Bioassay Test Results

Checkpoint Bioassay Test Results• Runs B, C & D Successful• Validated UV Performance per Original Bioassay• Run A Inconclusive• Phage Concentration at Inlet ≈ Outlet• Low Phage Concentration at UV Reactor Inlet• Poor Dispersion Suspected ** In Spite of Dispersion Test Prior to Checkpoint Bioassay Test• Regulatory Agencies Request Hydraulic Analysis

Acceptance of Checkpoint BioassayVelocity Measurements at Low Flow (Run A)• Hired WSU Water Research Center Researchers• Acoustic Doppler Velocimeter Measurements• Tests Designed per NWRI Guidelines• 0.3 m upstream of first bank• 0.3 m downstream of last bank• Cross-sections equally spaced• Not less than 3 x 3 grid per cross-section• Measurements 6 – 12 cm apart

Acceptance of Checkpoint BioassayVelocity Profile Measurement Selected Locations

Acceptance of Checkpoint BioassayActual VelocityActual VelocityTest Results

Acceptance of Checkpoint BioassayIssues• Non-ideal hydraulics evident from velocity testing• Successful checkpoint bioassays at 3 higher flows• Achievement of Class A Coliform Levels > 2 year• > 65% UVT typical for Warden WRF filtered effluentexceeds NWRI test conditions (55% UVT)• Reactor hydraulic residence time higher at low flows• Comparison to UV reactors at other Class A WRFs• ~10 x larger (8,423 gal/mgd vs 860-940 gal/mgd)• ~3 x power draw (33.0 kW/mgd vs 10-12 kW/mgd)

Acceptance of Checkpoint BioassayExtrapolating from Successful Test (Run B)• Run B (0.6 mgd)• Average velocity = 26.7 mm/sec• Validated UV dose = 115 mJ/cm 2 @ 55% UVT• Three UV modules achieved validated dose• Run A (0.07 mgd)• Highest measured velocity = 19.2 mm/sec• Reactor residence time Run A > Run B

Acceptance of Checkpoint BioassayConclusions• Run A UV dose > 115 mJ/cm 2 @ 55% UVT• Typical UVT in Warden UV Reactor > 65% UVT• Three modules delivers > 115 mJ/cm 2 @ 55% UVT• Three modules on at all times will deliver a validatedUV dose at flows up to 0.6 mgdWarden agreed to operate a minimum of three UVmodules at all times to ensure validated dose isdelivered at all times

Questions