UV Applications for Reuse and the New NWRI Guidelines ...

Most reuse UV applicationsfollow NWRI UV Guidance

Background to UV ReactorValidation Testing

Influent and effluent samplesdetermine log inactivationThe log inactivation of a tested microbe is translated to aUV “dose”, based on the UV inactivation kinetics of themicroorganism

Dose Monitoring viaCalculated Dose Algorithm

Third Ed. published in 2012

Third Ed. published in 20121. Drinking Water2. Reuse Water3. Protocolsa. MS2 dose-responseb. Checkpoint bioassayc. Data analysis

2 nd Ed.: MS2 dose-responsePrevious NWRI Guidelines defined quality control bounds

Carollo: MS2 quality boundsCorroborated by

3 rd Ed.: MS2 dose-responseNew guidelinesdefine a priori doseresponsebehaviorfor MS2 phageCensoring 150 mJ/cm 2removes valid data(25% of data inDuron example) butallows for theassumption oflinearity

3 rd Ed.: Bioassays replacevelocity profilingTheoretical scale-up (velocity profiling) replaced byperformance-based scale-up (checkpoint bioassay testing)Mahar et al.,WEFTEC2006Reliable UV disinfection requires more than good hydraulics!

NWRI Checkpoint BioassayRequirementso Installed system must provideminimum RED in at least 7 out of8 bioassay test conditionso MS2 bacteriophageo Demonstrate doses ofo 100 mJ/cm 2 (media filtered)o 80 mJ/cm 2 (MF effluent)o 50 mJ/cm 2 (RO effluent)o UV doses meet Title 22requirements, based on a 5-logpoliovirus inactivation goalstemming from the PomonaVirus Study (LACSD, 1977)oooNon-infectious virus(+)ssRNA30 nm φ

2 nd Ed.: Data analysis & sizing2003 NWRI

3 rd Ed.: Data analysis & sizingCapacity is defined by incorporating a “confidenceratio” based on validation testing, goodness of fitRED 0. 831NWRI REDpred

Xylem/Wedeco Duron Validation

WEDECO Duron UV SystemOpen-channel wastewater disinfection systemModular banks of twelve 600 W LPHO lampsReliable on-line UV intensity sensors for accurate UV dosepacingExtensive validation effort includes MS2, T1UV, T7 phage,B. pumilus sporesDirect measurement of additive bank effects, compared toprevious open-channel UV systems that assume perfectbank additivity

Minden WWTP Pilot

Photos of Minden test site

Photos of Minden test site

Snapshot of test matrix:Validated range envelopes

Duron: NWRI 2 nd Ed. Analysis

Duron: NWRI 3 rd Ed. Analysis2 nd Ed.: ~7 mJ/cm 2 offset. 3 rd Ed.: 0.92 confidence ratio.

Vendor B: NWRI 2 nd Ed. Analysis

Vendor B: NWRI 3 rd Ed. Analysis2 nd Ed.: ~7 mJ/cm 2 offset. 3 rd Ed.: 0.83 confidence ratio.

Understanding bank additivityCDUVAEUVABasing your design on Sbioassay-validated data helps avoid2AB UVAS 0GHUVAIUVAdangerous log i 10UVAassumptions before attempting Modules checkpointbioassays (e.g., assuming Q DLperfect bank additivity)2

What’s missing from NWRIGuidelines, 3 rd Ed.System sizing and operations depend on:• UVT (%): measurement of the UVA 254• Flowrate: average, max daily, etc.• Footprint or power limitations guide lamptechnology lamp choice (LP vs. MP)• Pretreatment: High SRT during secondarytreatment and good filtration reduces thefraction of particle-associated coliformBut what use is good design if the systemisn’t adequately monitored?

UVDGM provides clearguidance re: online UV sensorsin WTPsEach reactor must have at least oneonline germicidal UV sensor to monitorlamp outputDuring validation, online UV sensors mustbe within 10% of reference sensorsDuring operation, online sensors must bewithin 20% of reference sensors,measured at least once a month

NWRI Guidelines require UVintensity monitoring…Under “Monitoring and Alarm Design”

…but some UV disinfection systemsdo not adequately include UV sensorsignals in UV dose pacingRudimentary UV dose algorithm in UVDGMuses inputs of UV absorbance, flow (Q),number of banks (B), and relative UVsensor intensity (S/S o ) to “dose-pace” thereactorNo similar requirement in NWRI Guidelines

Sleeve fouling at WWTPimpairs UV disinfectionUncleaned sleeves (L)Cleaned sleeves (R)Livermore, CA UV PLCdisplayed equal UVdoses for eachWhat can engineersand utilities do whenthe design UV dose ≠the actual UV dose?

Benefits of Online UV Sensorso Real-time dosemonitoring, facilitatingmaintenanceo Full control ofmaintenance scheduleo True measurement ofdoseo Optimizes energy useo Not all systems use them,but they are stronglyrecommended

CAF Index Uses UV Sensors toMonitor Lamp Aging/Fouling“Combined aging and fouling factor” (CAF) is the ratioof the measured UV sensor intensity to thepredicted UV sensor intensity with new lamps andsleevesOnline UV sensor measurementSCAFS pSP10AexpBUVTPCReal-time monitoring of lamp aging and sleeve fouling,proactive maintenance, warranty guarantees

ConclusionsConsultants and vendors need to be awareof balance between accurate validationtesting, conservative sizing, and worry-freecheckpoint bioassay testingDifferences between 2 nd and 3 rd Ed. dependon the equipment, quality of validationtesting, and design goalBoth previous and current NWRI Guidelinesprovide good guidance for robustdisinfection of reuse water

Thank you!jbandy@carollo.com