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UV VALIDATION FOR WASTEWATER
APPLICATIONS: IS A UNIFORM
PROTOCOL POSSIBLE?
O. Karl Scheible
HydroQual, Inc.
ABSTRACT
With the release of the USEPA Ultraviolet Disinfection Guidance Manual (USEPA, November 2006), the protocols for UV reactorperformance validation reached a new level of standardization and acceptance. This paper addresses the concept of a uniformprotocol for wastewater applications, including reuse, secondary effluents and low grade wet-weather flows, modeled after theUVDGM and encompassing existing wastewater protocols published by NWRI and the USEPA ETV program. The suggestedapproach would allow for validation over a prescribed operating range (flow, UVT, power, etc.) as defined by the manufacturer,rather than assign a specific application. The protocol would introduce flexibility with respect to surrogate selection, include theuse of chemical actinometry with dyed microspheres, and emphasize the operating strategy of the system (intensity setpoint andcalculated dose control). Credit for validated performance would address experimental variability and the accuracy of key systemand experimental measurement components. The overall intent of this effort, which is underway, is to provide a modern, updatedprotocol that can be used universally and be accepted in the owner, design and regulatory communities.
Key Words: UV disinfection, treated wastewaters, reuse, validation protocols, surrogates
A number of verification and validation protocols exist that address the performance of UV systems designed for disinfection odrinking waters and treated wastewaters. An effort is underway that will attempt to unify these protocols, first focusing on thosthat deal with treated wastewater application, using the recently released UVGDM as a model template.
CURRENT VERIFICATIONPROTOCOLS
First, let us briefly review the status of current protocols.
1. USEPA UV Disinfection Guidance
Manual (UVDGM) (November 2006)
The UVDGM had been in development for nearly 5years, and was released in final form in November2006. Formal drafts were released for comment in June2003 and January 2005, and updates were givenlimited distribution in December 2005 and April 2006 these drafts were used for validations of systems forthe past several years. This document is expected tobecome the primary validation protocol reference fordrinking water applications. It is less prescriptive thanthe European protocols, and provides for flexibility intesting, while establishing QA goals that have to bemet for acceptance of test results, and which can affectthe RED accreditation for the targeted pathogens.Additionally, it offers alternative testing and analysisapproaches for different operating/dose-controlstrategies, and suggests a multivariate regression
analysis to establish the variability/uncertaintyassociated with a test program. There is globainterest in the UVDGM, with national agencies citingthe document and its validation requirements withintheir regulatory framework.
Regulators are expecting to require UVDGM validationon systems offered within their jurisdiction. Suchtesting has been underway at both validation centersin the United States (Portland OR and Johnstown NY)since 2003, generally for dose-control systems; thevalidation reports attempt to meet current UVDGMdata analysis requirements, or, at minimum, report
field data that will allow for credited RED or loginactivation analysis under the final UVDGM. Newvalidations will necessarily follow the UVDGMprotocols in order to attain inactivation credits for thetargeted pathogen.
Although directed to drinking water validations, theUVDGM validation protocol has raised the standard fothe concept itself it is comprehensive and flexible, hasundergone substantial peer review and regulatoryinput, essentially becoming the industry standard fovalidation. We strongly believe that it serves as the
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basis, in format, methods and data analysis techniques,for a uniform protocol across all water/wastewaterapplications.
2. NWRI/AwwaRF UV Design Guidance for
Reuse and Drinking Waters (2003)
This protocol (along with the ETV protocols discussedbelow), remain the only formally recognized testmethods for wastewater-related applications. Since
development of the first protocol, a new NWRI/AwwaRFedition has been published (2003) and there is someindication that this will undergo a second revision in thenear future. We are seeing interpretations of verificationreports (non-ETV) that suggest that the NWRI/AwwaRFguidance is leaning more to the approaches found inthe UVDGM. Specifically, these include limits to thedegree of replication needed, and the use of multiplelinear regression modeling to assess the data, determinedose-delivery as a function of operating variables andestablish uncertainty factors based on the MLR analysis.Scaling is accepted, and commissioning validatedsystems is addressed by hydraulic checks. New worksuggests alternate approaches to commissioning asystem, verifying expectations from the validation tests.
3. USEPA Environmental Technology
Verification Program (ETV)
The UV-related verifications within the ETV programare administered through NSF International, Ann ArborMI. Within the ETV program, there are four verificationprotocols:
A. ETV: UV Disinfection of Reuse Waters
This verification protocol is designed to mimic veryclosely the NWRI/AwwaRF protocols for drinkingwaters and reuse waters (NWRI/AwwaRF, 2000). Thesecond edition of the NWRI/AwwaRF (2nd Edition) wasreleased in 2003; the only validation modificationaddressed the size of the system to be tested the newversion allows testing of one reactor instead of aminimum of two reactors in series. It contains thebasic approach to validate dose-delivery performanceat alternate transmittance levels, representing varyinglevels of treatment prior to UV (granular filtration,membrane filtration and RO), and adds separateprotocols for verifying specific system design and
operational claims, including lamp aging and foulingattenuation factors, and velocity profiles.
B. ETV: UV Disinfection of Secondary Effluents
This is very similar to the Reuse ETV, except that itrequires incorporating tracer analyses to verifyhydraulic characteristics, and establishes differentdefault attenuation factors than suggested by theReuse ETV. Strictly followed, these differences meanadditional testing (and expense) to yield data that arestill within the operating range of the Reuse ETV. Thedifferences are more an artifact of existing practice
(and past tests) than due to any technical justificationAdditionally, the secondary protocols rely on MS2testing, which is now considered inappropriate fosuch low-dose applications.
C. UV Disinfection of Wet Weather Flows
This was written after extensive stakeholder input andreview, and subsequent modifications once vendorscommitted to conducting such tests. It requires testingin three phases, addressing dose-delivery undespecific UVT conditions in a non-particle matrix, thenin a primary effluent matrix, and, finally, verification othe units cleaning mechanism. These are similar tothe Reuse/Secondary effluent protocols, except thatthe testing phases are required in combination and arenot separated as independent optional ETVs.
D. UV Disinfection of Drinking Waters
Different than NSFIs Standards, such as Standard 55for small POU/POE UV units, the ETV program has averification protocol for application to drinking watersThese are generally intended for systems larger thanthe POU/POE units covered under Standard 55. Thefirst versions were limited in scope, generally verifyingdelivery of a targeted single dose at rated designconditions. It is our understanding that NSFInternational, at its 2003 stakeholders meetingdecided to craft a new protocol that is based on the
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USEPAs UV Disinfection Guidance Manual (UVDGM).This is not in place, possibly because the UVDGM hasbeen in draft form and has itself undergone significantmodifications. The final UVDGM is now available(USEPA, November 2006).
3. Other Validation Protocols
Other widely recognized protocols exist that influencethe industry:
A. DVGW (Germany)
This protocol was recently updated in 2003. It is veryprescriptive, and is directed only to verification ofintensity setpoints for system dose control. Because ofits limited nature, it has not been used extensivelyoutside of Germany. Testing by this protocol isgenerally done at a facility in Germany
B. ONORM (Austria)
Similar to the German protocol, this is protocol findslimited use outside of Europe, with testing done at a
facility in Austria.
UNIFIED PROTOCOL
There have been legitimate concerns regardingdissimilarities between protocols and their expense. Withthe release of the final EPA Guidance Manual for drinkingwaters, the evolution of the validation concept has reacheda point where we believe we can reach some unity in theapproach that validation protocols can use, leaving thedetails of their implementation with a well-designed testplan and QA guidance. This unified protocol couldeventually be applicable to both wastewater and drinkingwater. At this point we suggest that we focus on thewastewater protocols, since the UVDGM will essentially bethe standard for drinking water, even from a regulatorystandpoint. To this end, we are suggesting that a genericWastewater UV Disinfection protocol be developed, basedprimarily on the NWRI/AwwaRF, ETV and UVDGM protocols,and structured in a fashion similar to that of the UVDGM.
The approach we are taking is to:
First review and summarize the protocols in thecontext of the UVDGM.
Draft an extended outline for new wastewater
protocol, based on the comparisons to the UVDGM,and on testing methods that reflect currentapproaches to validation.
Subject the draft outline to critical review within theindustry.
Reflecting comments/editing suggested by reviewers,complete first draft will for critical review.
Once this first draft has been reviewed and a seconddraft prepared, the second draft will be distributed toa broader stakeholder group.
The final protocol is expected to be completed by the thefall of 2007.
At this point, based on our knowledge and understandingof the ETV, NWRI and UVDGM protocols, we anticipatereconsideration and adjustment of the following elementsin developing the generic, uniform protocol for wastewatevalidation:
1. Use the UVDGM format (contents and context
outline and checklists) as the format for the proposedprotocol.
2. Eliminate Directed UV Protocol specific to UVapplication (reuse, secondary, wet weather, etc.). Theindividual test plans written for a validation canaddress meeting specific requirements (e.g., Title 22)the protocol itself should focus on the procedures and accommodate the wide range of water quality (asexpressed by the UVT) expected for wastewaterapplications (e.g., 20 to 80% UVT). The manufacturewill determine the application and the operatingrange for its specific system.
3. Separate the protocols dealing with dose performance(the primary focus of this effort) lamp outputattenuation, fouling attenuation and cleaning deviceefficacy. .This is not the case in the ETV wet-weatheprotocol. Additionally, these ancillary protocolsshould be updated this is not currently the focus othis effort, but can be after it is completed. Inparticular, work and documents that have been underdevelopment by others should be reviewed andbrought into these updates.
4. Particle impacts can be studied separately and specificto an application. The ETV for wet-weather flows
requires testing in a primary effluent matrix to assessthe impact of particles. This is influenced by thecharacteristics of the wastewater used for the tests,which limits its application as a generic verificationWe propose eliminating this from the validationprotocol. Rather, a protocol can be written (as aseparate option) to develop dose-responserelationships in the laboratory for a particular siteapplication, addressing the effect of particle size (byfractionation, or serial filtration) on performance.
5. By making the different tasks independent, amanufacturer can choose one or more in the conductof a validation. From a practical standpoint, the doseperformance validation would be done separately(inclusive of technical testing that normallyaccompanies such a validation) because it generallyrequires larger systems and the testing can be done ina matter of weeks. The other validations requiredifferent setups and timeframes and can be done on asmaller scale.
6. Additionally, the test matrix should encompass anexpanded operational envelope for dose-deliverytesting, reduce the degree of replication and support a
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valid multivariate regression analysis. The verificationshould allow for flexibility in developing the test matrix a manufacturer may choose to verify performance in atargeted UVT range, instead of the specific targets (e.g.,40% for wet weather or 65% for secondary) suggestedin the current protocol. These steps bring this protocolcloser to the unified goal, allow for more cost-effectivevalidations, and give the manufacturer flexibility insetting the design operating range for verification.
7. Remove replication of dosimetry runs as arequirement, leaving the requirement to collect aminimum of three influent and three effluent sampleswith each test event (an event being defined as thecollection of the inf/eff samples at a prescribed set ofunit operating and water quality conditions flow,power, number of lamps, UVT, etc.). This allows for abroader spectrum of operating conditions, instead ofexpending budget on test repetitions. At the usersdiscretion, replication can be added to the testprogram, with the benefit of reducing the uncertaintyof the regression analysis. California has allowed this,conditioned on the collection of quality, low-variabilitytest data. Data across a wider, or more varied, testmatrix, will support the MLR approach, and gives thevendor a more marketable verification report.
8. Incorporate the reactor operating strategy into thedesign of the test plan for a specific reactor. This wouldfollow the UVDGM approach, which specificallydiscusses test matrices for sensor-setpoint and dose-algorithm strategies. As such, smaller systems wouldtypically be evaluated in the simpler setpoint approach,while larger systems that have dose-control (or arerequired to have dose control and readout) would betested over a broad operating envelope. Such flexibility
recognizes the diversity of commercial systems.9. Adopt the UVDGM dose-response collimated beam
protocol as a standard through all test ranges. Thissimply updates all protocols to the latest standard itis more rigorous, and has specific methods foranalyzing the data generated by the collimated beamtest. It would also assure that there is uniformityacross all applications and among laboratories.
10. Quality control limits for the dose-response curvesshould be updated. NWRI and the UVDGM showsuch limits for MS2; the UVDGM for B. subtilis. Newsurrogates that are in use should also have datadeveloped to support such an assessment. T1 and QBare examples.
11. Unify the attenuation factors. Default factors can beadopted for the different lamp technologies, with theflexibility to adopt factors that have beendemonstrated through a documented alternativestudy. Derivation and application of these factorswould be made consistent throughout all applications(this is not the case, for example, when comparing thereuse and secondary ETV protocols). Validations
typically combine the two to a single attenuationfactor, defined by the vendor. This typically becomesimportant when the setpoint approach is used. It inot necessarily an issue when evaluating the dosecontrol strategy, except to assess the sensor intensityas a function of power and/or UVT.
12. Incorporate intensity-power-UVT tests into theprotocol. This serves as very useful design andoperating data for validated RED estimates. From
these, one can estimate the level to which lamps andor fouling can deteriorate before RED performancegoals are affected.
13. Sensors are critical elements of any reactor designespecially for drinking water reactor applications. TheUVDGM approach for evaluating UV sensors issuggested making this consistent through alapplications. Design guidance, outside of thevalidation protocols, will set standards with respect tothe number of sensors that should be installed in areactor the validation protocol should only assess theresponsiveness of these sensors and their variability
relative to reference sensors. QA limits, asincorporated in the UVDGM, would be used across alapplications.
14. Eliminate the hydraulic tracer analysis requirementfound with the current secondary effluent ETVprotocol. Its use is outdated.
15. Add the multiple linear regression (MLR) approach tothe protocols for analysis of the biodosimetric test datadeveloped in the field. This is an important feature othe current version of the UVDGM and is a preferredapproach with reuse applications. This techniqueallows one to design the test matrix rationally, and
provides a correlation of the RED as a function of theunit operating parameters, such as UVT, powerbanks/modules, flow, etc. Examination of theuncertainty of the correlation (developed on the basisof the variability of the observed data about theregression line) can establish the lower confidencelevels, and the credited RED. This approach can use amanufacturers dose algorithm; the verification wouldsimply establish the variability of the observed dataabout the predictive relationship.
16. Low-dose alternative challenge microbes should bereadily allowed. MS2 validations are effective for RED
levels greater than about 30 mJ/cm2. This has led toissues when validating at lower doses. The UVDGMaddresses this with application of an RED bias, whichaccounts for differences that might occur in ahydraulically inefficient reactor when the targetedmicrobes (such as Crypto, E. coli, Giardia, fecacoliforms) are more sensitive to UV than the challengemicrobe. As described in the UVDGM, if there is noindependent, direct measurement of dose-distributionin a reactor, one can apply the RED bias as anuncertainty factor. Alternately, use a test surrogate that is
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closer in sensitivity to the targeted pathogen orpathogenic indicator (e.g., use T1 for low dosesecondary effluents). This should be addressed across aprotocols, and should provide for using a more sensitiveorganism than MS2, or demonstrate independently theactual dose-distribution within the reactor.
17. Establish the same QA goals as the UVDGM across alapplications. These specifically relate to flow metecalibrations; sensor variability relative to references
variability of the collimated-bean, dose-response dataradiometer calibrations; and spectrophotometecalibrations. Additionally, there are normal field andlab QA/QC analyses relating to field, trip and labblanks, and variability among influent and effluentsample sets.
18. Flexibility for Challenge Microbe Selection. Thisshould be allowed across all applications. There isconsiderable new work that has been done ondifferent challenge microbes, including investigationsinto high dose surrogates. Although choices will likelyfocus on current favorites, such as MS2, T1 and Q-
beta coliphage, the protocols should allow theflexibility to respond to new, acceptable organisms.
19. Incorporate dose-distribution measurement by dyedmicrospheres. This method is relatively new and canbe considered demonstrated (Blatchley, et.al., 2006aand 2006b, Shen and Scheible, 2007). It usefluorescent actinometry to determine the dosedelivered to individual particles injected into thefeedstream. By measuring thousands of suchparticles, one can determine the dose-distributionwithin a reactor. This is a critical parameter that ispecific to a reactors hydraulic behavior and intensity
field. Applying dose-response kinetics determinedfrom collimated beam measurements allows one toestimate the delivered dose for any targetedorganism. Establishing a protocol for the dyedmicrospheres approach would advance thetechnology, and provide a potentially cost-effectivemethod for validating a system.
Additional elements can be identified and discussed. Theobjective, however, is to introduce and incorporate acommonality to the protocols. Eventually, this will result ina testing protocol that simply addresses the operatingrange for a particular UV reactor design. From thisvalidated operating range, one can decide the applicationon a site-specific basis. For example, if a vendor designs asystem that is meant to operate in a UVT range of 40 to65%, it may have applications relating to wet weatheflows (stormwaters), secondary effluents or reuse watersUsing the format of the UVDGM will allow for a betterunderstanding of the protocols and encourage a greateruniformity as we move forward. We also anticipate thathis protocol would be adopted under the ETV program asan option to the manufacturer.
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REFERENCES
USEPA Ultraviolet Disinfection Guidance Manual for the FinalLong Term 2 Enhanced Surface Water Treatment Rule,United States Environmental Protection Agency, Officeof Water, EPA-815-R-06-007, November, 2006.
National Water Research Institute (NWRI)/AWWA ResearchFoundation (AwwaRF) Ultraviolet Disinfection Guidelinesfor Drinking Water and Water Reuse, Second Edition.
Fountain Valley, CA, 2003.USEPA Environmental Technology Program, Verification
Protocol for Secondary Effluent and Water ReuseDisinfection Applications NSF International Water QualityCenter, October 2002
USEPA Environmental Technology Verification Program,Generic Verification Protocol for High-Rate, Wet-WeatherFlow Disinfection Applications NSF International, Draft5.0, September 2001
DVGW UV Disinfection Devices for Drinking Water Supply,German Gas and Water Management Union (DVGW),
Bonn, Germany, 2003.NORM NORM M 5873-1, Plants for the Disinfection of
Water Using Ultraviolet Radiation: Requirements andTesting Low Pressure Mercury Lamp Plants,
sterreichisches Normungsinstitut, Vienna, Austria2001.
NORM NORM M 5873-2, Plants for the Disinfection oWater Using Ultraviolet Radiation: Requirements andTesting Medium Pressure Mercury Lamp Plantssterreichisches Normungsinstitut, Vienna, Austria2003.
Blatchley III, E.R., Shen, C., Naunovic, Z., Lin, L., Lyn, D.A.
Robinson, J.P., Ragheb, K., Grgori, G., Bergstrom, D.E.Fang, S., Guan, Y., Jennings, K., Gunaratna, N. DyedMicrospheres for Quantification of UV DoseDistributions: Photochemical Reactor Characterizationby Lagrangian Actinometry, Journal of EnvironmentaEngineering, ASCE, 132, 11, 1390-1403, 2006a.
Blatchley III, E.R., Shen, C., Scheible, O.K., Robinson, J.P.,Ragheb, K., Bergstrom, D.E., Rokjer, D. Validation ofLarge-Scale, Monochromatic UV Disinfection SystemsUsing Dyed Microspheres, conference proceedingsAWWA Water Quality Technology Conference, DenverColorado, November 5-9, 2006b.
Shen, C., Scheible, O.K. Validation of Full-Scale UVDisinfection Systems Using Dyed-Microspheresproceedings, WEF Disinfection conference, PittsburghPennsylvania, February 4-7, 2007.
