Validation Studies and Beyond: Key Implementation Issues

Transcription

1 Review of UV Disinfection Validation Studies and Beyond: Key Implementation Issues Paul D. Swaim, P.E., CH2M HILL Denver March 8, 2011

2 The Burden on State Regulators Has Increased Technology-Specific EPA Guidance for Drinking Water Treatment SWTR Compliance Guidance Manual: 580 pages addressing unfiltered systems, filtration, disinfection, residual monitoring, etc. Allows UV for virus inactivation (4 pages) Appendix O: Guidance to Evaluate Ozone Disinfection (80 pages) LT2ESWTR: Membrane Filtration Guidance Manual (332 pages) UVDGM (436 pages)

3 Coordination with State Will Vary by State Utilities, UV manufacturers, design engineers will need: Point of contact at the State Early identification of potential issues Clear understanding di of the State s t expectations ti (documentation, ti site visits, approval steps) Open, honest dialog

4 What s Not Addressed By UVDGM? Type of reactor or reactor configuration Type of sensor Type of UV lamp UVT data collection Backup power/power quality mitigation Requirements related to mercury release

5 Approval of UV Disinfection Applications Encompasses More than Validation Water quality data and design criteria Elements of UV design Hydraulic configuration I&C approach Consideration of potential off-spec operation Plan for commissioning Monitoring and reporting

6 Some Key UV Design Issues Proper flow control, distribution and measurement are essential: for compliance monitoring to ensure operation matches design conditions Generally, each reactor should have dedicated flow meter, although State may approve other methods Design to ensure UV reactors always flow full Isolation valve type and location Intertie with controls for upstream pumps or filters UV reactor start-up and shut-down sequences Coordination of I&C design with monitoring and reporting guidance from UVDGM and input from State

7 Elements of UV Design to Coordinate with Validation Installation hydraulics Validated d envelope or window = the range of conditions for which the UV reactor performance has been validated: Flow UVT Target microorganism and log inactivation Operating configurations (specific lamps on and off) Headloss Calculated dose approach - dose equations developed

8 Typical UV Disinfection Design Criteria Target Pathogen and Log Inactivation (Dose) Design Flowrate UV Transmittance Fouling/Aging Factor: Tie lamp aging to lamp life guarantee Tie sleeve fouling to cleaning method and frequency Level of redundancy Future considerations (expansion, new applications)

9 UV Installation Hydraulics A typical UV installation includes: common influent/effluent headers or channels influent isolation valve flow measurement UV reactor air release valve effluent isolation or flow control valve drain valves downstream water levelcontrol(eg (e.g., weir)

10 UVDGM Guidance for Validation and Installation Hydraulics WTP hydraulics should be better than validation UVDGM outlines 3 options: 1. Length of straight pipe at WTP equals that at validation, plus 5 u/s pipe diameters 2. Exact match for 10 u/s and 5 d/s pipe diameters 3. Velocity profiling within 20 percent Validation Configuration WTP Configuration Source: EPA UVDGM (January 2006)

11 Validation and Installation Hydraulics: Implications for Design Provide required lengths of straight-run piping to ensure validation results are applicable Retrofits may result in more challenges, especially to accommodate all potential bidders Unique piping configurations may result in site-specific validation requirements (on-site or custom off-site testing) CFD important in comparing hydraulic configurations and dose delivery

12 UVDGM Guidance for Off-Spec Operation Continuously monitor dose-monitoring parameters (i.e., at least every 5 minutes) for each reactor Record values at least once every 4 hours Record off-spec at minimum of 5-minute intervals until condition is corrected

13 Design Criteria Should be Selected to Minimize Off-Specification Operation Min and max design flows Range of water quality conditions UVT Lamp fouling/aging g g Power quality Pre-emptive emptive response to flow increases Alarms and responses

14 Additional Considerations for Off-Spec EPA recommends that all systems reduce off-spec operation State regulators have primacy and can enact more stringent requirements Many utilities have objectives of their own for off-spec operation Validation envelope should extend beyond anticipated operating conditions Consider zero off-spec water as an MCLG

15 Functional Testing Verifies Functionality First testing step following installation Verification of: Operation of each system component I&C systems Signals and scaling Alarms and responses Ancillary items (e.g., flowmeters, valves) Responsibility will typically reside with contractor and UV manufacturer to certify functionality of UV system

16 UV System Performance Testing Performance Testing: Assess operating performance of the UV facility Demonstrate performance under extended period at actual operating conditions during early stages of operation Verify manufacturer guarantees and claims Performance Testing may be as little as 48 hrs to as much as weeks or months in duration May require UV manufacturer and/or contractor involvement

17 Potential Issues on Validation Reports

18 What to Look for in a Validation Report UVDGM required information and appropriate data analysis Information to show test data are appropriate for the specific application: validation configuration vs. site configuration UVT range tested vs. design value? minimum expected value? Flow range tested vs. design value? maximum expected value? Conversion of dose-monitoring algorithm and tested conditions to range of acceptable installation conditions, and ultimately to validated operating conditions

19 Example UV Disinfection System Validation Utility s selected UV reactor validated at Portland UV Validation Facility in 12/05 and 1/06 Tested with MS2 and T1 phages as challenge organisms Tested with 90-degree bend immediately upstream of reactor for worst-case hydraulics Data analysis per Final UVDGM (2006). For 3-log Cryptosporidium inactivation: MS2 RED > 33.1 mj/cm 2 T1 RED > 16.5 mj/cm 2 Validation envelope: 1 to 25.5 mgd 70 to 98% UVT Validation Report (December 2007) by 3 rd Party

20 Use of Intensity Sensor Measurements Dose equation developed from validation: Where S is the sensor reading at a given condition Where S o is the sensor reading at 100% power, new lamp (after 100-hr burn in) With several intensity sensors, use the lowest reading or average reading? Dose equation developed using average value of S/S o and goodness of fit of U IN term (developed with average S/S o ) UVDGM allows use of average S/S o for monitoring Validation Report recommends use of minimum S/S o for dose monitoring and control at full-scale application State required use of minimum S/S o for additional conservatism

21 Design Value of Aging/Fouling Factor Design value is site specific and up to Engineer/Owner Should be based on third party certified test results (if available) Over-conservative value increases capital cost Under-conservative value increases O&M cost (or reduces ( system capacity)

22 Action Spectra Correction Factor If the UV reactor being validated uses MP lamps and a challenge microorganism other than MS2 Phage or B. Subtilis, a correction factor should be applied to the test results to account for differences in action spectra between the challenge microorganism and the target pathogen. Section explains... (UVDGM, page 5-9) How to calculate and apply Correction Factor? Validation with T1 and T7 phage will require e this analysisa s Differences in action spectra for MS2 and Cryptosporidium at wavelengths below 240 nm

23 Off-Spec Requirements for Giardia? LT2ESWTR requirements: 5% volume per calendar month If UV disinfection used for Giardia inactivation prior to LT2 taking effect: SWTR allows one day of off-spec per month UV prone to more frequent, but shorter duration off-spec events

24 The Potential Need for UV Re-Validation If a UV reactor is modified in a way that significantly impacts UV dose delivery or monitoring, validation testing should be conducted again. (UVDGM, page 5-54) Types of changes to evaluate: Wetted geometry changes (e.g., removal of baffle plate) Lamp technology changes (e.g., different lamp manufacturer) Ballast changes (e.g., changes to operating voltage, current, frequency, waveform) Quartz sleeve changes (e.g., different manufacturer with different quartz type) UV sensor changes (e.g., sensor characteristics or sensor location change) Simplified with LP or LPHO systems that emit and measure at 254 nm How would you handle a change to which specific lamps operate?

25 There Is No Ability to Update the UVDGM No document is perfect UV continues to develop The UVDGM addresses the potential for new developments (CFD, new challenge organisms) Validation reports are likely to have an issue or exception or two or three There will be new applications of UV with multiple objectives

26 Final Thoughts UV disinfection has unique design and implementation issues Regulator input varies by State, so your involvement is crucial New validation organisms and techniques are resulting in reduced O&M cost for UV installations Engineer must consider off-spec during planning, design, validation, and O&M - validated conditions should cover an envelope beyond expected conditions Selecting the best UV installation location requires plant specific analyses including hydraulics and costs Selection of UV supplier prior to design offers several advantages you will be asked for input early