Need for Alternative Reference Methods

1. Status of Alternative Reference Methods for Mercury Emission Measurements – Part 1Scott Hedges, USEPA, CAMDEPRI CEM Users Group MeetingPhoenix, AZMay 9 - 11, 2007

2. Need for Alternative Reference Methods • Reference methods will significantly help in performing RATAs of the mercury CEMS and sorbent trap monitoring systems required by CAMR • The currently-available reference method – Ontario Hydro – uses wet chemistry techniques and typically requires 2-3 weeks of laboratory analysis before the test results are known • The alternative reference methods should allow for RATA results to be known while the test team is on-site. • As such, timely alternatives to the lengthy and complex Ontario Hydro reference method are strongly desired • In fact, these alternative reference methods are needed as soon as possible • Most Hg CEMS and sorbent trap monitoring systems will need RATAs in 2008 to meet 1/1/2009 deadline • Many utilities are also planning RATAs this year

3. Evaluation and Validation of Alternative Reference Methods • EPA and industry (EPRI and others) are completing remaining field validation tests for the instrumental and sorbent trap-based reference methods • An instrumental reference method (IRM) that provides timely RATAs with immediate, real-time results is easier to implement than OH and is consistent with NOX and SO2 trading programs • A sorbent trap reference method is considered another viable alternative method. When it combines thermal desorption / direct combustion techniques, it allows for onsite analysis • EPA and EPRI are currently completing sorbent trap method comparison studies using a modified EPA Method 301 which compares existing data from sorbent trap systems against data from the Ontario Hydro reference method. • Body of sorbent trap data has been favorable (i.e., good agreement with Ontario Hydro)

4. Availability of Alternative Reference Methods EPA is preparing a rule package for both the instrumental and sorbent-based reference methods • Process being expedited through direct final rule making effort • Final rule tentatively scheduled for early August publication in the Federal Register • Would become final in October if no adverse comments are received • Methods will be made available at www.epa.gov/ttn/emc

5. Mercury Instrumental Reference Method (IRM) • Timely (real-time) • Performance-based • Amenable to multiple and new technologies • Test program-specific verification of data quality • Agency committed to performance-based methods (Federal Register Notice of Intent 62 FR 52098, 10/6/97) • Consistent w/ SOx & NOx instrumental methods • Key elements • Calibration error/linearity • System integrity/conversion efficiency • System response time • Interference test • Dynamic spiking (gaseous method of standard additions)

6. Mercury IRM Development • Used Methods 6C (SO2) and 7E (NOx) as starting point and factored in lessons learned from Hg CEMS demonstrations • Drafted Conceptual IRM and posted 2/28/06 at: www.epa.gov/ttn/emc/ • Evaluated in field by EPA/ORD, EPRI, and others

7. Planned Modifications to 2/28/06 Version of IRM • Requiring only pre-test dynamic spiking and making optional until 1/1/09 • Relaxing Hg0 calibration error criteria • Simplifying Hg2+ calibration to a system integrity check • Relaxing drift criteria • Making interference test optional • Waiving Hg stratification testing until 1/1/09 and adding a “low emitter cutoff”

8. Sorbent Trap Reference Method for Mercury • Performance-based • Amenable to new sorbents, equipment, and analytical technologies • Lab verification of sorbent performance and analysis • Test program-specific verification of data quality • Capability for timely results • Description • Known volume of stack gas is sampled through paired, in-stack 2-section sorbent traps (e.g., iodated carbon) • Analysis by any suitable system that can meet performance criteria (e.g., leaching, digestion, thermal desorption/direct combustion coupled with UV AF, UV AA, XRF)

9. Sorbent Trap Reference Method for Mercury, cont. • Key QA Elements • Laboratory • Matrix interference test (for wet digestion analyses) • Minimum sample mass determination • Analytical bias test (Hg0 and Hg2+) • Field (for each test) • Paired train agreement (assess precision) • Sorbent trap second section breakthrough • Field recovery test (assess bias)

10. Questions? Comments? THANK YOU!