CES Response to Veolia Incinerator Comments

Summary

Most of the issues raised in the comments were addressed in the Alternative Monitoring 

Petitions submitted by Eli Lilly and Company in 2005, particularly “Method 301 Evaluation of 

Candidate Conditional Methods” and more specifically Section 7.0 “Range of Method 

Application” which is presented in the Appendix of these comments. This appendix 

demonstrates the robustness of the Xact methodology and instrumentation over a broad range 

of source conditions. The remaining comments relate to the commercial viability of the Xact. 

CES conditions of sale are no different than those of other manufacturers of pollution control 

and monitoring instrumentation. These results plus those in the Appendix clearly show that 

the Xact has demonstrated its ability to operate accurately and reliably for extended periods of 

time under a wide range of stack conditions that includes those likely to be found in the Veolia 

stack, and that such monitors are commercially available from Cooper Environmental Services 

LLC.

1. Applicability to Veolia Incinerator

a. Comment: 

#48 Comment: OTM 16 and 20 are site-specific methods and are not 

applicable to Veolia’s operations. OTM 16 and 20 were written specifically for 

Eli Lilly and Co.’s (Lilly) source and instrument. While they would provide a 

starting place for another facility to develop their own site-specific method, one 

cannot assume that either could be used at another facility without significant 

modification. For example, the sample transport system in OTM 16 provides for 

a protocol for including the sample transport system into the instrument 

validation using either dynamic spiking of known gases or comparison to 

another method (instrumental or reference, M29, filters/tubes and Ohio 

Luminex, etc.). This was written specifically for the Lilly system using a Sigrist 

sampling system. It is not at all clear that an appropriate sample transport 

system could be designed and developed for Veolia’s stack gas 

conditions. Lilly spent considerable time and resources in developing both the 

laboratory and stack data underlying these methods. It is also not clear 

whether this instrument would tie into Veolia’s daily operations, alarms, and 

QA/QC procedures. It is likely that these two OTMs would need extensive work 

before they would be usable for the conditions in Veolia’s stack.

In addition, there is a good chance that the current QAG will not be able to 

produce quantitative mass of metals in the ranges required to calibrate/test the 

Xact. The QAG operates as a dynamic spiking into the probe/sample loop of 

the Xact system. Operation of this unit is dependent on the type of probe used, 

the flow in the sample loop, and gas conditions. Lilly spent a year developing 

this device to present the mass of metals specific to its sample loop 

(flow/moisture, etc.).
b. Response:

i. The above comment basically states that the demonstrated applicability 

of the Xact multi-metals CEMS (Xact) is based on site-specific testing 

that is not applicable to Veolia’s incinerator without significant 

modifications; and that the QAG has not demonstrated an adequate 

range. 

ii. Our general response to the site specific concern is summarized in the 

Appendix (Section 7.0), which discusses the broad range of sources and 

conditions to which the Xact has been successfully applied. It is 

important to emphasize that while these procedures were developed at 

Lilly’s stack, there is nothing in them that is specific to Lilly’s stack. 

Instead, they provide a general procedure that can be applied in many 

locations. In fact the Xact and its procedures have been successfully 

applied to coal combustion sources equipped with a baghouse and a 

wet scrubber under an EPA SBIR project with great success (EPA 

Contract Number EPD07026).

iii. Transport systems for the Xact have been developed for many different 

sampling conditions including at Lilly (downstream of a wet scrubber and 

a natural gas fired source), coal fired power plants - downstream of 

multiple control types including baghouses in combination with wet 

scrubbers, ESPs alone, and downstream of ESP's and wet scrubbers 

and with bituminuous, sub-bituminous and lignite fuels at munitions 

incinerators - Diesel fired sources downstream of a baghouse. 

Appropriate transport systems were installed at all of these locations. 

iv. QAG: It is difficult to understand where the commenter came to the 

conclusion that “...there is a good chance that the current QAG will not 

be able to produce quantitative mass of metals in the ranges required 

...”. Contrary to this statement, the QAG has been used to generate 

metals aerosols whose concentrations are traceable to NIST standards 

in the range of ng/m3 (used for the ambient/fence line Xact monitors) to 

mg/m3 used for stack monitors. This clearly covers the range required 

for any multi-metals CEMS based on the emission limits required as well 

as maximum concentrations expected. The QAG is broadly applicable 

to ambient as well as stack monitors and its application is independent 

of such conditions as the type of probe, probe flow or gas conditions. 

The QAG operating conditions can readily be adjusted to these 

variables in the field to deliver the concentration to meet the required 

permit range. The QAG can be mobilized and delivered for field work 

within days of receiving a purchase order for services.

2. Statement of Basis – A: Commercial Availability

a. Comment:

EPA’s statement that “Multi-metals CEMS are commercially available and have 

been demonstrated to be reliable for measuring mercury and other metal 
emissions from hazardous waste combustors” (Statement of Basis at 22) is 

incorrect or misleading. When the Statement of Basis was written, the Xact was 

offered by Pall Corporation. This is no longer correct. Pall no longer 

manufactures and sells the Xact unit. The marketing rights to the Xact have 

reverted to Cooper Environmental Services. It should also be noted that this 

instrument is not an instrument that is carried in inventory. If a facility wanted to 

purchase an Xact unit, Cooper Environmental Services has indicated that it 

would take them at least six months to build it. This is the time to build the 

instrument itself and does not include time to develop the site-specific sampling 

train or the time to develop the software interface between the instrument and 

the facility’s control systems. The software development process (custom 

software for that site) would take several months after the instrument was 

installed. Only one Xact unit has been installed and operated for an extended 

period of time at only one hazardous waste combustor, the combustor at 

Evoniks Tippecanoe Laboratories. Due to frequent maintenance issues and 

equipment failure, that Xact unit is no longer operating. (CRWI 6-7)

b. Response:

i. The fact that the marketing rights to the Xact have reverted back to 

Cooper Environmental Services LLC (CES) has little to do with its 

commercial availability. CES is the company that developed and first 

commercialized the Xact series of monitors and is having no problem 

returning to this position. In fact, CES took its first new order for an Xact 

at the end of March of this year and will be shipping that Xact by the end 

of this month (May, 2013). The fact that CES may have given a longer 

shipping time shortly after CES was informed of the return of the Xact 

rights to CES would have been because of the uncertainties associated 

with this time period. Now that contracts are in place with supply 

vendors, the uncertainties have been greatly reduced and the delivery 

times reduced.

ii. The fact that Xacts are not carried in inventor is not unusual in 

contemporary business, particularly for high end environmental 

instruments for which the condition, metals, requirements, etc. may be 

somewhat different for each source. Three to six months is not 

uncommon. As noted above, the longer lead times were associated 

with the initial uncertainties shortly after CES was informed of the Pall 

decision.

iii. Once a purchase order is received, many of the fabrication tasks can be 

conducted in parallel/simultaneously. As such, components such as 

probe and transport lines are included in CES’ time estimates and it isn’t 

necessary to wait until the unit is delivered. Similarly, although the 

DAHS interface maybe site specific, the DAHS software development 

process could begin immediately as the Xact utilizes standard 

communication protocols (Modbus) and has fixed and known register 

locations for data.
iv. The Xact operated reliably for 6 plus years at Lilly Tippecanoe 

laboratories incinerator as well as a year under Evonik. It is our 

understanding that Evonik elected not to complete a required repair on 

the Xact because there was not a regulatory requirement to operate the 

instrument. Below are summaries of the Xact's XRF audit and RATA 

results during its operation at Lilly. (CRWI 6-7)

Xact Quarterly Audit results Results

Xact RATA Results

In addition, similar CES multi-metal CEMS have been installed and operated on US Army 

hazardous waste incinerators.

3. Lack of Data Demonstrating Applicability at Veolia Moisture 

Conditions

a. Comment:

1 - The Statement of Basis states in subsection 4.0(D)(c): “Eli Lilly's stack 

gases at the Tippecanoe facility averaged approximately 8 percent moisture 

content and 140 degree F while the multi-metals CEMS was being 

operated. However, Pall Corporation has assured EPA that trial tests on its 

CEMS demonstrate that the unit can operate reliably at moisture contents 

above 40 percent. The only document in the record produced by EPA to 

This image cannot currently be displayed.

This image cannot currently be displayed.
support this statement is one email exchanged between Pall and EPA. EPA 

failed to consider the fact that Pall, which manufactures the multi-metals CEMS, 

has a financial interest to overstate the CEMS capabilities. No data or objective 

evidence exist in the record to demonstrate the Xact multi-metals CEMS can 

operate at moisture contents at or above 40 percent.

b. Response:

i. As noted in the Appendix (Section 7.0 of the Lilly AMP), the Xact has 

operated at a wide range of temperature and moisture conditions.

ii. It has operated successfully on saturated stacks at 125 to 140 degrees 

C (SBIR study and a coal fired power plant).

iii. Clearly, it should have no problem operating at the conditions in the 

Veolia stack.

4. Statement of Basis – B

a. Comment: 2- The Xact Multi-Metals CEMS is identified in the Statement of 

Basis as a system that uses reel-to-reel filler tape sampling technology followed 

by X-ray fluorescence analysis of metals in the deposit. The Statement of Basis 

represents that this is the only multi-metals CEMS technology currently 

commercially available. Pall Corporation is identified in the Statement of Basis 

as the marketer for the Xact multi-metals CEMS. The Statement of Basis 

discusses the use of a Xact CEMS at the former Eli Lilly incinerator. Eli Lilly's 

incinerator and Veolia's Unit 3 are not comparable. Most incinerators including 

the Eli Lilly incinerator employ wet scrubbers as their pollution control 

equipment or a combination of wet scrubbers and baghouses. The off gases 

from incinerators using wet scrubbers have similar moisture and temperature 

ranges. The suppliers of die Xact multi-metals CEMS claim that the Xact 

analyzes the off gas emitted from an incinerator to determine the amount of 

metals in the emissions stream. Unlike these wet scrubber systems, Veolia 

operates a dry pollution control system on Units 2, 3 and 4 of its Sauget 

facility. Dry systems are unique and to my knowledge the only other exclusively 

dry system in the United States is the Clean Harbors incinerator in Kimball, 

Nebraska. Veolia's dry pollution control systems operate at much higher 

moisture and temperature ranges than wet scrubber systems. The Xact multimetals CEMS has never been demonstrated to successfully operate in the high 

moisture and high temperature environment presented by Unit 3.

b. Response:

i. As noted in the Appendix (Section 7.0 of the Lilly AMP), the Xact has 

operated at a wide range of temperature and moisture conditions.

ii. More specifically, the Xact has demonstrated operation at temperatures 

up to about 500 degrees F (demilitarization incinerator) and in flue 

gases saturated at 140 degrees F. 
iii. Below in the following figure, are the results of a comparison of mercury 

results reported by EPA reference method 30B and the CES Xact. This 

data was collected at a coal fired utility boiler operating with dry controls 

at about 350 degrees F. 

iv. These results plus those in the Appendix clearly show that the Xact has 

demonstrated its ability to operate accurately and reliably for extended 

periods of time under a wide range of stack conditions that includes 

those likely to be found in the Veolia stack.

0

1

2

3

4

5

6

7

8

9

10

0 1 2 3 4 5 6 7 8 9 10 11 12 13

RATA Number

M

ercury

C

o

nc. (

g

/

dscm)

Xact

Method 30B

3.53% RELATIVE 

ACCURACY
Appendix

7.0 Range of Method Application

7.1 Overview

The results from the preceding section clearly demonstrate the ability of the XFM and XactIAP to accurately and precisely quantify metals in stack emissions over a broad range of 

concentrations, and that these methods are applicable to the quantitative measurement of the 

five validated metals in hazardous waste incinerators. The question then arises as to

What other source categories and elements is this technology applicable?

The answer to this question lies in how key features of the sampling and analysis procedures 

depend on and respond to changes in emission characteristics associated with different source 

categories. The EPA suggests in Method 301 that this might be addressed in part by conducting

a series of ruggedness tests, which are laboratory tests of a method’s sensitivity to key method

variables1,

29, 30

. This type of evaluation of the XFM and Xact-IAP was conducted during Phase 

I laboratory testing. In addition, a substantial body of previous laboratory and field test data on 

this reactive-filter based technology is also available that supports the

general applicability of these methods to most sources and elements.

The above tests and data are summarized in this section along with key aspects of the XFM 

and Xact-IAP methods, and relative characteristics of emissions. The objective of this 

review is to demonstrate that these methods should be considered generally applicable to a

wide range of emissions and elements including those from regulated sources. This review is 

presented in the following subsections:

• Method Applicability (7.2)

• Key Sampling and Analysis Features (7.3)

• Key Emission Characteristics(7.4)

• Filter Trapping Efficiency for Vapor Phase Metals (7.5)

• Applicable Concentration Range (7.6)
• Deposit Stability (7.7)

• Moisture (7.8)

• Holding Times (7.9)

• Other Related Tests (7.10)

• Applicable Elements (7.11)

• Sensitivity to Reactive Stack Gases (7.12)

The details of this review are presented in Appendix L and supporting reports are provided in 

Appendix M. The conclusion of this review is that there is a substantial body of information 

about the chemistry and physics of the methods and emissions as well as specific test data 

covering some of the more challenging of conditions that strongly supports the extension of 

these methods to other regulated source categories and elements.

7.2 Criteria for Candidate Method Applicability

It is clear that when a candidate method meets the requirements of Method 301, it is valid for 

the source tested, and may be applicable to the specific source category. Method 301 

recommends that additional test data be submitted to extend the applicability of the candidate 

method to other source categories. This recommendation, however, does not specify criteria 

that can be used to evaluate possible extension of a method’s applicability when direct test data

is not available. For the following discussion, it will be assumed that the candidate methods

will be applicable to an untested source category if differences in emission characteristics

between sources tested and candidate source emissions are such that they are unlikely to

contribute significantly to imprecision and bias in measured metal concentrations.

7.3 Key Sampling and Analysis Features

Both the XFM and Xact-IAP draw a representative sample of stack gas through a filter 

matrix where metals are concentrated prior to analysis. The XFM draws the stack gas 

through an upstream PTFE filter that removes PM from a gas stream and then through a 

downstream reactive filter that traps vapor phase metals. The Xact-IAP, on the other hand, 

uses a single reactive filter to trap both the PM and vapor phase metals. Both methods 

measure the mass of each metal deposited on the filter(s) using XRF analysis procedures

based on EPA’s IO Compendium Method 3.314. The concentration of metal in stack gas (C) is

calculated by dividing the mass of metal in the filter(s) deposit (M) by the volume of stack gas 

(V) that passed through the filter(s). That is;

C = M

V

Equation 26

Key sampling and analysis features are thus those that contribute to the quantitative accuracy

of the metal mass and volume determinations. Consequently, a method will likely be 

applicable to a particular source emissions category if the differences in stack gas 

characteristics are such that they do not significantly contribute to inaccuracies in volume

and mass measurements.
In the case of volume determination, both methods dilute, cool, filter, and dry the stack gas as 

well as denude the gas of corrosive species such as acids, SO2, etc. prior to volume 

determination. This dilution and extensive conditioning of the stack gas prior to volume 

determination makes it relatively insensitive to differences in stack gas characteristics. Thus, if

differences in stack gas characteristics are to significantly impact the accuracy of the measured

aerosol concentration, it must be through the metal mass determination.

Accurate determination of metal mass depends on two key factors, which may depend on 

stack gas characteristics:

• XRF analytical determination of metal mass in the filter deposit

• Filter trapping efficiency

Again, it is important to note that both methods use dilution to maintain and control such 

sampling conditions as temperature, dew point, and PM concentration in their optimal range. 

As such, the method’s sensitivity to specific stack gas characteristicsis significantly reduced 

even for these two factors. For example, when applying these methods, the applications 

engineer is directed to adjust non-critical parameters within specified limits such as dilution 

ratio and sampling time to optimize the method for a particular application. Furthermore, since

there is no direct interaction between stack gas and the analysis, the XRF determination of 

metal mass in the filter deposit is only indirectly dependent on the characteristics of the stack 

gas through how the stack gas impacts the characteristics of the deposit on the filter. Other than

the analyte metals of interest, the only species deposited on the filter are non- analyte PM

species, the total mass of which is controlled through the method application by selecting 

optimal sampling times and dilution ratios. None of the major components of stack gas are 

trapped on the filters and cannot therefore interfere with the XRF analysis.

For this reason, the only factor that might be sensitive to stack gas characteristicsis the filter 

trapping efficiency for PM and vapor phase metals. Filter trapping efficiencies for PM are 

well established and generally accepted to be greater than 99%23,31are not expected to be 

dependent on differences in stack gas characteristics. As such, filter trapping efficiency for 

vapor phase metals is the key factor that might be impacted by stack gas characteristics. The

primary focus of the next two sections is on the potential dependence of vapor phase metal 

trapping efficiency on flue gas conditions and the available data showing the range within 

which the method has demonstrated acceptable quantitation.

7.4 Key Emission Characteristics

Characterization of emissions depends on such factors as source type (combustion, process, 

fuel type, etc.), type of emissions (ducted or fugitive) and type of controls (filtration, 

electrostatic precipitators, scrubbers, absorbers, reactive, etc.). However, from the method 

applicability evaluation perspective, the characteristics of emissions that are most relevant are

those defined in terms of their physical (primarily temperature) and chemical (composition)

characteristics. Emissions are generally composed of varying amounts of air (N2, O2),

combustion products (NOx, SOx, CO2, CO, H2O, etc.), contributions from controls (Na, Ca,

H2O, NH3, etc.) and various process species, and can be further divided into categories such 

as PM, reactive and non-reactive gases, acid vapors, etc.
Species Phase II

Tippe, IN

CFPP-CES

Boardman, OR

CFPP-EPA

Midwest

HWC - TEAD

Tooele, UT

CO, dry

O2, dry 

CO2, dry 

NOx, dry

SO2, dry

HCl (equiv.), dry

H2O

PM @ 7% O2

Temp

ppm

%

% 

ppm 

ppm 

ppm

%

mg/dscm

°F

14

11

6

110

ND

2

9

4

170

< 10

4.5

12.5

200

225

NA

10

27

300

NA

12-15

4-8

70

20-35

NA

15-20% NA

160

10

14-15

5

1200

10

50

5

10

450

As discussed above, the filters used by the XFM and Xact-IAP have a high PM metals trapping

efficiency regardless of the stack gas physical and chemical characteristics when sampling

within the conditions specified by their SOPs. Some potential exists, however, for the vapor

phase collection efficiency to be impacted by the stack gas physical parameters and chemical

composition. For both the XFM and Xact-IAP, the sampling temperature, flow rate, and

pressures are controlled by the operator within the bounds of the SOP and are independent of 

the source type. Thus, the key characteristics of emissions that might impact the reactive filter’s

trapping efficiency are the sampling interferences caused by reactive

gases such as NOx, SOx, NH3, Cl2, HCl, HNO3, and H2SO4. Although this list is not 

complete, it does represent the more abundant and more reactive species likely to be present at

varying concentrationsin most stacks of regulatory interest. Oxygen was not listed, since it is

expected to be present in most emissions at ambient concentrations (21%) or less, and 

laboratory tests in Phase I demonstrated high trapping efficiency at the highest likely O2 

concentration. Potentially interfering reactive gases are listed below in Table 23 along with 

measured stack gas concentrations during supplemental testing discussed below and in 

Appendix L. Although this list is incomplete, the concentrations and conditions are 

representative of these sources and cover a broad range of concentrations and temperatures.

Table 23. List of stack conditions for which Xact-IAP and XFM tests have been conducted

NA: Not Available CFPP-CES: CES sponsored collection efficiency test at PGE CFPP 

ND: Not Detected CFPP-EPA: EPA sponsored test of Hg monitors

HWC-TEAD: US Army sponsored tests at demiliterization HWC

7.5 Filter Trapping Efficiency for Vapor Phase Metals

The Clean Air Act lists 11 metals as air toxics: Sb, As, Be, Cd, Cr, Co, Pb, Mn, Hg, Ni and 

Se10. Of these metals, Hg is the only one that is predominately in the vapor phase at the 

operating temperature of the Xact-IAP and XFM (180°F). For this reason, Hg is the most 

challenging to trap by filtration and most sensitive indicator of vapor phase metal trapping 

efficiency. Over the past several years, three series of Hg trapping and relative accuracy tests 

have been conducted in addition to Phase I and II tests described in the first part of this report. 

Whereas Phase II tests demonstrated high Hg trapping efficiencies under conditions

more representative of emissions from modern hazardous waste incinerators, these additional 

tests focused on emissions from coal-fired boilers. The supplemental tests were more 

challenging in part because of their lower Hg concentrations(<10 μg/dscm) but also because of 

the presence of higher concentrations(Table 23) of potentially interfering species such as
NOx, SO2, SO3, NH3, PM, etc. The first series of tests discussed below were sponsored by

CES and were conducted both in the laboratory and at a coal-fired utility boiler to define the 

concentration range of applicability for the reactive filters. The second and third series of tests

were sponsored by the EPA and the army, and focused on relative accuracy of the 

measurements at coal-fired boiler emissions. In the following summaries, an acceptable 

relative accuracy when compared to an EPA authorized reference method will be taken to 

imply an acceptable vapor phase trapping efficiency. The supplemental tests summarized 

below are discussed in more detail in Appendix L and supporting reports are provided in 

Appendix M.

7.5.1 CES Sponsored Trapping Efficiency Tests

A series of tests were conducted at CES and a coal-fired power plant in Boardman, OR to 

evaluate the Hg trapping efficiency of reactive filters under a variety of sampling conditions. 

For these tests, mercury was injected into either laboratory air or stack effluent and the trapping

efficiency evaluated with the XFM using two reactive filters in series. The mercury trapping

efficiency was determined by comparing the Hg trapped on the upstream filter with the total

mercury collected on both filters. Mercuric chloride laboratory tests in the temperature range

between 100 and 212°F exhibited capture efficiencies greater than 99% for

concentrationsranging in excess of 800 μg/dscm with sampling times up to one hour.

Similar tests were conducted at the coal-fired power plant using elemental Hg spiked into the

stack gas. In this case, the elemental Hg trapping efficiency was greater than 99% for 

concentrationsranging up to 300 μg/dscm.

7.5.2 EPA Sponsored Relative Accuracy Tests

CES tested the XFM filter approach during an EPA sponsored evaluation of mercury

measurement methods at a Midwest coal-fired power plant5. These tests, conducted in July

2003, compared simultaneous XFM and Ontario-Hydro Reference Method (OH) measured 

mercury concentrations between 1 and 6 μg/dscm. The accuracy of the reactive filter based

methods at low concentrations was demonstrated using an in-stack version of the XFM. A

total of 12 two-hour OH runs were conducted. For each OH run, two simultaneous 50 minute,

in-stack XFM samples were collected by CES. For these tests, the XFM and the OH results

were in good agreement with a relative accuracy of 11% for the nine valid runs, well within

the 20% criteria for conditional methods specified by EPA’s proposed Performance 

Specification 12

32

. Three of the 12 OH test runs were omitted from comparison by the EPA

contractors. Two were omitted because of poor OH replication (>40% difference) and one 

was omitted due to a plant upset. The remaining nine runs were used for comparison, the 

results of which are plotted in Figure 19. The high correlation of these results and low 

relative accuracy demonstrates the effectiveness of the reactive filter approach for trapping

and quantifying Hg concentrations between 1 and 6 μg/dscm.
XFM

C

onc. (μg/dscm)

6

5 n= 9

4 RA= 11%

Mercury

3

2

y = 0.908x + 0.152

1 R

2

= 0.962

0

0 1 2 3 4 5 6

OH Conc. (μg/dscm)

Figure 19. Comparison of Hg concentrations determined by XFM and Ontario Hydro 

reference method at a coal-fired power plant.

7.5.3 US Army Sponsored Relative Accuracy Tests

The U.S. Army sponsored a series of tests in January 2005 to evaluate a mercury-optimized 

Xact at a coal-fired power plant

33

. For these tests, mercury and arsenic were spiked into stack 

gas followed by simultaneous Hg and As measurements using the Xact and Reference Method 

29. The results from these tests demonstrated relative accuracies of 17% for these two 

elements, meeting the proposed 20% criteria proposed for Performance Specification 10.

7.5.4 Summary of Trapping Efficiency Sensitivity to Reactive Stack Gases

Unlike the physical filtration mechanism used to collect particulate metals, vapor phase metals

react with the chemically treated filter and bind to the filter substrate. Some stack gas 

constituents could potentially interfere with this process. However, the more abundant stack 

gas species such as N2, O2, CO2, CO, and vapor phase H2O are relatively inert, are not trapped

on the reactive filter, and test results indicate that they do not influence the filter trapping

efficiency. Oxidants within the gas stream such as Cl2 have been shown to improve the vapor

phase collection efficiency for Hg. Other minor stack gas components such as NOx, SOx, and

NH3, have the potential to interfere with vapor phase Hg trapping efficiency. However, this

potential to interfere has not been observed in the extensive testing that has been conducted to

date. For example, the possibility of NH3 interference was evaluated during EPA’s test of 

mercury measurement approaches at a Midwest coal-fired power plant with state-of-the-art

ammonia injection and selective catalytic reduction NOx control equipment34. Despite the use 

of ammonia, the XFM reactive filter demonstrated an 11% relative accuracy when compared to

the Ontario-Hydro Hg reference method concentrations,

which ranged from 1 to 6 μg/dscm. Similarly, minor reactive components such as NOx, and

SOx have the potential to impact vapor phase collection efficiency. However, there is no

indication that these species affected the Hg trapping efficiency at the concentrationslisted in

Table 22. Indeed, the 99+% trapping efficiency for elemental Hg at the Boardman site was 

completed with measured NOx concentrations of 200 PPM and SOx concentrations of about

225 PPM. In addition, there is no indication that high acidic concentrations affect the

trapping efficiency since nitric acid concentrations during Phase I and II testing was greater
7

than 50 PPM. The tests conducted to date and the range of key test parameters are 

summarized below in Table 24.

Table 24. List of test conditions and references used to evaluate method applicability.

Parameter

Concentration Range

Test Summary Test

Particulate Metals 3-2200 μg/dscm 1, 2

Elemental Mercury 1-314 μg/dscm 3, 4

Oxidized Mercury 1-880 μg/dscm 3, 5

Holding Time

XFM: Particulate Filter 12 Months 6, 7

XFM: Vapor Phase Filter 24 Months

a

8

Xact 12 Months 6, 7, 8, 9

Stack Type & Conditions

Moisture

Filters acceptable for Wet Stacks 3, 10, 11

Filters acceptable for Dry Stacks 1, 2, 4, 9

HWC Filters acceptable for HWC applications 1, 2, 9, 11

CFPP Filters acceptable for CFPP applications 3, 4, 10

Stack Temperature 450°F 1, 2

Filter Temperature

XFM Particulate Filter 400°F 12

XFM Vapor Phase Filter 185°F 4, 5

Xact Particulate/Vapor Phase Filter 185°F

Sampling Time

XFM 60 min 4, 5

Xact 30 min 10

Sampling Flow Rate

XFM 4.5 lpm/cm2 4, 12

Xact 2.4 lpm/cm2 12

Field Blank Det. Limits less than 2 μg/dscm

b

11

a) Correction factor of 0.5%/month required after six months.

b) One-sigma limits based upon analysis of 3899 filters measurements at Lilly's T149 Incinerator

1 HWC at TEAD production furnace (Section 2.3).

2 HWC at TEAD research furnace (Section 2.3).

3 EPA test at Midwest CFPP (Section 2.3).

4 CES Test at Oregon CFPP (Section 2.3).

5 CES Laboratory Tests (Section 2.3).

6 Reevaluation of Phase I Filters (Section 2.3).

7 EPA PM2.5 Speciation Program ; Reevaluation of Phase I Filters (Section 2.3).

8 CES Laboratory Evaluation of XFM Filters (Section 2.3).

9 CES Reanalysis of Xact Filter Tape from TEAD tests (Section 2.3).

10 Xact Test at IAAP CFPP (Section 2.3).

11 Evaluation of Blank Filters at Lilly's T149 Incinerator (Section 2.3).

12 Manufacturers Specifications

13 Phase II Tests at Lilly's T149 Incinerator
Xact C

onc. (μg/dscm)

7.6 Applicable Concentration Range

The applicable concentration range for these reactive filter based methods was extended to 

over 2000 μg/dscm during Xact and Reference Method 29 relative accuracy tests conducted in

2002 at an Army hazardous waste test incinerator

34

. Twelve Reference Method 29 test runs 

were conducted while the stack gas Pb concentrationsranged from a low of about 10

μg/dscm to over 2200 μg/dscm. The results from these twelve tests are compared to the 

corresponding Xact results in Figure 20. These results show a high degree of linearity over 

this broad range of concentrations and a high relative accuracy of 4% when compared to the 

Method 29 results. If these results are combined with those in the preceding subsection where

the Hg results were in good agreement with the reference method down to almost 1

μg/dscm, it is clear that the method is quantitative over at least three orders of magnitude and at

concentrations greater than 2200 μg/dscm.

2,500

2,000

1,500

n= 12

RA= 4%

Lead

1,000

500

0

y = 1.0585x + 1.2181

R

2

= 0.9997

0 500 1,000 1,500 2,000 2,500

Method 29 Conc. (μg/dscm)

Figure 20 Plot of Xact-IAP concentration versus Reference Method 29 measured 

concentrationsshowing excellent agreement over two orders of magnitude and at 

concentrationsin excess of 2,000 μg/dscm.

7.7 Deposit Stability

The Xact-IAP uses a reel-to-reel tape system to collect stack gas metal samples, which are then

transported to a position for XRF analysis. After analysis, the tape is drawn over a take up 

spool where the exposed filter deposits come into contact with following tape as it wraps over

the previously exposed tape. Some potential exists for transfer of metals from their original

deposit to the tape covering the deposit. If this transfer were significant, it would reduce the

potential to post-test validate Xact-IAP results with independent analysis of the deposits. As 

such, post test analyses were conducted on 72 deposits collected during relative accuracy tests

conducted in May 2002 at a US Army hazardous waste production incinerator at the Tooele

Army Depot (TEAD) in Tooele, UT

34

. During these tests, the Xact monitored emissions in an

instrument shed about 40 feet from the incinerator stack while EPA Reference Method 29 

samples were collected at the stack. Twelve Method 29 test runs were

conducted with concentrations varying from 5 to 300 μg/dscm. There was very good

agreement with the reference method as illustrated in Figure 21. The relative accuracy was

4% and the results exhibited a high degree of linearity.
Xa

ct C

o

n

c. (μ

g/d

s

c

m) Lab

C

onc. (μg/m3) July, 2002

Following these tests, the exposed filter tape was stored at room temperature at CES. Two 

months after the field tests were completed, the tape was removed from the spool exposing 

the previously collected deposits. These deposits were cut from the tape and analyzed with 

CES’ laboratory XRF analyzer. These laboratory results are compared to the original 

concentrationsreported by the Xact in Figure 22. Clearly, there is a high degree of 

agreement between the original Xact Pb results and the laboratory results. The slope and 

correlation suggests that there was not a significant transfer of Pb from the deposit to the 

covering tape at the level of a few percent.

160

140

120

100

80

n = 12

Lead

y = 1.09x - 9.60

40

R

2

= 0.98

20

0

0 50 100 150 200

Method 29 Conc. (μg/dscm)

Figure 21. Plot of Pb concentrations determined by Reference Method 29 and the Xact.

180

160

140

n =72

Lead

120

100

80

60

40 y = 0.9727x + 3.4259

R

2

= 0.9685 20

0

0 50 100 150 200

Xact Conc. (μg/m3); May, 2002

Figure 22: Comparison of results from laboratory XRF analysis in July, 2002 with Xact 

field test results from May 2002 relative accuracy tests at a hazardous waste incinerator

7.8 Moisture

Over the last three years, the Xact-IAP and XFM have been evaluated on both wet and dry

stacks (Table 25) using Method 29, Ontario-Hydro and the QAG reference aerosols. In all
cases, the Xact-IAP and XFM showed good relative accuracy and trapping efficiencies. For 

this reason, it is believed that the candidate measurement methods are valid for both wet and 

dry stacks as long as the probe and filter temperature remain above the water vapor dew point,

which are controlled primarily with dilution.

Table 25: Recent tests of Xact and XFM on wet and dry stacks.

Date Test

Location

Inc. 

Type

Air Pollution 

Control 

Technology

Wet or 

Dry 

Stack

Elements

Analyzed Results

March

2005

Eli Lilly 

Lafayette, 

IN

HWC Scrubber Wet As, Cr, Cd, 

Hg, Pb

Xact and XFM within

15% of QAG predicted 

for As, Cr, Cd, Hg, Pb

Jan.

2005

IAAP Ames,

IA CFPP Scrubber Wet As, Hg Xact RA of 17% vs. M29 for As, Hg

Sept.

2003

TEAD 

Tooele, UT HWC

High Temp. 

Baghouse

Dry Pb Xact RA of 4% vs.

M29 for Pb

May

2003 Midwest CFPP

Ammonia 

injection, SCR, 

baghouse

Dry Hg XFM RA of 11% vs.

OH for Hg

Aug

2002

Boardman, 

OR CFPP Scrubber Wet Hgo Trapping efficiency of99% for Hgo

7.9 Holding Times

Tests were also conducted to evaluate the holding times for the XFM and Xact-IAP filters. 

These tests included both the XFM PTFE filter and the reactive filter. During the December

2004 Phase I tests, the PTFE filter had collected particulate As, Cd, Cr, Hg, and Pb at 

concentrationsranging from 20 μg/dscm to 125 μg/dscm. In order to determine PTFE filter

holding times, CES reanalyzed filters from seven of these tests (Runs 1-4 and 21-24) in April

2005. During the five months between the initial and second XRF analysis, the filters were 

stored at room temperature in plastic petrie dishes. Both analyses were conducted using XRF 

following the IO Compendium Method 3.314. Overall, the average metal concentrations 

measured in April 2005 were within one percent of the concentrations determined five months

earlier. All measurements were within 4% of their original concentration, with no significant

bias. The good replication of the metal mass demonstrates the ability of the PTFE filters to

retain metal concentrations over a five month period.

Reactive filter tests were conducted to determine retention efficiencies and estimated holding 

times for vapor phase metals using Hg as an indicator species. These tests are based on

filters exposed to both elemental mercury and mercuric chloride vapors during tests conducted 

in June and August 2002 and filters from coal-fired power plant flue gas tests. All filters were

kept at room temperature and analyzed using IO Compendium Method 3.314. These filters were

reanalyzed periodically over the past two years and were found to have

lost on average about 10% of the original mercury over this period. This finding was
independent of laboratory or field application, or oxidation state of Hg trapped. A linear model

was developed which assumes the mercury loss from the reactive filter to be constant over

time. This model showed that, when using a correction factor that assumes a loss of about

0.5% per month, the mercury concentrations measured after two years were, on average, within

10% of the original mercury concentrations. The good agreement for all of these tests supports 

the use of a correction factor of 0.5% per month for filters that have been archived for more

than six months. This would allow the holding time to extend to at least two years.

7.10 Applicable Elements

The XRF analysis determination of metals in the filter deposit is based on EPA IO 

Compendium Method 3.3, which is generally applicable to elements with atomic numbers 

ranging from about 13 (Al) through 92 (U). This range of elemental applicability is expected 

to apply to the XFM PTFE filter but not to the reactive filter. In the case of the reactive

filter, the lowest atomic number element quantifiable with XRF analysis is Cr (24) because 

of significant impurities in the filter matrix.

The elements of primary regulatory interest are those the Clean Air Act Amendments classify as 

Air Toxics: i.e. Antimony (Sb), Arsenic (As), Beryllium (Be), Cadmium (Cd), Chromium (Cr), 

Cobalt (Co), Lead (Pb), Manganese (Mn), Mercury (Hg), Nickel (Ni), and Selenium (Se). 

These eleven elements have been sorted by volatility in the Maximum Achievable Control

Technology (MACT) rules

17

as follows:

• Non-enumerated metal compounds (N): Sb, Co, Mn, Ni, Se; equated to particulate 

matter in the MACT

• Low volatile metal compounds (L): As, Be, Cr

• Semi-volatile metal compounds (S): Pb, Cd

• High volatile metals (V): Hg

The metals tested in Phase I and II represented particulate matter as well as all of the metals in 

the three volatility categories except the low volatility element Be. The other elements not 

tested are non-enumerated metals, which the EPA has equated to particulate matter in the 

MACT rules. Although these eleven elements represent the primary focus of this discussion, it

is important to note that these filter based methods are expected to be applicable to most of

the elements listed in EPA IO Compendium Methods 3.3

14

and Be by IO Compendium

Method 3.435.

7.11 Other Related Tests

7.11.1 Sample Collection Times

The theoretical sampling time for the XFM and Xact-IAP is primarily limited by filter loading 

with PM since XRF correction factors may be required for high particulate deposit densities. 

However, the filter loading can be controlled in sources with high particulate levels by

adjusting the sampling times and dilution ratios up to 4:1. For this reason, it is believed
that, these filter-based methods can sample for periods up to four times greater than has 

currently been demonstrated; i.e. four hours for the XFM and two hours for the Xact-IAP.

7.11.2 Xact Blank Concentrations

The Lilly Xact, was installed on the T149 hazardous waste incinerator in May 2004 and 

operated throughout the summer of 2004. During this time, the Xact completed about 4000 

runs while the stack was not burning hazardous waste. These runs were treated as field

blanks and were used to statistically determine Xact-IAP detection limits. These statistically

determined detection limits were in good agreement with those calculated from the analysis of 

a few filters.

Table 26: Xact detection limits determined at Lilly’s T149 incinerator

Elem

DETECTION LIMITS

XFM

1

Xact

2

μg/dscm μg/dscm

CR

AS CD 

HG PB 

MN CO 

NI SE 

AG SB 

CU FE 

ZN BR 

SR TL

0.08

0.08

0.80

0.14

0.12

0.08

0.08

0.06

0.08

0.60

1.60

0.08

0.12

0.06

0.20

0.18

0.14

0.3

0.1

2.4

0.3

0.6

0.2

0.3

0.3

0.1

4.2

6.2

0.5

0.9

0.2

0.4

0.3

0.3

1) 95% Confidence, Interference free, 30 minute sample.

2) 95% of 3899 Xact blank measurements at T149 Incinerator

7.12 Applicable Source Categories

As discussed earlier, the filter-based sampling approach has been successfully tested in the 

laboratory and on two hazardous waste incinerators as well as three coal-fired boilers. Each of 

these tests showed good relative accuracy and trapping efficiencies. Source emissions can be

divided into two categories: fugitive and ducted emissions. Fugitive sources include emissions

from processes such as field-burning, slag-pouring, emissions from buildings, demolition

activities, forest fires, etc. in addition to passive fugitive emissions from sources such as windblown dust and dust suspended by vehicular traffic. These fugitive emissions are typically

characterized by substantially lower concentrations of possible reactive species
than the concentrations in the ducted emissions already successfully tested. As such, the 

XFM and Xact-IAP should be applicable, in general, to these fugitive emission sources 

because the characteristics of their emissions are less challenging than the ducted sources 

already tested.

Ducted sources, on the other hand, can have emission characteristicssimilar to those already 

tested, and in some cases may exceed the values for some parameters that may be more 

challenging than those already tested. As discussed earlier, the filter-based approach has shown 

consistent success over the past few years while sampling at two hazardous waste incinerators

and three coal-fired boilers with a wide range of controls (wet scrubbers, ESPs, high temperature

ceramic baghouses, ammonia injection, selective catalytic reduction, lime spray dryer absorber

for SO2 control, and a fabric filter for particulate control). In each case the relative accuracy in

comparison to the QAG, Ontario Hydro, and Method 29 was better than the EPA required 20% 

for conditional method consideration. In general, the filter-based approaches have been accurate

regardless of source category, emission control technology used, moisture content and stack

chemistry. As such, the Xact-IAP and XFM methods should be applicable to a wide range of 

source categories including incinerators, boilers, kilns, smelters, plating operations, foundries,

mineral processing and other industrial processes using a wide range of pollution control

technologies.