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Gossman Consulting, Inc.

TYPICAL METAL CONCENTRATIONS IN RCRA WASTE BURNED IN CEMENT KILNS


David Gossman

Gossman Consulting, Inc.


Presented at the 1993 Incineration Conference in Knoxville, TN

INTRODUCTION

The recent implementation of strict control and monitoring of metal concentrations in HWF based on the Boiler and Industrial Furnace (BIF) Regulations has raised the general interest level regarding metal concentrations in RCRA wastes. The original concept behind this report was to obtain data both from cement kilns and commercial incinerators burning RCRA wastes. Numerous inquiries, however, revealed that most commercial incineration facilities do not routinely monitor metals in wastes as burned and the data is generally unavailable. BIF facilities are required by regulation to perform this testing, and some cement kilns have been performing as burned analyses of hazardous waste fuel (HWF) since 1980.

In order to examine metal concentration data in HWF, it is first necessary to examine testing methods and sources of available data. The data obtained is then presented and discussed on a metal by metal basis. Conclusions regarding potential implications for future regulatory and permitting decisions are then discussed.

TESTING METHODS

Although it is a popularly held belief that SW-846 is the bible of analytical methods for hazardous waste, there are few situations within a RCRA facility's operations that require the use of SW-846 methods. In 1990, EPA acknowledged this, "Except for those situations where the RCRA regulations specify use of a particular method, it is appropriate for the chemist to use judgment, tempered by experience, in selecting an appropriate set of methods from SW-846 or the scientific literature for preparing and analyzing a given sample."(1)

Indeed, SW-846 methods do not work on many matrices including organics. "Sample preparation methods are not currently available in SW-846 to render non aqueous liquids in a form that can be analyzed by the atomic absorption or inductively coupled plasma atomic emissions (ICP) type analytical methods for six important elements. These elements are: mercury, arsenic, selenium, lead, barium, and silver."(2)

Finally, basic chemistry leads to the conclusion that none of SW-846's sample preparation techniques will take in to solution metals bound with silicates or found in other forms not readily solubilized by nitric and/or hydrochloric acids.

Early methods of metal testing at HWF facilities included modifications of EPA's oil dilution method using appropriate solvents. Although basically functional, the method would only work with selected AA and ICP instruments. Detection limits were high, and solids or liquids with large particles were problematic.

More recent modifications include the addition of microwave technology to SW-846 acid digestion procedures. Most of the data in this report was obtained using SW-846 microwave technique modified methods.

During a study (3) of the fate of trace metals in cement kilns, problems with the SW-846 procedures surfaced and a technique was obtained from the National Bureau of Standards. This digestion method can be found in Table I. Further research revealed a similar ASTM method (ASTM E926A) developed for refuse derived fuel. The ASTM method also uses nitric, hydrofluoric and perchloric acids to achieve complete sample dissolution.

Table I

Digestion Method Obtained from National Bureau of Standards (NBS)

Other methods in use within the industry include a microwave method that achieves complete dissolution through the use of hydrofluoric, nitric and boric acids; and energy dispersive x-ray fluorescence which can be used on both liquids and solids with minimum sample preparation.

AVAILABLE DATA

Data on burned HWF metal concentrations was obtained from two publicly available sources. One was the aforementioned study on metal fate. The other was copies of BIF compliance certifications obtained under the Freedom of Information Act. Because the BIF regulations generally require the spiking of metals to higher than normal levels during the BIF tests, care was taken to use only data showing concentrations of metals in HWF prior to spiking. If more than one analysis was performed on waste fuel burned during a given day or test condition, the values were averaged for use in this report. Data was obtained from a total of eleven different facilities and both solid and liquid HWF is included.

DATA REVIEW AND ANALYSIS

Table II provides a comprehensive list of the data obtained for this report as well as statistical summaries. The facility number, date, samples taken, digestion method used, and whether the sample was liquid (L) or solid (S) is also indicated. The data can also be found in Figure 1.

Arsenic

Of 32 available determinations, 14 had quantifiable amounts above quantitation limits. Quantitation limits for those not quantified varied from <.7 to <58 ppm. Of those with quantifiable amounts, the minimum concentration is 1.4 ppm, the maximum is 279 ppm, and the mean is 37.8 ppm. Of those with quantifiable amounts, the liquid mean concentration is 6.5 ppm and the solid mean concentration is 79.6 ppm.

Beryllium

Of 32 available determinations, 11 had quantifiable amounts above quantitation limits. Quantitation limits for those not quantified varied from <0.1 to <5 ppm. Of those with quantifiable amounts, the minimum concentration is 0.1 ppm, the maximum is 2.2 ppm, and the mean is 0.6 ppm. Of those with quantifiable amounts, the liquid mean concentration is 0.6 ppm and the solid mean concentration is 0.7 ppm.

Cadmium

Of 32 available determinations, 32 had quantifiable amounts above quantitation limits. The minimum concentration is 1.7 ppm, the maximum is 89.0 ppm, and the mean is 19.1 ppm. The liquid mean concentration is 22.5 ppm and the solid mean concentration is 6.8 ppm.

Chromium

Of 32 available determinations, 32 had quantifiable amounts above quantitation limits. The minimum concentration is 28.9 ppm, the maximum is 1,100 ppm, and the mean is 239 ppm. The liquid mean concentration is 134 ppm and the solid mean concentration is 616 ppm.

Lead

Of 32 available determinations, 32 had quantifiable amounts above quantitation limits. The minimum concentration is 25.8 ppm, the maximum is 3,510 ppm, and the mean is 606 ppm. The liquid mean concentration is 422 ppm and the solid mean concentration is 1,270 ppm.

Barium

Of 23 available determinations, 23 had quantifiable amounts above quantitation limits. The minimum concentration is 108 ppm, the maximum is 3,000 ppm, and the mean is 686 ppm. The liquid mean concentration is 534 ppm and the solid mean concentration is 1,030 ppm.

Mercury

Of 23 available determinations, 14 had quantifiable amounts above quantitation limits. Quantitation limits for those not quantified varied from <0.1 to <0.2 ppm. Of those with quantifiable amounts, the minimum concentration is 0.1 ppm, the maximum is 26.2 ppm, and the mean is 5.3 ppm. Of those with quantifiable amounts, the liquid mean concentration is 0.5 ppm and the solid mean concentration is 11.7 ppm.

Table II: Typical Metal Concentrations in Hazardous Waste Fuel Burned in Cement Kilns

Facility Date Method Liquid/Solid Arsenic Beryllium Cadmium Chromium Lead Barium Mercury Silver Antimony Thallium Nickel Selenium Vanadium Zinc
1 5/10/89 NBS L 5.29 <1 35.7 191 1158 491 <.2 2.56 31.5 <1 30.1 16.2 15.9 1035
1 5/24/89 NBS L 6.41 <1 70.9 284 1775 614 <.2 3.01 47.2 1.24 34.8 23.9 18.2 1254
1 6/7/89 NBS L 8.79 <1 20.7 59.9 361 108 <.2 <1 6.53 <1 8.91 32.7 6.43 503
1 11/13/89 NBS L <1 <1 13.3 110 438 306 0.423 1.26 48.8 <1 18.4 1.45 4.01 462
1 6/6/92 ASTM L <.694 0.79 7.27 101 329 573 0.238 2.42 32.5 <.694



1 7/25/92 ASTM L <.718 0.394 10.5 90 304 628 0.519 1.91 34.3 <.718



2 10/7/89 NBS L <1 <1 9.47 106 350 521 <.2 <1 27.3 <1 26.4 1.54 3.35 1005
2 10/14/89 NBS L <1 <1 6.53 143 422 495 <.2 <1 11.8 <1 20.1 <.5 3.73 779
2 10/21/89 ASTM L <1 <1 9.67 97.3 500 366 0.35 <1 17.7 <1 14.9 <.5 3.64 803
2 4/22/92 ASTM L <.698 0.612 3.69 120 314 662 <.1 0.563 8.94 <.698



3 6/12/92 SW846? L <22 <.2 7.03 147 528








4 5/19/92 SW846? L 4.77 <.4 20.7 250 515 483 0.507 <4 <20 <20



4 5/19/92 SW846? L 2.84 0.085 10.8 225 680 403 0.13 <5 <98 <21



5 6/20/92 SW846? L <58 <.4 87.3 160 515 1310 0.4 14.8 22 <20



6 7/14/92 SW846? L <20 <.5 13 98 220








6 7/15/92 SW846? L <20 <.5 5.35 45.5 120








6 7/16/92 SW846? L <20 <.5 3 35 94








6 7/18/92 SW846? L <20 <.5 46 170 275








6 7/19/92 SW846? L <20 <.5 23 104 200








6 7/20/92 SW846? L <20 <.5 22.5 28.9 25.8








6 7/21/92 SW846? L <20 <.5 89 120 110








6 7/22/92 SW846? L <20 <.5 26.1 45.6 110








7 6/1/92 SW846? S 50.1 0.183 7.55 369 748 671 14.6 4.78 4.12 <.3



8 3/27-30/92 SW846? S 278.5 <.2 1.88 378 693 585 2.98 3 141 <4



8 4/9-10/92 SW846? L 15.5 <.1 12.8 296 380 524 1.05 <2 8.5 <4



8 4/9-10/92 SW846? S 14.8 0.425 14.9 488 2358 1428 26.1 <4 <3 <4



9 5/13-14/92 SW846? S 58.8 0.26 5.7 436 680 672 12 4.4 9.6 <.2



9 5/9-10/92 SW846? S 71 0.35 6.825 538 710 768 11.4 5.28 10 <.3



9 8/19-20/92 SW846? S <30 <5 8.67 1103 3510 2995 3 <10 <30 <40



10 5/18/92 ASTM L 1.41 0.824 2.7 153 310 532 <.2 0.43 20.4 <.761



11 5/5/92 ASTM L 6.93 0.74 6.25 168 506 534 <.1 5.59 28.5 <.739



11 5/5/92 ASTM S 4.31 2.17 1.73 1000 164 112 <.1 0.506 16.8 <.739




Minimum
1.4 0.1 1.7 28.9 25.8 108.0 0.1 0.4 4.1 1.2 8.9 1.5 3.4 462.0
Maximum
278.5 2.2 89.0 1103.0 3510.0 2995.0 26.1 14.8 141.0 1.2 34.8 32.7 18.2 1254.0
Mean
37.8 0.6 19.1 239.4 606.3 686.1 5.3 3.6 27.8 1.2 21.9 15.2 7.9 834.4
Liquid Mean
6.5 0.6 22.5 133.9 421.6 534.4 0.5 3.6 24.7 1.2 21.9 15.2 7.9 834.4
Solid Mean
79.6 0.7 6.8 616.0 1266.1 1033.0 11.7 3.6 36.3 1.2



Figure 1

Silver

Of 23 available determinations, 14 had quantifiable amounts above quantitation limits. Quantitation limits for those not quantified varied from <1 to <10 ppm. Of those with quantifiable amounts, the minimum concentration is 0.4 ppm, the maximum is 14.8 ppm, and the mean is 3.6 ppm. Of those with quantifiable amounts, the liquid mean concentration is 3.6 ppm and the solid mean concentration is 3.6 ppm.

Antimony

Of 23 available determinations, 19 had quantifiable amounts above quantitation limits. Quantitation limits for those not quantified varied from <3 to <98 ppm. Of those with quantifiable amounts, the minimum concentration is 4.1 ppm, the maximum is 141 ppm, and the mean is 27.8 ppm. Of those with quantifiable amounts, the liquid mean concentration is 24.7 ppm and the solid mean concentration is 36.3 ppm.

Thallium

Of 23 available determinations, one had a quantifiable amount above quantitation limits which varied from <0.2 to <40. This value was a liquid with a concentration of 1.24 ppm.

Nickel

Of seven available determinations, seven had quantifiable amounts above quantitation limits. The minimum concentration is 8.9 ppm, the maximum is 34.8 ppm, and the mean is 21.9 ppm. The only determinations made were for liquids.

Selenium

Of seven available determinations, five had quantifiable amounts above quantitation limits. The minimum concentration is 1.5 ppm, the maximum is 32.7 ppm, and the mean is 15.2 ppm. The only determinations made were for liquids.

Vanadium

Of seven available determinations, seven had quantifiable amounts above quantitation limits. The minimum concentration is 3.4 ppm, the maximum is 18.2 ppm, and the mean is 7.9 ppm. The only determinations made were for liquids.

Zinc

Of seven available determinations, seven had quantifiable amounts above quantitation limits. The minimum concentration is 462 ppm, the maximum is 1,250 ppm, and the mean is 834 ppm. The only determinations made were for liquids.

CONCLUSION

It has been observed at many operating facilities that a number of the metals of concern to the agency do not appear at significant levels in HWF. The data gathered supports this contention. Concentrations of silver, barium, beryllium and thallium were present at levels well below that which would elicit concern from the perspective of emissions from a combustion device, especially when typical system removal efficiencies are accounted. The agency and permit writers should factor this issue into future testing requirement decisions in order to avoid diverting funds and attention from issues of real potential environmental impact.

REFERENCES

1. Federal Register, ,"EPA Proposed Rules - Preamble to SW-846 3rd edition"February 8, 1990,pages 4440-4445.

2. Ibid.

3. D. Gossman, M. Black and M. Ward, "The Fate of Trace Metals in the Wet Process Cement Kiln", from Proceedings of the Air & Waste Management Association International Specialty Conference, Kansas City, Missouri, April 1990.