Document ID: EPA-HQ-OPPT-2018-0649-0029
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2018-10-10T04:00Z

Overview and Summary of Dust Monitoring and Metals Leaching

The SEFA PMN products are all surface-modified calcined fly ash.  The commercial purpose of the surface modifications is to make the ash product more compatible with the matrix into with it will be incorporated, including, for example, vulcanized rubber, polyolefins, and polyurethanes.   In some cases, the surface modification simply makes the ash particles more hydrophobic; in other cases, the surface modification adds a functionality that in intended to react with and chemically bond with the matrix.  

The ash itself is typical fly ash.  In general, metals contained in the ash have low bioavailability.  To demonstrate this low availability, SEFA contracted to have the leaching testing (TCLP) done on samples of the fly ash.  The TCLP was performed a low pH to mimic "worst-case" metal availability.  Metal oxides and hydroxides are less soluble at higher pH (e.g., neutral or basic conditions).  In fact, water contaminated with toxic metals is most frequently treated with sodium hydroxide.  The hydroxide salts of the toxic metals precipitate out of solution, allowing for easy separation (and landfill of the precipitate).  Reviewing the TCLP results show low availability of the various toxic metals that might be contained in the fly ash.  In many cases, the levels of metals in the leachate were below the limit of detection.  

Surface modification has only a minor effect on the availability of the metals.  On the other hand, surface modification has a substantial affect on "dustiness."  Although we do not have measured data on dustiness, a beneficial side effect of most types of surface modification is to increase the cohesive attraction or "stickiness" and reduce the electrostatic repulsion of the ash particles, which carry negative charges on the surface of the particles.  The surface modifiers form a somewhat oily surface.  The result is that rather than a dusty as, the modified product looks and behaves as if it were slightly oily or moist.

We are submitting additional information relating to:
      1) Star-Processed Fly Ash -- Test results on the composition of SEFA fly ash (00207282.pdf).
      2) SHEALY Environmental Services: Report of Analysis Spherix Mineral Products -- TCLP metals leaching analysis (00213497.pdf).
      3) Artisan EHS Consulting: Dust Monitoring, Spherix Bagging, Lexington Facility -- Dust monitoring at SEFA's facility (00210278.pdf).  Note that measures total dust from the unmodified fly ash and a PMN-representative fly ash product.  

These various test results show very low level of exposure to the dust product and no detectable exposure to leachable metals in the respirable dust fractions.  

Composition of SEFA STAR fly ash product
Total analyte metals analysis shows the content of 23 metals in the fly ash product.  The analytic method involves complete digestion of ash using highly concentrated nitric acid.  The analytic conditions are in no way an approximation of biologic conditions.  Rather, it represents the total metal content embedded in the ceramic matrix of of the ash particles.  

TCLP leaching
The SHEALY report provides the results of TCLP analysis for five different SEFA products, including an unmodified product (Spherix 15) and four surface-modified products (Fortimix and Dispersix).  The TCLP analysis was done using hydrochloric acid at a pH of approximately 1.5.  Chromium, arsenic, and cadmium were the only metals detected above the detection limit.  

units: mg metal/L solution 

                                                              (detection limit)
0.25
0.1
0.15
0.05
0.05
0.4
Product
Cobalt
Chromium
Arsenic
Beryllium
Cadmium
Nickel
Spherix S-15
(Untreated) (POND)
ND
ND
5.5
ND
0.063
ND
F-15 SC-3n (treated)
(PMN 16-0460)
ND
ND
5.4
ND
0.062
ND
F-15 SC (treated)
(PMN-16-0460)
ND
0.34
3.1
ND
ND
ND
F-15 SC-2p  (treated)
(PMN 16-0194)
ND
ND
5.1
ND
0.061
ND
D-4 PC EXP2 (treated)
ND
0.7
1.9
ND
ND
ND

Dust monitoring

Artisan EHS Consulting performed industrial hygiene monitoring at a SEFA facility.  The results are shown in the following tables.  None of the respirable dust samples measured metal content above the detection limit.   

                       IH monitoring (mg metal/m[3] air)
                                       
                                     Total
                                     Dust
                                  Respirable
                                     Dust
                                      As
                                      Be
                                      Cd
                                      Cr
                                      Co
                                      Ni
                                   Personal
                                                                            6.5

                                                                         0.0034
                                                                    <0.00073
                                                                    <0.00073
                                                                      <0.037
                                                                     <0.0022
                                                                     <0.0015
                                   Personal
                                                                               
                                                                           0.48
                                                                     <0.0011
                                                                    <0.00057
                                                                    <0.00057
                                                                      <0.028
                                                                     <0.0017
                                                                     <0.0011
                                    Area 1
                                                                            2.7

                                                                     <0.0015
                                                                    <0.00073
                                                                    <0.00073
                                                                      <0.037
                                                                     <0.0022
                                                                     <0.0015
                                    Area 1
                                                                               
                                                                       <0.22
                                                                     <0.0012
                                                                    <0.00058
                                                                    <0.00058
                                                                      <0.029
                                                                     <0.0017
                                                                     <0.0012
                                    Area 2
                                                                        <1.1

                                                                     <0.0017
                                                                    <0.00084
                                                                    <0.00084
                                                                      <0.042
                                                                     <0.0025
                                                                     <0.0017
                                    Area 2
                                                                               
                                                                       <0.20
                                                                     <0.0011
                                                                    <0.00059
                                                                    <0.00059
                                                                      <0.029
                                                                     <0.0018
                                                                     <0.0011

                                  Bulk sample
                                       
                                      As
                                      Be
                                      Cd
                                      Cr
                                      Co
                                      Ni
                                 Total (mg/kg)
                                                                            150
                                                                            4.0
                                                                        <1.1
                                                                             44
                                                                             11
                                                                             29
                                  TCLP (mg/l)
                                                                            2.9
                                                                      <0.050
                                                                      <0.050
                                                                           0.14
                                                                       <0.25
                                                                       <0.40