Corporation Toxic Pollution Removal Credit Tables From Par 403 Pretreatment guidelines
It is most interesting that Chromium is regulated in Part 503  Surface Disposal subsection at 600 
ppm while unregulated Chromium may be land applied at  100,000 ppm in Table II
      
      Appendix G to Part 403—Pollutants Eligible for a Removal Credit
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 I.                                             Regulated Pollutants in Part 503 Eligible for a Removal Credit
                                                                  Milligram per kilogram
------------------------------------------------------------------------
                                                              Use or disposal practice
       Pollutants           ppm                        -----------------------------------------
                                                           LA                                 SD                                      I
------------------------------------------------------------------------
Arsenic.......................                            X-75                              X-73                                  X
Beryllium.....................                        ............                        ............                                  X
Cadmium.......................                          X-85                        ............                                  X
Chromium......................                      ............                             X-600                                 X
Copper........................                            X-4,300
Lead..........................                              X-840                    ............                                   X
Mercury.......................                            X-57                      ............                                   X                     
Molybdenum....................                        X-75
Nickel........................                               X-420                           X-420                              X
Selenium......................                           X-100
Zinc..........................                               X-7500
Total hydrocarbons............  ............  ............  X \1\
------------------------------------------------------------------------
Key:
LA_land application.
SD_surface disposal site without a liner and leachate collection system.
Table II indicates all credits were in parts per million (ppm). Therefore they are shown here as ppm. The 
Original Table included levels of grams per kilogram  \3\ (1,000 ppm) as well as milligram (1 ppm) per 
kilogram
                          II. Additional Pollutants Eligible for a Removal Credit
                                [Milligrams per kilogram_dry weight basis]
----------------------------------------------------------------------------------------------------------------
                                                                                Use or disposal practice
                                                                  -------------------------------------------------------
                     Pollutant                                                               Surface disposal
                                                                     LA                        --------------------------------                    I
                                                                                                Unlined \1\      Lined \2\
----------------------------------------------------------------------------------------------------------------
Arsenic.................................................         ............  .                .............       \3\ 100,000                  ........
Aldrin/Dieldrin (Total).................................           2.7                  ..............  .         .............  .               .......
Benzene.................................................      \3\ 16,000                     140                   3400                   ........
Benzo(a)pyrene..........................................          15              \3\ 100,000           \3\ 100,000               ........
Bis(2-ethylhexyl)phthalate..............................  ............           \3\ 100,000           \3\ 100,000               ........
Cadmium.................................................         ............           \3\ 100,000           \3\ 100,000                ........
Chlordane...............................................              86              \3\ 100,000            \3\ 100,000                ........
Chromium (total)........................................  \3\ 100,000              ..............            \3\ 100,000               ........
Copper..................................................           ............            \3\ 46,000                         100                1400
DDD, DDE, DDT (Total)...................................     1.2                      2,000                       2000               ........
2,4 Dichlorophenoxy-acetic acid.........................  ............                      7                             7               ........
Fluoride................................................                730                 ..............                   ..............             ........
Heptachlor..............................................                  7.4              ..............                   ..............              ........
Hexachlorobenzene.......................................          29                ..............                   ..............               ........
Hexachlorobutadiene.....................................         600               ..............                    ..............              ........
Iron....................................................            \3\ 78,000               ..............                   ..............              ........
Lead....................................................              ............          \3\ 100,000             \3\ 100,000                 ........
Lindane.................................................                   84            \3\  28,000              \3\  28,000                 ........
Malathion...............................................           ............                      0.63                        0.63                 ........
Mercury.................................................             ............          \3\ 100,000              \3\ 100,000                ........  
Molybdenum..............................................         ............                        40                           40                 ........
Nickel..................................................                ............              ..............               \3\ 100,000              ........
N-Nitrosodimethylamine..................................           2.1                          0.088                         0.088        ........
Pentachlorophenol.......................................           30                  ..............                 ..............                ........
Phenol..................................................                ............                     82                              82                ........
Polychlorinated biphenyls...............................             4.6                   <50                            <50                ........
Selenium................................................              ............                       4.8                              4.8               4.8
Toxaphene...............................................                10               \3\ 26,000                \3\ 26,000                 ........
Trichloroethylene.......................................   \3\ 10,000                     9,500                 \3\ 10,000                ........
Zinc....................................................                ............                    4,500                        4,500               4,500
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\1\ Active sewage sludge unit without a liner and leachate collection system.
\2\ Active sewage sludge unit with a liner and leachate collection system.
\3\ [original] Value expressed in grams per kilogram_dry weight basis-[converted to milligrams in this Table]
Key: LA_land application.
I_incineration.
[60 FR 54768, Oct. 25, 1995, as amended at 65 FR 42567, Aug. 4, 1999; 70 FR 60198, Oct. 14, 2005]