half-life (22.3 y). In cases where iron is associated with the GAC or the raw water has a pH less than 6.8, uranium and radium can also be found. These species can pose problems for the long-term disposal of the GAC.

No federal agency currently has legislative authority concerning the disposal of drinking-water treatment-plant residuals that contain naturally occurring radionuclides (Cornwell and others 1999). If the GAC is transported to a site for disposal, the Department of Transportation could regulate its shipment. EPA has published two guidelines that suggest how such wastes might be handled (EPA 1994c; 1990). However, the states are responsible for regulation of naturally occurring radioactive materials (NORM). There have been three detailed reviews of federal and state guidelines and regulations regarding NORM and how they might apply to disposal of GAC used to remove radon from water (Cornwell and others 1999; Drago 1998; McTigue and Cornwell 1994).

The EPA (1994c) guidelines for disposal of water-treatment residuals are centered on the levels of uranium and radium present (for example, in spent GAC or backwash residuals) (table 8.5). Unlike its 1990 draft guidelines, EPA's 1994 version did not cite specific action levels for 210Pb. Instead, because of a lack of conclusive technical data, EPA recommended that the impact of 210Pb contamination be considered case by case. Most states also address NORM wastes on a case by case basis (Drago 1998); the exceptions are Illinois, Wisconsin, and New Hampshire, which have established disposal criteria (Cornwell and others 1999).

The Conference of Radiation Control Program Directors published a draft set of suggested state regulations for technologically enhanced NORM (TENORM), naturally occurring radionuclides whose concentrations have been enhanced by technology (for example by such practices as water treatment). Lead-210 associated with GAC is not specifically addressed in this document, and materials with 226Ra or 228Ra at less than 0.19 Bq g-1 are exempt. The draft recommends flexibility

Table 8.5

EPA Suggested Guidelines for Disposal of Naturally Occurring Radionuclides Associated with Drinking-Water Treatment Residuals

Radionuclide

Bq g-1 (dry weight)

Suggested Disposal Site

Radium

<0.11

Landfill

 

0.11–1.85

Covered landfill

 

1.85–74

Possible RCRA facility (case by case review)

 

>74

Low-level radioactive-waste facility

Uranium

<1.11

Landfill

 

1.11–2.78

Covered landfill

 

2.78–27.8

Possible RCRA facility (case by case review)

 

>27.8

Low-level radioactive-waste facility

210pb

Caution and thorough state-agency review of water treatment and waste disposal plans

 

Source: EPA (1994c).



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