AWWA ACE61597

Current United States federal regulations mandate that community water systems not exceed contaminant levels of 5 pCi/L for combined radium and 30 µg/L for uranium. All treatment technologies to meet these standards generate residues with elevated radionuclide content. Water treatment residues may consist of either liquids or solids, depending on the treatment technology used to remove the radium or uranium. All or part of these residues may be managed directly by the water provider, enter public waste streams through sewers, or be directly transported to land disposal sites including Municipal Solid Waste (MSW) landfills. Liquid residues may be discharged to the sanitary sewer system and then to a wastewater treatment facility (WWTF). Radionuclides in the residual liquids may be retained and concentrated in solids in the sewage system and sludges (inorganic and biosolids) (Ainsworth et al., 1994) generated in the treatment facility. The WWTF sludges may then be disposed in landfills, land farmed, or placed in evaporation lagoons or dedicated landfills. This paper provides estimates of the radium concentrations that could be present in radium-bearing sewage sludge and solid water treatment residues that might be disposed in landfills, and estimates of the atmospheric radon concentrations that could result from such disposal. Mass balance calculations indicated that if sewage sludge containing radium from water treatment commingled with municipal solid waste in proportion to per capita water use and solid waste generation, the radium isotope activities in the resulting refuse would be very small and radon emissions would be insignificant. On the other hand, if the sludge disposal was concentrated in limited portions of the MSW landfill, numerical simulations indicated that radon emissions could result in atmospheric concentrations exceeding background directly above and downwind of the landfill by a factor of up to 8. The operation of a landfill gas collection system could significantly increase emissions and atmospheric concentrations of Rn-222 and Rn-220. Includes 8 references, figures.