Studies of long-term chemical and physical properties of mixtures of flue gas cleaning wastes. Final report

Abstract

Results of a 2 year study of physical and chemical properties of mixtures of flue gas cleaning wastes representing 70 compositions and 10 fly ashes are documented in this report. This study was aimed at developing information needed to provide the utility industry with a more sound basis for selection of disposal methods and viable utilization options for these wastes. FGC waste mixtures having high unconfined compressive strengths after 56 days of curing (above 7 MPa or 1000 psi) will be relatively impermeable. These high strengths will increase with time and will be accompanied by a decrease in permeability and porosity. Low strength FGC waste mixtures (less than 0.7 MPa or 100 psi) will lose strength during long term curing and will become even more permeable and porous. The behavior of mixtures which develop strengths between 0.7 MPa and 7 MPa will depend upon the type of fly ash present. The type of fly ash used in a FGC waste mixture will have a greater influence on leachate quality generated by the waste than the relative amount of fly ash present in the mixture. Leachates from cured FGC wastes have the potential to contaminate groundwater if disposed of improperly. Inmore » this study concentrations of arsenic, cadmium, chromium, selenium and silver were found to exceed EPA's primary drinking water standards on a case by case basis. Concentrations of iron, sulfate and pH consistently exceeded EPA's secondary drinking water standards Boron and molybdenum in many cases exceeded recommended limits for irrigation water. However, leachate concentrations by themselves will not determine groundwater contamination. Processes of dilution, dispersion, adsorption and filtration in the soils and liners beneath a waste disposal site could potentially mitigate contamination problems.« less