The new arsenic in drinking water regulation will require many utilities to implement
technologies for arsenic removal. Of the US Environmental Protection Agency (USEPA) identified treatment options, adsorption
onto solid media seems to be the most attractive for small treatment facilities, especially
in the arid Southwest. The arsenic bearing solid residuals from these adsorption processes
are to be disposed in non-hazardous landfills. The Toxicity Characteristic Leaching
Procedure (TCLP) test defines whether a waste is hazardous or non-hazardous (w.r.t.
landfill disposal) and most solid residuals pass the TCLP. However, the TCLP may not
correctly estimate the leaching potential of arsenic residuals. The TCLP poorly simulates
the alkaline pH, anaerobic microbial activity, mineralogical aging, high phosphate, and
concentrated organic characteristics of landfills. These same conditions are expected to
favor mobilization of arsenic from metal oxide adsorbents. This study quantifies leaching
of arsenic and other contaminants from solid residuals under landfill conditions and
compares this to the leaching observed using the TCLP. Activated Alumina (AA) and
Granular Ferric Hydroxide (GFH) have been identified as the adsorbents that will be
most widely used for arsenic removal. Consequently, this research focused on leaching
from these two residuals. Initially, small volume batch experiments were used to quantify
the extent of arsenic sorption as a function of pH and arsenic to solid mass ratio. The
results indicate arsenic partitions significantly more strongly to the aqueous phase in the
pH range and high arsenic loadings that characterize landfill conditions than in the
conditions created in the TCLP. Computer simulation results are compared to the
observed results from laboratory trials. This model effort indicates potential mechanistic
underpinnings for the observed behavior and allows prediction of leaching potentials
under a wider range of conditions. The work indicates that significantly greater arsenic
leachate concentrations can be expected than those predicted by TCLP results for both
activated alumina and GFH. It further indicates the more challenging WET procedure
may also underestimate arsenic mobilization in certain cases.
Includes 27 references, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 370 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 16 |
| Published : | 06/16/2002 |
