Transitions - Sustainable Design: The Science of Sustainability and Green Engineering - page 119

Table 3.5 Selected Waste Streams Commonly Requiring Treatability Studies

Treatment Technology Type

Thermal Thermal Particle

Contaminant Loss Stream Biological Chemical Extraction Desorption Destruction Immobilization Separation

Residual solids X X X X X X X

Wastewater X X X X X

Oil/organic compounds X X X

Leachate X a

Stack gas X X

Adsorption media X X

Scrubber water X

Particulates (filter/cyclone) X X

a Long term contaminant losses must be estimated using leaching tests and contaminant transport modeling similar to that used for sediment placed in a
confined disposal facility. Leaching could be important for residual solids for other processes as well.
Source : U.S. Environmental Protection Agency, Remediation Guidance Document, EPA-905-B94-003, Chapter 7, U.S. EPA, Washington, DC, 2003.

reliably estimating contaminant concentrations for the residues that remain after
treatment, as well as possible waste streams that could be generated by applying
a given technology. Treatability studies may be performed at the bench scale
(in the lab) or pilot scale (e.g., a real-world study but limited in the number
of contaminants, in spatial extent, or to a specific highly controlled form of
a contaminant such as one pure congener of PCBs rather than the common
mixtures). Most treatment technologies include post-treatment or controls for
waste streams produced by processing. The contaminant losses can be defined as
the residual contaminant concentrations in the liquid or gaseous streams released
to the environment. For technologies that extract or separate the contaminants
from the bulk of the sediment, a concentrated waste stream may be produced
that requires treatment off-site at a hazardous waste treatment facility, where
permit requirements may require destruction and removal efficiencies greater
than 99.9999% (called the rule of six nines ). The other source of loss for treatment
technologies is the residual contamination in the sediment after treatment. After
disposal, treated wastes are subject to leaching, volatilization, and losses by other
pathways. The significance of these pathways depends on the type and level of
contamination that is not removed or treated by the treatment process. Various
waste streams for each type of technology that should be considered in treatability
evaluations are listed in Table 3.5.
This life-cycle view also is the first step toward preventing problems. For
example, if we consider all possible contaminants of concern, we can compare
which must be avoided completely, which are acceptable with appropriate safe-
guards and controls, and which are likely to present hazards beyond our span
of control. We may also ascertain certain processes that generate none of these