Handbook of Solvents - George Wypych - ChemTech - Ventech!

23.2 Remediation technologies 1617
23.2 REMEDIATION TECHNOLOGIES AND APPROACHES FOR
MANAGING SITES IMPACTED BY HYDROCARBONS
Barry J. Spargo
U.S. Naval Research Laboratory, Washington, DC, USA
James G. Mueller
URS/Dames & Moore, Chicago, IL, USA
23.2.1 INTRODUCTION
Subsurface contamination of soils and aquifers by chlorinated hydrocarbons (CHC) and
non-chlorinated hydrocarbons (HC) is likely the largest environmental issue in industrialized
nations worldwide. Decades without controlled disposal practices, inadequate storage
and distribution systems, and accidental releases have resulted in a large number of contaminated
drinking water and aquifer systems. In addition, an untold number of ecosystems are
subject to future contamination by impinging hydrocarbon plumes. The extent of potential
contributors ranges from neighborhood facilities, such as laundries or gas stations, to major
fuel refineries, industrial operations and chemical manufacturing facilities.
While characterization, control, and cleanup of these impacted areas may seem daunting,
it is clear that not every impacted or potentially impacted area requires extensive remedial
efforts. In fact, many impacts do not represent a significant risk to human health or the
environment. In other areas, natural attenuation processes are effective in controlling the
migration of the dissolved-phase plume (see Chapter 23.1). If, however, the presence of
HCs elicits undesirable effects, then a number of strategies and developing remedial technologies
can be used. This chapter will discuss these technologies and strategies and present
a number of case studies documenting their effective implementation.
23.2.1.1 Understanding HC and CHC in the environment
As summarized by Mueller et al., 1 hydrocarbons have been produced in the environment
throughout geological time. Likewise CHCs are ubiquitous and are also of ancient ancestry.
2 It follows, therefore, that microorganisms have developed mechanisms for utilizing
these compounds as growth substrates. Depending on the inherent recalcitrance of the HC,
biodegradation mechanisms may be associated with various abiotic degradation processes.
While catabolic interactions are often complex and not fully elucidated, a more thorough
understanding of integrated processes allows today’s scientists and engineers to design and
implement more effective systems to mitigate situations where the concentration of HC in a
given environment exceeds a desirable value.
23.2.1.2 Sources of HC in the environment
Hydrocarbons found in the environment are of diverse structure and are widely distributed
in the biosphere, predominantly as surface waxes of leaves, plant oils, cuticles of insects,
and the lipids of microorganisms. 3 Straight-chain HC, or alkanes, with carbon number maxima
in the range of C17 to C21 are typically produced by aquatic algae. Conversely terrestrial
plants typically produce alkanes with C25 to C33 maxima. 4 Plants also synthesize
aromatic HC such as carotenoids, lignin, alkenoids, terpenes, and flavenoids. 5 Polycyclic