Environmental Engineering Reference
In-Depth Information
Fig. 1.1 In vivo and in
vitro design strategies.
(Source: Biotechnology in
Medicine and Agriculture
Principles and Practices)
neered biopiles. Soil treatment units consist of
soil contained and tilled (to supply oxygen) with
application of water, nutrients, and possibly mi-
crobial inocula to soil. Compost piles consist of
soil supplemented with composting material (i.e.,
wood chips, straw, manure, rice hulls, etc.) to
improve its physical handling properties and its
water- and air-holding capacities. Compost piles
require periodic mixing to provide oxygen to the
soil. Biopiles are piles of contaminated soil that
contain piping to provide air and water. Ex situ
solid applications involve the addition of water,
nutrients, and sometimes addition of cultured
indigenous microbes or inocula. They are often
conducted on lined pads to ensure that there is
no contamination of the underlying soil. Ex situ
slurry techniques involve the creation and main-
tenance of soil-water slurry as the bioremedia-
tion medium. The slurry can be maintained in ei-
ther a bioreactor or in a pond or lagoon. Adequate
mixing and aeration are key design requirements
for slurry systems. Nutrients and, perhaps, inocu-
lum may be added to the slurry.
1.4
Bioremediation Processes
and Technologies
Bioremediation techniques are divided into three
categories; in situ, ex situ solid, and ex situ slurry
(Fig. 1.1 ). With in situ techniques, the soil and
associated groundwater is treated in place with-
out excavation, while it is excavated prior to
treatment with ex-situ applications. The poten-
tial applications of biotechnology can be applied
in terms of the contaminated matrix, degrading
organisms of the contaminants, the type of reac-
tor technology used, and the types of compounds
present. The anaerobic and aerobic treatment
methods applied for reducing the pollution load
have been proved successful up to some extent.
Pump-and-treat systems, which are applied to
saturated-zone remediation, involve the removal,
treatment, and return of associated water from
a contaminated soil zone. The returned water is
supplemented with nutrients and saturated with
oxygen. Percolation consists of applying water,
containing nutrients and possibly a microbial in-
oculum, to the surface of a contaminated area and
allowing it to filter into the soil and mix with the
groundwater, if present. Bioventing supplies air
to an unsaturated soil zone through the installa-
tion of a well(s) connected to associated pumps
and blowers, which draw a vacuum on the soil.
Air sparging involves the injection of air into the
saturated zone of a contaminated soil.
Ex situ solid-phase techniques consist of
soil treatment units, compost piles, and engi-
1.5
Monitoring the Efficacy
of Bioremediation
The general acceptance of bioremediation tech-
nology as an environmentally sound and eco-
nomic treatment for hazardous waste requires
the demonstration of its efficacy, reliability and
predictability, as well as its advantages over con-
ventional treatments. An effective monitoring
 
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