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Technical Briefing
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How
METS works
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Why
METS works
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Treatment
agents
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Performance
and efficiency
- Health,
safety, environmental impacts
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How METS works. The METS
remediation process equipment is about the size of a large SUV. It is
fully mobile and self-propelled. Previously excavated soil is deposited
in the hopper at the top of the apparatus by a conventional front-end
loader. Very large debris, such as rock, concrete or asphalt, is usually
screened off at the hopper opening. From the hopper, the soil is
transferred in a regulated flow to a custom designed processing mill.
The mill impacts and shreds the soil, while blending a treatment
solution (chemical, biological, or both), along with air and moisture,
into the soil using a method that is proprietary to EarthWorks
Environmental. The contaminant molecules in the soil are already being
degraded or neutralized by the time the soil emerges from the processing
mill. The treated soil may be deposited directly to the ground from the
mill. However, the apparatus includes a conveyor system at the back end,
which may be used to deposit the soil in locations and configurations as
desired or to meet site space constraints.
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Why METS works. There is,
in nature a wide variability in soil conditions and soil content, even
within small distances. This is the principal barrier to effective and
efficient remediation of contaminated soil. The METS process is designed
to eliminate this variability in the soil while introducing one or more
chemical or biological reagent(s) known to degrade and/or neutralize the
specific contaminants in that soil. In other words, METS is able to
tailor the choice of chemical and/or biological reagent to the specific
type and severity of contamination, and to the specific soil conditions
at a site. Second, the METS process reduces the soil to a fine particle
state in order to maximize access to the contaminant molecules. Third,
the METS process ensures the even distribution of the reagent(s)
throughout this soil matrix, and the degradation/neutralization is
completed before the soil loses its homogenous and fine particulate
composition. Finally, to improve speed and efficiency, the METS process
creates a relatively high level of air entrainment in the soil, along
with a carefully calibrated level of moisture content.
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Treatment agents. METS is
designed to work with any chemical reagent or biological product that is
or can be delivered in an aqueous solution. The choice of what to use in
a given project is determined from analysis of the contaminant or
combination of contaminants in the soil, and from analysis of the soil
composition, moisture content, pH, etc. For example, commercially
available products that are commonly used to degrade hydrocarbons as
part of various cleaning and degreasing applications, can be adapted
successfully by METS. Other products that can be adapted for METS are
based on a chemical principle known as Fenton's Reagent Chemistry. FRC
provides for direct oxidation -- release of nascent oxygen -- via an
exothermic reaction between a peroxygen and a catalyst. The exothermic
reaction as well as oxygen release, dependent upon catalyst, degrades
the hydrocarbon molecule to its carbon and hydrogen elements. The
nascent oxygen reacts with these elements to form benign compounds (for
example, in the case of gasoline, the byproducts are water and carbon
dioxide). Chemical reactions based on this chemistry are reliable and
predictable, once the proper environment has been created.
Metals (for example, soluble
lead) are neutralized by chemical bonding at the molecular level,
resulting in byproducts that are stable and benign. METS is also able to
apply a variety of products that release cultured microbes proven to
degrade and/or neutralize various types of contaminants. In all known
cases, these are naturally occurring biological organisms that have been
found to thrive in environments where these contaminants have been
introduced by man-made events or by natural causes.
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Performance and efficiency.
The EarthWorks-manufactured line of remediation process equipment
includes four configurations designed to process from 40 to 320 tons of soil per hour. Actual throughout will vary somewhat depending
upon soil type, soil condition and moisture content. In many cases, the
contaminant has been degraded and/or neutralized almost as soon as it
exits the processing mill. In some cases, the degradation process must
continue over a period of hours or a few days, to achieve the desired
remediation level. When METS relies on a biological product to provide
most of the degradation/ neutralization, the process may take longer --
up to a few weeks -- to achieve the desired results.
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Health, safety, environmental
impacts. There are no significant, negative health, safety, or
environmental impacts associated with operation of METS. There are no
significant risks, direct or indirect, to the general public as long as
the equipment and work site are reasonably secure from unauthorized
entrance. Specifically:
- Chemical hazard. The
chemical and biological products used are biodegradable and
environmentally benign. Equipment operators are trained to handle
these materials with due care, with the most likely risk if any
being direct exposure to themselves before the products are
sufficiently diluted. There is no risk to the general public as long
as the products are secure from access or tampering.
- Noise. The soils
processing machinery, when operating, produces a noise level
comparable to a medium-sized residential gasoline generator. The
noise level is typically less than that produced by the loader
equipment being used to dump contaminated soil into the machinery.
Equipment operators are not required to wear protective hearing
devices.
- Air pollution. The
engine meets current emission control requirements for such
equipment.
- Water pollution. There
is no contact with groundwater during the process (the contaminated
soil is already excavated), nor is there any release of chemicals or
biological products, diluted or undiluted, into public sewers or
storm drains (note: some of these products, in a diluted form, are
in fact prescribed for use in cleaning sewers and storm drains).
Small amounts of the diluted treatment solution may puddle on the
ground as an incidental byproduct of operating the equipment. This
liquid quickly evaporates and/or is absorbed into the soil deposited
from the remediation process.
- Fugitive dust. The
process may produce incidental dust as a natural result of the
lifting and dumping of soil into the hopper, if the soil is
particularly dry. During the process, moisture is added to the soil.
As a result there is no dust that results from the action of
discharging the remediated soil back to the ground. Remediated soil
is in a fine particulate state. When it dries completely, which may
take several days, there is the potential for windblown dust off of
the soil stockpile. However, that dust is from remediated soil, and
should not pose a health hazard.
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