DISCUSSION OF BIOREMEDIATION PROCESS FOR SOIL
the contaminated soil will be treated to produce the smallest
size particle possible with either a shredding device or a
vibrating screen. Tightly compacted soil may need additives
to increase their permeability. The microbial product, PDM-7
HC and nutrients will be added to the soil by spray method
to insure inoculation of the maximum surface area. In most
soil treatment, faster remediation is obtained with nitrogen
and phosphorous concentrations of 100 PPM.
In our opinion,
bioremediation is best accomplished with Bio-augmentation,
the addition of large numbers of selected microorganisms grown
in the production laboratory. In addition to augmentation,
several physical and chemical parameters must be controlled
in order to obtain optimal growth and maximum degradation
in soil contaminants.
The major factors
that PHase III, Inc. control during Bioremediation are:
and moisture content
group of microorganisms in PDM-7 HC digest short and long
chain hydrocarbons, heavy tarry types of oil and grease, coal
tars, phenolic compounds, chlorinated organic solvents and
many toxic chemicals.
in PDM-7 HC are non-pathogenic and use petroleum products
or other chemicals in the soil for both a carbon source and
an energy source. They covert the toxic chemicals to cell
mass and to carbon dioxide and water.
a sufficient amount of PDM-7 HC product is applied to the
soil to give an initial population of one million organisms
per gram of soil. Our studies have shown that this concentration
insures that a sufficient population will be provided. It
is not the intent to provide a ready-made population to immediately
digest the contaminants, but rather to provide an inoculum
that will insure rapid growth. As the project progresses the
population of petrophillic organisms will show up to a one
thousand fold increase as they digest the contaminants.
Bio-augmentation with natural degradation, the former greatly
increases the rate of degradation. The microorganisms naturally
present, that can degrade petroleum products are usually present
only in the upper few inches of soil and in low concentrations.
These organisms are greatly diluted when mixed with a large
amount of excavated soil. The dilution factor can be so large
that it takes an excessively long time, if ever to establish
a working population of correct organisms.
needed for amino acid, purine and pyrimidine biosynthesis
and can be obtained by microorganisms from either inorganic
or organic sources. The most commonly used nitrogen sources
in bioremediation are ammonia and nitrate. Many of the bacteria
in PDM-7 HC have two pathways for ammonia assimilation and
which one functions depends on the ammonia concentration.
We purposely keep the ammonia concentration high in order
to allow the bacteria to utilize the most simple process.
is utilized as the nitrogen source it is reduced to ammonia
by a stepwise process. Nitrate is first reduced to nitrite
by a molybdenum containing enzyme and then to ammonia.
the form of phosphate) is utilized by microorganisms primarily
to synthesize phospholipids and nucleic acids (DNA and RNA).
to nitrogen and phosphorous, a variety of minerals is universally
required, such as potassium, calcium, magnesium and iron.
Many other elements are required only in trace elements. These
include zinc, copper, cobalt, manganese and molybdenum. These
metals function in enzymes or coenzymes.
of the microorganisms in PDM-7 HC require growth factors,
it has been observed that organic growth factors such as B
vitamins greatly stimulate growth and Bio-Degradation.
of aliphatic hydrocarbons by microorganisms is strictly an
aerobic process. The initial oxidation step of aliphatic hydrocarbons
involves molecular oxygen as a reactant and one of the oxygen
molecules is actually incorporated into the oxidized product.
group of hydrocarbons can be viewed as derivatives of benzene.
The breakdown od aromatic hydrocarbons involves the action
of either oxygenases or mixed function oxygenases. These two
reaction sequences both form catechol which can be degraded
in a number of ways leading to either acetyl CoA or TCA cycle
intermediates. If the benzene ring contains added methyl groups
or other constituents (as in toluene or xylene), these substituents
may be attacked before or after the ring is oxidized.
the oxygen concentration is the rate limiting factor in the
Bio-degradation of petroleum based products. Microbial activity
is most frequently limited by insufficient oxygen due to slow
rates of diffusion into the interior of the soil layers or
piles and into the center of soil aggregates. Generally, the
greater the mass of oxygen that can be distributed the more
rapid and complete the cleanup. Effective application can
result in greatly accelerated cleanups.
may be utilized in addition to the aeration process. Hydrogen
peroxide in addition to simply providing oxygen for microbial
use has been shown in our laboratory to greatly stimulate
the degradation of recalcitrant components of diesel fuel
such as benzopyrene.
Temperature and Moisture Control
bacteria in PDM-7 HC that were all isolated from the soil
and laboratory studies have shown that the optimum temperature
of the soil should be maintained as close to 28 Celsius (82
Fahrenheit) as possible. Similar studies have shown that soil
moisture should be maintained at 15-20% moisture.
OVER OTHER REMEDIATION METHODS
our product offers numerous advantages over the more conventional
means of remediation, which are excavation/relocation or incineration.
Both previous methods are very costly. For instance, on site
incineration costs approximately $500.00 per ton, while offsite
disposal runs as high as $300.00 per ton. Actual bio-remediation
costs will vary according to:
of site to be remediated
2. Size of
site to be remediated
rental or purchase cost
4. Labor cost
usage varies depending on the extent of the contamination.
However, the following are estimated figures:
One gallon of PDM-7 HC per 1000 gallons of wastewater
One gallon of PDM-7 HC per one to three cubic yards depending
upon site specifics.
of the product can vary from site to site depending on various
environmental factors, as well as the extent of the contamination.
Some of the more typical bio-remediation processes are:
Top Soil Bio-remediation (up to 18 inch depth)
product and the proper nutrients can be applied by merely
spraying the mixture onto the surface of the soil while simultaneously
rototilling the mixture into the soil. This application method
provides an even distribution of microbes throughout the soil,
as well as providing aeration for the microbes. Repeated rototilling
accelerates the biological degradation of the soil contaminants.
Sub-surface Soil Bio-remediation (over 18 inches in depth)
bio-remediation procedures require that the product and appropriate
nutrients be injected under pressure to a depth to be determined
by the depth of the contamination. The interval between injection
sites needs to be determined onsite in accordance to soil
composition and consistency. If necessary, nutrients or hydrogen
peroxide or both can be added at a later date, pending laboratory
analysis of soil samples obtained from the site.
of the treatments mentioned provide onsite treatment in which
the entire bio-remediation process can be completed without
any excavation or soil removal. This form of remediation has
significant environmental and economic advantages when compared
to other means of remediation.
Waste Lagoon Bio-remediation
lagoons can be treated by merely spraying the product and
the proper nutrients on the surface of the lagoon. Circulating
and aerating the lagoon with the use of a direct drive mixer
will greatly increase the rate of biological degradation.
ties and ballast can be cleaned and remediated by using the
following summarized treatment process:
1. Spray railroad
ties and ballast with Eliminator Microbial Cleaner/Degreaser.
Eliminator loosens the extensive oil and grease built up on
the ties, ballast and rock.
2. The pretreatment
is then followed by a high pressure wash, which removes the
oil and grease from the ties and ballast and deposits this
material on the soil below.
3. The ballast
and soil is further inoculated with PDM-7 HC and proper nutrients.
These petrophilic bacteria will digest the hydrocarbons which
were previously deposited on the soil below the ballast.
is presented as a general outline for the process for soil
bio-remediation. Each potential clean-up is site specific
and should be treated as such.