3. INTRODUCTION
• Bioremediation refers to the use of either naturally occurring
or deliberately introduced microorganisms to consume and
break down environmental pollutants, in order to clean a
polluted site.
• It is a process that uses mainly microorganisms but also plants,
or microbial or plant enzymes to detoxify contaminants in the
soil and other environments.
• The concept includes biodegradation, which refers to the
partial and sometimes total, transformation or detoxification
of contaminants by microorganisms and plants
4. The process of bioremediation enhances the rate of the natural
microbial degradation of contaminants by supplementing the
indigenous microorganisms (bacteria or fungi) with nutrients,
carbon sources, or electron donors (biostimulation,
biorestoration) or by adding an enriched culture of
microorganisms that have specific characteristics that allow
them to degrade the desired contaminant at a quicker rate
(bioaugmentation).
OBJECTIVES: The goal of bioremediation is to at least reduce
pollutant levels to undetectable, nontoxic, or acceptable levels,
that is, to within limits set by regulatory agencies or, ideally, to
completely mineralize organopollutants to carbon dioxide.
5. PRINCIPLE
• Bioremediation relies on stimulating the growth of certain
microbes that use contaminants like oil, solvents, and
pesticides as a source of food and energy.
• These microbes consume the contaminants, converting them
into small amounts of water and harmless gases like carbon
dioxide.
• Effective bioremediation needs a combination of the right
temperature, nutrients, and food; otherwise, it may take much
longer for the cleanup of contaminants.
6. • If conditions are not favorable for bioremediation, they can be
improved by adding “amendments” to the environment, such
as molasses, vegetable oil or simply air.
• These amendments create optimum conditions for microbes
to flourish and complete the bioremediation process.
• The process of bioremediation can take anywhere from a few
months to several years.
• The amount of time required depends on variables such as
the size of the contaminated area, the concentration of
contaminants, conditions such as temperature and soil
density, and whether bioremediation will take place in situ or
ex-situ.
7. How Does Bioremediation
Work?
Uses naturally occurring microorganisms
to break down hazardous substances into
less toxic or nontoxic substances.
8. 2 TYPES
• Microbial Remediation
• Micro-organisms are well known for their ability to break down a huge
range of organic compounds and absorb inorganic substances. Currently,
microbes are used to clean up pollution treatment in processes known as
bioremediation.
• Different microbial systems like bacteria, fungi, yeasts, and actinomycetes
can be used for removal of toxic and other contaminants from the
environment.
• Microorganisms are readily available, rapidly characterized, highly diverse,
omnipresent, and can use many noxious elements as their nutrient source.
• They can be applied in both in situ and ex-situ conditions; in addition,
many extreme environmental conditions can be cleaned by such entities.
9. • Although many microorganisms are capable of degrading
crude oil present in soil, it has been found beneficial to
employ a mix culture approach than the pure cultures in
bioremediation as it shows the synergistic interactions.
• • Different bacteria can be used for the removal of
petroleum hydrocarbon contaminants from soil.
• • The bacteria that can degrade major pollutants
include Pseudomonas, Aeromonas, Moraxella,
Beijerinckia, Flavobacteria, chrobacteria, Nocardia,
Corynebacteria, Acinetobacter, Mycobactena, Modococci,
Streptomyces, Bacili, Arthrobacter, Aeromonas, and
Cyanobacteria.
10. Phytoremediation
• Phytoremediation is a bioremediation process that
uses various types of plants to remove, transfer,
stabilize, and/or destroy contaminants in the soil and
groundwater.
• There are several different types of phytoremediation
mechanisms
• 7 TYPES
11. 1. Rhizosphere biodegradation. In this process, the
plant releases natural substances through its roots,
supplying nutrients to microorganisms in the soil.
The microorganisms enhance biological degradation.
2. Phyto-stabilization. In this process, chemical
compounds produced by the plant immobilize
contaminants, rather than degrade them.
3.Phyto-accumulation (also called phytoextraction). In
this process, plant roots absorb the contaminants along
with other nutrients and water. The contaminant mass is
not destroyed but ends up in the plant shoots and
leaves. This method is used primarily for wastes
containing metals.
12. • 4. Hydroponic Systems for Treating Water Streams
(Rhizofiltration). Rhizofiltration is similar to
phytoaccumulation, but the plants used for cleanup are
raised in greenhouses with their roots in water. This system
can be used for ex-situ groundwater treatment. That is,
groundwater is pumped to the surface to irrigate these
plants. Typically hydroponic systems utilize an artificial soil
medium, such as sand mixed with perlite or vermiculite. As
the roots become saturated with contaminants, they are
harvested and disposed of.
• 5. Phyto-volatilization. In this process, plants take up water
containing organic contaminants and release the
contaminants into the air through their leaves.
13.
14. • Technologies can be generally classified as in
situ or ex-situ.
• • In situ bioremediation: It involves treating
the contaminated material at the site.
• • Ex situ bioremediation: It involves the
removal of the contaminated material to be
treated elsewhere.
15.
16. Biostimulation and Bioaugmentation
• As the name suggests, the bacteria is stimulated to initiate the
process. The contaminated soil is first mixed with special
nutrients substances including other vital components either
in the form of liquid or gas. It stimulates the growth of
microbes thus resulting in efficient and quick removal of
contaminants by microbes and other bacteria.
• At times, there are certain sites where microorganisms are
required to extract the contaminants. For example –
municipal wastewater. In these special cases, the process of
bioaugmentation is used. There’s only one major drawback in
this process. It almost becomes impossible to control the
growth of microorganisms in the process of removing the
particular contaminant.
18. APPLICATIONS
• • Bioremediation is used for the remediation of metals,
radionuclides, pesticides, explosives, fuels, volatile organic
compounds (VOCs) and semi-volatile organic compounds
(SVOCs).
• • Research is underway to understand the role of
phytoremediation to remediate perchlorate, a contaminant that
has been shown to be persistent in surface and groundwater
systems.
• • It may be used to clean up contaminants found in soil and
groundwater.
• • For radioactive substances, chelating agents are sometimes
used to make the contaminants amenable to plant uptake.
19. ADVANTAGES
• As it only uses natural processes, it is a relatively green
method that causes less damage to ecosystems.
• It often takes place underground, as amendments and
microbes can be pumped underground to clean up
contaminants in groundwater and soil; therefore, it does not
cause much disruption to nearby communities.
• The process of bioremediation creates few harmful byproducts
since contaminants and pollutants are converted into water
and harmless gases like carbon dioxide.
• Bioremediations is cheaper than most cleanup methods, as it
does not
20. • • Bioremediations is cheaper than most cleanup methods,
as it does not require a great deal of equipment or labor.
• • Bioremediation can be tailored to the needs of the
polluted site in question and the specific microbes needed to
break down the pollutant are encouraged by selecting the
limiting factor needed to promote their growth.
21. DISADVANTAGES
• The toxicity and bioavailability of biodegradation products are
not always known.
• Degradation by-products may be mobilized in groundwater or
bio-accumulated in animals.
• Additional research is needed to determine the fate of various
compounds in the plant metabolic cycle to ensure that plant
droppings and products do not contribute to toxic or harmful
chemicals into the food chain.
• Scientists need to establish whether contaminants that collect
in the leaves and wood of trees are released when the leaves
fall in the autumn or when firewood or mulch from the trees
is used.
• Disposal of harvested plants can be a problem if they contain
high levels of heavy metals.
22. • The depth of the contaminants limits treatment. In most cases, it is limited to shallow soils,
streams, and groundwater.
• Generally, the use of phytoremediation is limited to sites with lower contaminant
concentrations and contamination in shallow soils, streams, and groundwater.
• The success of phytoremediation may be seasonal, depending on location. Other climatic
factors will also influence its effectiveness.
• The success of remediation depends on establishing a selected plant community. Introducing
new plant species can have widespread ecological ramifications. It should be studied
beforehand and monitored
• If contaminant concentrations are too high, plants may die.
• Some phytoremediation transfers contamination across media, (e.g., from soil to air).
• Phytoremediation is not effective for strongly sorbed contaminants such as polychlorinated
biphenyls (PCBs).
• Phytoremediation requires a large surface area of land for remediation.
23. BIOPILES
• Excavated soils are mixed with soil amendments and placed in
aboveground enclosures.
• This process also includes leachate collection systems & is
used to reduce concentrations of petroleum constituents in
excavated soils through the use of biodegradation.
• It is an aerated static pile composting process in which compost
is formed into piles and aerated with blowers or vacuum
pumps.
• Moisture, heat, nutrients, oxygen, and pH can be controlled to
enhance biodegradation.
• The treatment area will generally be covered or contained with
an impermeable liner to minimize the risk of contaminants
leaching into uncontaminated soil.
24. • The drainage itself may be treated in a bioreactor before
recycling.
• The air distribution system is typically buried under the soil &
passes air through the soil either by vacuum or by positive
pressure.
•
• Soil piles may be covered with plastic to control runoff,
evaporation, and volatilisation and to promote solar heating.
• If VOCs are in the soil - these will volatilise into the air stream,
thus air treatment would be required.
• Biopile is a short-term technology (few weeks - several
months).
25. USES
• Treats non-halogenated VOCs, fuel
hydrocarbons, halogenated VOCs, SVOCs, &
pesticides.
• The process effectiveness will vary and may be
applicable only to some compounds within
these contaminant groups.
26. LIMITATIONS
• Excavation of contaminated soils is required.
• Treatability tests required to determine the
biodegradability of contaminants and appropriate
oxygenation and nutrient loading rates.
• Questionable effectiveness for halogenated compounds.
•
• Similar batch sizes require more time to complete cleanup
than slurry phase processes.
• Static treatment processes may result in less uniform
treatment than processes that involve periodic mixing.
27.
28. LAND FARMING
• Contaminated soil, sediment, or sludge is excavated,
applied into lined beds, and periodically turned over
or tilled to aerate the waste.
• Land farming is a full-scale bioremediation
technology, which usually incorporates liners and
other methods to control leaching of contaminants,
which requires excavation and placement of
contaminated soils, sediments, or sludges.
• Contaminated media is applied into lined beds and
periodically turned over or tilled to aerate the waste
29. • Soil conditions are often controlled to optimize
the rate of contaminant degradation. Conditions
normally controlled include:
• Moisture content (usually by irrigation or
spraying).
• Aeration (by tilling the soil with a predetermined
frequency, the soil is mixed and aerated).
• pH (buffered near neutral pH by adding crushed
limestone or agricultural lime).
• Other amendments (e.g., Soil bulking agents,
nutrients, etc.).
30. APPLICATIONS
• Ex situ landfarming has been proven most
successful in treating petroleum
hydrocarbons. Because lighter, more volatile
hydrocarbons such as gasoline are treated
very successfully by processes that use their
volatility (i.e., soil vapor extraction)
31. LIMITATIONS
• The use of aboveground bioremediation is usually limited to
heavier hydrocarbons.
• As a rule of thumb, the higher the molecular weight (and the
more rings with a PAH), the slower the degradation rate.
• Also, the more chlorinated or nitrated the compound, the
more difficult it is to degrade. (Note: Many mixed products
and wastes include some volatile components that transfer to
the atmosphere before they can be degraded.)
