bioremediation for hazardous wastes

1. BIOREMEDIATION FOR HAZARDOUS WASTES
Dr. V.C. SRIVASTAVA
Department of Chemical Engineering, Indian Institute of Technology- Roorkee,
Roorkee-247667 (UA), India
It is probably not unscientific to suggest that somewhere or other some
microorganism exists which can, under suitable conditions, oxidize
any substances which is theoretically capable of being oxidized.
E.F. Gale, The Chemical Activities of Bacteria (1952)
INTRODUCTION
For thousands of years, human civilization has benefited from biologically
medicated processes
Rapid industrialization and urbanization have resulted in soil, surface and
ground water contamination involving a wide variety of natural and
anthropogenic chemicals.
Remediation: biological, physicochemical, or thermal ( ascending order of cost)
Either singly or in combination
Bioremediation is the least expensive
Bioremediation is a general term used to describe the use of biological
contaminants to destroy,transform, or immobilize environmental contaminants
to protect potential sensitive receptors
The acceptance of bioremediation has followed from biotechnological advances
that provide and increasingly through knowledge of the system and knowledge
about optimizing the process to achieve not only high removal efficiencies but
also to achieve these treatment efficiencies over long periods of time with
minimal maintenance.
Bioremediation processes are currently used to treat a wide range of chemicals
in ground water, soils, and sediments.
BIOREMEDIATION
Biology “Remediate” = To solve a problem
Bio-Remediate = to use biological organisms to solve an environmental problem

2. PRINCIPLES OF BIOREMEDIATION
Bioremediation is based on the idea that organisms are
capable to take in things from the environment and use it to
enhance their growth and metabolism. With this unique
characteristic lay the fundamental principle of
Bioremediation, to use microorganism to take in
contaminated substances from the environment or convert it
to a nontoxic form. Bacteria, Protista, and fungi are well
known for degrading complex molecules and transform the
product into part of their metabolism.
PROCESS OF BIOREMEDIATION
1. Microbes releases enzyme to break down the contaminant into digestible pieces
2. The contaminant of organic substances is ingest and digest as food along with other
energy source by the cell.
Bioremediation is beneficial because:
Consume organic waste
Grow and reproduce rapidly in selected environment
Digest the waste quickly and completely
Work without causing odors or poisonous compounds
Non-pathogenic - (Does not cause disease in humans or animals)
Generate environment friendly and less toxic substances such as:-
Carbon dioxide
Water
Smaller, less toxic organic compounds
Where can apply bioremediation
Bioremediation can be used to decompose or degrade:
Crude oil spills
Sewage effluent
Chlorinated and non-chlorinated solvents in the industrial areas
Coal Products: phenols and cyanide
BTEX compounds
Soils, lagoons, sludges, and process-waste streams

3. Agricultural chemicals and pesticides in groundwater and rivers
Gasoline and fuel oil contamination
Creosote contaminants(wood preservatives)
Ethylene glycol (antifreeze), methanol, methylethylketone (MEK), ether
Where bioremediation is less effective
Biodegradation is not very effective at sites with high concentrations of the following
materials which are toxic to microorganisms.
Metals - solidification/stabilization is the usual treatment process
Highly chlorinated organics such as
Inorganic salts
Heavy metals are not biodegradable, but bacteria can be used to concentrate them into a
more easily disposable form.
Mercury: experiments with bacteria are on-going
Uranium: iron-eating bacteria can remove low levels of radioactive waste from
water.
Other metals may be Ag, Al, As, Be, Cd, Cu, Fe, Ni, Pb, Se, Zn Radioactive
elements and there derivatives* (Meagher 2000, Allen 2002)
On the basis of metabolic reaction pathway bioremediation can be classified as :
Aerobic (with oxygen) - Microorganisms use available atmospheric oxygen to
function. Food sources are converted to energy by the transfer of electrons to oxygen,
which is an electron acceptor.
Anaerobic(without oxygen) - Microorganisms break down chemical compounds to
release the energy required to function. As electron acceptors, they utilize:
- nitrates
- sulfates
- carbon dioxide
- ferrous metals (such as iron)
How bioremediation proceed (Mechanism):-
Bioremediation is based on the idea that organisms are capable to take in things from
the environment and use it to enhance their growth and metabolism. With this unique
characteristic lay the fundamental principle of Bioremediation, to use microorganism to
take in contaminated substances from the environment or convert it to a nontoxic form.
Bacteria, Protista, and fungi are well known for degrading complex molecules and
transform the product into part of their metabolism.
- Microbes releases enzyme to break down the contaminant into digestible
piece
- The contaminant of organic substances is ingest and digest as food along
with other energy source by the cell.
What are the optimum conditions for the better bioremediation?
To optimize and accelerate the bioremediation of contaminants follow some conditions,
such as:-

4. Food:- organic waste containing water (moisture content between 30-80%) added
nutrients (Nitrogen, Phosphorous, Sulfur) present organic matter content in waste
serves as a source of carbon, nutrients energy for the metabolic reactions during
bioremediation process.
Micronutrients in addition to N, P S many other micronutrients are needed to a
lower concentration such as K, Ca, Mg, Fe, Ni others
Oxygen if required (aerobic types):- 3-5 pounds of oxygen per pound of
hydrocarbon to be converted
Moderate pH:- between 6-9, neither too acidic nor too alkaline
Moderate Temperatures:- 50o to 100o F
Enzymes:- Chemical catalysts to break waste materials into smaller pieces
SOME MICROORGANISMS USED IN BIOREMEDIATION
Microorganism Characteristics Significance
Yeast aerobic/
micro-aerophilic
EXAMPLES OF MICROBES USED FOR SPECIFIC CHEMICALS
Typical Bacteria Species include:
(in descending order of occurrence)
Degrades complex
compounds
Cyanobacteria aerobic/
micro-aerophilic/
anaerobic
Self-sustaining,
light is primary
energy source
Oligotrophs aerobic Removes TRACE
concentrations of
organic substances
Compound Name Microorganisms Conditions
Aliphatics
(non-halogenated)
Ex. Acrylonitrile
Mixed culture and
activated sludge
Aerobic
Aliphatics
(halogenated)
Ex.
Trichloroethane
Marine bacteria,
sewage sludge,
soil bacteria,
methanogens
Aerobic +
Anaerobi c
Aromatic
compounds
Ex. BTEX,
creosol, phenol
Pseudomonas spp.,
Bacillus spp.,
Rhodococcus spp.,
Mycobacterium
spp.
Aerobic +
Anaerobic

5. Pseudomas, Arthobacter, Alcaligenes, Corynbacterium, Flavobacterium,
Achrombacter, Acinetobacter, Micrococcus, Nocardia, Mycobacterium
Summary of Metabolism Reactions
Various Bioremediation Methods
Biostimulation
Adding Oxygen
-Bioventing
-Biosparging
Bioremediation
in situ
Engineered Intrinisic
Adding Oxygen
and Nutrients
Bioaugmentation
Adding Oxygen,
Nutrients and Bacteria
ex situ
Landfarming Bioreactor
Bioremediation methods
Bioremediation technologies can be broadly classified as ex situ and in situ.
Ex situ technologies are those treatments which involve the physical removal of the
contaminated material for treatment process.
In situ in situ means to examine the phenomenon exactly in place where it occurs
(without removing it in some special medium etc.) so this techniques involve treatment
of the contaminated material on site.

6. Source http://www.envirotools.org/factsheets/images/bioremediation2.gif
Some of the bioremediation methods are as follows:
Land farming : Solid-phase treatment system for contaminated Soils.
Composting: Aerobic, thermophilic treatment process in which contaminated
material is mixed with a bulking agent; can be done using static piles or aerated
piles.
Bioreactors: Biodegradation in a container or reactor; may be used to treat
liquids or slurries.
Bioventing: Method of treating contaminated soils by drawing oxygen through
the soil to stimulate microbial activity.
Biofilters: Use of microbial stripping columns to treat air emissions.
Bioaugmentation: Addition of bacterial cultures to a contaminated medium;
frequently used in both in situ and ex situ systems.
Biostimulation: Stimulation of indigenous microbial populations in soils or
ground water by providing necessary nutrients.
Intrinsic bioremediation: Unassisted bioremediation of contaminant; only
regular monitoring is done.
Pump and treat: Pumping ground water to the surface, treating, and
reinjecting.

7. Phytoremediation comprise growing plants on contaminated sites so that polluting
components percolate through the radical system of the plants and accumulate in
various parts of plants. Plants have a natural capicity to accumulate essential heavy
metals (Fe, Mn, Zn, Mg, Mo and Ni) from soil or water for their growth and
development.
Organics Organic contaminants like pesticides, organ chlorines, polychlorinated
biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), synthetic dyes, wood
preservatives, munitions waste and synthetic polymers can be either degraded or
converted into less toxic forms by bioremediation.
Fungal bioremediation Synthetic dyes/pesticides/PCBs are introduced into the
environment by the agricultural, sanitization, textile, dying, paint, refinery, and
electrical industries. Fortunately, bacteria and several soil fungi (e.g. fusarium,
Penicillium) are now known to degrade pesticides, with greater efficacy.
Biosparging is an in situ remediation technology that exploits and stimulates
indigenous microorganisms to degrade organic contaminants in saturated soil. Via
borehoes, air is injected into the saturated zone (below the water table) to increase the
activity of the soils indigenous microorganisms through increased oxygen dissolution.
The increased oxygen enhances aerobic biodegradation of the contaminants present in
the soil or groundwater. Biosparging can be used to reduce petroleum constituents that
are adsorbed to soil within the capillary fringe, below the water table or dissolved in
groundwater.
Biosparging is commonly used at sites with mid-weight petroleum products such as
diesel fuel; lighter petroleum products tend to volatilise swiftly and are removed very
rapidly through sparging. Soil permeability is a key factor in the effectiveness of the
technology.
Bioventing is a promising new technology that stimulates the natural in situ
biodegradation of petroleum hydrocarbons in soil by providing oxygen to existing soil
microorganisms. In contrast to soil vapor vacuum extraction, bioventing uses low air
flow rates to provide only enough oxygen to sustain microbial activity. Oxygen is
commonly supplied through direct air injection into residual contamination in soil. In
addition to degradation of adsorbed fuel residuals, volatile compounds are biodegraded
as vapors move slowly through biologically active soil.
Two basic criteria must be satisfied for successful bioventing. First, air must be able to
pass through the soil in sufficient quantities to maintain aerobic conditions; second,
natural hydrocarbon-degrading microorganisms must be present in concentrations large
enough to obtain reasonable biodegradation rates.
Bioventing techniques have been successfully used to remediate soils contaminated by
petroleum hydrocarbons, nonchlorinated solvents, some pesticides, wood preservatives,
and other organic chemicals.
BIOAUGMENTATION can be defined as
The addition of pregrown microbial cultures to enhance microbial populations at a
site to improve contaminant clean up and reduce clean up time and cost.

8. Biodegradation is the major process affecting natural attenuation of contaminants.
During the process contaminants are metabolized into less toxic or non-toxic
compounds by naturally occurring organisms.
PHYTOREMEDIATION: This technology typically involves the use of plants to
remove, transfer, stabilize, or destroy contaminants in soil, sediment, or groundwater.
The mechanisms of phytoremediation include enhanced rhizosphere biodegradation
(takes place in soil or groundwater immediately surrounding plant roots).
Phytoremediation applies to all biological, chemical, and physical processes that are
influenced by plants (including the rhizosphere) and that aid in cleanup of the
contaminated substances.
Phytoremediation may be applied in situ or ex situ to soils, sludges, sediments, other
solids, or groundwater
Phytoextraction (also known as phytoaccumulation, the uptake of contaminants by
plant roots and the translocation/accumulation of contaminants into plant shoots and
leaves).
Phytodegradation (metabolism of contaminants within plant tissues), and
phytostabilization (production of chemical compounds by plants to immobilize
contaminants at the interface of roots and soil).
Phytotransformation - In this process, the plant absorbs and breaks down organic
chemicals in contaminated soil and groundwater through its metabolic processes.
MECHANISM FOR PHYTOREMEDIATION
http://www.itrcweb.org/PHYTO2.pdf

9. COST ADVANTAGE OF PHYTOREMEDIATION

10. Biofiltration is a low-cost and highly
effective air pollution control (APC)
technology in which vapor-phase
organic contaminants are passed through
a bed of porous media and sorb to the
media surface where they are degraded
by microorganisms in the media.
Specific strains of bacteria may be
introduced into the filter and optimal
conditions provided to preferentially
degrade specific compounds.
Typical Biofiltration Reactor
EXAMPLES OF BIOFILTRATION INCLUDE
Bioswales, Biostirps biobags
Constructed wetlands natural wetlands
Slow san filters
Green belts
Living walls
Riparian zones, Riparian forests
Applicability
As with other biological treatment processes, biofiltration is highly dependent upon the
biodegradability of the contaminants. Under proper conditions, biofilters can remove
virtually all selected contaminants to harmless products. Biofiltration is used primarily
to treat nonhalogenated VOCs and fuel hydrocarbons. Halogenated VOCs also can be
treated, but the process may be less effective. Biofilters have been successfully used to
control odors from compost piles.
Gases where can apply the Biofiltration
Rapidly
Reactive VOCs
H2S
NOx
SO2
HCl
NH3
PH3
SiH4
HF
Rapidly degradable
VOCs
Alcohols
Aldehydes
Ketones
Ethrs
Esters
Organic acids
Amines
Thiols
Other molecules with O2
N or S functional groups
Halogenated
hydrocarbons
Polyneric
hydrocarbons
CS2
Hydrocarbons
Phenols
Methylene chloride
Very Slowly
degradable VOCs
Slowly degradable
VOCs

11. BIOREMEDIATION: A Choice to Make
Advantages
Why use bioremediation
Minimal exposure of on site workers
to the contaminant
Long term protection of public health
The Cheapest of all methods of
pollutant removal
The process can be done on site with a
minimum amount of space and
equipment
Eliminates the need to transport of
hazardous material
Uses natural process
Transform pollutants instead of simply
moving them from one media to
another
Perform the degradation in an
acceptable time frame
Disadvantages
Potential problems
Cost overrun
Failure to meet targets
Poor management
Climate Issue
Regulatory compliance concern
Release of contaminants to
environment
Unable to estimate the length of time
it’s going to take, it may vary from
site. It can takes a few month to as
long as a few years.
Not all organic compounds are
biodegradable
There are some concerns that the
products of biodegradation many be
more toxic then it’s parental form
CONCLUSION
Bioremediation offers a viable alternative to the regular use of physicochemical
methods of decontamination, which are not generally cost effective. The
bioremediation process is influenced by various factors- existence of a specific
microbial population, bioavailability of contaminants, and environmental factors (Soil
type, temperature, pH, Nutrients and presence of oxygen or other electron acceptors).
Although bioremediation may not completely detoxify inorganic pollutants (Metals
Radio nuclides), yet it can be alter the oxidation state, aiding in adsorption, uptake,
accumulation and concentration in micro- or microorganisms.