EXPLAINS THE MEANING OF BIOREMEDIATION, TYPES AND METHODS.

1. DR. N. BANU
ASSOCIATE PROFESSOR
VELS UNIVERSITY
BIOREMEDIATION

2. BIOREMEDIATION
ENGINEERING STRATEGIES FOR
BIOREMEDIATION
 Site characterization:
 The chemical nature of contamination
 The geohydrochemical properties and
 The biodegradation potential for the site.
 Pollutant characterization:
composition, conc., toxicity, bioavailability, solubility,
sorption and volatilization.
Geohydrochemical characterization:
Physical and chemical properties of the geological
material.
geohydrological conditions of the site
Direction and velocity direction of the underground
flow.

3. ENGINEERING STRATEGIES FOR
BIOREMEDIATION
 MIROBIOLOGICAL CHARACTERIZATION
 Degradative capacity of microbial flora and native
flora.
 SUITABILITY OF THE SITE FOR
BIOTREATABILITY TESTS:
 To know its specific requirements.
 Biotreatability: performed at mesocosm level,
trying to maintain the environmental conditions
that will prevail during treatment in the field.

4. BIOTREATABILITY
 Shallow strata: Large trays or jars to hold several
pounds of soil could be used.
 Maintenance of humidity and homogenity.
 Uniform micribial activity throughout the soil
volume.
 Watertable: columns packed with contaminated
soil.
 Necessary to determine the ground water flow
rate to define the operating mechanism of the
columns.

5. ENGINEERING STRATEGIES FOR
BIOREMEDIATION
 Bioaugmentation:
 When the microbial population will degradative
potential is limited or practically zero, the addition
of exogenous microorganisms is necessary.
 Alternative methods:
 1. addition of commercial compound – lease
success.
 2. isolation of few degradative microbe during site
characterizatin and promote its growth to obtain
pure culture and used as inoculum. Require
longer time to increase the microbial biomass.

6. ENGINEERING STRATEGIES FOR
BIOREMEDIATION
 Purpose of biotreatability:
 To predict the behaviour of the process
 To determine the nutritional requirement for the
microorganisms to perform biodegradation.
 Measures:
 1. Oxygen consumption
 2. CO2 generated
 3. Exhaustion of added nutrients (N and P)
 4. Contaminant removal.

7. From laboratory to field
Bioavailability
The concept of bioreactor
The supply of oxygen
Mass transfer

8. Bioavailability
 For biotransformation, the contaminants to be
made ready for attack by microorganisms.
 Enzymatic reactions occur in water.
 But pollutans are insoluble in water e.g.
Hydrocarbon
 Surfactant are incorporated to the medium and
improve the bioavailability.
 Surfactant act by solubilizing organic
contaminants in the aqueous medium thus
making accessible to the enzymes of microbe.

9. The concept of bioreactor
 Pollutant present in shallow soil layers
 Biopile – The contaminated materials is piled on
the ground surface
 Biocell – excavation in a clean site to deposit the
material for further treatment.
 If the contaminants reached water table:
 The bioreactor built through bore-holes

10. Oxygen supply
 Many Degradative process – anaerobic.
 Aerobic – complete mineralization.
 Sources of carbon lack of oxygen – oxygen
demand for their degradation are higher.

11. Mass transfer
 Homogeneity of the system.
 The same microenvironmental conditions exist to
promote microbial activity.
 Nutrient conc., humidity, pH and conc. of oxygen.

12. Types of bioremediation
 In situ bioremediation:
 Microbes are responsible for the stabilization and
treatment of waste products containing organic
matter.
 Limiting factors:
 They require min. oxygen and
 Available nutrients.

13. Intrinsic In situ bioremediation
 Relies on naturally occurring supplies of e-
acceptors, nutrients and other necessary
materials to develop a biologically active zone
(BAZ) and prevent the migration of contaminants
away from the source.
 It doesnot accelerate the rate of cleanup.
 No engineering principles involved.
 Long term monitoring of site is necessary.
 Well suited for ground water with high e-
acceptors and adequate conc. of nutrients.

14. Engineered in situ bioremediation
 Used to speed up the process of contaminant
removal from the solid phase.
 Increased inputs of stimulating materials.
 The ideal site :
 1. the hydraulic conductivity is relatively
homogenous, isotrophic and large.
 2. residual conc. are not excessive.
 3. contamination is in shallow, thus minimize the
cost of drilling and sampling.

15. Engineered in situ bioremediation
Types:
Bioventing
Biosparging/ Air sparging
Bioaugmentation/ stimulation

16. Bioventing
 Increased oxygen supply with vapour extraction.
 A vacuum is applied at some depth in the
contaminated soil.
 This draws any volatile organic compound.
 Supplementation with nutrients.
 Increased o2 favours aerobes and faster the
reaction.
 Effective for volatitle compounds.

17. Biosparging/ Air sparging
 To increase the biological activity of soil by
increasing the supply of oxygen by sparging air or
oxygen into the soil.
 Supply of Hydrogen Peroxide – toxic at low conc.
to microbe.
 Success depends on the structure of the soil.

18. Bioaugmentation/ stimulation
 Stimulation of the degradative activities of
endogenous microbes by the provision of nutrients or
external electrons or by the introduction of competent,
exogenous microbes with or without nutritional
enrichment.
 Bioaugmentation failures:
 Limited population of microbes.
 Conc. of contaminant is not sufficient to support
growth.
 Environment may contain substances that inhibit
growth.
 Predation by protozoa.
 Microbe use some other substrate in the environment.
 Microbe my not be able to penetrate the soil and get
the contaminant.

19. Bioaugmentation/ stimulation
 Examples:
 Bacteria – Methlosinus trichosporium (degrades
TCE)
 Fungi – Absidia cylindrospora degrade fluorene.
 Cladophialophora sp. degrades BTEX.

20. Ex-situ bioremediation
techniques
 Contaminated soils can be excavated and treated
in above ground or ex situ.
 Solid phase system
 Land Farming
 Compost heaps
 Engineered biopiles
Slurry phase system
Aerated lagoons
low-shear airlift reactor
fluidized bed soil reactor

21. Ex-situ bioremediation techniques
 Solid phase systems:
 It includes organic wastes(leaves, animal manures
and agricultural wastes)and problematic wastes
(domestic and industrial wastes, sewage sludge and
municipal solid wastes)
 Land farming:
 Simplest process
 Mixing of the soil by ploughing or mechanical tilling.
 This increases the o2 level in the soil and distributes
the contaminants more evenly, which increases the
rate of degradation.
 Well suited for shallow soil surface contamination.
 Average half-life for degradation of diesel fuel and
heavy oil is 54 days.

22. Ex-situ bioremediation techniques
 Compost heap:
 Compost materials like straw, bark and wood chips
are mixed with the contaminated soil.
 Piled into heap to maintain the water, air holding
capacity.
 This process increases temp. to 60C and favours
thermophiles.
 Useful for highly contaminated sites.
 E.g. TNT – Phanerochate chrysosporium.
 RDX – Pseudomonas fluorescnes, P. aeruginosa.

23. Ex-situ bioremediation
techniques
 Engineered biopiles:
 Piling up of contaminated soil within a lined area
to prevent leaching.
 The piles are covered with polythene and liquid
nutrients applied to surface.
 Aeration is supplied via network of pipes inserted
in the piles.
 Leachate collected by pipes at the base.
 Useful for limited space.

24. Slurry phase bioremediation
 Contaminated solid material, microbe and water
formulated into slurry and brought to a bioractor.
 It is a triphasic system:
 Water; suspended paniuculate matter; air.
 Aerated lagoons; low-shear airlift ractor and
fluidized bed soil reactor.
 Best for pesticides, petroleum hydrocarbons, pcp,
polychlorophenol, pcbs, coal tars, wood
preserving wastes and so on.

25. Factors affecting slurry phase
bioremediation
 pH – opt. 5.5 – 8.5
 Moisture content
 Temp. 20 – 30 c
 O2
 Aging
 Mixing (mechanical and air mixing)
 Nutrients (N, P and micro)
 Microbial populations
 Reactor operation.