MICROBIAL BIOREMEDIATION AND FOOD

SAFETY

Green revolutionIndustrial revolutionBrown fieldsNearly 1,00,000 human made chemicals are added in last 50 yearsApproximately 1000 new chemicals are added every year

Sources of pollution

Farm lands with excess pesticidesand inorganic fertilisersIndustrial pollutantsSpillages, leakages during handling and production or use of industrial materialsMining and oil drillingDisposal sites and dump yards

Bioremediation

Destruction of contaminants by biological mechanisms, including microorganisms (e.g. yeast, fungi or bacteria), and plants.Removal and reduction of man made pollution of environment

Microorganisms in Bioremediation of soil

Bacteria – Achromobacter, Acinetobacter, Alcaligenes, Arthrobacter, Bacillus Fungi - Rhodotorula, Mortierella, Aspergillus and Penicillium.Trichoderma etc.Phenerochaete chrysosporium has wide degradative capacity due to production of lignases which utilize peroxide.

Microbes in BioremediationBACTERIA TAKE UP LARGE AMOUNTS OF METALS AND MINERALS

BACTERIA CONVERT Hg, Cr, Se etc. TO VOLATILE ELEMENTAL FORM BY REDUCTION AND BY CHANGING THEIR OXIDATION STATE

BACTERIA AND ALGAE PRODUCE SECRETIONS THAT ATTRACT METALS THAT ARE TOXIC AT HIGH LEVELS

FUNGI DEGRADE POLYAROMATIC CHEMICALS LIKE LIGNIN

FUNGI METHYLATE As, Se TO GASSEOUS FORM

ALGAE AND PLANTS GOOD IN ABSORBING N, P, S, MINERALS, METALS FROM THE ENVIRONMENT

DEGRADATION OF POLLUTANTS BY MICROBES

METABOLISM OF CONTAMINANT TO

CELL MASS, CARBON DIOXIDE AND WATER - AEROBIC CONDITIONS

CARBON DIOXIDE, METHANE, HYDROGEN TRACES., SULFIDES, NITREOGEN GAS DEPENDING ON PRESENCE OF ELECTRON ACCEPTORS –

ANAEROBIC CONDITIONS

COMETABOLISM OF CONTAMINANT TO

NON TOXIC COMPOUNDS BY ENZYMES PRODUCED WITH METHANE UTILIZATION BY METHYLOTROPHS

MICROBIAL GENES CODE FOR DEGRADATIVE ENZYMES FOR

OXIDATIONREDUCTIONDEHALOGENATIONDEALKYLATIONDEAMINATION HYDROLYSISMETHYLATION ETC.OF THE POLLUTANTS INTONON TOXIC ENDPRODUCTS

METHODS OF BIOREMEDIATION

BIOSTIMULATION

BIOAUGMENTATION

BIOFILTERS

BIOREACTORS

BIOVENTING

COMPOSTING

LAND FARMING

PHYTOREMEDIATION

BIOAUGMENTATION Addition of organisms or enzymes to a material to remove unwanted chemicals

Bioaugmentation is used to remove byproducts from raw materials and potential pollutants from waste.

Bacteria are the most common bioaugmentation organisms.

BIOFILTERS

The removal of organic gases by passing air through compost or soil containing microorganisms capable of degrading the gases.

Used to remove volatile organic compounds (VOC's) from air.

BIOREACTORS

The treatment of a contaminated substance in a large tank containing organisms or enzymes.

Bioreactors are commonly used to remove toxic pollutants from solid waste and soil.

BIOSTIMULATION

The use of nutrients or substrates to stimulate the naturally occurring organisms that can perform bioremediation.

Fertilizer and growth supplements are the common stimulant.

The presence of small amounts of the pollutant can also act as a stimulant by turning on operons for the bioremediation enzymes.

BIOVENTING Involves the venting of oxygen through soil to stimulate the growth of natural and introduced bioremediation organisms.

Used predominantly for soils contaminated with petroleum products.

Not suitable for removing halogenated gases that contribute to ozone layer damage.

COMPOSTING

Mixing contaminated materials with compost containing bioremediation organisms.

The mixture incubates under aerobic and warm conditions.

The resultant compost can be used as a soil augmentation or be placed in a sanitary landfill.

LANDFARMING

The use of farming tilling and soil amendment techniques to encourage the growth of bioremediation organisms in a contaminated area.

Used successfully to remove large petroleum spills in soil.

PHYTOREMEDIATION the use of plants to remove or transform contaminants

Plant hyper-accumulating metals (direct action).Plants stimulating microbes in rhizosphere (indirect action).Microbes in soil with soybean plants mineralised TCE twice as fast as soil without plants

IN-SITU BIOREMEDIATION This involves the use of organisms or enzymes to remove pollutants in the location that is polluted.Cheaper as no excavation, transportation, labourer charges involved.The average time frame for In-situ bioremediation is 12 to 24 months hence needs longer time.Ground water pollution due to contaminant mobility is possible

EX-SITU BIOREMEDIATION This involves the removal of contaminated material where it can be treated using bioremediation.Better control over area, depth, nutrients, oxygen, moisture, temp etc. The average time frame for Ex-situ bioremediation is 60 to 90 days hence faster compared to In situ BioremediationUse of liners prevent ground water pollution Costlier as excavation of soil, transportation, labour cost , Space requirements etc.

FACTORS INFLUENCING BIOREMEDIATIONPresence of microorganims with pollutant degradative capability

Depth, Area, and Concentration of contamination

Soil factors:

Organic matter content and nutrient level

pH and texture of soil

Permeability and water holding capacity

Compettition for oxygen and presence of other electron acceptors

Presence of toxic compounds for microbes

LIMITATIONS IN BIOREMEDIATION

Cleanup goals may not be attained if the soil matrix prohibits contaminant-microorganism contact.  The circulation of water based solutions through the soil may increase contaminant mobility and necessitate treatment of underlying ground water. Preferential colonization by microbes may occur causing clogging of nutrient and water injection wells.

Preferential flow paths may severely decrease contact between injected fluids and contaminants throughout the contaminated zones. The system should not be used for clay, highly layered, or heterogeneous sub-surface environments because of oxygen (or other electron acceptor) transfer imitations.  High concentrations of heavy metals, highly chlorinated organics, long chain hydrocarbons, or inorganic salts are likely to be toxic to microorganisms.  Bioremediation slows at low temperatures.

ENHANCED BIOREMEDIATIONEnhanced bioremediation is a process in which indigenous or inoculated micro-organisms (e.g., fungi, bacteria, and other microbes) degrade (metabolize) organic contaminants found in soil and/or ground water, converting them to innocuous end products. Nutrients, oxygen, or other amendments may be used to enhance bioremediation and contaminant desorption from subsurface materials.

Enzyme based Bioremediation

HCZyme approved by EPA

Contains no bacteria or enzymes

Treatment of Hydrocarbons and

chlorinated hydrocarbons

1 lit Conc. HCZyme per 6 cubic meter of soil per five weeks treatment

costed US $ 15 to 50 per Cubic meter

Helped in removing contaminants

GENETICALLY ENGINEERED MICRO-ORGANISMS

FuelVolatile oranic compoundsSemi volatile organic compoundsPesticidesBioremediation changes valence state of inorganics and cause adsorption, immobilisation to soil particles Pptation, uptake, accumulation and concentration of inorganics in microorganisms & macroorganisms

St. Gabriel Louisiana US plant site Ciba Giegy Corpn

19000 Cubic meter Atrazine contaminated soil in

8 hectares of Biological Clean up unit

LAND FARMING: Ploughing a 4 times a Week

BIOSTIMULATION : 880 Kg fertiliser/H PK(13:13:13)

BIOAUGMENTATION: 2000 L Pseudomonads culture

Initial Atrazine Conc. 100 mg/Kg of soil

After 20 weeks Atrazine conc. 10 mg/Kg of soil

Cost of Bioremediation : US $ 1,050,000

For lifting and dumping : US $ 5,300,000

At waste disposal unit

Soil Degradation Data A three week pilot project was conducted on soil samples extracted from the site. Heterotrophic populations increased from 1,500,000 to 150,000,000 colony forming units (CFU)/gram. Soil concentrations were degraded from 1,543 ppm to 562 ppm.

Three week pilot test data

Soil concentrations

1,543

562

290

0

200

400

600

800

1,000

1,200

1,400

1,600

TP

H, p

pm

Day 0 Day 14 Day 21

Heterotrophic populations

1,900,000

115,000,000

49,000,000

0

20,000,000

40,000,000

60,000,000

80,000,000

100,000,000

120,000,000

Pla

te c

ount

No.

Day 0 Day 14 Day 21

Extended pilot test data

TPH soil concentrations dropped below 100 mg/Kg for a 93.7 % reduction in 50 days

Pilot test data

1,543

562

290390

720

97

0

200

400

600

800

1,000

1,200

1,400

1,600

TP

H, m

g/kg

0 14 21 27 35 50

Successful Bioremediation Programs

Bioremediation was the method of treatment opted to treat 1500 cubic yards of diesel contaminated soil at the former King’s Truck Stop in Sacramento, CA.

The project reduced the diesel contaminant levels from 3000 PPM to less than 30 PPM in approximately 62 treatment days.

In situ bioremediation was necessary to clean up contamination from a ruptured transfer line that led to a loss of 300 to 400 gallons of solvent at a depth of 38 inches beneath the surface along 120 feet of the track.

A continuously recirculating ground injection system was designed and installed to treat the contaminated soil. Following a clean up program of nine months with the bioaugmented system, a 99.5% degradation of the contaminants was achieved ( Table ).

Table

Component 09/24/84 10/31/84

04/04/85

% RED

Chemical (ppb) (ppb) (ppb) (ppb)

Benzene N/A 96 31 67.7

Carbon Tet N/A 65 Nil 99.9

Chlorobenzene

9,050 227 37 99.6

1,1 DCE N/A 508 341 32.9

Ethyl Benzene 154,000 1,119 382 99.8

Toluene 31,000 1.276 526 98.3

111 TCA N/A 82 Nil 99.9

Xylene 1,249,000

16,825 1,979 99.8

N/A – not analyzed for

A bioremediation project involving 32,000 cubic yards of soil contaminated with various lubrication and form oils is indicated that the contamination levels have been reduced from a high of 1800 PPM down to 125 PPM in the most contaminated cell.

In a lesser contaminated cell, the levels have been taken from 1400 PPM down to below the action level of 100 PPM. 

COUNTRIES AND RELATIVE COSTS OF BIOREMEDIATION

USA, UK, BRAZIL, FRANCE, NIGERIA ETC.IN USA – 75000 SITES – 1100 BILLION US $IN EUROPE -495000 SITES- 1000 BILLION US$BIOREMEDIATION COST US $ 52-131/cubic m INCINERATION US $ 327-1046 LAND FILLING US $ 196-327USA BIOREMEDIATION MARKET IS AROUND 10-15 BILLION US $ AND ANNUAL GROWTH RATE IS ABOUT 10-15 % PER YEAR

The microbes will have the last word

Louis PasteurFather of Microbiology