in-situ bioremediation for contaminated soil

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In-Situ Biomediation

In-Situ Bioremediation for Contaminated SoilPresented by :A.R.M Sharif NawyazMonisha AlamSharmeen Moushumi

Outline Definition Methods Process Descriptions Advantages & Disadvantages Applicability Limitation Cost & Performance Case Study Conclusion & Recommendations

What is In-Situ Bioremediation?

In place, on siteRemediation by Microorganisms

In-situBioremediation

Process of In-Situ BioremediationContaminant intake

Digestion & Metabolism

Non-toxic end products released

Non Toxic End Products- CO2 & H2O (Aerobic) CH4 , SO4 2- etc. (Anaerobic)

In-SituBioremediation

Intrinsic/Natural Attenuation(no site manipulation)Enhanced/Engineered Bioremediation(site & microbial manipulation)BiostimulationBioaugmentationBioventingAir SpargingPhyto-remediationLand FarmingMethods of In-Situ Bioremediation

5

Alteration or manipulation of environmental conditions to enhance microbial growth & activity

Lack of proper condition to survive & growth

Bio-stimulationAddition of adequate nutrients (N, P, S, Ca, Mg etc)Biostimulation

Soil unsaturated zone mostly aerobic O2 required

Modification of Soil Vapor Extraction (SVE)

Low air flow rate

O2 in soil air above 2%

Bioventing processBioventing

Landfarming

Tilling soil, adding fertilizer, surfactants etc.

Bioaugmentation

AdvantagesDisadvantages

Easy & Low costCombines with other technologiesLess Fugitive emission

Public acceptance

Requires long time Contaminant mobility increases, leaching ground water

Less certainty of uniform treatmentComplete destruction, no residualsAdvantages & Disadvantages

Site ConditionsFactors affectingContaminant propertiesRequired Data: Soil properties and contaminants physical & chemical propertiesApplicability

Microorganisms present in soil able to degrade the contaminants Adequacy of Nutrients sufficient N, P, S, Ca, Mg etc. pH- 6 to 8 Temperature optimum 20 C to 30C Moisture Content 40-60% of the field capacity Bioavailability of contaminants to microorganism Oxygen availability for aerobic microorganisms Soil Permeability & Homogenity Organic fraction of soil

Favourable Site Conditions

Sandy soil ,ornic fraction high or low,tunelling/channlling while adding nutrition due to homegeneoutty12

Following properties of contaminants affect applicability: Biodegradability Source Distribution in soil Solubility & sorption coefficient Chemical reactivity VolatilityContaminant Properties

Polyaromatic Hydrocarbons (PAH) Semi Volatile Organic Compounds (SVOCs, TCE & PCE) BTEX (Benzene, Toluene, Ethylene, Xylenes) Petroleum Hydrocarbons (PHC) (Gasoline, diesel, fuel) Pesticides Organic Solvents Wood Preservatives

Treated Contaminants

PAH Biodegradation

PAH as toxic but the end product was nontoxic and ,its kind of modified biodegradation 15

Limited to following site conditions:

Low temperature slows down biodegradation Clay, highly layered, or heterogeneous soil- limiting transfer of oxygen or other electron acceptor

Limited for contaminants:Highly chlorinated organics like PCB heavy metalsinorganic saltBiodegradation resistant, because-Toxic for microorganismMicrobes prefer feeding on other substrateLack of microbes genetic capability to use them as source of Carbon & energy

Limitations

PBs are calitrant16

Operational Limitations:Capacity of bioventing wells decreases with timeProfuse microbial growth-clog the injection wellsCirculation of water-based solutions through soil increases contaminant mobility and necessitate treatment of underlying ground waterLimitations (contd..)

Effective if cleanup achieved in a compatible time frame

Simultaneous treatment of soil & ground water

High efficiency of bioventing combined with SVE.

Remediation time: 1 to several years

Higher MW compounds take longer to degrade

Performance

Less expensive over ex-situ methodsCost depends on: Site condition & ContaminantsLarger site: lower unit costIn-situ bioremediation cost/m3Enhanced bioremediation: $30 to $100Bioventing: $ 79 to $928Phyto-remediation: $147 to $2322

Other process cost/m3In-Situ - SVE: $405-$1275, Solidification/Stabilization: $150-$250Ex-Situ - Biopiles: $130-$260Composting: $370-$442

Cost

Site name & LocationContaminantsCost DurationReduction in Contaminant ConcentrationToronto, CanadaBTEX, TPHApprox. $42/m3Approx. 4 months (1995) 7,000 ppm to

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