Bioremediation (Biological Remediation Technologies)

1. Bioremediation(Biological Remediation Technologies) • Overview and Principles • Bioremediation Technologies Ex Situ Biopiles Landfarming Bioslurry Reactors In Situ Pump and Treat Bioventing

2. BIOREMEDIATION - Overview and Principles • Aim of Bioremediation? • use biological systems to destroy / modify the chemical components of contaminated soil • Destructive process • organics • inorganics • Contaminants as substrates for microorganisms • Complexity and recalcitrance • concentration and toxicity • Accessibility • natural or anthropogenic • Microbes • Indigenous (habituated, acclimated) • Specific Inocula

3. Overview and Principles • Metabolism • Aerobic • supply of oxygen • Anaerobic • absence of oxygen • alternative electron acceptors • Cometabolism • analogue • non-analogue • Enzymes • specificity • degradative pathways (Tol plasmid) • Biosurfactants

4. Overview and Principles Operational Requirements • Competent Biomass • Pilot Study • Suitable contaminant • petroleum hydrocarbons, solvents, aromatics • Ideal physiological conditions • Temperature • pH, buffering • Nutrients • Oxygen (electron acceptor), H2 (electron donor) • Engineering considerations • complexity of site • in situ, ex situ

5. Overview and Principles • Advantages of Bioremediation • permanent solution • soil structure retained • biomass is self-generating (cheap) • low energy • low-tech (adaptation of agricultural implements) • Cost (relatively cheap) • Limitations • limited range of applications • ground conditions, hydrology • presence of inhibitors, mixed contaminants • Rate of biodegradation • Extent of Biodegradation • simple substrates 98% • complex substrates 50% - 85% (e.g. PAH) • dead-end metabolites • Cost (In-vessel)

6. Ex Situ Bioremediation Biopiles (Engineered Soil Banks, Static Piles) • Pretreatment • oversize removal • homogenisation • amendments • Bed Construction • aeration - pressure or vacuum pipes • drainage channels, porous base • heating • Surface covers and insulation • Control and Monitor • oxygen, water, contaminant, etc. • Dispose of Treated Soil • landfill, site backfill • Costs • £70 - £140 per m3

7. biopiles

8. Ex Situ Bioremediation Landfarming, Windrows (Composting) • Large Areas • Mechanically mixed by Agricultural equipment • Prepared base • drainage galleries • membrane • Bed Construction • 400mm lifts • 2m high windrow • Irrigation • leachate recycle • Covers (sheeting) • Rain protection, heat retention • Costs • Landfarming £60 per m3 • Windrows £110 per m3

9. Landfarming, windrow

10. Case Study 1 (ex situ) • Site • Wood Treatment Facility, USA • Contamination • 15,000 tonnes soil • PAH up to 63,000 mg/kg • Remediation Method • Landfarming • Performance • Total PAH from 700 mg/kg to 155 mg/kg • Benzo(a)pyrene 23mg/kg to 10 mg/kg • Time • 3 to 6 months • Cost • £60 per m3

11. Case Study 2 (ex situ) • Site • old coking plant site • Grassmoor Lagoons, Derbyshire • Contamination • 65,000 m3 sediment / sludge • PAH 10,000 mg/kg • Remediation Method • Biopile • mix with ameliorants (wood chip, mine spoil, peat, fertilizer) • Performance • 80% degradation ( poor for 4 and 5-ring PAH) • Time • 240 days • Cost • not published

12. Ex Situ Bioremediation Bioslurry Reactors • High Solids Biological Stirred Tank Reactors • controlled conditions • Pretreatment • Screening, Soil Washing • biomass development • Biodegradation • few hours aeration • Dewatering • settlement, centrifuges, presses • Time • Hours to days in tank, site time months • Cost • Not well established (medium to high)

13. In Situ Bioremediation Pump and Treat (Biorestoration, Bioslurping) • Nutrients and oxygen added into soil through water abstraction and reinjection • Pure Oxygen , H2O2 • biodegradation in situ • External Treatment • Phase separation • Biofilter (SAF) • degradation ex situ • Requirements • favourable soil and geological conditions • Time • 3 to 48 months • Costs • wide range £5 - £170 per tonne

14. Pump & treat

15. Case Study (in situ) • Site • Petrol Station, Holland • Contamination • Petrol at 1% in soil, 90 mg/l in groundwater • 15,000 m3 soil to a depth 4m • Remediation Method • Pump and Treat • Performance • Acceptable but variable (uneven re-circulation) • Time • 12 months • Cost • 15 - 40% less than landfill

16. In Situ Bioremediation Natural Attenuation • Spontaneous process • mostly biological • BTEX half life (chemical =108 yr , biological = <1 yr) • Long Term • Risk Based Corrective Action (RBCA) • Environmental benefit v. Cost • may be better to address consequences than to treat the source (e.g. borehole contaminants) • Lines of Evidence • Primary (concentration v. time, concentration v. distance) • Secondary (supportive) (DO level, pH, electron acceptors, active microbes)

17. In Situ Bioremediation Monitored Natural Attenuation • Not a Do-Nothing Option • quantify the natural breakdown process • Monitor Plume • position of the 10 ppm threshold Sentinel well Receptor Monitoring wells flow

18. In Situ Bioremediation Monitored Natural Attenuation Examples • Perchloroethylene (PCE) , Trichloroethylene (TCE) • anaerobic dead-end product Vinyl Chloride (VC) • VC degraded aerobically to CO2 • restricted redox range (FeIII will oxidise VC) • sequential reducing / oxidising is best • Addition of reducing agent • molasses (generates reducing conditions) • Chromium (VI) converted to Chromium (III) (Cr(III)hydroxide insoluble) • SO42- reduced to S2- (metal sulphides precipitate)

19. In Situ Bioremediation Bioventing • Enhanced natural biodegradation through air and nutrient supply • vacuum extraction of air • air injection well (with or without vacuum extraction) • air sparging with vacuum extraction • Nutrients • infiltration wells • Vadose zone • extended by lowering water table • Treatment of extracted air • e.g. VOC removal • Time • months to years • Costs • Low £6 - £50 per m3

20. bioventing

21. Others • Phytoremediation • Uptake of metals by plant roots • Individual species of hyperaccumulators for example cadmium and zinc • Mycorrhizal fungi • mobilise contaminants • extracellular enzymes (degrade aromatics) • White rot Fungi • Phanaerochaete sordida • aromatics e.g. PCP, PAH