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), H 2 (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 m 3

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 m 3 –Windrows£110 per m 3

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 m 3

11. Case Study 2 (ex situ) Site –old coking plant site –Grassmoor Lagoons, Derbyshire Contamination –65,000 m 3 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, H 2 O 2 –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 m 3 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 =10 8 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 Receptor Monitoring wells Sentinel well flow

18. In Situ Bioremediation Monitored Natural Attenuation Examples Perchloroethylene (PCE), Trichloroethylene (TCE) –anaerobic dead-end product Vinyl Chloride (VC) –VC degraded aerobically to CO 2 –restricted redox range (Fe III 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) –SO 4 2- reduced to S 2- (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 m 3

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