Multiphase Extraction (MPE):

Transcription

1 Multiphase Extraction (MPE): Remediation Trials in New Zealand 2010 Richard Howard Senior Environmental Scientist URS New Zealand Ltd CHRISTCHURCH

2 2 Contents Background to Multiphase Extraction (MPE) Introduce Mobile MPE Unit BP MPE Trial Case Study Summary Results of 6 MPE trials Potential MPE use in NZ Simon Hunt

3 3 Acknowledgements Scott Purdue and Sarah Schiess (Wellington) Andrew King (Melbourne) Bryan Threadingham (Sydney - Hydrocarbons) Kevin Tearney (Wellington) and Simon Hunt (Auckland)

4 4 Remediation Techniques for Hydrocarbon Contaminated sites Passive Techniques Natural attenuation (NA) Passive LNAPL skimmers / adsorbent socks Insitu Techniques Enhanced NA eg ORC injection, ozone treatment Less intrusive Very Slow Inexpensive $ Active LNAPL skimmers Pump and Treat total fluids / pumping Soil Vapour Extraction (SVE) Dual Phase Extraction Multiphase Extraction (MPE) Air Sparging Thermal Oxidation Ex Situ Techniques Excavation of contaminated soils (Dig and Dump) Land Farming, Bio Piling (Dig and Treat) More intrusive Relatively Fast Very Expensive $$$$

5 5 Multiphase Extraction (MPE) - MPE is an insitu remediation technique - Sometimes called vacuum enhanced remediation, or bio-slurping - Objective is to recover petroleum hydrocarbons present in soil and groundwater - Uses high vacuum (up to -60KPa) to extract 3 hydrocarbon phases simultaneously 1. vapour phase (volatilised), 2. separate phase (LNAPL) (main target for BP / URS) 3. dissolved phase (in groundwater)

6 LNAPL Skimmer - Concept 6 Skimmer Remediate by skimming LNAPL from well and immediate surrounding formation Groundwater level is static Leaking underground storage tank LNAPL Unsaturated Zone Saturated Zone

7 Soil Vapour Extraction (SVE) - Concept 7 SVE Blower (-10KPa) Air and hydrocarbon vapour flow Attacks unsaturated zone Volatilises LNAPL and absorbed soil contamination Groundwater level is static Immobile LNAPL in saturated zone untouched Unsaturated Zone Saturated Zone

8 Pump and Treat - Concept Total Fluids Dual Phase Extraction Enhanced SVE (by dewatering) 8 Treatment Groundwater Skim LNAPL or SVE Unsaturated Zone (De-watered) Saturated Zone Submersible pump

9 9 MPE - Concept Drop tube (Stinger) Extracting Vapour LNAPL Dissolved Phase Vacuum Vessel (-60 KPa) Unsaturated Zone Saturated Zone

10 10 For MPE Need sealed surface for best vacuum effect Need suitable well design and monitoring network

11 11 URS Video Introducing Transpacific s Mobile MPE Unit

12 12

13 Monitoring Equipment 13 Anemometer Air sample pump and Organic Vapour detector Vacuum gauges Oil / Water interface probe Bailer (with LNAPL)

14 Typical MPE Layout 14

15 URS Trials 2010 (for BP) 15 6 sites contaminated with LNAPL across NZ 2-3 day trials using existing monitoring well networks Wide range of land uses - retail fuel sites / commercial sites / industrial sites Wide range of geological profiles - tight silts to alluvial gravels, confined / unconfined, preferential flow pathways Range of contamination petrol / weathered diesel / kerosene, onsite / offsite plumes Range of remediation drivers inhalation risk to properties, offsite discharges, commercial reasons, regulatory drivers

16 16 What did we measure? Mass Removal of Hydrocarbons LNAPL removed (dipping tank) Dissolved phase / Emulsion (TPH concentration x waste volume) Vapour removed (vapour concentration x flow rate) Multiphase Individual rates of vapour and liquid removal at each well Radius of influence i.e hydraulic drawdown and vacuum influence in satellite monitoring wells LNAPL rebound / response to MPE

17 17 Case Study Site A Large closed retail fuel station and truck stop Diesel plume Silty SAND - unconfined 3 wells with between m initial LNAPL thickness MPE 1 well at a time 2-3 hours Then manifold 3 wells for 1 full day

18 Example Results Site A Hydraulic Drawdown Influence 18

19 Example Results Site A Vacuum Influence (unsaturated zone) 19.0m 21.0m 19

20 20 Collecting tank sample for TPH analysis Recording well head vacuum

21 LNAPL response to MPE MW12 21

22 22 Site A Case Summary Total Fluids Extracted Total LNAPL Recovered Total Dissolved Phase / Emulsion Total Vapour Recovered ~15200 Kg ~ 0 Kg ~ 120 Kg ~ 95 Kg TOTAL HYDROCARBON MASS REMOVED ~ More relevant - rates of removal per well 13 Kg / hour dropping to 2 Kg / hour Post MPE LNAPL response reduced to zero after MPE ceased rebounded to original thickness in 24 hours Increased markedly after 2months 215 Kg (approx 270 Litres)

23 23 MPE Summary - 6 Trial sites Site Hydrogeology Contamination A Silty SAND, unconfined Diesel LNAPL, beneath aquifer former filling area B Tight SILT (1.5m), over SAND, concrete lined tank pit, tidal effect. Gravel yard. C Silty SAND, drain backfill Widespread Diesel LNAPL Hydraulic Radius of Influence Vacc Influence HC Mass Removal rate Post MPE LNAPL Response (compared to initial thickness) ~20m 25m Kg /hr V fast rebound to initial thickness in 24 hour. 2 months later marked increase in thickness ~10m (short circuit) ~30m 2.5 Kg / hr 4 months later - 4 wells have significantly reduced thickness ~10m Kg / hr 4 months later - sig reduction in LNAPL thickness 40 Kg / hr 2 weeks later - sig LNAPL reduction in all wells. 3 months later 1m drop in SWL and sig increase in LNAPL thickness initial 0.2m to 0.9m. Inconsistent with normal pattern in Oct. Diesel LNAPL in 2 wells ~20m (along drain in drain backfill backfill) D SILT (2m), over loose Petrol LNAPL beneath sand, over gravel warehouse and in former aquifer tank pit. 32mm wells, ~30m limited - but 20m along known short circuit E Separate Petrol and CLAY (4m), over gravel Kero plumes. Migrated aquifer beneath residential properties. 32mm wells. ~20m none 4 kg / hr 1 month later - sig reduction in all wells form >1.5m down to <5cm Diesel plume migrating beneath residential garden ~35m none Kg / hr 2 weeks later - sig LNAPL reduction in 2/3 wells. Slight increase in 3rd well (still much less than maximum observed). F Pumacious SILT over gravel

24 24 Conclusion : Potential for MPE in NZ Simon Hunt LNAPL recovery trials MPE / SVE Short term MPE Events road trips Emergency Response

25 25 Question Time? Thank you for listening.