In Situ Thermal Remediation and Principles of Electrical Resistance Heating (ERH)

Transcription

1 In Situ Thermal Remediation and Principles of Electrical Resistance Heating (ERH) Reusing Contaminated Land Conference Session 1C Cleanup Approaches that Work Seattle WA, October 2, 2014 David Fleming (425) CarbonFree Partner

2 TRS ERH Experience - Washington Everett Lake Forest Park Ballard Greenwood Ave Fox Ave Seattle Rainier Valley So Seattle Tacoma Ft. Lewis (4)

3 How Likely is Matrix Diffusion after ERH? Courtesy of Lee Ann Doner & Tom Sale, Colorado State University Fluorescein E into mixed heterogeneity system with low permeability layers Prolonged diffusion of Fluorescein E from low permeability layers occurs

4 Boiling Temperature and Dalton s Law A substance boils when its vapor pressure is equal to the ambient pressure TCE 87 C PCE 121 C TCE/Water 73 C PCE/Water 88 C TCE/Water 2:1 PCE/Water 1:2 Water 100 C What about the vadose zone?

5 In-Situ Steam Generation during ERH Electrode Electrode Zooming in on this region. Low permeability lens Current flowing between electrodes heats soil directly

6 In-Situ Steam Generation during ERH DNAPL Low permeability lens Reductive dehalogenation creates a halo of chloride ions in CVOC hot spots

7 In-Situ Steam Generation during ERH Uniform soils would lead to parallel ERH current lines but soils aren t uniform

8 In-Situ Steam Generation during ERH Low permeability lenses and CVOC hot spots attract current

9 In-Situ Steam Generation during ERH Regions with higher current density heat slightly more quickly. Steam bubbles form more quickly at NAPL due to interfacial tension and reduced boiling temperatures.

10 TRS ERH PROCESS Sand Saturated Zone Groundwater Flow Clay Clay Bedrock

11 TRS ERH ERH PROCESS Electricity is directed into the subsurface area. TRS Power Control Unit

12 TRS ERH ERH PROCESS Electricity is directed into the subsurface area. TRS ERH PROCESS TRS Power Control Unit

13 Brownfield Redevelopment ERH Cleanup Seattle

14 Brownfield Redevelopment ERH Cleanup Seattle Former drycleaner and auto shop Building demolished Sand, gravel, silt and clay Groundwater 8 ft bgs Begin PCE DNAPL - 140,000 µg/l Mass estimate - ~2,000 lbs SFPR contract energy or remedial goal

15 Remedy Selection Seattle 2013 Evaluated SVE unreliable for DNAPL ISCO high soil demand, oxidant costly Excavation and Disposal - $90 to $600/ton ERD timeframe for GW good ERH $71/ton Selected ERH soil and shallow GW ERD interim and deep GW

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17 Brownfield ERH Design Parameters Seattle ,500 sq ft; 4 40 ft bgs; 43,300 yd electrodes w/ co-located VR wells Injection wells Estimated energy 6,640,000 kwh VR airflow 1,490 scfm 9 of mercury Remedial goal 1,000 µg/l PCE in shallow groundwater

18 Permitting - Seattle Utility Power Drop Seattle City Light 29,800V 12,800V step down transformer Air permit PSCAA - 97% efficiency Two 5,000 lb GAC vessels primary, secondary in series 3 rd vessel for backup Wastewater Seattle Metro Discharge Permit LGAC - Sanitary sewer

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20 Brownfield Redevelopment Seattle 2013

21 Brownfield Redevelopment Results Seattle

22 Brownfield Results 2 Months Post ERH Seattle micrograms per liter (ug/l) 70,000 60,000 64,000 50,000 40,000 30,000 20,000 10, ,900 MW-F Before ERH After ERH MW-G12

23 Brownfield Redevelopment Results Seattle days of operations, 100% energy used Mass removed 6x est. or ~12,373 lbs Average >99% reduction PCE in GW Total project cost $71 + $32 = $103/yd 3 ERH saved ~$10M compared to excavation ERD onsite GW and down gradient plume

24 Guaranteed ERH PCE + TCE, Mineral Spirits Under Active Facility - Fox Ave, Seattle Fox Ave Seattle

25 Guaranteed ERH Fox Ave, Seattle 2013

26 Guaranteed ERH Under Active Facility Fox Ave, Seattle 2013 Silt, sand, GW 6 ft bgs, flow 2 ft/day Hydraulic control 26,744 sq ft, variable depths, 42,100 cu yds 158 electrodes co-located with VR wells 12 TMPs - 8 sensors

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28 Guaranteed ERH Under Active Facility Design Parameters - Fox Ave, Seattle 2013 Begin max. TCE + PCE 4,210 mg/kg Remedial goal - <10 mg/kg PCE + TCE Mass estimate 22,500 lb Elevated TOC Vapor treatment economics

29 Permitting - Fox Ave, Seattle Utility Power Drop Seattle City Light 29,800V 12,800V step down transformer Air permit required 98% efficiency - PSCAA 1,500 scfm total flow - 1,000 Thermox (1550⁰F) and 500 scfm GAC Wastewater King County Industrial Waste LGAC - Sanitary sewer Wastewater discharge authorization

30 PCE and TCE mg/kg Guaranteed ERH - PCE + TCE Soil Results Fox Ave, Seattle ,500 4,210 4,000 3,500 3,000 2,500 2,000 1,500 1, GP-86 GP-38 GP-57 1,700 1,169 1, GP-84 GP-77 GP-70A GP-74 GP-42 ERH Sample Location 1.78 GP GP-35 Post-ERH Pre-ERH Pre-ERH Post-ERH

31 PCE+TCE (µg/l) PCE + TCE GW Results - Fox Ave, Seattle ,000 60,000 50,000 40,000 30,000 pre ERH post ERH 20,000 10, % Reduction 99% Reduction 82% Reduction Loading Dock 1st WBZ Main Source 1st WBZ Main Source 2nd WBZ

32 Guaranteed Results - Fox Ave % of design energy used, 126 days Mass removed ~25,000 lb (200 lbs/day) 60% Mineral Spirits, 40% TCE + PCE >99.9% reduction; 65% reduction in PCP Water discharged ~28% to King County TRS $88 + Client $31 = $119/ cu yd Saved owner at least $250K ~90% decline in downgradient concentrations