In-Well Stripping and Two-Phase Extraction Methods. Presenter Mehmet Pehlivan, PG, CHG Bays Environmental Remediation Management

Transcription

1 In-Well Stripping and Two-Phase Extraction Methods Presenter Mehmet Pehlivan, PG, CHG Bays Environmental Remediation Management

2 In-well stripping methods use wells to strip VOCs from groundwater which incorporates water recirculation, air injection, vapor extraction and a vapor treatment unit.

3 VOC Stripping During Two Phase Extraction Table below shows VOC stripping ratio observed during two phase extraction within extraction wells from several pilot tests. Similar stripping rates are also observed in VacCirc Vacuum Driven in-well stripping and recirculation method application TABLE 6. Comparative Analysis of the Test Results TEST 1 Los Angeles TEST 2 Lawndale TEST 3 Los Angeles TEST 4 Yorba Linda TEST 5 Antioch Depth (ft) to Groundwater Extraction Vacuum (inches of W.C.) Vapor Flow (CFM) ~50 ~ Water Flow (gpm) <1.0 6 < Average MTBE Stripping Ratio in the well 92% 47% 80% 74% 98% Average BTEX Stripping Ratio in the well 98% 90% >99% 40% >99% 3

4 Vacuum Driven in-well Stripping and Recirculation System Groundwater recirculated in same wells or two adjacent wells under a moderate to high vacuum/vapor flow. Method requires no moving parts in the subsurface. Water is removed from one zone and released into the next zone using air lift under vacuum. Method strips up to 99 % VOCs from water during removal and re-circulates for further stripping. Method also aerates the recirculated water increasing DO content.

5 VacCirc TM System Specifications The VacCirc System is very simple to install and operate. No moving parts in the recirculation well components. All PVC construction: drop tubes and wells. Very easy to cleanout the wells and drop tubes. The VacCirc System has the following main components: Recirculation wells and monitoring/sampling piezometers Vacuum blower Vapor treatment unit Conveyance piping Extraction/injection wellhead assembly with vapor/water separator Gauges and meters

6 TO VAPOR TREATMENT UNIT REMOVAL TUBE RETURN TUBE RETURN WELLHEAD DETAIL REMOVAL WELL RETURN WELL 6

7 Wellhead Measurements Drop Tube Vacuum Measuring and Vapor Sampling Port Annulus Vacuum Measuring Port Allows annulus and stinger vacuum measurements Allows water level measurements during extraction Allows water sample collection using ½-inch bailer from the extraction well Allows installation of two 1-inch drop tubes for high yielding formations Elbow Connecting the Drop Tube Water Level Measuring, and Water Sampling Port

8 VacCirc TM Applications VacCirc can be applied as a single well, dual well in vertical and slant well pairs and/or two separate vertical well pairs. VacCirc can be applied as a source removal and interim remediation VacCirc can be applied as a final polishing remediation VacCirc can be applied as a barrier to prevent further plume migration and control. VacCirc can be applied to supplement existing SVE system to increase/perform groundwater remediation. VacCirc can be applied with insitu chemical oxidation to enhance chemical delivery, distribution in the subsurface.

9 VacCirc TM Single Well Blower Vapor Treatment Recirculation Well Pairs

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11 Single Well Pilot Test A pilot test was performed using two-phase in-well stripping method. The method involved extracting water from the water table at 100 feet below grade using twophase extraction and reinjecting at the vadose zone at 60 feet below grade using a dual screen/dual well system. Water levels were measured using two piezometers installed in the well annulus. Water samples were collected from these two piezometers to assess effectiveness of in-well stripping and chemical composition of extracted and injected water 11

12 Single Well In-Well Stripping A TYPICAL IN-WELL STRIPPING DATA OBSERVED DURING TWO-PHASE EXTRACTION AND RE-CIRCULATION SAMPLE LOCATION TPH-G (ug/l) Benzene (ug/l) Toluene (ug/l) Ethyl benzene (ug/l) Xylene (ug/l) MTBE (ug/l) TBA (ug/l) POST-EXTRACTION (injection/post stripping) WATER ND<10 PRE-EXTRACTION (pre-stripping) WATER ND<10 % IN-WELL STRIPPING 97% 99% 99% 99% 97% 53% NA The test was performed using a single borehole dual completion well. Water was extracted from 12

13 VacCirc TM Slant Well Pair Blower Vapor Treatment Release Well

14 Dual-Well Schematic Blower Vapor Treatment Water Flow Extraction Well Injection Well

15 VacCirc TM System Layout Vapor Treatment Blower Source Treatment Treatment barrier GW FLOW DIRECTION 15

16 Dual Well Pilot Test REMOVAL TUBE TO VAPOR TREATMENT UNIT A gas station site in New York Separate Extraction Well (EW) and Injection Well (IW) were used Depth to water ~25 ft Total depth of EW and IW is 40 ft. Distance between EW and IW is 35 ft. EXTRACTION WELL WATER TO INJECTION WELL 16

17 Dual Well Pilot Test, EW Wellhead Extraction well head and air/water separation column. Clear 4-inch container was used to measure water flow.

18 Dual Well Pilot Test Info 1 Day Test Over 32 ft ROI for vacuum Response Over 27 ft of ROI for Water Drawdown Extraction Well had over 8 ft. Drawdown Injection Well had over 6 ft. of head 18

19 Calculated Zone of Influence Calculated zone of influence based on distance drawdown and distance head graphs. Considering water flow from High elevation to lower elevation when there is a 6 feet of head in one well and 8 feet of drawdown in the other it is almost imperative that extraction well to capture over 90 % of the injected water.

20 Modeled Zone of Influence A two dimensional analytical model was prepared to evaluate steady state condition of the recirculation cell. Model show that 100% of the injected (release) water is recaptured by the extraction (collection) well. This will make a closed loop treatment cell.

21 Field Zone of Influence Zone of influence of drawdown and water mound based on water level data collected during the pilot test.

22 Dual Well Pilot Test VOC Stripping Sample Location Benzene Ethylbenzene MTBE Toluene Xylene (Total) Extraction Well 670 2, ,700 Injection Well % VOC Stripping 99% 99% 92% 90% 98% 22

23 VacCirc TM System Benefits VacCirc System removes (strips) up to 99 % of the volatiles from groundwater during each recirculation cycle. VacCirc eliminates a need for treatment and disposal of the extracted water and enhances naturally occurring biodegradation. Re-circulates Groundwater multiple times in the contaminated zone and removes up to 99 % of VOCs from groundwater during each cycle. VacCirc may be combined with ISCO, EISB, isoc, UV or Ozone generation system in the subsurface. VacCirc will remove even hard to strip compounds such as 1,4-dioxane after multiple recirculation and stripping cycles. Given that each cycle strips 10% to 20% of 1,4-dioxane, after 10 to 20 recirculation cycles, 60% to 98% of the 1,4-dioxane will be removed.

24 VacCirc TM System Cost The cost estimate varies based on site specific parameters, depth to groundwater, type of contaminant and vapor treatment alternative. Bays Environmental Remediation Management (BERM) will assist with well design and installation, wellhead assembly design and installation for a unit cost of per recirculation cell. BERM will also provide startup assistance for each installation. Please call ext: 102 or send an to mp@baysgrp.net get a site specific evaluation and cost estimate.