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Title: In situ air sparging for bioremediation of groundwater and soils

Abstract

Activities at a former petroleum products depot resulted in the hydrocarbon contamination of soil and groundwater over a 30,000-m{sup 2} area. Site remediation activities consisted of three phases: site-specific characterization and treatability study, pilot-scale testing, and full-scale bioremediation. During Phase 1, a series of site/soil/waste characterizations was undertaken to ascertain the degree of site contamination and to determine soil physical/chemical and microbiological characteristics. Treatability studies were carried out to simulate an air sparging process in laboratory-scale columns. Results indicated 42% mineral oil and grease removal and 94% benzene, toluene, ethylbenzene, and xylenes (BTEX) removal over an 8-week period. The removal rate was higher in the unsaturated zone than in the saturated zone. Phase 2 involved pilot-scale testing over a 550-m{sup 2} area. The radius of influence of the air sparge points was evaluated through measurements of dissolved oxygen concentrations in the groundwater and of groundwater mounding. A full-scale air sparging system (Phase 3) was installed on site and has been operational since early 1994. Physical/chemical and microbiological parameters, and contaminants were analyzed to evaluate the system performance.

Authors:
; ; ; ;  [1]
  1. Biogenie, Inc., Sainte-Foy, Quebec (Canada)
Publication Date:
OSTI Identifier:
467730
Report Number(s):
CONF-950483-
ISBN 1-57477-003-9; TRN: 97:008319
Resource Type:
Conference
Resource Relation:
Conference: 3. international in situ and on-site bioreclamation symposium, San Diego, CA (United States), 24-27 Apr 1995; Other Information: PBD: 1995; Related Information: Is Part Of In situ aeration: Air sparging, bioventing, and related remediation process; Hinchee, R.E. [ed.] [Battelle Memorial Inst., Columbus, OH (United States)]; Miller, R.N. [ed.] [Air Force Center for Environmental Excellence, Brooks AFB, TX (United States)]; Johnson, P.C. [ed.] [Arizona State Univ., Tempe, AZ (United States)]; PB: 630 p.; Bioremediation, Volume 3(2)
Country of Publication:
United States
Language:
English
Subject:
02 PETROLEUM; REMEDIAL ACTION; HYDROCARBONS; BIODEGRADATION; IN-SITU PROCESSING; GAS INJECTION; OIL SPILLS; SITE CHARACTERIZATION; PERFORMANCE TESTING

Citation Formats

Lord, D., Lei, J., Chapdelaine, M.C., Sansregret, J.L., and Cyr, B.. In situ air sparging for bioremediation of groundwater and soils. United States: N. p., 1995. Web.
Lord, D., Lei, J., Chapdelaine, M.C., Sansregret, J.L., & Cyr, B.. In situ air sparging for bioremediation of groundwater and soils. United States.
Lord, D., Lei, J., Chapdelaine, M.C., Sansregret, J.L., and Cyr, B.. Sun . "In situ air sparging for bioremediation of groundwater and soils". United States. doi:.
@article{osti_467730,
title = {In situ air sparging for bioremediation of groundwater and soils},
author = {Lord, D. and Lei, J. and Chapdelaine, M.C. and Sansregret, J.L. and Cyr, B.},
abstractNote = {Activities at a former petroleum products depot resulted in the hydrocarbon contamination of soil and groundwater over a 30,000-m{sup 2} area. Site remediation activities consisted of three phases: site-specific characterization and treatability study, pilot-scale testing, and full-scale bioremediation. During Phase 1, a series of site/soil/waste characterizations was undertaken to ascertain the degree of site contamination and to determine soil physical/chemical and microbiological characteristics. Treatability studies were carried out to simulate an air sparging process in laboratory-scale columns. Results indicated 42% mineral oil and grease removal and 94% benzene, toluene, ethylbenzene, and xylenes (BTEX) removal over an 8-week period. The removal rate was higher in the unsaturated zone than in the saturated zone. Phase 2 involved pilot-scale testing over a 550-m{sup 2} area. The radius of influence of the air sparge points was evaluated through measurements of dissolved oxygen concentrations in the groundwater and of groundwater mounding. A full-scale air sparging system (Phase 3) was installed on site and has been operational since early 1994. Physical/chemical and microbiological parameters, and contaminants were analyzed to evaluate the system performance.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Dec 31 00:00:00 EST 1995},
month = {Sun Dec 31 00:00:00 EST 1995}
}

Conference:
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  • Air sparging has sparked considerable controversy in the remediation industry. Some feel air sparging is a significant advance in remedial technology, whereas others feel that air sparging is a very limited technology. A central question in this debate is the presence (or lack thereof) of groundwater mixing during air sparging. Groundwater mixing is important to overcome the diffusion limitations of sparging caused by air channeling and effectively deliver oxygen for in situ bioremediation. Possible mechanisms of groundwater mixing include physical displacement, capillary interactions of air and water, frictional drag, makeup of evaporative loss, thermal convection, and movement of fines. Physicalmore » groundwater displacement and groundwater movement resulting from capillary pressure gradients are the two most likely and most commonly effective mechanisms. An important question is the relative degree of groundwater mixing during nonsteady-state and steady-state sparging. Evidence indicates that mixing occurs primarily during nonsteady-state air sparging. Because groundwater mixing is important to overcome the diffusion limitations of air sparging, it is important to operate sparging systems to maximize mixing. Field data show that pulsed sparging, which emphasizes the nonsteady-state aspects of air sparging, greatly enhances groundwater mixing.« less
  • Groundwater contamination was discovered at a manufacturing site in New York State. The contamination was due to the use of a burn pit to dispose of waste solvents, primarily toluene and a mixture of chlorinated ethenes. These solvents were partiality absorbed into a sandy fill. Over a period of time, these adsorbed solvents leached into the groundwater and eventually impacted a local wetlands. Of longer term environmental concern was the existence of a municipal water well approximately 1,200 ft downgradient of the site. Air sparging was chosen as the remedial method to address the soil and groundwater contamination on site.more » Air sparging was chosen as a direct volatilization method and as an oxygen source for bioremediation. This case history illustrates the efficacy and limitations of air sparging for in situ bioremediation applications. The purpose of the paper is to discuss the selection, design, and operation of an air sparging/bioremediation system so that a remediation practitioner can adequately evaluate the use of air sparging for in situ bioremediation applications.« less
  • In-situ air sparging is a developing remediation technique that has significant potential for use in VOC-contaminated saturated soils and groundwater. This technique consists of injecting air below the contaminated area to partition the dissolved, sorbed and free phase VOCs into the gas phase and to enhance the aerobic biodegradation of the VOCs. Because of the buoyancy effect, the VOCs in the gas phase are transported by air to the vadose zone where they are removed and subsequently treated by a soil vapor extraction system. Currently, the design, operation, and monitoring of air sparging systems is based mainly on an empiricalmore » approach with limited field experience. Extreme care must be exercised in designing and implementing the air sparging system so that the contaminants are removed efficiently and without adverse effects on the subsurface environment, particularly the spread of the contaminants to the clean areas. The current state of knowledge is inadequate for the design of effective air sparging systems which also prevent the spreading of contaminants into the clean areas. This paper first outlines the fundamentals of air sparging and then presents an overview of previous air sparging field and laboratory investigations. The paper then details a critical assessment of modeling studies which predict contaminant transport during the air sparging process. Finally, the paper outlines an ongoing comprehensive research program that involves developing the most efficient and economical air sparging systems. This research program, which is being conducted at the University of Illinois at Chicago (UIC), includes performing laboratory aquifer simulation tests to characterize the basic mechanisms of air sparging, developing a contaminant transport model to optimize the different design variables in a typical air sparging system, and conducting a field demonstration of the optimal air sparging system. 42 refs., 5 figs., 1 tab.« less
  • Air sparging column experiments were conducted using coarse sand and fine sand subjected to both continuous and pulsed air injection in order to determine the effectiveness of pulsed air injection when compared to continuous air injection. For this study, the soil samples were saturated with a known concentration of benzene solution. Compressed air was then injected into the soil column under pre-selected pressure and flow rates. Three injection regimes were used: continuous air injection, pulsed air injection with a period of two hours, and pulsed air injection with a period of six hours. During testing, benzene concentration profiles were measuredmore » in the soil at different time intervals by sampling pore water from sampling ports and analyzing using gas chromatography (GC). This study demonstrated that pulsed air injection did not offer any appreciable advantages over continuous injection in tests using the coarse sand; however, pulsed air injection led to substantial reductions in system operating time for tests performed in fine sand. Therefore, pulsed air injection systems may lead to more efficient and fiscally attractive remediation programs for the application of in-situ air sparging to finer sandy soils.« less
  • Over 60 years of refining operations have resulted in petroleum hydrocarbon contamination of soil and groundwater at the 74-acre former Golden Eagle Refinery in Carson, California. Successful negotiations with the California Regional Water Quality Control Board (RWQCB)-Los Angeles Region, and the California Department of Toxic Substances Control (DTSC) resulted in the use of a phased approach, separating the soil and groundwater remediation activities. Based on the findings of site assessments conducted to define and characterize the soil and groundwater contamination at the site, remediation of the soil was initiated first. By obtaining agency approval on the soil cleanup, the sitemore » could proceed with development during the groundwater remediation activities. Prior to groundwater remediation, an air sparging pilot test was performed at the site on a highly heterogeneous site consisting of mostly low permeability soils in southern California. This paper how the pilot test was performed, the test results and the accuracy of the results when scaled up to the full operating system.« less