1、FIELD STUDIES OF BTEX AND MTBE INTRINSIC BIOREMEDIATION H aith and Envir mental Scie Publication Number 4654 October 1997 s Department American Petroleum Q Institute American Petroleum Institute Environmental, Health, and Safety Mission and Guiding Principles MISSION The members of the American Peml
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3、 and others to develop and to use natural resources in an envimnmentally sound manner while protecting the health and safety of our employees and the public. To meet these responsbiZities, API members pledge to manage our businesses according to the following principles using sound science to pnorin
4、ze rish and to implement cost-effective management practices: 0 To recognize and to respond to comunity concerns about our raw materiais, products and operations. PRINCIPLES o To operate our plants and facilities, and to handle our raw materiais and products in a manner that protects the environment
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7、ources and to conserve those resources by using energy efficiently. 0 To extend knowledge by conducting or supporting research on the safety, health and environmental effects of our raw materiais, products, processes and waste materiais. o To commit to reduce overail emission and waste generation. o
8、 To work with others to resolve problems created by handling and disposai of hazardous substances from our operations. o To participate with government and others in creating responsible laws, regulations and standards to safeguard the community, workplace and environment. o To promote these princip
9、les and practices by sharing experiences and offering assistance to others who produce, handle, use, transport or dispose of similar raw materiais, petroleum products and wastes. STD.API/PETRO PUBL 4b54-ENGL 1997 = 0732290 05712bli 73T I Field Studies of BTEX and MTBE Intrinsic Bioremediation Health
10、 and Environmental Sciences Department API PUBLICATION NUMBER 4654 PREPARED UNDER CONTRACT BY: ROBERT C. BORDEN, ROBERT A. DANIEL, NORTH CAROLINA STATE UNIVERSITY AND LOUIS E. LEBRUN, IV DEPARTMENT OF CIVIL ENGINEERING OCTOBER 1997 American Petroleum Institute FOREWORD API PUBLICATIONS NECESSARILY A
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14、 electronic, mechanical, phorocopying, recording, or otherwise. without prior written permission from the publisher Contact the publisher, API Publishing Services, 1220 L Street, N. U!, Washington, D.C. 20005. Copyright Q 1997 American Pemleum Institute iii ACKNOWLEDGMENTS THE FOLLOWING PEOPLE ARE R
15、ECOGNIZED FOR THEIR CONTRIBUTIONS OF TIME AND EXPERTISE DURING THIS STUDY AND IN THE PREPARATION OF THIS WORE Bruce Bauman, Health and Environmentai Sciences Department RS OF THF, SOIL ethylbenzene; toluene; o-, m-, and p-xylene; and methyl tert- butyl ether. A rural North Carolina underground stora
16、ge tank release site was selected for study. The site was insumented with more than 50 observation wells monitored for several years to allow quantitative characterization of the downgradient mass transport of the dissolved compounds. Companion laboratory and modeling studies were conducted to facil
17、itate interpretation of the field data. Three dimensional field monitoring of the dissolved gasoline plume showed rapid decay of toluene and ethylbenzene during downgradient transport with slower decay of xylenes, benzene, and MTBE under mixed aerobic-denitrifying conditions. Background dissolved ox
18、ygen concentrations range from 7 to 8 ma, and nitrate concentrations range from 7 to 17 mgL as Nitrogen (N) because of extensive fertilization of fields surrounding the spill. Sampling results indicate that the plume is not growing and has reached a pseudo-steady-state. Field-scale decay rates were
19、determined by estimating the mass flux of contaminants across four plume cross-sections. First-order decay rates for all compounds were highest near the source and lower farther downgradient. Effective fmt-order decay rates vaned from O to 0.0010 d“ for MTBE; 0.0006 to 0.0014 d- for benzene; 0.0005
20、to 0.0063 d- for toluene; 0.0008 to 0.0058 d- for ethylbenzene; 0.0012 to 0.0035 6 form-, p-xylene; and 0.0007 to 0.0017 d- for o-xylene. In a companion study, laboratory microcosm studies confirmed MTBE biodegradation under aerobic conditions; however, the extent of biodegradation was limited. STD.
21、API/PETRO PUBL 4h54-ENGL 1997 0732270 05712bB 385 R BIOPLUME II and a 3-D analytical model were evaluated for thek, abiity to simulate the transport and biodegradation of MTBE and BTEX at the site. Neither model could accurately simulate contaminant concentrations throughout the length of the plume.
22、 . STD-API/PETRO PUBL 4h54-ENGL L797 0732270 057LZb7 2LL m TABLE OF CONTENTS ChaDter m EXECUTIVE SUMMARY e5-1 1 . INTRODUCTION . 1-1 1.1. INTRODUCTION . 1-1 1.2. BTEX BIODEGRADATION 1-1 1.3. MTBE BIODEGRADATION . 1-4 1.4. RESEARCH OBJECIIVES 1-5 2 . SITE DESCRIPTION 2-1 2.1. BACKGROUND . 2-1 2.2. GE
23、OLOGIC SETI?NG . 2-4 2.3. SlTE HYDROGEOLOGY 2-4 ANALYTICAL AND FIELD METHODS . 3-1 3 . 3.1. MONITORING WELL CONSTRUCTION . 3-1 3.2. MONITORING WELL LOCATIONS . 3-1 3.3. GROUNDWATER SAMPLING . 3-3 3.4. LABORATORY ANALYTICAL METHODS . 3-5 4 . SPATIAL DISTRIBUTION OF BTEX AND INDICATOR PARAMETERS 4-1 4
24、.1. GEOCHEMICAL INDICATOR PARAMETERS . 4. 1 4.2. VARIATION OF BTEX WITH TIME 4-2 4.3. HORIZONTAL AND VERTICAL DISTRIBUTION OF CHLOF2DE. OXYGEN. “TRATE. AND INORGANIC CARBON . 4-4 4.4. HORIZONTAL AND VERTICAL DISTRIBUTION OF MTBE AND BTEX . 4-11 4.5. DISCUSSION OF FELD MONITORING RESULTS 4-19 5 . MAS
25、S FLUX ESTIMATION OF CONTAMINANT DEGRADATION RATES 5-1 5.1. MASS FLUX ESTIMATION 5-1 5.2. VARIATION IN MTBE AND BTEX MASS FLUX WITH TIME 5-4 . STD.APE/PETRO PUBL 4b54-ENGL 1977 0732270 0573270 T33 5.3. VARIATION IN MTBE AND BTEX MASS FLUX WITH DISTANCE 5-8 5.4. DISCUSSION OF MASS FLUX RESULTS 5-15 6
26、 . MODELING STUDIES . 6-1 6.1. MODEL DESCRIPTIONS 6. 1 6.2. SIMULATION OFMTBE TRANSPORT AND BIODEGRADATION . 6-3 6.2.1. BIOPLUME II Results . 6-3 6.2.2. 3-D Analytical Solution 6.2.3. Comparison of MTBE Simulation Results . 6-8 Results Using Bioplume II And The 3-D Analytical Solution . 6-11 6.3. SI
27、MULATION OF BTEX TRANSPORT AND BIODEGRADATION . 6-11 6.3.1. BIOPLUME II Results For 6.3.2. 3-D Analytical Solution Results For Total BTEX And Individual Compounds . 6. 14 Total BTEX . 6-11 6.4. MODEL COMPARISON 6-16 SUMMARY AND CONCLUSIONS 7-1 REFERENCES R- 1 7 . APPENDICES A . B . C . D . HYDROGEOL
28、OGIC DATA A-1 FIELD SAMPLING DATA B-1 MODELING WITH BIOPLUME II . C-1 MODELING WITH THE ANALYTICAL SOLUTION . D- 1 - - _ - _ STD-APIIPETRO PUBL 4b54-ENGL 1997 S 0732290 0573273 7T II LIST OF FIGURES Fipure ES-1. 2-1. 2-2. 2-3. 3-1. 4-1. 4-2. 4-3. 4-4. 4-5. 4-6. 4-7. 4-8. 4-9. Schematic Representatio
29、n of Part of the Sites Monitoring Well ES-3 Site Map Showing Major Features, Monitoring Well Locations, and Approximate Horizontal Plume Centerline (A-A) . 2-2 Cross Section along Line A-A from Figure 2-1 Showing Screened intervals and Approximate Vertical Plume Centerline (B-B).2-3 MTBE Breakthroug
30、h at the Most Downgradient Wells for Various Groundwater Velocities 2-7 Monitoring Well Location Map . 3-2 Variation in Totai BTEX Concentration with Time and Water Table Elevation in (A) MW-3s and in (B) MW-1 lm and MW-12m (Julian Day O = 1/1/92) 4-3 Variation in MTBE and BTEX Components with Time
31、in MW-17m April 1,1995, Chloride Concentration Distribution (mg/L): Plan and Profile Views 4-6 April 1,1995, Dissolved Oxygen Concentration Distribution (mgL): Plan and Profile Views 7 April 1,1995, Nitrate Concentration April 1,1995, Carbon Dioxide Concentration Distribution (ma): Plan and Profile
32、Views 4-9 April 1,1995, MTBE Concentration Distribution (pg/L): Plan and Profile Views . 4-12 April 1,1995, Benzene Concentration April 1,1995, Toluene Concentration (Julian Day O = 1/1/92) . 4-5 Distribution (mg/L): Plan and Profile Views 4-8 Distribution (I 1995, Ethylbenzene Concentration April 1
33、,1995, m-, p-Xylene Concentration Distribution (pgL): Plan and Profile Views . 4-16 Apni 1,1995, o-Xylene Concentration Disribution (pg/L): Plan and Profile Views . 4-17 Proportion of BTEX Compounds in Each Cross Section of the Most Contaminated Well for the Apni 1995 Sampling Event . 4-20 Theissen
34、Polygon Plot for Cross-Section B Showing Ten Polygons Used to Calculate Contaminant Mass Flux . 5-3 MTBE, Benzene, Toluene, Ethylbenzene, m-, p-Xylene, and (2) the type and amount of electron acceptors present (e.g., oxygen, nitrate, ferric iron, and sulfate); (3) the quantity and quality of nutrien
35、ts; (4) temperature; (5) pH; and (6) oxidation-reduction potential. If aerobic conditions exist in an aquifer, oxygen will be utilized as an electron acceptor for hydrocarbon biodegradation. Oxygen is a Co-substrate for the initiation of hydrocarbon metabolism and is the preferred electron acceptor
36、because microbes gain the most energy from aerobic reactions. Numerous studies have shown the BTEX compounds are readily biodegradable in the presence of excess oxygen (Jamison et al., 1975; Gibson and Subramanian, 1984; Barker et al., 1987; Wilson et al., 1986; Alvarez and Vogel, 199 i), and many o
37、ther studies have documented BTEX biodegradation with other electron acceptors (Le., anaerobic ES- 1 STD.API/PETRO PUBL 4b54-ENGL 1997 0732290 0571275 515 biodegradation), including nitrate (Hutchins et al., 199 1 b; Krumholz et al., 1996). There are a few well-documented cases of MTBE biodegradatio
38、n in the literature, Lee (1 986), Jensen and hin (1 990), Suflita and Mormile (1 993), Salanitro et al. (1 994), Yeh and Novak (1 994), Barker et al. (1 990), Hubbard et al. (1 994). These studies show that while MTBE can be biodegraded under certain conditions, biodegradation will often be slow and
39、 may only occur under specific environmental conditions. OBJECTIVES The overall objective of this project was to examine the effectiveness of intrinsic bioremediation in controlling the migration of dissolved benzene; ethylbenzene; toluene; o-, m-, and p-xylene; and methyl tert-butyl ether released
40、from a gasoline spill in Sampson County, N.C. Intrinsic bioremediation is a corrective action technology involving careful characterization and monitoring of the transport of dissolved plume constituents, and documentation of their mass loss due to biodegradation by the naturally occurring bacteria
41、at a site - without attempting to enhance the biodegradation rate (e.g., by adding nutrients or oxygen). This technique may be used alone to contain small releases or in combination with other remediation techniques to complete aquifer restoration. A gasoline release field site was selected, an exte
42、nsive monitoring well network installed, and the site was monitored for more than three years to allow calculation of “real world” in situ biodegradation rates. Using aquifer materials from this site, laboratory microcosm experiments were performed to further characterize the biodegradation of BTEX
43、and MTBE under ambient, in situ conditions. Finally, groundwater modeling studies were conducted to facilitate the interpretation of field data, and to evaluate various approaches for predicting the fate and transport of these gasoline constituents in the subsurface (Borden et al., 1 997). ES-2 SITE
44、 CHARACTERTSTICS A mai underground storage tank (UST) release site in the Coastal Plain of North Carolina was selected for study. The USTs had been removed along with some contaminated soil in the late 1980s. A detailed field characterization of the site was performed to clearly delineate the periph
45、ery of the dissolved plume emanating from the remaining residual gasoline present at and below the water table, and to identi hydrologic or geochemical conditions that might influence the rate of biodegradation, The site was instrumented with more than 50 multi-level observation wells, including fou
46、r monitoring well transects each established perpendicular to the direction of groundwater flow (Figure E-1). Each transect contained up to five or six monitoring well clusters, and each of the clusters contained three wells to allow sampling at the water table, at the bottom of the aquifer, and at
47、a point midway between. One transect was located through the source area, and the three others were established at 36 m, 88 m, and 177 m downgradient from the source. Wells at the site were sampled on a regular basis for more than three years. The mass flux of BTEX and MTBE moving through the plane
48、of each transect could then be determined, which allowed quantitative characterization of the downgradient mass transport of these dissolved compounds 0.0010 d = 0.1% mass loss of that compound per day MODELING BIOPLUME II and a 3-D analytical model (Dominico, 1987) were evaluated for their ability
49、to simulate the transport and biodegradation of MTBE and BTEX in the shallow aquifer. in both models, MTBE biodegradation was represented by a constant first-order decay rate. As a consequence, predicted MTBE distributions using both models were very similar. Both models provided reasonable predictions of MTBE concentrations in the middle of the plume but significantly underestimated concentrations at the most downgradient wells. The poor match between predicted and observed concentrations at the most downgradient wells is primarily
