BTEX -Contamination and Remediation SEMINAR REPORT BTEX-CONTAMINATION AND REMEDIATION Submitted By MANASY PURUSHOTHAMAN PILLAI Guided By Ms. ANU CHERIAN DEPARTMENT OF CIVIL ENGINEERING MUSALIAR COLLEGE OF ENGINEERING AND TECHNOLOGY PATHANAMTHITTA-689645 2009-2010 Dept Of Civil Engg:, M.C.E.T, Pathanamthitta 1
Submitted By MANASY PURUSHOTHAMAN PILLAI Guided By Ms. ANU CHERIAN DEPARTMENT OF CIVIL ENGINEERING MUSALIAR COLLEGE OF ENGINEERING AND TECHNOLOGY PATHANAMTHITTA-689645 2009-2010
Dept Of Civil Engg:, M.C.E.T, Pathanamthitta
1
BTEX -Contamination and Remediation
ACKNOWLEDGEMENT
I would like to extend my sincere thanks to Mr. A. Shihabudeen Prof & Head of the Department of Civil Engineering, MCET College o
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BTEX -Contamination and Remediation
SEMINAR REPORT
BTEX-CONTAMINATION AND REMEDIATION
Submitted ByMANASY PURUSHOTHAMAN PILLAI
Guided ByMs. ANU CHERIAN
DEPARTMENT OF CIVIL ENGINEERINGMUSALIAR COLLEGE OF ENGINEERING AND TECHNOLOGY
PATHANAMTHITTA-6896452009-2010
Dept Of Civil Engg:, M.C.E.T, Pathanamthitta 1
BTEX -Contamination and Remediation
ACKNOWLEDGEMENT
I would like to extend my sincere thanks to Mr. A. Shihabudeen Prof & Head of the Department of Civil Engineering, MCET College of Engineering and Technology, Pathanamthitta for his cooperation and encouragement.
I express my profound gratitude to Ms. Anu Cherian (Lecturer, department of civil engineering) for her valuable guidance and wholehearted cooperation in preparation of this paper “BTEX- Contamination and remediation”. Without which this seminar would not have seen the light of day.
I am greatful to Mrs. Sreejakunjamma (Advisor) Lecturer, department of civil engineering.
Gracious gratitude to all the faculty of the Civil Engineering department & friends for their valuable advice.
Above all, I thank the Almighty GOD without whose blessing; I would never have been able to complete this work successfully.
Dept Of Civil Engg:, M.C.E.T, Pathanamthitta 2
BTEX -Contamination and Remediation
ABSTRACT
BTEX contamination is a threat to the mankind as well as to animals and plants. Prolonged exposure to the compounds even in small quantities is highly fatal. Due to massive usage of petroleum products, BTEX contamination is considered as one of the major environmental pollution. They are highly toxic and soluble in water and its presence will be significant hazard for all forms of life on earth.
There are different advanced techniques on detections and treatments that have been developed recently. BTEX presence can be alerted to avoid the usage of contaminated water by the public. This paper presents a detailed study on BTEX contamination with effective detection methods like microchip induced laser fluorescence (LIF). The treatment of BTEX contamination has become one of the challenging techniques. The different treatment like in situ chemical oxidation (ISCO) is one of the most well developed and widely used as it needs only relatively short remediation period compared to other methods.
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BTEX -Contamination and Remediation
CONTENTS
LIST OF ABBREVIATIONS
LIST OF FIGURES
LIST OF TABLES
1. INTRODUCTION 1
2. BTEX 3
2.1 COMPONENTS OF BTEX
2.2 BTEX CONTAMINATION
2.3 BTEX HEALTH EFFECTS
3. DETECTION OF BTEX CONTAMINATION 9
3.1 RAMAN DIPSTICK METHOD
3.2 BIOASSAY METHOD
3.3 MICROCHIP INDUCED LASER FLUROSCENCE SENSOR
4. TREATMENT 16
4.1 ORGANOCLAY AND CARBON TREATMENT
4.2 DIRECT PUSH GROUNDWATER CIRCULATION WELLS
4.3 REMEDIATION USING IN SITU CHEMICAL OXIDATION
5. CONCLUSION 23
REFERENCES 24
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BTEX -Contamination and Remediation
LIST OF ABBREVIATIONS
NO ABBREVIATION EXPANSION
1. BTEX Benzene, Toluene, Ethylbenzene, and Xylenes
2. COC Chemical Oxidation Of Carbonates3. DO Dissolved oxygen4. DP-GCW Direct push groundwater circulation well5. EPA Environmental Protection Agency6. GCW Groundwater circulation well 7. ID Inside diameter8. ISCO In situ chemical oxidation9. LIF Laser-Induced Fluorescence10. MCL Maximum Contaminant Levels11. MTBE Methyl tertiary butyl ether12. PAH Polycyclic aromatic hydrocarbons13. PMT Photomultiplier tubes14. PPA Parts per million15. TDO Toluene Dioxygenase Coupling 16. TOSC Technical Outreach Services for
Communities17. TPH Total petroleum hydrocarbons18. UV Ultra violet
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BTEX -Contamination and Remediation
LIST OF FIGURES
Figure Name Page no
1.1 Sources of Groundwater Contamination 1
2.1 Components of BTEX in Gasoline 42.2 Different phases of contamination from a gas 5
Station2.3 Routes Of Pollutant Intake 63.1(a) Portable Raman spectrometer 93.1(b) A simplified diagram of a Raman spectrometer 9
Operation3.2 Schematic diagram of experimental apparatus 124.1 organoclay and carbon treatment 164.2 Typical in-well aeration application 174.3 Typical ISCO Injection 194.4 Injection System Process Flow Diagram 20
LIST OF TABLE
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BTEX -Contamination and Remediation
Table Name Page no
2.1 MCL set by the EPA for each compound in 7
drinking water
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BTEX -Contamination and Remediation
1. INTRODUCTION
1.1 GENERAL
As we plunge into the new millennium our environment is being polluted by
different man made activities. One of the major source of water is the groundwater which
is considered to be consumable without much treatment. There are numerous chemicals
associated with federal, commercial, industrial, and agricultural operations that are
considered hazardous to humans, animals, plants, and the ecological environment.
Groundwater becomes contaminated when hazardous chemicals leak into the ground and
drain through the soil matrix into aquifers. Once they reach the aquifer, chemicals either
float or sink depending on their specific gravity (i.e., whether they are lighter or heavier
than water). Gradually, the chemicals dissolve into groundwater and flow down gradient
to impact additional aquifers, water reservoirs, land, and sea, expanding the risk to human
health and the environment.
Fig1.1 Sources of Groundwater Contamination
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BTEX -Contamination and Remediation
Petroleum has been recognized as a potential environmental contaminant since
shortly after the beginning of the Twentieth Century. Organic compounds can be a major
pollution problem in groundwater. Their presence in water create hazard to public health
and the environment. The term BTEX reflects that benzene, toluene, ethylbenzene and
xylenes are often found together at contaminated sites. Because they are all highly toxic
and soluble in water, they represent a significant hazard for humans.The main source of
BTEX contamination is the leakage of gasoline from faulty and poorly maintained
underground storage tanks. They are considered one of the major causes of
environmental pollution because of widespread occurrences of leakage from underground
petroleum storage tanks and spills at petroleum production wells, refineries, pipelines,
and distribution terminals.
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BTEX -Contamination and Remediation
2. BTEX
2.1 GENERAL
Benzene, Toluene, Ethyl Benzene and Xylene (BTEX) are the volatile
components commonly associated with petroleum products. Benzene, toluene and
xylenes are found naturally in petroleum products like crude oil, diesel fuel and gasoline.
Ethylbenzene is a gasoline and aviation fuel additive. Because of the high concentration
of BTEX compounds in petroleum and the massive use of petroleum products as energy
source, as solvents and in the production of other organic chemicals, their presence in
water creates a hazard to public health and the environment. Contamination of
groundwater with the BTEX compounds is difficult to remedy because these compounds
are relatively soluble in water and can diffuse rapidly once introduced into an aquifer.
2.2 COMPONENTS OF BTEX
BTEX is the abbreviation used for four compounds found in petroleum products.
The compounds are benzene, toluene, ethylbenzene and xylenes. These organic chemicals
make up a significant percentage of petroleum products like crude oil, diesel, gasoline
etc. Ethylbenzene is a gasoline and aviation fuel additive. They are also used extensively
in manufacturing processes. Benzene is used in the production of synthetic materials and
consumer products, such as synthetic rubber, plastics, nylon, insecticides and paints.
Toluene is used as a solvent for paints, coatings, gums, oils and resins. Ethylbenzene
may be present in consumer products such as paints, inks, plastics and pesticides.
Xylenes are used as a solvent in printing, rubber and leather industries.
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BTEX -Contamination and Remediation
The BTEX chemicals are present in a standard gasoline blend in approximately
18%(w/w), and the group is considered to be the largest one that is related to any health
hazards.
Fig. 2.1 Components of BTEX in Gasoline
(Source: Publication of hazardous substance research centers, TOSC publications)
Naphthalenes make up only 1%(w/w) of gasoline. Benzene, which is recognized
as the most toxic compound among BTEX, represents 11%, toluene represents 26%,
ethylbenzene 11% and xylene 52% of the total BTEX fraction in gasoline.
2.3 BTEX CONTAMINATION
BTEX contamination of soil and groundwater can occur by the accidental spill of
gasoline, diesel fuel and leakage from underground storage tanks in pumping stations.
Once released to the environment, BTEX can volatilize, dissolve, attach to soil particles
or degrade biologically. Volatilization occurs when chemicals evaporate, allowing them
to move from a liquid into the air. Volatilization of the BTEX components of gasoline
commonly occurs when you pump gasoline into your car, and is responsible for the
characteristic odour. This phenomenon can also occur within the air pockets present in
soils. BTEX can also dissolve into water, allowing it to move in the groundwater.
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BTEX -Contamination and Remediation
Since BTEX can "stick" to soil particles, these chemicals move slower than the
groundwater. BTEX can also dissolve into water, allowing it to move in the ground
water. Because of their polarity and very soluble characteristics, BTEX will be able to
enter the soil and groundwater systems and cause serious pollution problems. If oxygen is
present in sufficient quantities, BTEX can also degrade biologically, though very slowly.
Fig. 2.2 Different phases of contamination from a gas station
(Source: Publication of hazardous substance research centers, TOSC publications)
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BTEX -Contamination and Remediation
2.4 BTEX HEALTH EFFECTS
Exposure to BTEX can occur by ingestion, inhalation or absorption through the
skin. Inhalation of BTEX can occur while pumping gasoline or while showering or
bathing with contaminated water. Absorption of these chemicals can occur by spilling
gasoline onto one's skin or by bathing in contaminated water. Acute exposures to high
levels of gasoline and its BTEX components have been associated with skin and sensory
irritation, central nervous system depression and effects on the respiratory system.
Fig 2.3 Routes Of Pollutant Intake
(Source: Publication of hazardous substance research centers, TOSC publications)
These levels are not likely to be achievable from drinking contaminated water, but
are more likely from occupational exposures. Prolonged exposure to these compounds
causes the kidney, liver and blood systems disorder. According to the U.S. Environmental
Protection Agency (U.S. EPA), there is sufficient evidence from both human and animal
studies to believe that benzene is a human carcinogen. Workers exposed to high levels of
benzene in occupational settings were found to have an increase incidence in leukaemia.
2.5 BTEX REGULATIONS
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BTEX -Contamination and Remediation
The U.S. EPA has established permissible levels for chemical contaminants in
drinking water supplied by public water systems. These levels are called Maximum
Contaminant Levels (MCLs). To derive these MCLs, the US EPA uses a number of
conservative assumptions, thereby ensuring adequate protection of the public. The MCL
is set so that a lifetime exposure to the contaminant at the MCL concentration would
result in no more than 1 to 100 (depending on the chemical) excess cases of cancer per
million people exposed.
Table2.1 MCL set by the EPA for each compound in drinking water
(Source: Publication of hazardous substance research centers, TOSC publications)
Dept Of Civil Engg:, M.C.E.T, Pathanamthitta 14
ChemicalMCL
(mg/liter or ppm)benzene 0.005
toluene 1
ethylbenzene 0.7
xylene (total) 10
BTEX -Contamination and Remediation
2.6 REDUCING EXPOSURE TO BTEX
The U.S. EPA recommends that exposure to BTEX be
minimized. To avoid or reduce exposure to BTEX, people should use water supplies
having concentrations of these compounds that are below the MCL or apply appropriate
water treatment or filtration systems. If necessary, short-term reductions in exposure may
be accomplished by using bottled water for food and beverage preparation and avoiding
bathing or showering with the contaminated water. With in-home treatment processes,
such as activated charcoal filtration, it is usually possible to remove sufficient BTEX
from water to meet the MCL and thereby minimize health risks. If benzene is present
above the MCL, treatment should be applied to all household water because of inhalation
hazards.
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BTEX -Contamination and Remediation
3. DETECTION OF BTEX CONTAMINATION
Since the BTEX compounds are very toxic to humans and aquatic life, their
sensitive and rapid determination is of critical importance. There are many established
methods for determining BTEX contaminants in water, namely liquid-liquid extraction,
solid phase extraction, gas chromatography, air stripping etc. But these methods exhibit
high levels of sensitivity and selectivity. So they require well-trained personnel for its
successful operation. If a small error occurs during sampling, the analytical result
obtained using the best instrument will be inevitably wrong. Most existing methods for
detecting BTEX are time-consuming, complicated and very expensive for routine
screening. Also these methods require skill for its operation. There has been a lot of
development in this area recently and many advanced techniques for the detection of
BTEX contaminations have been developed. The use of lasers and optic fibers are some
among them.
Some advanced techniques of detection of BTEX contamination are:
1. Raman Dipstick method
2. Bioassay method
3. Detection using Microchip Induced Fluorescence Sensor
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BTEX -Contamination and Remediation
3.1 RAMAN DIPSTICK METHOD
Raman dipstick method is the detection of BTEX contamination using long path
length fiber optic Raman dipstick. Determination of BTEX components via optical
remote sensing is attractive because eliminates many of the problems in other established
methods. Samples are interrogated through the long-path length ‘dip-stick’. It is directly
inserted into the liquid of interest or an extension hose is attached to the end of the ‘dip-
stick’, providing a low profile and more flexible means of sample interrogation.
Fig3.1 (a) Portable Raman spectrometer Fig3.1 (b) A simplified diagram of a
Raman spectrometer’s operation
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BTEX -Contamination and Remediation
Fiber-optic spectroscopic techniques used for detection include visible
absorption, infrared absorption, fluorescence and Raman spectroscopy. Of these
techniques, Raman spectroscopy is particularly better method for detecting BTEX
analytes in water because it offers a high degree of selectivity and is compatible with
aqueous matrices. Even though this method is very simple and cheaper, practically a lot
of problems are there. Turbidity of the sample could block collection of Raman scattering
from the sample. Also the presence of interfering compounds can lead to diminished
sensitivity. If the interfering compounds are fluorescent it will mask Raman signals.
3.2 BIOASSAY METHOD
Bioassays are typically conducted to measure the effects of a substance
on a living organism. Bioassays may be qualitative or quantitative. This is a quantitative
bioassay using Pseudomonas putida F1, which has been well characterized genetically
and possesses a diverse metabolism of aromatic compounds. Detection of BTEX
compounds using Toluene Dioxygenase peroxide coupling reaction is called bioassay
method. It is simple, sensitive, whole-cell-based bioassay system for detection of bio-
available BTEX compounds based on a method developed for screening of oxygenase
activity. Pseudomonas putida F1 is known to express TDO capable of oxidizing
compounds i.e., it is involved in the conversion of aromatic compounds to their
corresponding catechols. As pseudomonas putida is capable of both monooxygenation
and Dioxygenase reactions a screening of oxygenase is provided using whole cell system.
This bioassay system requires no sophisticated instruments and exquisite techniques. The
bioassay has long term storage stability so that it can be used for field monitoring of
BTEX compounds and its tracking in contaminated water. The convenience of multiple
sample-handling makes this whole cell assay an attractive method to be developed as a
field diagnostic method for on-site BTEX contamination. The main disadvantage of this
method is that pseudomonas putida doesn’t oxidize xylene and ethylbenzene.