Feasibility Test of Applying Complex Remediation Technology for
Organic Contamination in Soil and Groundwater
3*
1
2
1
1
1
Szu-Ping Tseng , Wen-Chi Lai , Ping-Wan Yang , Yi-Cheng Chou , Pao-Wen Liu , Yi-Minh Kuo
1. Department of Safety Health and Environmental Engineering, Chung Hwa University of Medical
Technology, Tainan 71703 , Taiwan
2.
3.
Department of Environmental Engineering, Kun Shan University, Tainan 71003 , Taiwan
Department of Marine Environmental Engineering National Kaohsiung Marine University,
Kaohsiung 81157, Taiwan
*
e-mail: chubibenbi@gmail.com
Abstract
Most gas stations in Taiwan store gasoline and diesel fuel in underground tanks. Storage tanks and
pipeline of gas stations in the early days often fractured to due age or accidents, leading to fuel leakage
which contaminated soil and groundwater. When concentration of contaminants exceed controlled
standard, a remediation procedure for soil and groundwater is necessary. Most remediation of fuel
contaminated soil/groundwater need to be divided into stages and apply 2-6 techniques, thus the initial
installation fee of equipment and operator training fees have increased respectively. Therefore, the
integration of dual phase extraction and advanced oxidation processes is studied, and a complex
remediation technology with market competitiveness, efficiency and feasibility is developed as solution
for current fuel contamination problems in soil and groundwater.
In the current phase of lab research and development, more highly contaminated soil is collected
from a polluted site, and a lab column is used for simulation of contaminated soil behavior. After being
treated with advanced oxidation system, the groundwater with high concentrations of ozone and
oxygen is injected back into the soil to simulate in-situ contamination remediation. The experiment
results show that the total petroleum hydrocarbons in diesel fuel contaminated soil can degrade to 95%
after nine experimental testing processes, and that various indices of the groundwater are below legally
limited levels. Initial results indicate that the complex remediation technology can eliminate most
diesel fuel contaminants within limited time, which may have good removal effect on in-situ diesel fuel
contamination. If further applied in in-situ pilot, the operating parameters of its in-situ application can
be rectified and the potential limiting factors can be examined.
Keywords: advanced oxidation treatment technology, soil column, total petroleum hydrocarbons in
water
A.
Introduction
The 2009 Annual Report of Environmental Protection Administration (EPA) found that the
potential of gas stations’ underground storage tanks contaminating soil and ground water in Taiwan is
very high. According to the statistic data of the Bureau of Energy, Ministry of Economic Affairs, in
November of 2009, there are over 2,600 gas stations in Taiwan. If a gas station has 4 underground
storage tanks, it is calculated that there are at least 10,400 tanks nationwide. If these storage tanks are
to leak fuel and contaminate surrounding soil and groundwater, it will cause severe impact on the
ambient environment and the health of habitants. The amount of gas station announced to be controlled
in 2005-2009 has increased by 61 sites in five years (Fig. 1). Among the major contaminants in soil,
total petroleum hydrocarbons is the most with 42 sites polluted; followed by benzene and p-xylene with
17 and 11 site, respectively. Contaminants in groundwater are mostly benzene and toluene with 44 and
11 sites, respectively [1].
1
Fig. 1 Amount of controlled gas stations in the last five years
The complex technology adopted in this study integrates the dual phase extraction and the
advanced oxidation, which were announced by EPA and included 19 sophisticated techniques applied
worldwide in remediation for fuel contaminated sites [2]. Advantages of the dual phase extraction
include being suitable for soil and groundwater, applicable in field of biology and physics, and able to
eliminate vapor, residual and dissolved phases of contaminants in soil and groundwater polluted by fuel
storage tanks. The advanced oxidation treatment has been commercialized, and is applied in treatment
of various remediations for contaminants in soil and groundwater [3][4][5]. The advanced oxidation
process (AOP) primarily uses substances, such as ‧ OH, O3, KMnO4, H2O2, F2, Cl2, and Br2, as
oxidants for oxidizing gasoline and diesel fuel [3]. As ozone (O3) is highly oxidative and will not cause
second contamination, it is selected for the AOP in this study.
B.
Experimental Materials and Procedure
In order to achieve complete removal in in-situ simulation, this study chose a pollution site,
conducted in-situ hydrogeology tests and site quality investigation, and established am experimental
column similar to the soil environment based on its qualities for testing contaminant removal rate. This
study primarily simulated the dual phase extraction by drawing polluted groundwater, treating the
organic contaminant contained with ozone advanced oxidation process, and sending the effluent
containing ozone residues back to the experimental column to simulate the impact of ozone-containing
effluent on contaminant removal rate in soil and groundwater, as this effluent forms oxygen in soil
layer after being recharged and further increases the oxygen content in soil layer; the equipment is as
shown in Fig. 2. Since this technique is an integrated dual phase extraction as method for drawing
polluted oily water and soil vapor in soil and groundwater, the suitable in-situ conditions should
comply with the basic requirements of dual phase extraction. The experimental methods are as follows:
1.
Experimental method
(1)
Remediation procedure: this study conducts remediation by runs, and a batch is treated every
two days. The primary operation is drawing groundwater and recharging it back after AOP. In
addition, samples of groundwater and 10 g soil are collected every 3 and 7 runs for analysis.
(2)
Contaminant analysis
The contaminants analyzed primarily are total petroleum hydrocarbons in soil and total
hydrocarbons as diesel in groundwater. Furthermore, to understand the effects and status of
in-situ pollution remediation, groundwater D.O. and COD should be measured during each stage
of experiment depending on situations.
i. Total petroleum hydrocarbon, TPH
ii. Total petroleum hydrocarbon of diesel, TPHd
iii. Chemical oxygen demand, COD
2
iv. Groundwater dissolved oxygen (D.O.)
v. Groundwater O3 content
Fig. 2 Illustration of column experiment
C. Results and Discussion
1.
Contaminants in soils at polluted sites
The initial contents of contaminants in soil used to fill the experimental column are as shown in
Table 1. Test results indicate that there are no toluene, p-xylene, ethyl benzene and naphthalene; the
benzene content is 0.02 mg/kg, which is 1/250 of the control amount (5 mg/kg), thus is within
standard. The total petroleum hydrocarbon (TPH) in soil is 1,800 mg/kg, which is 1,000 mg/kg above
control standard. This study further divided TPH into TPH as gasoline and TPH as diesel (TPHd) and
found that the contents contained in the soil are 39.7 mg.kg and 1,760 mg/kg, respectively.
Table 1 Initial contents of contaminants in soil of experimental column
2.
Contaminant
Unit
Test Result
NIEA Test Method
Control Value
TPH
mg/kg
1,800
S703.61B
1,000
TPHd
mg/kg
1,760
S703.61B
--
Benzene
mg/kg
0.02
M711.01C
5
Toluene
mg/kg
<0.0019
M711.01C
500
Xylene
mg/kg
ND
M711.01C
500
Ethylbenzene
mg/kg
<0.0015
M711.01C
250
Naphthalene
mg/kg
<0.01
M711.01C
--
Experimental soil column
The changes in TPHd content of in-situ polluted soil in experimental column are as shown in Fig.
3. The initial concentration of in-situ polluted soil was 1,800 mg/kg, and after process of 15 runs (34
days), it decreased to below legal standard (1,000 mg/kg). The analysis results of TPHd after process of
21 and 27 runs (48 and 62 days) are also below detecting limit (N.D. < 57 mg/kg) with a degradation
rate of approximately 95%. Its GC-FID map is as shown in Fig. 4, and it can be observed that there is
no significant existence of diesel contaminant.
3
2000
1800
1600
TPHd in soil (mg/kg)
1400
1200
1000
800
TPH Standard Of Soil
600
400
200
0
0
10
20
30
40
50
60
70
Treatment Runs
Fig. 3 TPHd changes in soil in experimental column
10
21 runs
8
6
4
mv
2
0
10
8
27 runs
6
4
2
0
0
10
20
30
40
50
minutes
Fig. 4 TPHd content of soil in experimental column and its GC-FID map
3.
(1)
Groundwater experimental column
TPHd content in groundwater
The changes in TPHd content of groundwater are as shown in Fig. 5. It can be observed that, in
the initial processing, the TPHd in the water inclined to increase and did not decease until after
treatment of 30 runs. Compared with the soil TPHd concentration in experimental column, it is found
that the main reason for the removal of TPHd may be because the organic substance in the soil was
directly decomposed by the O3 residue in the water; other small amount soluble organic substances
were removed with the drawing of groundwater. The initial results indicate that, by directly oxidizing
with Os the TPHd in groundwater, its concentration can be below detectable limits after treatment.
20
TPHd in Groundwater (mg/L)
18
16
14
12
TPHd Standard of
Groundwater
10
8
6
4
2
0
0
5
10
15
20
Experimental Runs
4
25
30
35
Fig. 5 TPHd content in groundwater in experimental column
(2)
Chemical oxygen demand (COD) in groundwater
The groundwater COD is analyzed in the experiment as indicator for organic contaminant in the
water. COD results are shown in Fig. 6. The initial COD concentration was 396 mg/L, and after 20 runs
of treatment (48 days), it can be consistent with the 100 mg/L effluent standard regulated in the Water
Pollution Control Act. In addition, the groundwater COD becomes quite stable after 28 runs (67 days);
its value is between 30~20 mg/L with an average of approximately 25 mg/L.
Chemical Oxygen Demand (mg/L)
500
400
300
200
COD Standard of Groundwater
100
0
0
10
20
30
40
50
Experimental Runs
Fig. 6 COD content in groundwater
(3)
Ozone (O3) in groundwater
As shown in Fig. 7, the O3 content in the groundwater extracted from experimental column was
0-0.23 mg/L, with an average of 0.061 mg/L; after advanced oxidation process (AOP), it increased to
0.1-1.7 mg/L, with an average of 0.54 mg/L. Both concentrations are within 95% confidence interval
and have statistic significance (p=0.036). Observing from the trends, the initial O3 content is lower, this
might be because the water had a higher concentration of organic contaminant in the initial stage,
which consumed partial O3 after reaction; but as the concentration of organic substances decreased, the
O3 content becomes stable after 21 runs. This result is consistent with the trend of COD.
1.8
O3 in groundwater
1.6
O3 in treated groundwater
Concentration (mg/L)
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
10
15
20
25
30
35
40
Experimental Runs
Fig. 7 O3 content in groundwater
(4)
Dissolved oxygen (D.O.) in groundwater
The D.O. in extracted groundwater is 2.49-7.69 mg/L, with an average of 4.04 mg/L; after AOP,
5
it increases to above 20.0 mg/L. The D.O. content in groundwater did not show a significant trend, as
shown in Fig. 8. Further, the upper limit of the D.O. meter used in the experiment is 20.0 mg/L, and the
D.O. after AOP exceeds this limit, indicating that the D.O. of the treated groundwater is saturated
because O3 had decomposed into oxygen.
DO in groundwater
DO in treated groundwater
Upper Detection Limit
Concentration (mg/L)
25
20
15
10
5
0
5
10
15
20
25
30
35
Experimental Runs
Fig. 8 D.O. content in groundwater
D. Conclusion
This study used a soil column to simulate the actual pollution of a site, and the complex
remediation technology to treat polluted soil and groundwater. The performance results show a TPHd
degradation rate of above 95% in soil; the groundwater COD data indicate treatment results are within
legal standards. If this can be further applied in in-situ pilot, the operating parameters of its in-situ
application can be rectified and the potential limiting factors can be examined.
E. References
[1]EPA, Executive Yuan, 2009 Annual Report of Soil and Groundwater Pollution Remediation, Soil
and Groundwater Pollution Remediation Fund Management Board, Taipei (2009).
[2]EPA, Executive Yuan, “Manual for Fuel Storage Tank Systems: Selection of Soil and Groundwater
Pollution Remediation Technique, and Essentials and Notes for System Design”, 2006.
[3]Mota, A.L.N., L.F. Albuquerque, L.T.C. Beltrame, O. Chiavone-Filho, A. Machulek Jr., and C.A.O.
Nascimento “Advanced oxidation processes and their application in the petroleum industry: a review, ”
Brazilian Journal of Petroleum and Gas, Vol. 2, No. 3, pp. 122-142 (2008).
[4]Villa, R.D., A.G. Trovo, R.F.P.Nogueira “Soil remediation using a coupled process: soil washing
with surfactant followed by photo-Fenton oxidation, “ Journal of HazarD.O.us Materials, Vol. 174, pp.
770-775 (2010).
[5]Qiang, Zhimin, C. Liu, B. D.O.ng, Y. Zhang, “Degradation mechanism of alachlor during direct
ozonation and O3/H2O2 advanced oxidation process, “ Chemosphere, Vol. 78, pp. 517-526 (2010).
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