Study of the Treatment of Oily Sludge by Bio-slurry Method
Jing Wang
a
, Yue Ma
b
and Changtao Yue
*c
China University of Petroleum, Beijing, China
Keywords: Bio-slurry, Bacillus, Oily Sludge, Four-Component Analysis.
Abstract: In this manuscript, the bio-slurry method was used to treat oily sludge. Four strains of bacillus were selected
in the laboratory to biodegrade the crude oil in oily sludge. During the reaction, the residual oil rate was
measured regularly, and after the reaction, the degraded crude oil was separated into four components. The
results showed that JZ-2 and JZ-3 were effective in biodegradation. The crude oil degradation rate was 72.5%
and 74.3%, respectively, and the residual oil rate was decreased from 12.55% to below 2%, among which the
degradation rate of saturates was the fastest. It is concluded that the biological treatment of oily sludge can
achieve great results and has the potential of field application.
1 INTRODUCTION
1
The quantity of oily sludge in China is large, the
pollutant composition is complex, and the treatment
is difficult. If it is not handled properly, a large
amount of harmful substances will enter the soil and
groundwater, causing serious environmental
pollution. Oily sludge treatment technology mainly
includes physical method, chemical method and
biological method, among which biological method
is an environmentally friendly and low-cost method
(Gao, 2017;
Wael, 2013). Bio-slurry reactor is a
typical biological treatment technology, which uses
hydrocarbon degrading bacteria to treat oil pollutants
in oily sludge. By controlling various reaction
parameters, it provides the best conditions for the
growth of microorganisms, reduces the reaction time
and improves the reaction efficiency (Giulio, 2010;
Sunita J., 2017; FM, 2004).
In this study, the basic properties of oily sludge
samples were determined first, and then the bio-
slurry method was used to evaluate the crude oil
biodegradability of four strains of Bacillus, seeking
an economical and feasible method for the harmless
treatment of oily sludge.
2 MATERIALS AND
EXPERIMENTAL METHODS
In this study, four strains were screened from the
laboratory, all of which were Bacillus (Kishore,
2007). The strains were numbered JZ-1, JZ-2, JZ-3
and JZ-4 respectively. The oily sludge was collected
from Xinjiang oilfield. The moisture content, pH
value and oil content were measured, and the results
are shown in Table 1.
Table 1: Moisture content, pH value and oil content of oily sludge.
Num-ber
Moist-ure
conte-nt (%)
Aver-age
value (%)
pH value
Aver-age
valu-e
(
%
)
Dry base
oil cont-
ent
(
%
)
Aver-age
valu-e (%)
1 8.68 6.43 7.08
2 8.53 8.64 6.25 6.40 7.29 7.24
3 8.72 6.51 7.34
a
https://orcid.org/0000-0001-8029-7745
b
https://orcid.org/0000-0002-1724-9924
c
https://orcid.org/0000-0001-8438-3878
Wang, J., Ma, Y. and Yue, C.
Study of the Treatment of Oily Sludge by Bio-slurry Method.
DOI: 10.5220/0011218800003443
In Proceedings of the 4th International Conference on Biomedical Engineering and Bioinformatics (ICBEB 2022), pages 501-504
ISBN: 978-989-758-595-1
Copyright
c
2022 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved
501
The experimental device of the bio-slurry reactor
is shown in Figure 1, which is composed of a constant
temperature water bath, a mechanical stirrer, and a
beaker. The experimental steps are as follows: ○,
1
200 g of dried sludge samples were added into 5 1L
beakers, and then adding 400 mL of inorganic salt
medium and the prepared bacterial liquid. ○,
2
T h e
beakers were placed in water baths at a temperature
of 45°C and stir with a stirrer at a speed of 250 rpm.
○,
3
Plastic films were covered on the beakers to
reduce water loss. Distilled water was added to the
beakers and water baths regularly to keep the liquid
level in the beakers basically unchanged. ○,
4
A n
appropriate amount of slurry was taken out every 7
days to measure their oil contents.
Figure 1: Bio-slurry reactor.
The content and composition of residual
petroleum pollutants in the oily sludge after
biodegradation are the main indicators for evaluating
the effect of the bio-slurry method in the treatment of
oily sludge. In this experiment, the gravimetric
method was used to determine the total extracted
organic (TEO) matter of the oily sludge.
Dichloromethane was used as the extraction agent to
carry out soxhlet extraction experiment. According to
the quality reduction of the sample after extraction,
the oil content could be obtained, and then the residual
oil rate of oily sludge could be calculated (Firouz,
2015;
Apourv, 2018; Douglas O., 2017). The
extracted solvent was dried, and then the biodegraded
crude oil was separated into four components to
characterize the biodegradation effect.
3 RESULTS AND DISCUSSION
After 35 days of biological treatment, the oil content
of oily sludge decreased significantly. Figure 2 to
figure 6 show the residual oil rates and degradation
rates of adding JZ-1, JZ-2, JZ-3, JZ-4 and blank
samples of the initial, 7 d, 14 d, 21 d, 28 d and 35 d.
It can be seen from the figures that the residual oil rate
of each sample has been reduced. Among them, JZ-3
had the highest degradation rate and the lowest
residual oil rate, followed by JZ-2 and JZ-1, and JZ-4
had the worst degradation effect, and the blank
sample also has a certain degree of degradation.
0 7 14 21 28 35
0
2
4
6
8
Residual oil rate
Degradation rate
Time /d
Residual oil rate /%
0
10
20
30
40
50
60
70
Degradation rate /%
Figure 2: Residual oil rate and degradation rate of sample
JZ-1.
0 7 14 21 28 35
0
2
4
6
8
Residual oil rate
degradation rate
Time /d
Residual oil rate /%
0
15
30
45
60
75
Degradation rate /%
Figure 3: Residual oil rate and degradation rate of sample
JZ-2.
0 7 14 21 28 35
0
2
4
6
8
Residual oil rate
degradation rate
Time /d
Residual oil rate /%
0
15
30
45
60
75
Degradation rate /%
Figure 4: Residual oil rate and degradation rate of sample
JZ-3.
ICBEB 2022 - The International Conference on Biomedical Engineering and Bioinformatics
502
0 7 14 21 28 35
0
2
4
6
8
Residual oil rate
Degradation rate
Time /d
Residual oil rate /%
0
10
20
30
40
Degradation rate /%
Figure 5: Residual oil rate and degradation rate of sample
JZ-4.
0 7 14 21 28 35
0
2
4
6
8
Residual oil rate
degradation rate
Time /d
Residual oil rate /%
-5
0
5
10
15
20
25
30
Degradation rate /%
Figure 6: Residual oil rate and degradation rate of blank
sample.
It can be seen from Figures 2, 3, and 4 that, the oil
content of samples JZ-1, JZ-2 and JZ-3 have been
greatly reduced in the first 7 days. The oil was
observed, which may have been stripped from the
surface of sediment particles by microorganisms. At
this time, the degradation rates reached 34.7%,
40.3%, and 36.9%, respectively. The oil content also
decreased to a certain extent in the next 14 days, but
the oil content changed less at 21-35 days. This may
be because the oily sludge contained a large amount
of easily degradable organics in the initial stage of
treatment. Under this condition, microorganisms
could quickly use this part of the organics to grow and
reproduce. As time goes by, the content of easy-to-use
nutrients decreased, and a large amount of difficult-
to-degrade organic matter remained, so the
degradation rate slowed down, and the bacterial
concentration also decreased.
The device was operated continuously for 35 days,
and the residual oil rates of the three sludge samples
were reduced to about 2%, which were 2.4%, 1.9%
and 1.8%, respectively. The three bacteria had a good
effect on the degradation of oily sludge, the
degradation rates were 67.4 %, 72.5 % and 74.3 %,
respectively. The results indicated that JZ-3 had the
best effect, the effect of JZ-2 was not much different
from that of JZ-3, and the effect of JZ-1 was relatively
poor.
As can be seen from Figure 6, the residual oil rate
of blank sample also decreases during the reaction
time, which may be that part of the organics in the
slurry is volatile, but it is more likely that the oily
sludge sample contains hydrocarbon-degrading
indigenous microorganisms, which use the residual
oil in the slurry to grow, leading to the reduction of
residual oil rate. The treatment effect of JZ-4 was
better than that of blank sample, and the removal rates
of the two sample were 38.1% and 28.3%
respectively, but the removal rate of JZ-4 was lower
than that of other samples.
saturates
Aromatics Resin
asphaltene
0
15
30
45
60
75
Relative content /%
Crude oil components
initial blank
JZ-1 JZ-2
JZ-3 JZ-4
Figure 7: Changes of crude oil components in oily sludge
before and after biodegradation.
After 35 days of treatment, crude oil components
in all oily sludge samples were separated, and the
results are shown in Figure 7. Comparing with the
initial sample, the relative contents of saturates in
other samples decreased, among which JZ-1, JZ-2 and
JZ-3 samples decreased significantly, reaching 9.3%,
12.5% and 14.0%, respectively. The relative contents
of aromatics and resin increased, which was
equivalent to the changes of saturates in each sample.
This is because the saturates is more easily used by
microorganisms, so the content change is more
obvious compared with other components. However,
due to the relatively low content of asphalt, its content
does not change significantly.
The content changes of each component in oily
sludge are shown in Table 2. After 35 days of
biodegradation, the content of four components in
each sample decreased compared with the four
components in the initial oil sludge, among which the
saturates changed most obviously, and the other three
components also decreased significantly. Among the
samples, JZ-3 had the best biodegradation effect. The
degradation rate of saturates reached 79.8%; the
Study of the Treatment of Oily Sludge by Bio-slurry Method
503
degradation rate of aromatics was 65.5%; the
degradation rate of resin was 57.35%; the degradation
rate of asphalt reached 72.9%. The degradation rates
of JZ-2 were 77.7%, 64.9%, 56.3% and 65.3%,
respectively. The degradation rates of JZ-1 were
71.0 %, 62.3 %, 50.6 % and 58.0 %, respectively. The
degradation rates of JZ-4 were 42.5 %, 32.2 %,
22.7 % and 34.0 %, respectively.
Table 2 SARA analysis results of oil in different sludge samples
Numb-er
Saturate
(g/kg oily
slud
g
e
)
Aromatic
(g/kg oily sludge)
Resin
(g/kg oily
slud
g
e
)
Aspha-ltene
(g/kg oily
slud
g
e
)
Initial 47.70 15.40 7.12 2.18
Blank 32.97 11.70 5.62 1.62
JZ-1 13.36 5.80 3.52 0.92
JZ-2 10.62 5.41 3.11 0.76
JZ-3 9.65 5.31 3.04 0.59
JZ-4 27.41 10.45 5.50 1.44
4 CONCLUSIONS
In this study, four strains of Bacillus were used to
biodegrade oily sludge by the bio-slurry method. The
residual oil rate decreased significantly within the
first 7 days of biodegradation. After 35 days of
biodegradation, the content of the four components of
crude oil in each sample was lower than those in the
initial oily sludge, and the saturates had the most
obvious change. Among them, JZ-2 and JZ-3 had
better effects on crude oil degradation.
The application of biotechnology to the research
of oily sludge treatment will play a positive role in
promoting safe production and sustainable
development of the petroleum industry, creating and
maintaining a healthy ecological environment, which
has important theoretical and practical significance.
ACKNOWLEDGMENTS
This work was financially supported by the high value
utilization technology and demonstration of urban
organic solid waste (SQ2019YFC190052).
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