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Biodegradation of 2 4-dinitrophenol under denitrification conditions.

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ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING
Asia-Pac. J. Chem. Eng. 2010; 5: 919–924
Published online 17 December 2009 in Wiley Online Library
(wileyonlinelibrary.com) DOI:10.1002/apj.416
Short Communication
Biodegradation of 2,4-dinitrophenol under denitrification
conditions
Jian-Hang Zhu* and X.i-Luan Yan
Key Laboratory of Poyang Lake Ecology and Bio-Resource Utilization of Ministry of Education, Department of Chemical Engineering, School of
Environmental and Chemical Engineering, Nanchang University, Nanchang, Jiangxi 330029, China
Received 19 August 2009; Revised 2 November 2009; Accepted 2 November 2009
ABSTRACT: Nitrophenols are often found in industrial wastewaters for a wide range of processes; they are highly
toxic and potentially carcinogenic. Anaerobic biodegradation of nitrophenols has advantages of relatively low cost, less
sludge produced, and high efficiency, when compared with aerobic biodegradation and physical/chemical treatments,
although available published results are often contradictory. This paper reports on 2,4-dinitrophenol biodegradation in
an anaerobic bioreactor operated in a continuous mode in order to determine optimal operating conditions, and the
effects of the main operating parameters such as hydraulic retention time and chemical oxygen demand (COD) loading
on the process efficiency.
In this study, an 80-day gradual enrichment of an anaerobic culture has been carried out at 25 ◦ C in an anaerobic
bioreactor for continuously treating a synthetic wastewater containing 210 mg/l 2,4-dinitrophenol and 100 mg/l nitrate.
The results showed that the enriched culture could utilize 2,4-dinitrophenol as a sole electron donor and nitrate as
an electron acceptor at the end of the enrichment (on Day 80). Almost all nitrate and 95.5% 2,4-dinitrophenol could
be simultaneously removed at a hydraulic retention time of 12 h in the anaerobic bioreactor. The removal of 1 g of
the added nitrate required about 4.60 g COD (as provided by the 2,4-dinitrophenol) as the electron donor, and the
removal of 2,4-dinitrophenol by this enriched culture was strongly dependent on the presence of nitrate.  2009 Curtin
University of Technology and John Wiley & Sons, Ltd.
KEYWORDS: 2,4-dinitrophenol; denitrification; simultaneous removal; anaerobic bioreactor
INTRODUCTION
Nitrophenols, identified as highly toxic and potentially carcinogenic pollutants, have become increasingly abundant in some raw wastewaters from industrial
sources, such as steel, plastic, pharmaceutical, textiles,
and petroleum refinery.[1] The U.S. Environmental Protection Agency has listed 2-nitrophenol, 4-nitrophenol,
and 2,4-dinitrophenol as ‘Priority Pollutants’ and recommended restricting their concentrations in natural
waters less than 10 ng/l.[2]
Anaerobic biodegradation of nitrophenols attracts
more attention due to its low cost, little sludge, as
well as high efficiency, when compared with aerobic
biodegradation and physical/chemical treatments.[3 – 7]
However, the results of previous biodegradation of
nitrophenols in anaerobic systems were different and
even contrary. Some works have shown that nitrophenols are not easily biodegraded under anaerobic
*Correspondence to: Jian-Hang Zhu, Key Laboratory of Poyang
Lake Ecology and Bio-Resource Utilization of Ministry of Education, Department of Chemical Engineering, School of Environmental
and Chemical Engineering, Nanchang University, Nanchang, Jiangxi
330029, China. E-mail: envzjh@ncu.edu.cn
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
conditions and inhibitory to micro-organisms at high
concentrations,[3 – 6] while other studies have shown that
nitrophenols could be detoxified by sulfate-reducing
bacteria and methanogenic bacteria to their respective
aminophenols, and these aminophenols could be reductively deaminated to phenol.[7 – 10]
Biodegradation of nitrophenols under denitrificaiton
condition is of particular interest because the electron
acceptors needed are highly soluble in water and
coexists in the wastewater along with nitrophenols.
Continuous biotransformation of several nitrophenols
under denitrification conditions has been studied with
high chemical oxygen demand (COD) loading.[11,12]
However, there was little information about the removal
of 2,4-dinitrophenol under denitrification conditions
with 2,4-dinitrophenol as the main COD loading. Owing
to the low operation cost and high efficiency of the
anaerobic process and advances in process control, there
is a renewed interest in developing continuous anaerobic
processes to treat inhibitory industrial wastewaters.
Literature survey on 2,4-dinitrophenol biodegradation
reveals that most of the papers focused on the biodegradation pathway, while only a few displayed a technological orientation. This paper aimed at investigating
920
J-H. ZHU AND X-L. YAN
Asia-Pacific Journal of Chemical Engineering
denitrification and 2, 4-dinitrophenol biodegradation in
an anaerobic bioreactor operated with nitrate as an electron acceptor and 2, 4-dinitrophenol as the sole carbon
source. The effects of the main operating parameters,
including hydraulic retention time (HRT), COD loading etc., on process efficiency were also investigated
with a view to define optimal operation conditions.
Four 250-ml conical flasks were used in parallel
for the batch experiments. Experiments were carried
out at 25 ◦ C under anaerobic conditions. One conical
flask was served as the control, which was free of
2,4-dinitrophenol, and the other conical flasks were
fed with 2,4-dinitrophenol concentration of 10, 20, and
30 mg/l, respectively. The batch tests were conducted
for 3 h in order to minimize the effect of endogenous
respiration of the micro-organisms in the anaerobic
sludge. In each test, the initial mixed liquor suspended
solids (MLSS) concentration was kept around 300 mg/l,
while phenol concentration was maintained at 150 mg/l.
The experiments were conducted in triplicate, and the
averaged data were presented.
MATERIALS AND METHODS
Chemicals
The 2,4-dinitrophenol used was in powder form (above
98% purity) with slight yellow color supplied by
Jiangsu Huada Chemical Group Co., Ltd (Changzhou,
China). All other reagents (analytical grade) were purchased from Sinopharm Chemicals (Shanghai, China)
unless otherwise indicated.
Enrichment culture
Before enrichment, the original anaerobic sludge was
washed with a synthetic wastewater containing 240 mg/l
phenol and 200 mg/l NO3 − -N. Development of the
enrichment culture and acclimation to synthetic wastewaters with 2,4-dinitrophenol as the sole carbon source
was carried out in two self-prepared anaerobic bioreactor (2.5L).[13] In each anaerobic bioreactor, 300 ml
of the washed original anaerobic sludge with MLSS
of 6390 mg/l and 1.7 l of synthetic wastewater containing 240 mg/l phenol, 30 mg/l 2,4-dinitrophenol,
and 200 mg/l NO3 − -N were added into the bioreactor to initiate the enrichment. Synthetic wastewaters
were continuously fed. The loading of phenol, 2,4dinitrophenol, and NO3 − -N, the influent C/N ratio, as
well as HRT were controlled according to Table 1. The
enrichment was conducted under the following conditions: hydraulic volume, 2000 ml; gently stirring with
a magnetic stirrer; temperature, 25 ◦ C; pH between 6.8
and 7.4 controlled with 0.1 N HCl or 0.1 N NaOH. On
Day 80, the enriched anaerobic culture was obtained.
Culture medium
Synthetic wastewaters containing the following components were used for the enrichment: 0.87 g/l K2 HPO4 .
3H2 O; 0.54 g/l KH2 PO4 ; 0.2 g/l MgSO4 .7H2 O; 0.02 g/l
CaCl2 .2H2 O; 0.01 g/l FeSO4 .7H2 O; 0.005 g/l MnSO4 .
H2 O; 0.001 g/l CuSO4 .5H2 O; 0.001 g/l Na2 MoO4 .
2H2 O; and various amounts of COD and NO3 − -N. Phenol and 2,4-dinitrophenol were used to provide COD,
and potassium nitrate was used to provide NO3 − -N.
Table 1 summarized the properties of synthetic wastewaters used for the 80-day gradual enrichment. Before
being fed, synthetic wastewaters were purged with
nitrogen gas for 20 min to drive off the dissolved oxygen and establish an anaerobic environment.
Influence of 2,4-dinitrophenol on the original
anaerobic sludge
Operation of anaerobic bioreactor
An anaerobic culture previously acclimatized to phenol
as the sole carbon source was used as the original anaerobic sludge in the experiment.[13] The original anaerobic
sludge was a mixed liquor sample which could remove
high concentration of phenol under denitrifying conditions.
After the enrichment, the influent C/N concentration
was decreased in steps from 4.65 (Phase IV) to 4.31
(Phase V), and then to 3.96 (Phase VI), as listed in
Table 2, to investigate the C/N removal ratio [equals
to the ratio of COD removal ability (CRA) to NO3 − N removal ability (NRA)] in the bioreactor. Other
Table 1. Strategy for the enrichment of anaerobic culture in the anaerobic bioreactor.
Phase (Days) Phenol (mg/l) 2,4-dinitrophenol (mg/l) NO3 − N (mg/l) COD loading (g-COD/l day) Influent C/N HRT (h)
I (1–20)
II (21–40)
III (41–60)
IV (61–80)
240
160
80
0
30
90
150
210
200
160
120
100
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
0.64
0.78
0.80
0.95
3.18
3.64
4.42
4.75
24
18
16
12
Asia-Pac. J. Chem. Eng. 2010; 5: 919–924
DOI: 10.1002/apj
Asia-Pacific Journal of Chemical Engineering
BIODEGRADATION OF 2,4-DINITROPHENOL
Table 2. C/N stoichiometry in anaerobic bioreactor at
HRT of 12 h.
Effluent
C/N
2,4-dinitrophenol
(mg/l)
NO3 − -N (mg/l)
2,4-dinitrophenol
(mg/l)
NO3 − -N (mg/l)
MLSS (mg/l)
C/N
removal
ratio
Phase
V
Phase
VI
4.65
210
4.31
210
3.96
210
100
9.4
110
2.4
120
2.2
Removal (%)
Influent
Phase
IV
50
45
Phenol
40
Nitrate
35
CODcr
30
2,4-DNP
25
20
15
10
5
0.6
89
4.56
7.2
73.7
4.63
16.7
64.8
4.67
Note: Phase V and Phase VI were from Day 81 to Day 95 and
from Day 96 to Day 110, respectively. C presents for COD (mg/l)
and N presents for the added NO3 − -N (mg/l). All data shown were
expressed as the average of five data detected in the last 5 days of
each phase when the anaerobic bioreactor was at a steady state.
operation conditions were kept the same as Phase IV.
In Phases V and VI, CRA and NRA of the anaerobic
bioreactor reached a steady state within about 8 days
after phase transition. Samples were then collected at
three time points for analysis.
Batch biodegradation
At the end of the enrichment, certain amount of the
enriched culture was taken from the bioreactor and
washed with the synthetic wastewater (neither 2,4dinitrophenol nor nitrate were added). Four 100-ml conical flasks were used in parallel for the batch biodegradation experiments to evaluate its biodegradation without the addition of nitrate as the electron acceptor.
Experiments were carried out at 25 ◦ C under anaerobic
conditions. In each test, the initial MLSS concentration
was kept around 200 mg/l, and the conical flasks were
fed with 100 mg/l 2,4-dinitrophenol and varied nitrate
concentrations, respectively. The experiments were conducted in triplicate, and the averaged data were presented.
Analytical methods
During the enrichment, periodic sampling was conducted and about 2 ml was drawn into an Eppendoff
tube each time. After 10 000 rpm centrifugation, the
supernatant was transferred into a glass vial and stored
at −20 ◦ C for the following analysis.
Determinations of chemical oxygen demand determined by K2 Cr2 O7 (CODCr ) and MLSS were carried out according to standard methods. Concentrations of NO3 − -N and NO2 − -N were analyzed by ion
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
0
0
10
20
2,4-DNP (mg/L)
30
Figure 1. Influence of 2,4-dinitrophenol on phenol, chemical oxygen demand (CODCr ), nitrate, and alachlor removal
under anaerobic conditions. The control consisted of anaerobic culture without the addition of 2,4-dinitrophenol.
chromatography (Shimadzu model LC-10) with Shimpack IC-A3 column with a detectable level of 0.1 mg/l.
2,4-Dinitrophenol was detected by HPLC (Waters,
USA) with 3.9 × 150 mm Symmetry C18 column. A
mixture of methanol/reverse osmosis water (Millipore
Co., Ltd.)/glacial acetic acid (60 : 38 : 2, v/v/v) was used
as the solvent and the flow rate was maintained at
0.7 ml/min and detected at 275 nm.
RESULTS AND DISCUSSIONS
Influence of 2,4-dinitrophenol on the original
anaerobic sludge
Although biological treatment of 2,4-dinitrophenol is
widely studied in anaerobic conditions, its removal
is often limited at high concentrations because 2,4dinitrophenol is recalcitrant in these cases. The effect of
initial 2,4-dinitrophenol concentrations on the removal
abilities of the original anaerobic sludge was
investigated in Fig. 1. The phenol and nitrate removal
would be remarkably restrained by the presence of
2,4-dinitrophenol. For example, when 2,4-dinitrophenol
concentration was 30 mg/l, only 16.3% CODCr and
22.3% NO3 − -N were removed after the treatment of
3 h, both of which were remarkably lower than the control in which the removal of CODCr and NO3 − -N were
39.2% and 42.2%, respectively. Moreover, less than
10% 2,4-dinitrophenol was removed under three 2,4dinitrophenol concentrations investigated, indicating its
poor biodegradability. The reduced treatment activities
of the original anaerobic sludge and the poor biodegradability of 2,4-dinitrophenol indicated the unfeasibility of
utilizing the original anaerobic sludge treatment process
to treat wastewaters containing 2,4-dinitrophenol. It is
necessary to enrich a suitable culture for the removal of
2,4-dinitrophenol.
Asia-Pac. J. Chem. Eng. 2010; 5: 919–924
DOI: 10.1002/apj
921
J-H. ZHU AND X-L. YAN
Asia-Pacific Journal of Chemical Engineering
Enrichment culture for the removal
of 2,4-dinitrophenol
50
5
45
4.5
40
4
35
3.5
30
3
25
2.5
20
2
15
1.5
10
1
5
0.5
NRA, CRA, MLSS, C/N (g or g/(g MLSS•d)
As shown in Table 1, during the first 60 days, phenol
as a preferred carbon source to the micro-organisms
was added with a reduced concentration in each phase
into the influent wastewater to maintain the proliferation
of micro-organisms. After Day 60, no phenol was
added and 2,4-dinitrophenol became the sole carbon
source in the synthetic wastewater. During all four
phases of the enrichment, nitrite was undetectable in
the effluent.
The yield of MLSS is a direct index describing the
amount of excess anaerobic sludge produced in biological wastewater treatment systems. Fig. 2 revealed that
the sludge yield was significantly dependent on the transient change of 2,4-dinitrophenol concentration in the
influent or HRT. In the initial days of each phase, MLSS
concentration in the bioreactor was reduced firstly and
then increased. For example, MLSS concentration was
reduced from 1178 mg/l on Day 40 to 967 mg/l on Day
43 within the transition period from Phase II to Phase
III. Within Phase III, MLSS concentration increased in
step and reached its highest concentration at the end of
Phase III.
As shown in Fig. 2, on Day 20 (the HRT was 24 h),
the effluent phenol, 2,4-dinitrophenol, and NO3 − -N concentrations were 8.3, 6.3 and 40.7 mg/l, respectively,
during which MLSS content was 993 mg/l, CODCr
removal ability (CRA) and the added NRA of the
culture were 585.6 mg/(g MLSS· d) and 158 mg/(g
MLSS· d), respectively. After the enrichment of 80 days
(the HRT was 12 h), the content of MLSS in the
bioreactor was increased to 1178 mg/l; all CODCr
was provided by 2,4-dinitrophenol in the bioreactor. Meanwhile, CRA and NRA were increased to
Phenol, Nitrate, 2,4-DNP (mg/L)
922
0
0
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85
Time (day)
Figure 2. Performance of the anaerobic bioreactor during
the 80-day enrichment. ( ) MLSS (mg/l); (ž) C/N removal
ratio; () NRA [mg/(g MLSS· d)]; () effluent NO3 − -N
concentration (mg/l); () CRA [mg/(g MLSS· d)[; () effluent
2,4-dinitrophenol concentration (mg/l); (♦) effluent phenol
concentration (mg/l).
°
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
769 mg/(g MLSS· d) and 169 mg/(g MLSS· d), respectively. This clearly showed that the enriched culture obtained increased capabilities to remove 2,4dinitrophenol.
During the transition period of each phase, both the
increased 2,4-dinitrophenol concentration in the influent and the reduced HRT resulted in increased 2,4dinitrophenol concentrations in the anaerobic bioreactor, and further remarkably influenced the treatment
activities of the culture. As shown in Fig. 2, during the
transition period from Phase II to Phase III in which
HRT was changed from 18 to 16 h, 2,4-dinitrophenol
accumulated rapidly in the bioreactor with its concentration increasing from 9.6 mg/l on Day 40 to 35.5 mg/l
on Day 41, while the concentration of NO3 − -N was
almost not changed.
Accompanied with the increase in the influent 2,4dinitrophenol concentration, as well as with the decrease
in HRT, CRA of the culture decreased from 621 mg/(g
MLSS· d) on Day 40 (at this point CODCr was provided
by 160 mg/l phenol and 90 mg/l 2,4-dinitrophenol)
to 597 mg/(g MLSS· d) on Day 41 (at this point
CODCr was provided by 80 mg/l phenol and 150 mg/l
2,4-dinitrophenol), but increased rapidly to 678 mg/(g
MLSS· d) on Day 45. Meanwhile, NRA also showed
the same change, i.e. decreased from 154 mg/(g MLSS·
d) on Day 40 to 142 mg/(g MLSS· d) on Day 41,
and then increased to about 167 mg/(g MLSS· d) at
the end of Phase III. The possible reason might be
that drastically increased 2,4-dinitrophenol concentrations inhibit the treatment activities of the culture.
However, NRA and CRA recoveries of the culture
showed that such inhibitory effects could be impermanent and the anaerobic bioreactor could resist drastically deviated treatment conditions. As compared to
CRA and NRA, the 2,4-dinitrophenol treatment ability of the sludge showed a different change with the
increased 2,4-dinitrophenol concentration. During each
transition period, 2,4-dinitrophenol treatment ability of
the sludge still increased with the rapid change of 2,4dinitrophenol in the influent.
Fig. 2 also illustrated the C/N removal ratios during the whole enrichment. The influent C/N ratio
was controlled at different levels in different phases.
The C/N removal ratio increased in the four investigated phases from 3.69 (Day 15) to 4.56 (Day
80). When CRA and NRA achieved steady states
in the bioreactor in Phase IV, the C/N removal
ratio fluctuated at the level of 4.56. In the bioreactor, the consumption of COD was mainly used for
biomass growth and as electron donor for denitrification. In-depth investigation of the stoichiometric relation between COD and NO3 − -N removal would be
important to elucidate the efficiency of the bioreactor to simultaneously remove 2,4-dinitrophenol and
nitrate as well as to optimize the operation of the
bioreactor.
Asia-Pac. J. Chem. Eng. 2010; 5: 919–924
DOI: 10.1002/apj
Asia-Pacific Journal of Chemical Engineering
BIODEGRADATION OF 2,4-DINITROPHENOL
After Phase III, 2,4-dinitrophenol became the sole carbon source in the bioreactor. By varying the concentrations of NO3 − -N, three levels of influent C/N ratio
were used to investigate the C/N removal ratios in
the anaerobic bioreactor (Table 2). When the influent
C/N ratio was controlled at 4.65, the effluent NO3 − N concentration was as low as 0.57 mg/l, while that
of 2,4-dinitrophenol was 9.4 mg/l. The incomplete 2,4dinitrophenol removal could be caused by the insufficient supply of electron acceptor (NO3 − -N) in the bioreactor. However, when the influent C/N ratio decreased
to 4.31, the effluent NO3 − -N concentration increased
to 7.11 mg/l, while that of 2,4-dinitrophenol decreased
to 2.4 mg/l. The accumulation of NO3 − -N might have
been resulted from the lack of electron donor (2,4dinitrophenol) in the bioreactor. Among three investigated batches, the C/N removal ratio deviated a little
within the range between 4.56 and 4.67, clearly indicating that a stoichiometry between 2,4-dinitrophenol and
NO3 − -N removal exists in the anaerobic bioreactor.
Several C/N removal ratios have been reported
from 3.18 to 5.3 under denitrifying conditions.[13 – 17]
It has been widely reported that the consumption of
COD could be utilized for the proliferation of microorganism, i.e. the increase in MLSS and for the denitrification of NO3 − -N. Theoretically, removal of 1 g NO3 − N into nitrogen chemically requires 2.86 g COD.[18] The
coefficient of 2.86 is equivalent mg O2 per mg NO3 − -N,
which can be derived from the following reactions:
O2 + 4H+ + 4e− = 2H2 O
NO3 − + 6H+ + 5e− = 0.5N2 + 3H2 O
(1)
(2)
Equations (1) and (2) yield the following: (32/4)/
(14/5)=2.86 mg O2 /mg NO3 − -N. This calculation is
based on the assumption that nitrate is the sole electron acceptor. In the present study, the observed mean
C/N removal ratio was about 4.60 g COD/g NO3 − N. Although 2,4-dinitrophenol is more recalcitrant than
phenol, the observed C/N removal ratio was obviously higher than the previously reported one (3.18)
obtained in the anaerobic bioreactor for the simultaneous removal of phenol and nitrate.[13] Although
the nitro group of nitrophenols enhances the resistance of the aromatic ring to biodegradation, bacterial strains able to utilize nitrophenols as sole carbon and nitrogen sources have been described.[19,20]
The observed higher C/N removal ratio (∼4.60) might
have been caused by the contribution of possible electron acceptors derived from the degradation of nitro
group in the molecule of 2,4-dinitrophenol.[1] Further
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
investigation of the degradation mechanism of 2,4dinitrophenol under denitrifying conditions in the anaerobic bioreactor would be helpful to elucidate this phenomena.
When the anaerobic bioreactor was continuously
operated at the steady state, in which MLSS in the
anaerobic bioreactor, CRA, and NRA of the anaerobic
bioreactor remained constant, the mean MLSS value
(phase V) in the effluent was 69.2 mg/l, meaning 5.9%
of MLSS in the bioreactor was flashed out when the
HRT was 12 h. Hence, the solids’ residence time in the
bioreactor could be calculated to be 203 h during the
continuous operation.
Batch experiment
The higher C/N removal ratio was observed in the
anaerobic bioreactor under denitrification conditions.
As previously reported, nitrophenols could be used
as the sole carbon and nitrogen source. As shown
in Fig. 3, under anaerobic conditions, the 2,4-dinitrophenol removal abilities of the enriched sludge were
remarkably dependent on the existence of nitrate. When
the initial nitrate concentration was 60 mg/l, 82% of
2,4-dinitrophenol could be removed after the treatment
of 5 h. With the decrease in nitrate concentration, the
removal of 2,4-dinitrophenol decreased. For example,
less than 5% of 2,4-dinitrophenol could be removed
after the treatment of 5 h when no nitrate was added
in the synthetic wastewater, indicating the unfeasibility of utilizing the enriched culture to treat wastewaters containing only 2,4-dinitrophenol. When the higher
C/N removal ratio (∼4.60), which indicated that 2,4dinitropehnol might have been served as electron acceptor as well as electron donor, was taken into account, the
biodegradation of 2,4-dinitrophenol under denitrification conditions might concern complicated mechanisms
which needs in-depth researches.
120
100
Removal (%)
Stoichiometry of C/N removal by the enriched
culture
80
Nitrate
2,4-DNP
60
40
20
0
0
20
40
Nitrate concentration (mg/L)
60
Figure 3. The dependence of 2,4-dinitrophenol biodegradation on nitrate under anaerobic conditions at 5-h batch
tests.
Asia-Pac. J. Chem. Eng. 2010; 5: 919–924
DOI: 10.1002/apj
923
924
J-H. ZHU AND X-L. YAN
CONCLUSIONS
The present study showed that 2,4-dinitrophenol and
nitrate with high concentrations in a synthetic wastewater could be simultaneously removed in an anaerobic
bioreactor fed with the inocula originated from the
anaerobic bioreactor for the simultaneous removal of
phenol and nitrate.[13] At the end of the enrichment
(on Day 80), 95.5% of 2,4-dinitrophenol and almost
all nitrate could be simultaneously removed at a HRT
of 12 h in the bioreactor. The removal of 1 g of the
added nitrate required about 4.60 g COD as the electron donor. And the removal of 2,4-dinitrophenol by this
enriched culture was strongly dependent on the existence of nitrate.
Acknowledgements
This work was partially supported by the Key Program
of the State Education Ministry of China (No. 206079),
as well as the Open Project Program of the State
Key Laboratory of Bioreactor Engineering, East China
University of Science and Technology.
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Asia-Pacific Journal of Chemical Engineering
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DOI: 10.1002/apj
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