close

Вход

Забыли?

вход по аккаунту

?

Carrier effects on oxygen mass transfer behavior in a moving-bed biofilm reactor.

код для вставкиСкачать
ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING
Asia-Pac. J. Chem. Eng. 2009; 4: 618–623
Published online 25 May 2009 in Wiley InterScience
(www.interscience.wiley.com) DOI:10.1002/apj.302
Special Theme Research Article
Carrier effects on oxygen mass transfer behavior
in a moving-bed biofilm reactor
Jie Ying Jing, Jie Feng and Wen Ying Li*
Key Laboratory of Coal Science and Technology (Taiyuan University of Technology), Ministry of Education and Shanxi Province, Taiyuan 030024, China
Received 2 September 2008; Revised 17 October 2008; Accepted 22 February 2009
ABSTRACT: This study investigates the carrier effects on the oxygen mass transfer behavior of a gas–liquid biofilm
surface, and aims to provide evidence for parameter optimization in the practical operation of a moving-bed biofilm
reactor (MBBR) during the coking-plant wastewater process. By using the dynamic oxygen dissolution method, the
volumetric oxygen mass transfer coefficient KLa was measured by varying the suspended carrier stuffing rate and the
intensity of aeration. Within the range of fluidizable flow rate, the efficiency of oxygen mass transfer increased with
suspended carrier stuffing rate, and KLa reached its peak value when the stuffing rate was 40%. KLa has an increasing
trend with an increase of the aeration intensity, but high aeration intensity was not favorable for reactor operation. Better
oxygen mass transfer effect and higher oxygen transfer efficiency could be achieved when the aeration intensity was
0.3 m3 h−1 and the suspended carrier stuffing rate was 30–50%. The possible mechanisms that can account for carrier
effects on oxygen mass transfer are the changes in the gas–liquid interfacial area. The ammonia nitrogen removal
performance of the coking-plant wastewater in MBBR was satisfied by using the above-suggested conditions.  2009
Curtin University of Technology and John Wiley & Sons, Ltd.
KEYWORDS: moving-bed biofilm reactor; oxygen; mass transfer; aeration intensity; carrier; NH4 + –N removal
INTRODUCTION
The primary purpose of a bioreactor is to provide
such an environmental condition to the microorganisms
that will carry out the required reaction or conversion
optimally. In many aerobic bioreactors, the critical
limiting factor in providing the optimal environment
is the oxygen transfer from the gaseous phase to the
liquid phase because of the low solubility of oxygen
in water.[1 – 9] As a result, the volumetric oxygen mass
transfer coefficient KLa is often quantified in order to
allow proper system design.[1,10,11]
The moving-bed biofilm reactor (MBBR) has
emerged as a compact treatment alternative to conventional activated sludge reactors for the treatment of
industrial wastewater. It is a highly effective biological
treatment process that was developed on the basis of the
conventional activated sludge process and the fluidizedbed reactor.[2,12] Researchers have shown that MBBR
has many excellent traits such as high biomass, high
Chemical Oxygen Demand (COD) loading, strong tolerance to loading impact, relatively smaller reactor size,
*Correspondence to: Wen Ying Li, Key Laboratory of Coal Science
and Technology, Taiyuan University of Technology, Taiyuan 030024,
China.
E-mail: ying@tyut.edu.cn
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
no sludge bulking problem, etc.[13 – 17] One of the most
important factors is the existing bio-carriers. The biocarriers provide the place where microorganisms accumulate; at the same time, the bio-carriers can disperse
the bubbles released from the bubble aeration diffuser
and thus have a large impact on KLa . Therefore, the
carrier effects on oxygen mass transfer in MBBR must
be considered to ensure that the system is not oxygenlimited, or over designed; ideally, the reactor should
have a maximum oxygen mass transfer rate at an efficient mixing and a minimum energy input. In order to
achieve this goal, the attractive method is to improve
the structure of the reactor so that the oxygen transfer
from the gaseous phase to the liquid phase becomes better. Generally speaking, the reactor is divided into two
compartments: the riser section and the downcomer section, which can provide satisfactory liquid circulation
and mixing. Besides this, many researchers have been
interested in finding how KLa was influenced by variable exoteric factors. Littlejohns et al .[1] investigated
the effect of different solid phases on oxygen mass
transfer, and showed that a higher enhancement of KLa
was observed for small, inert solid particles. He et al .[18]
have reported the influence of bubble aeration diffusers
on the oxygen mass transfer, which indicated that the
size, shape, model, etc. of the bubble aeration diffusers
play a key role in the process of oxygen mass transfer.
Asia-Pacific Journal of Chemical Engineering
CARRIER EFFECTS ON OXYGEN MASS TRANSFER BEHAVIOR IN MBBR
There is doubtless more than one factor that impacts
on the oxygen mass transfer in MBBR, and it is of
significance to investigate the carrier effects on the oxygen mass transfer. Furthermore, by studying the oxygen
mass transfer behavior of the gas–liquid interface of
the biofilm surface in MBBR, evidence for parameter
optimization in practical operation of MBBR can be
provided.
The objective of the present work is to investigate
the carrier effects on oxygen mass transfer behavior
by varying of suspended carrier stuffing rate and the
intensity of aeration, and to seek the optimal operating
conditions under which MBBR can be run at high
efficiency and with a low power expense. Also, the
ammonia nitrogen (NH4 + –N) removal performance of
coking-plant wastewater was investigated using MBBR
in the optimal suspended carrier stuffing rate and the
aeration intensity at the laboratory scale.
In this experiment, the OC is determined by Eqn (4)
OC = KLa (20) × CS × V
where V is the volume of the wastewater in the reactor,
and the other parameters have the same meanings as
before.
NH4 + –N concentration is measured using the Nesslerization method[20] by reading the absorbance at
425 nm. In order to obtain the NH4 + –N concentration
in coking wastewater, first, a standard graph is drawn
to show the connection between the ammonia nitrogen
mass (mN ) and the calibrated absorbance obtained at
different concentrations of standard ammonia nitrogen
solutions. Then, the mN in coking-plant wastewater can
be checked from the calibrated graph and, finally, the
NH4 + –N concentration can be calculated by Eqn (5)
CNH4 + −N =
EXPERIMENTAL
The dynamic oxygen dissolution method was used for
the determination of the KLa value. The various oxygen
solubility values at different times could be obtained
conveniently with a fast-responding oxygen electrode.
In the process, the oxygen absorption capability of the
MBBR is characterized in terms of KLa and the oxygen
capability (OC).
The oxygen absorption rate dC
dt is related to KLa (T )
as shown in Eqn (1)[19] :
(1)
where CS is the saturation concentration of dissolved
oxygen in water and CL is the actual instantaneous
concentration. It is assumed that the response of the
oxygen electrode to a change in the dissolved oxygen
concentration is sufficiently fast in the analyzer.
Integration of Eqn (1) for CL = C0 at t = 0 leads to
Eqn (2):
Cs − CL
) = −KLa t
(2)
ln(
Cs − C0
A plot of the left side of Eqn (2) against time was
used to obtain the slope as −KLa .
In order to compare the data measured under different
conditions and apply these data to a practical project,
KLa is modified with the following formula[1] (Eqn (3)):
KLa (20) =
KLa (T )
(T −20)
1.024
mN
VW
(5)
where CNH4 + −N means the concentration of ammonia
nitrogen, mN is the ammonia nitrogen mass, and VW is
the volume of the wastewater.
Determination of the KLa value
dC
= KLa (T )(CS − CL )
dt
(4)
(3)
where T is the actual temperature in the experiment and
KLa (20) is the KLa value at 20 ◦ C.
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
Bioreactor
The bioreactor used was a cylindrical reactor with an
inside diameter of 12 cm and a working volume of 2 l
(Fig. 1). All experiments were conducted at a temperature of 17–18.5 ◦ C, and measurements were taken in
duplicate with the average value being reported. Experiments were performed with various suspended carrier
stuffing rate (ε) and the intensity of aeration (Ug ). The
suspended carriers used were a mixture of polyethylene and inorganic particles, which were introduced
purposely to enlarge the surface area and roughness
of the carrier for better microorganism accommodation. The bio-carrier model used was WD-F10-4 BioM
(DaLian WeDo Environmental Process and Technology
Co., Ltd.) and has an outside diameter of 10 mm, a
length of 10 mm, a wall thickness of 0.4–0.6 mm, a
density of 0.96–0.98 g cm−3 , and a specific surface
area of about 900 m2 m−3 . The aeration was accomplished by an air pump (ACO-318, Guangzhou Haili
Co., Ltd.).
RESULTS AND DISCUSSION
The effect of suspended carrier stuffing rate
on the KLa value
Table 1 shows the change of KLa with no bio-carriers
existing in the MBBR (ε = 0%) at different aeration
Asia-Pac. J. Chem. Eng. 2009; 4: 618–623
DOI: 10.1002/apj
619
620
J. JING, J. FENG AND W. LI
Asia-Pacific Journal of Chemical Engineering
Influent
Air
Sieve
Effluent
Tank
Carriers
Oxygen probe
Sludge
MBBR
Dissolved oxygen meter
Figure 1. Schematic diagram of MBBR. This figure is available in colour
online at www.apjChemEng.com.
Table 1. Volumetric oxygen mass transfer coefficient
in different aeration intensity (ε = 0%).
Aeration
intensity Ug
(m3 h−1 )
0.12
0.18
0.24
0.30
0.45
The curve
obtained
s − C0
ln C
C s − Ct
s − C0
ln C
C s − Ct
s − C0
ln C
C s − Ct
s − C0
ln C
C s − Ct
s − C0
ln C
C −C
s
t
Table 2. Carrier effects on KLa and OC with the varying
aeration intensity.
(a) KLa values with various suspended carrier stuffing rate
at different aeration intensities (min−1 )
KLa (20)
OC
(min−1 ) (mg min−1 )
= −0.070t
0.07
1.21
= −0.076t
0.08
1.33
= −0.089t
0.09
1.54
= −0.113t
0.12
1.96
= −0.127t
0.13
2.21
Aeration intensity Ug (m3 h−1 )
Stuffing
rate (%)
0.12
0.18
0.24
0.30
0.45
10
20
30
40
50
0.08
0.12
0.13
0.14
0.12
0.10
0.15
0.18
0.19
0.17
0.12
0.18
0.20
0.24
0.22
0.14
0.22
0.23
0.26
0.24
0.18
0.27
0.28
0.29
0.27
(b) OC values with various suspended carrier stuffing rate
at different aeration intensity (mg min−1 )
intensities. It is clear that KLa increases with increasing aeration intensity when the carrier stuffing rate is
0%, and this trend is more obvious when the aeration is
high. When the intensity of aeration increased from 0.12
to 0.18 m3 h−1 , KLa rose slightly to about 0.01 min−1 .
However, KLa increased to 0.12 min−1 when the aeration intensity was 0.30 m3 h−1 .
Table 2 shows the carrier effects on the oxygen
transfer behavior. Compared with the operation of
no suspended carriers in the reactor, the adoption of
suspended carriers would make KLa nearly twice at the
stuffing rate of 40%. When the aeration intensity is
0.30 m3 h−1 , as shown in Table 1, the OC is 1.96 mg
min−1 when no suspended carriers were stuffed; OC
increased to 2.37 mg min−1 when 10% suspended
carriers existed in the reactor. Two-fold increase of OC
(4.33 mg min−1 ) could be observed when the suspended
carrier stuffing rate was 40%. With the suspended
carriers stuffing rate was rising, OC increased slowly.
When the suspended carrier stuffing rate was 50%,
because of the difficulty for the suspended carriers to
flow freely in the reactor, a decrease in both KLa and
OC was seen in the test.
There might be two factors contributing greatly to the
increase of KLa and OC. When the suspended carriers
were packed in the reactor, the bubbles released from
the bubble aeration diffuser moved through the interspace among carriers from the bottom to the top. During
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
Aeration intensity Ug (m3 h−1 )
Stuffing
rate (%)
0.12
0.18
0.24
0.30
0.45
10
20
30
40
50
1.38
1.96
2.11
2.31
2.04
1.71
2.42
2.94
3.14
2.86
2.01
2.92
3.37
3.97
3.69
2.37
3.62
3.88
4.33
4.05
2.96
4.43
4.66
4.85
4.53
this process, the bigger bubbles were broken up into
small or tiny bubbles, which increased the gas–liquid
interfacial area and therefore was more favorable for
oxygen transfer. On the other hand, because of the
aeration, the liquid was fluidizable and its turbulence
was greater than that with no suspended carriers, which
accelerated the renewal of the gas–liquid interface and
boosted the oxygen transfer from the gas to liquid.
The more the number of suspended carriers packed,
the stronger the dispersing and turbulence phenomenon
among carriers. However, when the stuffing rate of the
suspended carriers was higher, i.e. 50%, it was difficult
for the suspended carriers to flow freely in the reactor,
which led to a decline in the liquid turbulence; therefore,
KLa and OC decreased.
It is true that within the fluidizable flow rate range,
the oxygen mass transfer efficiency increased with
Asia-Pac. J. Chem. Eng. 2009; 4: 618–623
DOI: 10.1002/apj
Asia-Pacific Journal of Chemical Engineering
CARRIER EFFECTS ON OXYGEN MASS TRANSFER BEHAVIOR IN MBBR
the suspended carrier stuffing rate, and KLa reached
its peak value when the stuffing rate was 40%. In
practical operation, considering both efficiency and
power expense, it is reasonable to run the MBBR
with a suspended carrier stuffing rate between 30 and
50%.
The effect of the intensity of aeration on the
KLa value
Figure 2 shows the trend of KLa with variable aeration
intensity. It is obvious that increasing the intensity of
aeration is beneficial to the increase of KLa . During
the process of oxygen mass transfer of gas–liquid
of the biofilm surface, with the increase in aeration
intensity, the driving force is increased by decreasing
the liquid concentration at any given time as well as
by possibly enhancing the gas–liquid mass transfer.
Take the suspended carrier stuffing rate of 30% as an
example. When the aeration intensity is 0.12 m3 h−1 ,
KLa is 0.12 min−1 ; and KLa increases to 0.24 min−1
when the aeration intensity 0.3 m3 h−1 . There are some
possible reasons for this phenomenon. The increase
in aeration intensity could dramatically enhance the
gas holdup and the number of bubbles in the reactor.
This would increase the interfacial area where oxygen
transfer occurs and boost the turbulence between the
suspended carriers and liquid. All of these reduce the
resistance encountered in oxygen transfer from the gas
phase to the liquid phase. Also, with the formation,
coalescence, and dispersion of bubbles, the turbulence
accelerates interface renewal.
Compared to the impact of the suspended carriers on
KLa , it is easier to increase KLa by raising the intensity
of aeration. However, it is impossible to enhance KLa
by boosting the aeration intensity without limit. As the
0.32
0.45 m ⋅h
0.30 m3⋅h-1
3
0.28
0.24 m3⋅h-1
0.18 m3⋅h-1
0.12 m3⋅h-1
0.24
KLa / min-1
-1
0.20
0.16
0.12
0.08
0
10
20
30
40
Suspended carrier stuffing rate / %
50
Figure 2. Trend of KLa with the change of suspended carrier
stuffing rate and the intensity of aeration.
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
intensity of aeration became higher, i.e. 0.5 m3 h−1 ,
it was found that the bubbles easily coalesced and
swelled to cause turbulent flow and could run over
the reactor with a high velocity, which increased
the power expense. Other than this, the loss of the
suspended carriers, difficulty in accumulating biofilm,
etc. might take place. Therefore, considering a high
oxygen transfer efficiency and low power expense, the
aeration intensity of 0.3 m3 h−1 is suggested in the
practical operation.
Analysis of carrier effects on oxygen mass
transfer behavior
In order to gain the relationship between the suspended
carrier stuffing rate and KLa , the following equations
were calculated by linear regression from Fig. 2 and
the results are as followings:
Ug = 0.12 m3 h−1 , KLa = −0.00396ε2 + 0.003ε
+ 0.074
(R 2 = 0.923)
Ug = 0.18 m3 h−1 , KLa = −0.00538ε2 + 0.005ε
+ 0.081
(R 2 = 0.957)
Ug = 0.24 m3 h−1 , KLa = −0.00579ε2 + 0.006ε
+ 0.094
(R 2 = 0.964)
Ug = 0.30 m3 h−1 , KLa = −0.00718ε2 + 0.007ε
+ 0.117
(R 2 = 0.950)
Ug = 0.45 m3 h−1 , KLa = −0.01129ε2 + 0.009ε
+ 0.134
(R 2 = 0.965)
According to the above equations, it is easy to get
the theoretical optimal suspended carrier stuffing rate
at which the KLa reaches its peak value with different
aeration intensities. The calculated values show that
the theoretical optimal suspended carrier stuffing rate
fluctuates between 38 and 49%, while in the previous
experiment in this paper, KLa reached its peak value
when the suspended carrier stuffing rate was 40%;
because of the high oxygen transfer efficiency and
low power expense, a suspended carrier stuffing rate
between 30 and 50% is suggested to run the MBBR in
practical operation.
Considering the practical and theoretical results
together, in the range of permissible error, it is reasonable to conclude that the above equations go well
with the actual phenomenon observed in the experiment. It can be viewed as theoretical evidence for
parameter optimization in practical operation of the
MBBR.
Asia-Pac. J. Chem. Eng. 2009; 4: 618–623
DOI: 10.1002/apj
621
J. JING, J. FENG AND W. LI
Asia-Pacific Journal of Chemical Engineering
Application to coking-plant wastewater
treatment
In order to prove the practical performance of the chosen optimal condition, we applied the above conclusions
to the NH4 + –N removal performance of the cokingplant wastewater in MBBR. Under the conditions of
temperature between 22 and 25 ◦ C, hydraulic retention
time of 48 h, aeration intensity of 0.3 m3 h−1 , and a
suspended carrier stuffing rate of 30%, the NH4 + –N
removal experimental results were recorded and are
shown in Fig. 3.
In the process of NH4 + –N removal, dissolved oxygen
plays an important role for the nitrification process, as
it is the electron receptor of the products generated
during the organic compounds’ catabolism and the
oxygen transfer dominates the wastewater process by
influencing the absorption of nutriments and the growth
of the microorganisms. Eventually, it has a great impact
on the efficiency of the wastewater treatment.
In this experiment, from the first day to the eighth
day, NH4 + –N removal efficiency fluctuated around
70%. The effluent NH4 + –N was about 100 mg l−1 .
Good nitrification was not achieved because the
microorganisms attached to the bio-carriers required an
acclimation process to the coking-plant wastewater after
they were in a new environment; also the slow growth
of the nitrifying bacteria contributed to it. After the
10th day, the NH4 + –N removal efficiency increased
to over 93% and the effluent NH4 + –N concentration
decreased to 23.5 mg l−1 . The measured dissolved oxygen (DO) concentration during the aerobic stage was
3.9 mg l−1 , which was enough for nitrification, and the
autotrophic nitrifiers could be easily overgrown by the
heterotrophs in the presence of substantial amounts of
organic compounds.[21] The other reason for the higher
NH4 + –N removal efficiency was that nitrifiers tended
to grow more inside the biofilm, so when the aeration
400
100
80
300
60
inlet
200
outlet
40
efficiency
100
0
20
0
10
20
30
40
Time / day
50
NH+4-N removal efficiency / %
NH+4-N concentration / mg⋅L-1
622
0
60
Figure 3. Variation of the inlet and outlet NH4 + –N
concentration and NH4 + –N removal efficiency with time.
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
rate was proper, the dissolved oxygen could diffuse into
the inner of biofilm and nitrification could take place.
Under the chosen optimal conditions, the NH4 + –N
removal performance for the coking-plant wastewater
in the MBBR is satisfied, indicating that the aeration
intensity (0.3 m3 h−1 ) and the suspended carrier stuffing
rate (30–50%) are proper and suitable to treat the
coking-plant wastewater.
CONCLUSIONS
It was shown that within the fluidizable flow rate range,
the oxygen mass transfer efficiency increased with an
increase of the suspended carrier stuffing rate, and
KLa reached its peak value when the stuffing rate was
40%. The suspended carriers influenced KLa mainly by
affecting the bubble size and the gas–liquid interfacial
area.
KLa had an increasing trend with increase in the
aeration intensity, but high aeration intensity was not
favorable to the reactor operation.
A better oxygen mass transfer effect and higher
oxygen transfer efficiency could be achieved when the
aeration intensity was 0.3 m3 h−1 and the suspended
carrier stuffing rate was 30–50%.
The ammonia nitrogen removal performance of the
coking-plant wastewater in MBBR was satisfied under
the optimal conditions.
Acknowledgements
This work was financially supported by the Biochemical
Engineering Program of 211 Project in Taiyuan University and Technology, Shanxi Nature Science Foundation (No.20051017), Shanxi Returned Scholar Research
Project (No.2005-21) and Program for Changjiang
Scholars and Innovative Research Team in University
in MOE (IRT0517), China.
NOMENCLATURE
ε
CS
CL
DO
dC
dt
KLa (T )
KLa (20)
Suspended carrier stuffing rate
Saturation concentration of dissolved oxygen
in the water (mg l−1 )
Actual instantaneous concentration of dissolved oxygen in the water (mg l−1 )
Dissolved oxygen concentration (mg l−1 )
Oxygen absorption rate (mg l−1 min−1 )
The volumetric oxygen mass transfer coefficient at certain temperature (min−1 )
The volumetric oxygen mass transfer coefficient at 20 ◦ C (min−1 )
Asia-Pac. J. Chem. Eng. 2009; 4: 618–623
DOI: 10.1002/apj
Asia-Pacific Journal of Chemical Engineering
MBBR
mN
NH4 + –N
OC
Ug
V
VW
CARRIER EFFECTS ON OXYGEN MASS TRANSFER BEHAVIOR IN MBBR
Moving-bed biofilm reactor
Mass of ammonia nitrogen (mg)
Concentration of ammonia nitrogen (mg l−1 )
Oxygen capability (mg min−1 )
Aeration intensity (m3 h−1 )
Volume of reactor (l)
Volume of sample (ml)
REFERENCES
[1] J.V. Littlejohns, A.J. Daugulis. Chem. Eng. J., 2007; 129,
67–74.
[2] J.A. Currie, N.R. Harrison, L. Wang, M.I. Jones, M.S. Brooks.
Asia Pac. J. Chem. Eng., 2007; 2, 460–467.
[3] Z.A. Manan, S.R. Wan Alwi. Asia Pac. J. Chem. Eng., 2007;
2, 544–553.
[4] H. Odegaard. Water Sci. Technol., 2006; 53, 17–33.
[5] A.R. Rao, B. Kumar. Asia Pac. J. Chem. Eng., 2007; 2,
592–598.
[6] X. Wang, S. Xia, L. Chen. J. Tongji Univ., 2006; 34, 514–517.
[7] H. Horn, E. Morgenroth. Chem. Eng. Sci., 2006; 61,
1347–1356.
 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
[8] T.C. Jorgensen, L.R. Weatherley. Asia Pac. J. Chem. Eng.,
2008; 3, 57–62.
[9] E. Dumont, Y. Andres. Biochem. Eng. J., 2006; 30, 245–252.
[10] M. Rodgers, X.M. Zhan, A. Casey. Water Air Soil Pollut.,
2004; 151, 165–178.
[11] A.I. Galaction, D. Cascaval, C. Oniscu. Biochem. Eng. J.,
2004; 20, 85–94.
[12] B. Li, J.Q. Zhang. Ind. Saf. Environ. Prot., 2007; 33, 6–8.
[13] E. Germain, L. Bancroft, A. Dawson. Water Sci. Technol.,
2007; 55, 43–49.
[14] D.H. Shin, W.S. Shin, Y.H. Kim. Water Sci. Technol., 2006;
54, 181–189.
[15] S. Chen, D.Z. Sun, J.S. Chung. Waste Manage., 2008; 28,
339–346.
[16] S. Luostarinen, S. Luste, L. Valentin. Water Res., 2006; 40,
1607–1615.
[17] P.M. Sutton, A.P. Togna. Water Environ. Technol., 2006; 18,
44–49.
[18] Q.B. He, K. Liu, J.N. Qu. J. Tongji Univ., 2003; 31, 982–985.
[19] B. Jajuee, A. Margaritis, M.A. Bergougnou. Chem. Eng. Sci.,
2006; 61, 4111–4119.
[20] American Public Health Association. Standard Methods for
the Examination of Water and Wastewater, 20th edn, APHA:
Washington, DC, 1998; pp.279–281.
[21] L.M. Van, L. Tijhuis, J. Wijdieks. Water Sci. Technol., 1998;
31, 163–171.
Asia-Pac. J. Chem. Eng. 2009; 4: 618–623
DOI: 10.1002/apj
623
Документ
Категория
Без категории
Просмотров
1
Размер файла
110 Кб
Теги
moving, carrier, mass, effect, behavior, transfer, reactor, bed, biofilm, oxygen
1/--страниц
Пожаловаться на содержимое документа