Application of Lab-Scale MBBR to Treat
Industrial Wastewater using K3 Carriers: Effects
of HRT, High COD Influent, and Temperature
Ahmadlouydarab Majid* and Mehrazaran Mahna
Faculty of Chemical & Petroleum Engineering, University of Tabriz, Iran
Submission: April 22, 2019; Published: June 28, 2019
*Corresponding author: Ahmadlouydarab Majid, Faculty of Chemical & Petroleum Engineering, University of Tabriz, Iran, Po Box: 51666-16471
How to cite this article: Ahmadlouydarab M, Mehrazaran M. Application of Lab-Scale MBBR to Treat Industrial Wastewater using K3 Carriers: Effects of HRT, High COD Influent, and Temperature. Int J Environ Sci Nat Res. 2019; 20(2): 556031. DOI:10.19080/IJESNR.2019.20.556031
In current study, the efficiency of a lab-scale MBBR was studied using K3 Kaldnes carriers. COD containing contaminant of 1000 to 3500mg/l was used to examine the system performance by measuring BOD and COD at different HRTs, temperature and inlet CODs. It should be noted that K3 Kaldnes carriers was not used in previous studies. To determine optimal HRT, BOD and COD of the effluent were examined at different HRTs of 3, 5, 8, and 12 hours. The optimum HRT was 8 hours with COD removal efficiency more than 80%. Despite of HRT=12 hours with the highest COD removal efficiency ~86%, HRT=8 hours were chosen as the optimal HRT due to the time-consuming refinement process with only a slight difference of 3% in removal efficiencies. Additionally, the effects of temperature in the range of 19 to 32°C were studied at optimal HRT. The results indicate that there is a sharp change in COD removal efficiency slope at a temperature range between 20 to 25°C due to the high activity of microorganisms, leading to an increase in the COD removal efficiency from 70% to ~90%. By increasing the temperature beyond 25°C, the rate of increase in COD removal efficiency is reduced by as much as 94%. According to the results, 27°C may be considered as the optimum temperature. Studying the effects of different inlet CODs up to 3500mg/l reflects a non-monotonic behavior in MBBR’s performance. In general, for all inlet CODs, MBBR system shows more than 80% removal efficiency.
Keywords: K3 carriers; MBBR; Wastewater; Lab-scale; High COD; MLSS
Abbrevations: ACC: Activated Carbon Concentration; MFR: Media Filling Ratio; TPH: Total Petroleum Hydrocarbon; TSS: Total Suspended Solid; BOD: Biological Oxygen Demand; COD: Chemical Oxygen Demand; ASP: Activated Sludge Process; MBR: Membrane Bioreactor System
With industrial development in most countries, industrial wastewater effluents are also increasing. On the other hand, nowadays, the problem of water scarcity of the world has become one of the major concerns of the societies. Therefore, it is important to find an optimal and cost-effective way to recycle wastewater effluents. Industrial wastewater is made by water consumption in industrial activities and during various stages of production. Sometimes, they constitute the most dangerous type of wastewater. The bulk of industrial wastewater also contains contaminants that are characterized by organic matter (soluble or insoluble) which are the most important contaminates. The most important compounds of industrial wastewater are arsenic, cadmium, mercury, and lead. If they are not properly collected and routed to the wastewater treatment plant, these materials will enter flowing water streams and so to the environment, which will have irreversible harmness to the environment and human beings. The quantity and quality of wastewaters or industrial effluents in different factories and industries vary depending on the type of production, which lead to have variable treatment processes.
In the treatment of domestic and industrial wastewaters, physical and biological treatment methods are used to obtain environmental certification. The most important issue in the treatment of industrial wastewater is to understand its nature and the quality of elements and factors such as toxic compounds, decomposing factors, Total suspended solid (TSS), (biological oxygen demand) BOD, (chemical oxygen demand) COD and color. With solid knowledge about these factors, it will be possible to design appropriate treatment methods for industrial wastewater and effluents.
Among the available techniques, scavenging, flotation with soluble air, adsorption, and membrane filtration are physical methods. Also, chemical methods include chemical oxidation, electrochemical oxidation, and coagulation. However, physical and chemical methods are expensive because of the high cost of chemicals, equipment, and the need to remove excess sludge. Therefore, biological methods are preferred due to simplicity, affordability and environmental compatibility .
The biological methods involve two types of aerobic and anaerobic systems. Different biological aerobic systems for wastewater treatment such as activated sludge process (ASP),
membrane filtration system (MBR), (up flow anaerobic sludge
bioreactor) UASB system are utilized. However, all these systems
have drawbacks that cannot be ignored . In the activated
sludge process (which is currently one of the most widely used
methods for industrial wastewater treatment), there should be
sludge returning cycle, which is costly. In addition, the removal
efficiency of organic matters from wastewater is not satisfactory
due to the complexity of chemicals in the wastewater industrial.
Moreover, activated sludge system is continuously exposed
to changes in pH, temperature, solids concentration, erosion,
and other parameters. Overall, these parameters decrease the
system’s life and efficiency . Compared to the membrane
bioreactor system (MBR) with the same apparent volume,
(moving bed biofilm reactor) MBBR provides more specific
volume (high capacity) for biological treatment. In MBR systems,
membranes should also be cleaned regularly, which results in
waste of time. The rest of the systems are not recommended due
to the costs and low efficiency over long periods. Indeed, these
are two main factors of being a non-optimal system. Thus, MBBR
can be considered as an innovative and cost-effective with high
removal efficiency [4-6].
In 1980, for the first time in history, the MBBR system was
used in Norway for wastewater treatment. These bioreactors
have advantages such as low-pressure drop. Their resistance
to factors such as temperature changes, pesticides, pH changes
are also very good. Today, more than 500 MBBR systems are
used to treat wastewaters and remove BOD, COD, nitrification,
etc. all around the world [7,8]. It is also an optimal system
for processes such as organic matters removal, nitrification,
and denitrification since it has high efficiency in eliminating
and reducing biodegradable organic and inorganic matters.
Basically, the MBBR system is an evolved type of fixed bed and
activated sludge system defined based on biofilms so that, the
microorganisms can stick to polyethylene carriers and start
the process of filtration. In aerobic processes, the movement
of carriers is due to the aeration while in anaerobic reactors,
using a mixer (with a horizontal or vertical shaft) helps carriers
to move. MBBR system does not require secondary treatment.
Additionally, the whole volume of the reactor can be used for
microorganisms’ growth . Todays, MBBR systems are used
in textile wastewater domestic wastewater, sewage, livestock,
poultry, refineries, and petrochemicals , industrial
wastewaters  and so on.
In 2006, Xiao et al.  conducted a test to present the
structural features of biomass in the hybrid MBBR aeration tank
. The experiment took place in two subsequent periods,
which differed in hydraulic and substrate loads. The physical
characteristics of attached-growth biomass, such as biofilm
thickness, density, porosity, and inner and surface fractal
dimensions were studied. Moreover, parameters of suspendedgrowth
biomass including floc size distribution, density, porosity,
inner and surface fractal dimensions, were investigated and
compared to those of attached-growth biofilms. The authors used
the activated sludge, and MBBR systems with filling ratio of 70%
from Kaldnes carriers in two subsequent periods. The average
density of attached-growth biofilm was 5 - 13 times higher than
that of activated sludge flocs, though they were coexisting in the
same reactor and same ecological environments. The boundary
fractal dimension of biofilm was found to be always higher than
that of activated sludge flocs.
In 2007, Choi and his colleagues  conducted a
research on two different systems i.e., MBBR system and an
integrated continuous bed activated sludge (ICBAS) system
. Researchers used these systems for nitrification and
denitrification in both summer and winter seasons. The results
showed that the MBBR system performs better than ICBAS in
ambient air conditions in removing ammonia. In addition, the
limited conditions for refining were not an obstacle for MBBR
to have higher performance compared to that of ICBAS. Similar
experiment was carried out by Motsch et al.  at Water
Protection and Prevention Agency in Virginia-USA . During
the operation, favorable outcomes were obtained e.g., for the
MBBR system the ammonia removal efficiency was higher than
that of ICBAS. The tough environmental conditions for treatment
process when using ICBAS, resulted in changes in the mixed
liquor suspended solid (MLSS) level.
In 2010, Ferrai and colleagues  studied the kinetic and
stoichiometric parameters by testing MBBR biofilms for urban
wastewater treatment . Authors used isolated and nonisolated
samples from a large-scale laboratory MBBR, and oxygen
uptake rate (OUR) heterotrophic sections of biomass for study. It
was then modeled using ASM3 system. Isolated biofilms showed
more tendency to sediment inside the bioreactor compared to
non-isolated biofilms. Additionally, it was observed that there is
a limited growth of biomass inside sediment sludge.
In other experimental research, Stamper and his colleagues
studied the effects of combining MBBR system with an anaerobic
system for better and stronger treatment . Authors predicted
that the anaerobic systems are prone to failure and require a lot
Also, in 2015, Mr. Barwal and his colleagues  investigate
the effects of bio-carriers on the oxygen uptake rate in the
effluent of the reactor with an aim to provide optimized filling
ratio for the practical operation of a MBBR . The value of
OUR increased 2-3 times with the augmentation of carrier filling
ratio, but it decreased when more carriers were added inside the
In 2015, Goswami et al.  compared ASP and MBBR
systems performance in composting wastewater treatment
plant made of chrome . The plant contained desensitizable
substances such as phosphorus, sulfur, chromium, and other
toxic substances. Authors concluded that the higher the number
of biofilms was, the higher the concentration of biomass was.Additionally, the results indicated that COD removal rate in
MBBR was 80%, which was much higher than that of ASP (60-
70%). However, there was no difference in nitrogen removal for
In 2016, Sayyah-Zadeh and colleagues  tried to improve
the efficiency of the MBBR system in order to treat hydrocarbons
using active carbon monoxide carriers . Researchers
monitored the performance of the system by filling the carrier’s
holes with activated carbon granules made of almonds and
walnuts. Parameters i.e., activated carbon concentration (ACC),
COD, and media filling ratio (MFR) were measured. The results
showed that the removal efficiency of COD and total petroleum
hydrocarbon (TPH) in the MBBR using carriers filled by almond
and walnut is higher than that of polyethylene carriers.
In the same year, Young et al.  conducted research to study
effects of low temperatures on the ammonia removal efficiency
in a MBBR bioreactor . The process was carried out between
1 and 20°C. Various biofilms were observed inside the carriers
in 20°C rather than 1°C. Authors could thicken the biofilm
thickness at 1°C. Results indicated that under hard conditions
(low temperature, chocks, and so on) the removal efficiency of
ammonia gets lower mainly due to low mass transfer.
Recently, Haung and his colleagues  prepared a report
on the importance of attached biomass in IFAS, MBBR and
MBR systems . The results showed that MBBR had better
performance in naphthenic acids removal. Most recently, a study
was done on the removal of organic solids from the wastewater
using MBBR system. As an important result, it became clear
that the MBBR system had the power to break down the drug
The main objectives of this study, considering literature
review, can be summarized as follow:
a) In previous studies, effects of a limited range of
temperature on the amount of COD removal has been
addressed. Studied rages are 1 to 20 ºC and 30 to 50 ºC
[20,25]. This means that there is not a comprehensive
understanding about the temperature effect on the MBBR
system behavior. In this experimental study to enhance
the current knowledge, the removal efficiency of different
amounts of COD and the activity of microorganisms on the
lab-scale MBBR system where temperature ranges from 19
to 32 ºC will be studied.
b) Literature review shows that the maximum studied
COD in the wastewater stream was 2500mg/l. In current
research, evaluation of the performance of a lab-scale MBBR
system will be investigated using different input CODs up to
c) There is lack of comprehensive knowledge about
the optimal HRT determination as well as its effects on
BOD removal efficiency. Therefore, in this study, while
determining the optimal HRT, its effects on the removal of
BOD and COD will be addressed.
d) Despite the previous studies in which K1 and K2
carriers have been used, in this research, K3 carriers will be
utilized in industrial wastewater treatment process.
Generally, in order to build the MBBR reactor, the following
steps were considered. Moreover, necessary chemicals were
prepared, and mandatory tests were carried out.
At first step, the lab-scale MBBR was designed and made
to conduct the tests, which will be described in section 2.1.
At second step, industrial wastewater sludge was prepared,
and then specific volume of sludge was poured into the MBBR
reactor. Consequently, artificial wastewater was added to the
primary sludge. After that, the system was aerated. Subsequently,
microorganisms were adapted to refine and remove organic
matters. After ensuring that the sludge was compatible with
artificial wastewater and COD was stable inside the bioreactor,
COD and BOD removal rates were investigated at different HRTs
Figure 1 represents the schematic diagram, and Figure 2
shows the experimental setup of the MBBR system studied in
The bioreactor is made of Plexiglas, which has a thickness
of 6mm. The length of the bioreactor is 30cm, and its width is
15cm. It’s pure and wastewater filled heights are 40 and 24cm,
respectively. In order to control inlet and outlet of the fluids and to sample wastewater from the bioreactor, five valves were
connected to the rectors as follow: one valve was connected
to the bottom of the reactor and four valves connected to the
bioreactor’s walls with distances of 5, 10, 25, and 35cm from
bottom of the bioreactor. To run the bioreactor, 12 liters of the
bioreactor volume was filled with dense sludge (Return sludge
of Pegah Co. East Azerbaijan). Then the total volume of the fluid
inside the bioreactor was reached to the 24 liters by adding
artificial wastewater. The experimental set-up of the MBBR
system is shown in Figure 2.
From standard Kaldnes packing medias, the K3 carrier
manufactured by Pakzist Co., was used to fill the bioreactor.
Figure 3 shows the different types of Kaldness carriers including
K1, K2, and K3. The characteristics of the K3 packing media
used in this study are presented in Table 1. In order to suspend
carriers inside the bioreactor and supply the required oxygen,
three small air pumps with a total aeration rate of 8 liters per
minute were used.
Molasses, potassium dehydrogenase phosphate and urea
were utilized to make artificial wastewater. Molasses were used
to stabilize the COD of the sewage entering the bioreactor and
to fix the COD of the initial wastewater contained within the
bioreactor. Also, K2HPO4 was used to stabilize phosphorus level
in the initial wastewater contained within the bioreactor. In
addition, urea (CH4N2O) was used to stabilize nitrogen level in
the initial wastewater inside the bioreactor.
At first step, to adapt the slurry environment for the
activity of microorganisms, synthetic wastewater as feed was
injected into the MBBR system daily. Meanwhile the system was continuously aerated to stabilize the MLSS of the wastewater
in the bioreactor. After one month of commissioning the
system, the MLSS and COD parameters were sampled from the
bioreactor for the measurement purpose. During the period of
adaptation of the sludge and microorganisms, the temperature
of the laboratory was between 16 and 17°C. After 90 days, the
system’s MLSS was stabilized at 3200mg/l. Moreover, the COD
removal rate was about 45%, indicating the adaptation of the
sludge and microorganisms . Finally, the pH of the system
was adjusted to about 7, which is very suitable for growth of the
microorganisms . It should be noted that at the end of the
adaptation period, the very first biofilm layers were observed
on the internal surfaces of the K3 carriers. At the same time the
external surfaces of the carriers became slippery.
Following procedure was used to sample and analyze. First,
after a specific period, the aeration pump was turned off to allow
the sludge to be deposited inside the bioreactor. Then, for the
COD test, 500ml of wastewater sampled from the bioreactor.
According to the results of the COD removal, a certain amount
of the same sample selected for BOD measurement. Due to
the aerobic nature of the process of microorganism activity
inside the system, supply of oxygen for microorganisms is very
important. Therefore, by performing regular tests pH control
parameters and MLSS were evaluated. When MBBR was running,
the pH of the system was kept at an average of 7, and the MLSS
was maintained at a range of 3500-3000mg/l .
As already mentioned, at the end of the MBBR system
compatibility period, biofilm formation was observed on the
surface of the carriers and the external surfaces of the carriers
got slippery . After approximately one week (since the end
of the adaptation period) the number of biofilms increased
significantly. Figure 6 shows the inner and outer surfaces of
K3 carrier before and after the formation of the biofilm layers.
It should be noted that on the outer surfaces of some media
packings, only a very thin layer of biofilm is observed. This is
due to aeration and collision of the carriers which causes that
the biofilm sticking to the outer surface of them is peeled and
become a suspended biomass. For this reason, the inner surface
of the media packings is considered an effective surface for
The removal efficiency of COD and BOD at different HRTs for
the constant loading of COD=1000mg/l was investigated to find
the optimum HRT. It worth mentioning that in previous studies,
the MBBR system functionality evaluated at low HRTs, had a
maximum COD removal at HRT of 2 hours .
Figure 7 shows the amount of effluent COD and BOD at a
constant loading rate of COD=1000mg/l and BOD=490 mg/l at
different HRTs. As shown in both Figure 7a & 7b, the COD and
BOD effluent at HRT of 12 hours is the lowest which means
both COD and BOD removals are the highest. In addition, the
efficiency of both BOD and COD removals have been compared
at different HRTs in Figure 8. As known, the amount of COD
removal is always higher than BOD removal as COD represents
both organic and non-biodegradable organic compounds, but
BOD only contains biodegradable organic compounds. Also
Figure 8 indicates that at low HRTs, COD is more eliminated in
comparison with BOD. The reason is the lack of required time to
start the activity of microorganisms in order to remove organic
matter with biological treatments.
By increasing HRT, enough time to start the activity of these
microorganisms is provided. On the other hand, as shown in
Figure 8, the removal efficiency of COD and BOD at HRT of 12h
is more than the others, which is 87% and 75%, respectively. At
HRT of 8 hours, these efficiencies were calculated 84% and 71%,
respectively. As the biological treatment processes are time
consuming, and there is a marginal difference between removal
efficiencies at HRT of 8 and 12 hour, someone may choose HRT =
8h as an optimal HRT.
Since industrial wastewater has high CODs, treatment
process should be done by a system which saves both time and
cost. In the Figure 9, effects of inlet COD up to 3500mg/l on the
MBBR system performance (COD removal efficiencies) has been
shown. It should be considered that the COD of the system was
continuously increased from 1000 to 3500mg/l. As the results
indicate, the COD removal follows a non-monotonic behavior
along with increasing the amount of inlet wastewater COD. This
can be understood considering behavior of the microorganisms.
At inlet COD range between 1000 to 2000mg/l, microorganisms
still have the capacity to absorb more organic compounds.
Therefore, with increasing COD up to 2000mg/l, the removal
efficiency also increases. However, beyond COD~2000mg/l
microorganism’s capacity for further COD removal is full.
Therefore, an increase in inlet COD amount up to ~3000mg/l
results in accumulation of COD inside bioreactor. Thus, this ends
in reduction of COD removal efficiency. However, when resident
time increases the MBBR system gets compatible with high
CODs (~3000mg/l). Subsequently, this leads to an increment
in both activity and number of microorganisms. Consequently,
these result in COD removal increase. As Figure 9 also shows, the
MBBR system has higher efficiencies > 80% at high CODs, which
can indicate that the MBBR system is suitable for industrial
wastewater treatment processes.
As already mentioned, temperature is one of the most
important parameters in biofilm growth rate and compatibility
during system stabilization for testing . Due to the lack of
sufficient knowledge about the effects of temperature on the
performance of the MBBR system, and in order to enhance
current knowledge, the system performance was studied at
a temperature range of 19 to 32°C. Effects of temperature
variation on the COD removal efficiency has been shown in
Figure 10. According to the results, the COD removal efficiency
diagram can be divided into three phases. As shown in phase
(a), the COD removal efficiency is increases very slowly to ~72%
between 19 to 21°C. In phase (b), there is an abrupt increase
in the removal efficiency reaching up to 90%. In phase (c), the
removal efficiency is increased slightly.
Overall, this behavior of removal efficiency can be rationalized
as follow: In phase (a) (approximately less than 20°C) due to the limited ability of microorganism’s adaption with low temperature
conditions; the COD removal efficiency increases very slowly
up to ~72%. By increasing the temperature of the system
from 20°C up to about 25°C (phase b), due to the sudden rise
in the microorganism’s activity, sharp increase in COD removal
efficiency from ~72% to ~92% happens. At the same time, the
thickness of biofilms also increases. The highest COD removal
efficiency of 94% occurs at a temperature of 32°C in phase (c),
which is much better than the results reported in literature .
However, from 25 to 32, as mentioned, the removal efficiency
rate increases slowly. For example, the COD removal efficiency is
92% at 27°C. The biofilm thickness observed in inner surfaces of
the carriers at 32°C is higher than the biofilm thickness at 27°C.
In general, increasing the thickness of the biofilm reduces the
mass transfer and decreases the rate of increment in removal
efficiency. Hence, it is expected that due to the reduction in mass
transfer, the COD removal efficiency will grow very slowly by
increasing temperature from 25 to above 32°C.
MBBR is one of the modern and innovative systems for
urban and industrial wastewater treatment. Many studies have
been done to prove that this system is suitable for wastewater
treatment process in comparison with others. MBBR does not
have common problems such as sludge bulking and rising,
foaming, poor sludge settling, and carriers clogging. Some
features such as strong resistance to impact, and no need to
return the sludge make the system much easier to operate .
Besides, it is tenacious at high temperatures and CODs, as well
as against shocks such as pH  etc.
In this study, after adaptation of microorganisms and their
accumulation on K3 carriers, system performance was studied
by examining the removal efficiency of BOD and COD at different
HRTs, temperature, and wastewater inlet CODs. Studied COD
range was 1000 to 3500mg/l. It was for first time that K3 carriers
were used to study the MBBR system.
The BOD and COD parameters were determined at HRTs of 3,
5, 8, and 12 hours with a filling ratio of 50%. Although the HRT
of 12 hours had a COD removal efficiency of 86%, but because of
a slight difference of 3% and shortening the treatment process,
HRT of 8 hours was selected as an optimum HRT.
In addition to choosing the optimal HRT, the effects of
different temperatures ranging from 19 to 32°C were also
investigated. The results indicate that there is an abrupt change
in the COD removal efficiency at temperature range between
20 to 25°C because of high activity of the microorganisms. By
raising the temperature to 25°C, the activity of microorganisms
is relatively reduced, and the rate of COD removal efficiency
increment is decreased. According to the results, the optimum
operating temperature was suggested to be 27°C.
In MBBR systems, high level of inlet wastewater COD is
also an essential and important factor in system’s performance
detection, since in industrial and urban wastewaters the number
of organic compounds is high. Therefore, the effects of different
inlet CODs up to 3500mg/l were studied. The results indicate
a non-monotonic behavior of the MBBR system, which can be
understood considering the behavior of microorganisms in
different CODs. In general, for all COD values, the MBBR system
always has a removal efficiency more than 80%.
Ning S, Mustafizur R, Ying Q, Mirela LM, Hector R, et al. (2009) Complete solution and partial delignification of wood in the ionic liquid 1-ethyl-3-methylimidazolium acetate. Green Chemistry 11: 646-655.
Padilla V, Rangel MG, Bullon J, Rodríguez-Malaver A, Gonzalez AM, et al. (2002) Surface Activity of Lignin Fractions Obtained by Membrane-Separation Technologies of Industrial Black Liquors. Iberoam Congr Pulp Pap Res 10: 10-12.