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LAB SCALE STUDY ON MOVING BED BIOFILM REACTOR-
AN EFFECTIVE PERSPECTIVE IN BIOLOGICAL
WASTEWATER TREATMENT
Yogita Sindhi
1, Mitali J. Shah
2
M.E, Environmental Engg., Sarvajanik College of Engg. & Tech., Gujarat, India1
Assistant Professor, Civil Engineering, Sarvajanik College of Engg. & Tech., Gujarat, India
Abstract: The Moving Bed Biofilm Reactor (MBBR) technology is a leading-edge
biological solution for wastewater treatment based on the aerobic biological principle. The
general introduction of moving bed technology is given. The basic treatment of Moving bed
Biofilm Reactor, development and detachment of biofilm, advantages, disadvantages and
application of MBBR has been discussed. In this study, the lab-scale experiments were
carried out to to analyse BOD and COD removal from municipal wastewater. The COD
and BOD removal efficiencies of 60-64% and 80-85% respectively, with 20 minutes HRT
and 4 hours settling time were observed. It is clear from the literature survey and lab-scale
experiment that MBBR is an effective method in order to remove COD and BOD from
municipal wastewater.
Keywords: Biofilm, BOD, COD, Moving Bed Biofilm Reactor
INTRODUCTION
Limited water resources and increasing urbanization require a more advanced
technology to preserve water quality. One of the important factors affecting water quality is
the enrichment of nutrients in water bodies. Wastewater with high levels of organic matter
(COD) Phosphorus (P) and Nitrogen (N) cause several problems, such as eutrophication,
oxygen consumption and toxicity, when discharged to the environment. It is, therefore,
necessary to remove these substances from wastewaters for reducing their harm to
environments. Biological processes are a cost-effective and environmentally sound
alternative to the chemical treatment of wastewater. [4]
Biological treatment processes are systems that use microorganisms to degrade
organic contaminants from wastewater. In wastewater treatment, natural biodegradation
processes have been contained and accelerated in systems to remove organic material and
nutrients. Excess microbial growth is removed from the treated wastewater by physical
processes.
There are already many different Biofilm systems in use, such as trickling filters,
Rotating Biological Contactors (RBCs), fixed media submerged bio-filters, granular media
bio-filters, fluidized bed reactors, etc. They all have advantages and disadvantages. Two
technologies are commonly used for biological treatment of sewage: activated sludge and
trickling filters. A moving bed biological reactor (MBBR) is a compilation of these two
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technologies. The biomass in the MBBR exists in two forms: suspended flocs and a biofilm
attached to carriers. It can be operated at high organic loads and it is less sensitive to
hydraulic overloading. [6]
At the core of the technology are specially designed polyethylene carriers that
provide a large protected surface area for the microorganisms (that eat the waste) to grow and
multiply. This allows a higher concentration of active biomass to be maintained in the reactor
for biological treatment without increasing the reactor size. The result is more treatment
capacity in a smaller area which saves you valuable space, money and allows you to install in
tighter spaces. Besides offering an overall footprint reduction compared to an equivalent
SBR system, the MBBR process also offers a buffer against shock loads. [6]
The MBBR was developed in Norway at the Norwegian University of Science and
Technology in co-operation with a Norwegian company Kaldnes Miljǿteknologi (now Anox
Kaldnes AS). The first MBBR was installed in 1989. Although it is a relatively new
technology to the United States (first introduced in 1995), there are now over 400
installations worldwide in both the municipal and industrial sectors with over 36 in North
America. [4]
REVIEW ON LITERATURE
Ahmad Jalaleddin Mollaei et al has studied that “MBBR is recommended because its
efficiency for treating anionic surfactants in those ranges. In his experiment, the removal
percentage of Sodium Dodecylbenzene Sulfonate (anionic detergent) for up to 200 mg/L
concentration at HRT of about 24 hours was 99.2%, which was more sufficient than other
processes such as electro-Fenton that removed 50 mg/L of anionic surfactant, and activated
sludge which had 99% removal efficiency for only 5 mg/L detergent in wastewater. The
MBBR process was nominated as a sufficient, cost-effective, easy-operating, and suitable
bioprocess, an alternative for treating the pollutants.” [1]
Arti D. Galgale et al has studied that “An aerobic MBBR can be used to remove
phenol from high TDS wastewater. The effect of attached growth biomass on pollutant
removal was much better than suspended growth biomass in MBBR. Three experiments were
conducted in laboratory scale reactor to determine optimum hydraulic retention time (HRT)
in the reactor at 1400 mg/L phenol concentration and 1500 mg/L TDS, effect of increased
TDS (up to 19000 mg/L) on COD removal efficiency of the reactor and to study performance
of the suspended and attached growth biomass in MBBR.” [2]
A. Zafarzadeh et al has studied “partial nitrification/denitrification process in the
moving bed biofilm reactors system can be an acceptable performance for treatment of
wastewater with high load of organic carbon and organic nitrogen compounds. In this
research, the continuously operated laboratory scale Kaldnes (k1) moving bed biofilm
reactors (MBBRs) under partial nitrification-denitrification process were used for treatment
of synthetic wastewater containing ammonium and glucose. During optimum conditions, the
average removal efficiency of total nitrogen (TN), ammonia and soluble organic carbon
(SCOD) occurred as 98.23%, 99.75% and 99.4%, respectively.” [3]
Husham T. Ibrahim et al has investigated that “combination of anoxic/aerobic
MBBR achieves high COD removal ranging from 76.24 to 98.6% corresponding to HRTs of
4.95 to 8.25 h, from domestic wastewater. These MBBRs was able to remove more than
98.0% of ammonium nitrogen, 71% of total nitrogen and 90% of total phosphorus from
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influent wastewater at HRT of 6.2 h which is highly preferable to conventional biological
nutrient removal.”[8]
Javid, A.H. et al has sfound that “MBBR is not F/M-parameter-sensitive. It can fully
maintain its stability in organic loads several times higher than conventional systems such as
activated sludge, trickling filters, RBCs, ABF, etc. This is considered a very important
advantage of the process. Compared to the old conventional processes, this system requires
less HRT to reduce wastewater organic load to the optimal level. This can lead to reduced
volume of aeration tank. Therefore, MBBR can be used to increase the capacity of WWTPs
and upgrade them to improve effluents quality. Furthermore, by combining this system with
anoxic and anaerobic systems (in remaining aeration tank) the output nutrient rate can be
reduced to an acceptable level. Thus, the current WWTPs can be upgraded.” [10]
M. Kermani et al has studied on “Application of Moving Bed Biofilm Process for
Biological Organics and Nutrients Removal from Municipal Wastewater. They found that
Aerobic phosphate removal rate has a good correlation to the anaerobic phosphate release
rate. During optimum conditions, close to complete nitrification occurred in the aerobic
reactor with average ammonium removal efficiency of 99.72%.” [11]
M. Makowska et al has studied on “Treatment of Septic Tank Effluent in Moving Bed
Biological Reactors with Intermittent Aeration. Three hybrid reactors with intermittent
aeration were simultaneously operated in laboratory.Various groups of organisms were
observed in both – activated sludge flocks and biofilm. The highest concentration of
filamentous microorganisms was observed in the reactor with the highest COD loading.
Rotifers were much more abundant in biofilm than in flocks, due to their relatively long
growth time” [12]
MOVING BED BIOFILM PROCESS
A. Basic Treatment Process:
The idea of the MBBR is to combine the two different processes (attached and
suspended biomass) by adding biofilm small High Density Polyethylene (HDPE) carrier
elements into the tank and biofilm attachment and the growth has been proposed. The kind of
system is usually referred as IFAS (Integrated Fixed-film Activated Sludge) process. In these
systems the biomass grows both as suspended flocs and as attached biofilm. In this way, the
carrier elements allow a higher biomass concentration to be maintained in the reactor
compared to a suspended growth process, such as activated sludge. This increases the
biological treatment capacity for a given reactor volume. [15]
Figure 2 shows the anaerobic, aerobic reactors and the biofilm carrier used for MBBR
process. [7]
Figure 1: The principle of Moving Bed Biofilm Reactor and the shape of biofilm carrier
[6]
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The agitation pattern in the reactor is designed to provide an upward movement of the
carrier across the surface of the retention screen which creates a scrubbing effect to prevent
clogging, so that the whole reactor volume is biologically active resulting in higher biomass
activity.
The foremost difference between the MBBR and IFAS system is the presence of a
return activated sludge stream that remains central to the IFAS process. In the MBBR
process, biomass is remained in the bioreactor through attachment to suspended carrier
material using sieves. [15]
B. Attachment and detachment of biofilm:
The majority of carbon input to wastewater treatment plants constitutes particulate
organic matter in the form of slowly biodegradable organic matter. Particles entering a
MBBR are either degraded by microorganisms in the biofilm or pass straight through the
process. The particles may be completely degraded and taken up by microorganisms but they
could also be partially degraded and then released back into the bulk liquid. A fraction of
partially degraded particles will join under graded particles that pass straight through the
process, most of the partially degraded particles are however likely to come in contact with
biofilm again for further degradation. [15]
Figure 2: Development of Biofilm on carrier [6]
Completely degraded substrate is transported through the bacterial membrane, where
it is used for respiration and production of new biomass. Almost 50% of the energy in the
substrate is bound in new biomass. Biomass eventually detaches from the carrier surface
mainly due to shear forces and degradation in the interior biofilm. Thus, to some extent,
biodegradation transforms organic matter in influent water to particles of biomass. [15]
C. Advantages of MBBR
Compact unit with small size
Increased treatment capacity
Complete solid removal
Improved settling characteristics
Low head loss
No filter channeling
No need for periodic backwashing
Reduce sludge production and no problems with sludge bulking [15]
D. Disadvantages of MBBR:
Upstream fine screening
Medium/ coarse bubble aeration
Media retention screen assemblies
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Limited degree of process control
Less common process [16]
E. Applications
The moving bed biofilm process has been used for many different applications. In
figure, some common flow diagrams for applications has been shown. [5]
Pre- settling is normally used as pre-treatment primarily to avoid clogging of the bioreactors
sieves. Pre-settling is not prerequisite, however, very often useful because it aids flexibility,
for instance by allowing pre-cogulation.[5]
Figure 3: Typical Moving Bed Biofilm process flow diagram for different applicatons
[6]
EXPERIMENTAL
A. Collection of wastewater sample
The sewage wastewater sample was collected from GNFC Township sewage
treatment plant, Bharuch, Gujarat
B. Experimental Setup and Procedure
The three sewage samples were taken on different days. The reactor was made up of
acrylic having the volume of 0.064 m3. 15 lit samples of sewage wastewater were put in the
reactor where packing media was provided. The characteristics of barrier used are shown in
the following table. Two submerged pipe aerators of capacity 180 lit/hr were provided in the
tank to supply air. The samples were allowed to treat for 30 minutes. Then 4 hours settling
was provided. The samples were analysed for COD and BOD before and after treatment.
TABLE 1 CHARACTERISTICS OF THE CARRIER
Material High Density Polyethylene
Surface area of media 400 m2/m
3
Number of media used 350
Density of media > 0.9 GM/CC (grams per cubic centimetre
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Figure 5: Experimental setup of waste water
I. RESULT
The following table shows the results of lab scale treatment of three different sewage
samples
TABLE 1: RESULT OF LAB SCALE EXPERIMENT
Sample Initial
BOD
Final
BOD
% BOD
removal
Initial
COD
Final
COD
% COD
removal
1 122 18 85 318 127 60
2 155 31 80 346 129 63
3 139 21 85 332 119 64
CONCLUSION
In this research, an experimental study to evaluate the application of MBBR system
for COD and BOD removal from sewage wastewater is described.
The lab-scale MBBR system was a very effective treatment to remove COD and BOD
with removal efficiencies 60-64% and 80-85% respectively, with 20 minutes HRT
and 4 hours settling time.
According to the resultsof lab-scale experiments and literature review, we can suggest
that the moving bed biofilm process could be used as an efficient and effective
treatment for BOD and COD removal from sewage wastewater.
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