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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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Sodium Dodecylbenzene Sulfonate by Moving Bed Biofilm Reactor, Using Synthetic

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[02] Arti D. Galgale, Neha B. Shah, Dr. Nirav G. Shah, Treatment of Wastewater Containing

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Performance Of Moving Bed Biofilm Reactors For Biological Nitrogen Compounds

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