Comparison of MBR and MBBR Technologies in
Industrial Wastewater Treatment
By Joanna
Kucharska – Ciszek, Łukasz Szewczulak
Coauthor:
Katarzyna Pisek
INTRODUCTION
In
the current era of dynamically developing high-performance
technologies (also in the context of wastewater treatment processes),
there is a tendency to search for unconventional and at the same time
increasingly effective technical and technological solutions. This
has led to highly efficient wastewater treatment facilities across
various industrial sectors.
The
consequence of modern technologies is the continuous improvement of
the quality of discharged industrial wastewater. Furthermore,
increasingly stringent laws regarding the quality of purified
wastewater discharged into the environment (for example, a receiving
body such as a river), drives the use of new technological solutions
in order to obtain better efficiency and effectiveness of wastewater
treatment systems. Formal and legal issues (acts, regulations,
standards, etc.) therefore remain a key issue when designing modern
wastewater treatment plants and selecting the right method of their
treatment, both for newly built, as well as modernized and expanded
production plants.
Formal
and legal issues therefore remain a key issue when designing modern
wastewater treatment plants and selecting the right method of their
treatment. In addition, the factors determining the selection of the
appropriate wastewater treatment method should also include
environmental, social and economic benefits, as well as advantages in
terms of land development, reduction of odor and noise emissions,
generation of waste (including sludge) and many others.
2. HIGH-PERFORMANCE
ACTIVATED SLUDGE TECHNOLOGIES
2.1 INTRODUCTION
The
criteria that modern industrial wastewater treatment systems should
meet have prompted technologists to attempt to modify and intensify
the well-known and decades-old process based on conventional
activated sludge (CAS). These procedures have led to the creation of
modern, high-performance versions and variants of the activated
sludge process, often referred to as the ‘thickened activated
sludge’ technology, which is part of the Best Available Technology
(BAT). These technologies are Membrane Biological Reactor (MBR) and
Moving Bed Biofilm Reactor (MBBR). These two processes allow for the
design of treatment plants dedicated specifically to the treatment of
industrial wastewater (chemical, food, pharmaceutical, refinery and
petrochemical industries, etc.) with high biochemical
oxygen demand,
chemical
oxygen demand,
or ammonium nitrogen loads.
2.2 MBR
TECHNOLOGY
The
leading process in MBR technology is the separation of solids and
liquids by means of a semi-permeable membrane placed directly in the
aerated activated sludge chamber, or as a separate device in a
separate tank. This solution ensures that the membrane maintains the
biomass (activated sludge) in the bioreactor, and the purified sewage
is discharged to the receiver.
The
technology is based on the following system elements:
-
Biological reactor with activated sludge
-
Membrane tank
-
Activated sludge recirculation system
-
System for removing excess sludge
-
Auxiliary systems
Achieving
high-quality standards for treated wastewater using MBR technology
allows for its direct discharge into sensitive receivers, as well as
its use in applications such as plant irrigation or toilet flushing.
This also creates the possibility of a potential direct supply of
reverse osmosis (RO) modules.
Thanks
to the separation role of the membrane in the MBR bioreactor, it is
also possible to remove some colloids, viruses and bacteria, as well
as other pathogens from the treated wastewater, thus initiating the
preliminary disinfection stage.
2.3 MBBR
TECHNOLOGY
MBBR
technology is based on a biological reactor with a biofilm covering a
moving biological bed in the form of plastic shapes. As a result of
aeration of the reactor chamber, these shapes move (moving bed),
providing microorganisms with a surface for proper growth. This
technology is based on four basic components of the system:
-
Biological reactor with activated sludge on biofilm carriers
-
Sewage aeration installation
-
Sewage mixing installation
-
Excess sludge settling tank (clarifier
or dissolved air flotation (DAF))
The
proper selection of each and the correct incorporation of these
components determines the effective and efficient treatment process.
This
technology combines the technology of submerged beds with the
traditional technology of CAS, creating the possibility of treating
sewage in both an aerobic and anaerobic environment.
One
of the significant advantages of MBBR technology is the possibility
of its adaptation to existing and used tanks, using the existing
infrastructure and equipment. MBBR technology is known for its
flexibility, relatively simple operation and ability to effectively
cope with variable loads as well as poorly biodegradable and toxic
substances.
2.4 COMPARISON
MBR AND MBBR TECHNOLOGY
When
comparing MBR and MBBR technologies, the following aspects are
considered:
-
Degree of reduction of chemical compounds.
-
Sensitivity to fluctuations in sewage parameters and hydraulic loads.
-
Demand and consumption of electricity.
-
Operational aspects, including operational and repair.
-
Use of construction materials.
-
Building area/construction space.
-
Ratio of estimated capital expenditure (CAPEX) investment outlays to
operating expenditure (OPEX) operating outlays.
The
basic features of both technologies are listed in Table 1:
Table
1 List of basic features of MBR and MBBR treatment technologies
MBR
|
MBBR
|
Process
based on membrane filtration for the separation of solids and
liquids
|
A
process based on suspended biofilm carriers for wastewater
treatment
|
Higher
quality wastewater owing to advanced membrane filtration process
|
Reliable,
efficient wastewater treatment with a smaller footprint
|
Requires
regular cleaning/maintenance of membranes
|
Has
lower maintenance requirements due to the lack of membranes
|
Is
more susceptible to contamination/clogging
|
Is
less susceptible to contamination/clogging
|
Higher
mixed liquor suspended solids (MLSS) from CAS
|
|
The
tabular comparison of both technologies is presented in Table 2:
Table
2 Comparison of MBR and MBBR purification technologies
MBR
|
MBBR
|
Technology
|
Wide
reactors and membrane modules separating biomass from treated
wastewater
|
Plastic
carriers on which the wastewater treatment biofilm is formed and
grows
|
High
pollution reductions
|
Suspension,
colloids, pathogens
The
degree of retention of suspended solids in the separation process
on MBR membranes is more effective compared to that obtained using
DAF
|
Organic
compounds, nitrogen, phosphorus
|
Advantages
of the solution
|
Purified
sewage with potentially more favorable quality parameters,
suitable for reuse in technological processes or for discharge
into the environment
|
Owing
to its ability to regenerate and adapt, biofilm is resistant to
sudden hydraulic loads or pollution loads with exceeded quality
parameters
Better
resistance to oily wastewater compared to MBR technology
|
Disadvantages
of the solution
|
Sensitivity
to sudden hydraulic loads and loads from sewage with exceeded
quality parameters (especially organic compounds)
High
risk of membrane fouling due to exposure to sewage with
above-standard parameters, which may even result in the need to
replace the membranes
|
Purified
sewage with higher concentration of total suspended solids (TSS)
compared to MBR technology
May
require tertiary treatment (i.e. filtration)
|
Electricity
demand and consumption
|
Greater
demand for electrical energy to maintain the required wastewater
pressure and overcome membrane resistance
|
Lower
demand for electricity
|
Material
|
Ceramic
membranes are characterized by better resistance to organic
compounds in wastewater than polymer membranes, which clog more
quickly
|
High-Density
Polyethylene (HDPE) and polypropylene are the optimal materials
due to their resistance to most organic compounds, with
polypropylene having greater resistance than HDPE
|
Building
area
|
Less
space is required than for conventional biological treatment
plants
|
The
MBBR system may require more space and larger reactors to
accommodate the carriers and ensure sufficient contact time in the
biological process
|
Operational
and maintenance aspects
|
The
MBR system requires regular washing of the membranes, which is a
specialized and time-consuming process
In
the case of repeated fluctuations in the concentration of
pollutants in sewage, resulting in clogging/fouling of membranes,
it may be necessary to replace them, however, it is difficult to
estimate the frequency of this because it depends on the sewage
parameters. Replacing membranes may require partial or complete
stopping of the treatment process, which is both expensive and
time-consuming.
Fouling
prevention requires:
-
Operator supervision and monitoring of transmembrane pressure.
-
Potentially increasing the frequency of membrane cleaning even
daily (chemically enhanced backwash (CEB)), which will
consequently translate into:
a)
higher consumption of chemicals (acid, caustic soda, chlorine
compounds).
b)
work safety.
c)
the need to install additional instrumentation and control.
d)
the need to employ qualified operating staff whose competences
will fully cover the needs in the scope of specialist service of
the entire installation, with particular emphasis on the membrane
part (current operation, cleaning, replacement, emergency
conditions, etc.).
All
MBR systems would likely require two separate aeration basins to
maintain operability when membrane replacement is required (two
75% reactors are recommended)
The
results of wastewater treatment in the MBR system are visible
shortly after start-up.
It
is necessary to provide the membrane modules with lines supplying
cleaning chemicals and their storage for operating and servicing
activities. The installation is much more extensive in terms of
the complexity of the hydraulic system (lines, fittings, dosing
pumps, control and measurement instruments, etc.)
|
In
the MBBR system, occasional replacement of carriers may be
necessary. However, this does not require stopping the process,
because it only involves replenishing the carriers in the reactors
The
period of biofilm formation and growth in MBBR can take more than
three weeks. The time needed to remove toxins, in the case of bed
poisoning, is also longer
A
less complicated system in terms of flow hydraulics
|
CAPEX
investment outlay estimate
|
30%-40%
bigger than MBBR*
|
Comparing
MBBR and MBR technologies reveals their advantages and limitations.
Both
have unique features that make them suitable for specific
applications.
Choosing
the right technology requires considering the specific needs of
investment.
MBBR
offers a cost-effective solution for wastewater treatment with high
efficiency and low energy consumption. The biofilm substrate
contained in it supports biological treatment, effectively removing
organic contaminants.
An
existing CAS can be converted to an MBBR system when organic loads
increase across operating plants.
However,
MBR provides higher wastewater quality. It combines biological
treatment with membrane filtration, eliminating suspended solids and
ensuring high levels of pathogen removal. MBR systems do not require
secondary settling tanks or tertiary filtration, which reduces the
required surface area.
2.5 CONCLUSIONS
Due
to the advantages of MBR and MBBR technologies over conventional CAS
technology, these technologies are gaining increasing popularity and
are now widely used in industrial wastewater treatment plants.
Moreover, they are among the most widespread variants of the
biological wastewater treatment process.
The
compact design of the systems ensures a higher concentration of
biomass. In the case of MBR bioreactors, biomass is maintained in a
correspondingly smaller tank. In the case of MBBR bioreactors,
biomass is concentrated thanks to the immobilized microorganisms of
activated sludge on a bed suspended in sewage.
This
gives both technologies the features of high-performance and
high-efficiency treatment systems using simple processes, while
ensuring their flexibility, which in turn gives wide possibilities of
expansion. As a result, the treated sewage meets the highest quality
standards in relation to physicochemical and microbiological
properties.
Both
methods are future-proof solutions that allow for maximizing
efficiency, minimizing costs, including operating costs, while
meeting strict environmental law requirements and are used in
wastewater treatment plants from various production processes
(refining, petrochemistry, chemistry, pharmacy, food production,
energy, municipal wastewater).
Fluor’s
global expertise and experience in delivering projects of varying
scales for diverse clients has equipped us with deep market insight
and the ability to select the most suitable wastewater treatment
technologies. Whether driven by spatial optimization, restrictions on
the quality of the treated wastewater, or accelerated implementation
timelines, Fluor can tailor solutions to meet specific project needs.
Beyond
technology selection, we support clients throughout the entire
project lifecycle – from the initial feasibility study through to
construction and commissioning. Our market knowledge and hands-on
experience enable us to deliver solutions that meet the requirements
of even the most demanding users.
Selecting
the right wastewater treatment technology amid growing environmental
and legal pressures is vital step toward sustainable development –
cost-effective, energy efficient, environmentally responsible
solutions that are an investment in future generations. With our
proven expertise, Fluor is well-positioned to implement these
solutions at scale.