An introduction to MBBR (moving bed biofilm reactor )/
FM Reactor/ FAB /FMR Reactor wastewater treatment
When communities of
microorganisms grow on surfaces, they are called biofilms. Microorganisms in a
biofilm wastewater treatment process are more resilient to process disturbances
compared to other types of biological treatment processes. Thus, biofilm
wastewater treatment technologies can be considerably more robust especially
when compared to conventional technologies like activated suldge process..
In the MBBR biofilm
technology the biofilm grows protected within engineered plastic carriers,
which are carefully designed with high internal surface area. These biofilm
carriers are suspended and thoroughly mixed throughout the water phase. With
this technology it is possible to handle extremely high loading conditions
without any problems of clogging, and treat industrial and municipal wastewater
on a relatively small footprint.
System
description
The MBBR™ biofilm
technology is based on specially designed plastic biofilm carriers or biocarriers that are suspended and in continuous
movement within a tank or reactor of specified volume. The design of
associated aerators, grids, sieves, spray nozzles and other integral parts to
the reactor is also of great importance in making up the system as a whole .
The industrial and
municipal wastewater is led to the MBBR™ treatment reactor where biofilm,
growing within the internal structures of the biocarriers, degrade the
pollutants. These pollutants that need to be removed in order to treat
the wastewater are food or substrate for growth of the biofilm. The
biocarrier design is critical due to requirements for good mass transfer of substrate and oxygen to the microorganisms
. Excess biofilm sloughs off the biocarrier in a natural way .
An aeration grid located at the bottom of the reactor supplies
oxygen to the biofilm along with the mixing energy required to keep the
biocarriers suspended and completely mix within the reactor.
Treated water flows from
reactor through a grid or a sieve, which retains the MBBR™ biocarriers in the
reactor. Depending on the wastewater, the reactors are may be equipped with
special spray nozzles that prevent excessive foam formation.
The MBBR is a biological aerobic degradation of organic
pollutants. The process utilizes millions of tiny, polyethylene biofilm
elements that provide a high surface area as a home for a vast, highly active
bacteria culture. This fixed film process features a flexible reactor design,
the ability to handle load increases without the need for extra tankage, and
remains stable under large load variations, including temperature, strength or
pH. Like the activated sludge process, the MBBR process utilizes the whole
volume of an open tank. Unlike an activated sludge reactor, it
does not require sludge return to operate effectively. In MBBR ,
addition of media quantity and Air Quantity is the Key Factor.
Total reactor volume of the MBBRs is designed for different
hydraulic retention time for different types of waste water at average flows
and than checked against peak flows. Essentially nutrient levels and DO levels
are the only control points for the system.
Moving Bed Biofilm Bioreactor (MBBR) process uses the whole tank
volume for biomass growth. It uses simple floating media, which are carriers
for attached growth of biofilms. Biofilm carrier movement is caused by the
agitation of air bubbles. This compact treatment system is effective in removal
of BOD as well as nitrogen and phosphorus while facilitating effective solids
separation.
Design and Construction Principles
Neutralised and settled wastewater
passes through MBBR for reduction in BOD/COD. Most of the MBBR plants are
provided with vertically or horizontally mounted rectangular mesh sieves or
cylindrical bar sieves. Biofilm carriers are made up of high density (0.95 g/cm3)
polyethelene. These are normally shaped as small cylinders with a cross inside
and fins outside. The standard filling of carrier is not more than 465 m2/m3. Generally, design
load for COD-BOD removal is 20 g COD / m2d. Smaller carriers need
smaller reactor volume at a given loading rate (as g/m2d) when the
carrier filling is same.
It is advisable to use MBBR in
combination with a DEWATS as a pre-treatment
unit, depending on the local conditions and input characteristics. It is a very
robust and compact alternative for secondary treatment of municipal wastewater,
having removal efficiency for BOD 90 – 95% (low rate) and that of 75 – 80% for
high rate. Average nitrogen removal is about 85%. There is no need for sludge
recirculation. Phosphorus and faecal coliform reduction is feasible with
additional passive (non-mechanical) or active (mechanical) system components.
A constantly operating MBBR does
not require backwashing or return sludge flows. It has minimal head-loss.
Coarse-bubble aeration in the aeration zone in the wastewater treatment tank
provides ease of operation at low-cost. Agitation continuously moves the
carrier elements over the surface of the screen thus preventing clogging.
Maintenance of MBBR system includes screening, influent equalisation, clarifier
system, sludge handling and integrated control system. There is no need to
maintain f/M ratio as there is self-maintenance of an optimum level of
productive biofilm. Skilled labour is required for routine monitoring and
operations of pumps and blowers.
Calculations!:Aeration Tank
Volume, HRT, MLSS Values.
|
|||
I am working in a STP &
ETP plant. I need to know how to calculate:
1. Volume of Aeration tank
2. HRT
3. F/M Ratio
4. MLSS value.
The relevant details of the ETP
are as below:
Influent flow = 10 m3 / day
In. flow BOD = 1200 mg / L
In.flow COD = 2200 mg / L
TSS = 850 mg / L
Jeyaroopa
jeyaroopa79@gmail.com
|
