FlooBed - MBBR - Highly Efficient and Compact Wastewater Treatment Bioreactor

Ovivo’s MBBR technology (Moving Bed Biofilm Reactor) is called FlooBed process. In MBBR process most of the microbes live attached on the freely moving plastic carrier elements. Sometimes this technology is also referred as SCBP (Suspended Carrier Biofilm Process). The principle is to have a continuously operating, non-clogging biofilm reactor with a high specific biofilm surface area.

When microorganisms grow on surfaces, they are called biofilms. In a biofilm microorganisms are protected by a slimy layer of extracellular polymeric substances, which the microorganisms will produce naturally by themselves. Under this protective layer microorganisms are much better protected from changes in the surrounding conditions than the microorganisms living freely in the suspension. In addition in biofilm processes the total amount of biomass is greater than in the conventional activated sludge processes – up to 5 times higher. Hence, biofilm wastewater treatment technologies are considered more robust and efficient when compared to the conventional suspended growth technologies like activated sludge.

However, the conventional biofilm processes have had some serious drawbacks that limit their usage. These drawbacks include media blocking by precipitation or by excessive biofilm growth, limited biomass control and limited overall process control.

FlooBed MBBR technology was develop in the beginning of 1990’s to combine the advantages of the suspended growth and biofilm processes, while at the same time eliminate their weaknesses.

Due to the efficiency of the biofilm when compared to the suspended growth processes the loading of the MBBR process can be up to 10 times higher than with the conventional activated sludge processes. Because of this considerable savings can be achieved in construction costs. MBBR process is also easy to operate, because it is tolerant against peaks of organic load, possible toxic spills and variations in flow rate.

FlooBed carrier elements have a large protected surface area and a density close to water density. Ovio has developed different carrier types for different kind of wastewaters. FlooBed carrier RF438 is designed for high concentrated fiber containing industry wastewaters, which promote high biomass growth. FlooBed carrier RF127 has a high surface area and it is especially suitable for municipal, petrochemical and food & beverage wastewaters. Carriers can be made of either virgin or recycled polyethylene. The size and shape of the carrier elements are designed so that the structure is strong and durable, while at the same time they are open so water, air and wastewater compounds can easily move through them.

The reactors are completely mixed and the free-swimming carriers are kept in continuous suspended motion with specially designed bottom aeration system. In FlooBed MBBR reactors aeration system always covers the entire bottom area so that there are no dead zones inside the reactor. Ovivo has specially designed two different kind of aeration systems for MBBR process: robust stainless steel aerator system for the applications where the mixing air amount is the limiting factor and an energy saving plastic diffuser system with high oxygen transfer rate. There are no mechanical mixers inside the FlooBed MBBR.

Aeration air is produced with separate aeration blowers. Normally MBBR reactors are equipped with dissolved oxygen measurement, which will be used to optimize the energy consumption.

Carrier elements are retained inside the reactors with specially designed screens that are placed in front of the inlet and outlet. Different kinds of screens are used for different carrier types. Screens are robust design and made of stainless steel.

Depending of the inlet wastewater quality and the treatment requirements FlooBed MBBR process can have one or several reactors in series or parallel. MBBR process can also be followed by an activated sludge process, at which time it is called as FlooBed BAS process. In this kind of process combination the MBBR stage is designed to be heavily loaded system while the activated sludge basin acts as a low loaded process where the concentrations of the impurities are reduced to the minimum level.

FlooBed MBBR technology is very suitable also for the capacity increment of the existing treatment plants. A separate bioreactor can be installed in front of the existing biological process or the existing aeration basins (whole volume or just a part) can be converted to MBBR process. The geometrical shape of the aeration basin is not a problem, because MBBR can be build inside a rectangular or circular basin and the water depth can be anything between 2 – 20 m.

Biological nutrient removal is many times a challenging task for the treatment plants using activated sludge processes. The required long sludge age may produce some difficult problems like sludge bulking and the operation of the plant is complicated. MBBR is an ideal solution to enhance the biological nitrogen removal. When MBBR reactor is used for nitrification the theoretical sludge age can be considerably shorter. This equals with smaller tank volumes and less sludge recycling and hence eases the operation of the biological process.

Solid separation, if required, after the MBBR process can be performed with conventional sedimentation clarifier, lamella clarifier or with a dissolved air flotation (DAF).

Typical design parameters for FlooBed MBBR

• Hydraulic retention time: 1 – 6 h
• Carrier filling degree: 20 – 60 %
• Organic load range: 1 – 20 kgBOD/(m3*d)
• Biomass concentration inside the reactor: 4 – 12 kgVSS/m3
• Biomass bound on the carriers: 70 – 80 % of the total amount
• Sludge recirculation rate: 0 – 15 %

Creating Value

• Long and extensive experience of full-scale references.
• Energy savings with Ovivo aeration system.
• Smaller foot print => savings in construction costs.
• Low sludge load to following solids separation units. Possibility to use lamella clarifier and/or DAF => additional space saving.
• Lower sludge production with multistage FlooBed BAS process.
• Tailor-made solutions according to the customer’s needs.