MBBR Media Used in Wastewater Treatment

Aeration tank: The tank is similar to an activated sludge tank. The aeration is used to keep in motion the activated sludge and carriers. The MBBR system separates the excess bacteria and sludge which are directed to the final separator.

Special plastic carriers: They provide a surface for biofilm growth. Carrier materials are made of materials with a density close to that of water (1g/cm3) an example is high-density polyethylene (HDPE) with a density of 0.9g/cm3. These carriers are moved in the tank through the aeration system. This ensures good contact between the wastewater and the biomass on the carriers.

Benefits of MBBR Technology

• Saving of space due to its compactness
• Easy to maintain
• Good for a high volume of load
• Extension and expanding are easy. This made possible by increasing the filling degree of carriers.
• Lower discharge costs
• MBBR is not affected by toxic shock
• Independent process performance because there is no return line for sludge; the MBBR eliminates the return activated sludge (RAS)
• It has high effectiveness of sludge retention time (SRT) which enhances the nitrification process
• Production of sludge is lower
• It does not need recycling of the sludge-like activated sludge system
• MBBR media is installed to retrofit existing activated sludge tanks in order to increase its capacity

Design of MBBR Systems

It uses a combination of activated sludge process i.e. suspended growth and biofilter i.e. attached growth.? It uses the entire tank volume for biomass growth by implementing the carriers for attached growth of biofilm. Movement of carriers is enabled by air bubbles through agitation.

The reactor can be in any shape and support different load depending on carrier filling. MBBR design of reactor depended on the actual wastewater characteristics and locality.? The plants come either with vertical or horizontal mounted rectangular mesh sieves. The reactor can also be fitted with cylindrical bar sieves.

MBBR carriers are cylinders having a cross inside and fins outside to increase the surface area. The standard used is below 70% of carriers in an area of not more than 465m2 per m3. MBBR is used together with a septic tank or a pre-coagulation step for pre-treatment. MBBR technology can be designed with additional non-mechanical or mechanical system to enhance phosphorus and fecal coliform reduction.

Application of MBBR

Biological Oxygen Demand (BOD) removal – It requires only one wastewater tank with the MBBR and clarification.

Nitrification – It uses two tanks one for BOD removal and the other for nitrification.

Denitrification – It?uses four aeration tanks in this order before emptying in the clarification with pre denitrification, BOD reduction, nitrification and post denitrification.

MBBR technology is applicable in industries, marine and for municipal wastewater treatment.

Operation and Maintenance of MBBR

MBBR which is in constant use does not require backwashing or return sludge flows. Wastewater treatment tank operation is at low cost because of the coarse-bubble aeration in the aeration zone. The agitation constantly moves the carriers over the service eliminating clogging.

Maintenance of the MBBR system is mainly done in the form of screening, sludge handling, influent equalization and it also involve maintaining the integrated control system and clarifier system. The MBBR requires skilled personnel for the routine monitoring of pump and blower operation. MBBR technology has a self-maintenance mechanism for the level of biofilm.

MBBR vs MBR

Membrane bioreactor is based on a combination of conventional activated sludge and biofilm media. Comparison between MBR and MBB can be done using the following key criteria:

• Capital investment of MBR is higher than of MBBR
• MBR requirement for screening is higher than that of MBBR technology
• MBBR system does not require chemicals in its operation like MBR system
• MBR system is difficult to operate as compared MBBR
• MBR requires recirculation pump and air scouring blowers which are not applicable in MBBR
• Both systems require aeration blowers
• In case of power shutdown, MBR can last up to 24 hours while MBBR lasts up to 10 hours after which the bacteria forms bio-cakes.
• MBR is better in shifting of complex or toxic substances than MBBR
• MBR effluent water quality is superior but MBBR`s is suitable for irrigation purpose only
• Both are susceptible to oil and grease for MBR membrane can be cleaned well or replaced but for MBBR technology the carriers need to be changed and the plant will require a ten-day restarting time.

Conclusion

The quantity of biomass plays a big role in the removal efficiency of the MBBR system, it can be increased through the volume of carriers per unit. The carrier’s performance needs to be proven for specific wastewater treatment for application of different cases. Design of a water treatment plant should not be based on assumption or estimation but the correct material should be used for the carrier and the volume required calibrated.

MBBR technology is effective for wastewater treatment if the regulation concerning the effluent water discharge. The system is flexible in its application and can easily be relocated. Wastewater treatment as required for ecological reasons can be done using the MBBR.