Improved Moving Bed Biofilm Reactor for domestic wastewater treatment

In general, Moving Bed Biofilm Reactors include floatable media, an aeration grid, and a sieve to restrain the media inside the reactor. The here presented hydro-dynamically improved MBBR process is an adapted form of this treatment technology and intends to

• increase efficiency of the MBBR approach by enhancing biofilm growth as a result of improved hydrodynamics
• reduce the overall treatment time and volume of the reactor as compared to conventional MBBRs
• reduce the energy requirement for keeping the media in suspension due to enhanced hydrodynamics as compared to conventional MBBRs

In order to enhance the number of microorganisms to treat the wastewater, just as the MBBR approach, this technology uses floating plastic carriers (media) inside an aeration tank. Organic matter is consumed by the microbes, which gradually multiply and grow on the media. The media offers surface area for the growth of microorganisms in the reactor to cling to and thrive. The areal footprint of the tanks is smaller due to the greater specific surface area of floatable media for the organic matter degradation. Diffused aeration provided at the bottom maintains the required dissolved oxygen (DO) level and keeps the media in suspension. These special features offer greater effectiveness and value as compared to traditional suspended growth processes.

By enhancement of the hydrodynamics in the reactor, improved MBBR intends to facilitate the floatable media to utilise the whole volume of the reactor, which is generally not seen in conventional MBBR system. The biofilm growth on the floatable media increases due to the improved hydrodynamics of the MBBR.

Up-gradation and retrofitting of conventional MBBRs can also be carried out by introducing the concept of improved hydrodynamics. This modification aims to result in the increment of overall removal efficiency for major parameters like suspended solids, BOD and COD of the wastewater.

A screen in the primary stage is provided to remove the floatable inorganic and suspended large particles, which also prohibits the entering of large particles potentially causing hinderance in downstream units. Thereafter, grits are removed in a grit removal chamber. The next stage is an oil and grease trap where fat, oil and grease gets removed. In the reactor soluble organics present in the wastewater are removed. The suspended solids or the degraded biomass is removed in the settling tank. In  the configuration presented in this factsheet, the secondary treated wastewater is thereafter passed through multi-grade filter and disinfected using chlorine. The final treated wastewater has many applications, for instance gardening, green belt development and toilet flushing, etc.

More information on the conventional Moving Bed Biofilm Reactors (MBBR) technology can be found by clicking on here.

This technology is resistant to clogging and shock loads. Due to the large quantity of mixed liquor suspended solids (MLSS) inside the reactor, this type of system can take shock loads without reducing the plant performance. It is a compact treatment system, increased treatment capacity and improved settling characteristics, best used to remove biological contaminants from wastewater. It is important to note that continuous power supply is required for aeration and fluidization.

In general terms, this type of system requires low maintenance and is comparably easy to operate, since no periodic backwashing is required, and the sludge production is low and there are no problems with sludge bulking.

However, operation staff needs to be skilled to perform the following tasks:

• proper monitoring of the inlets and outlets of sewage treatment units for free flow of wastewater
• ensuring the sewage is being pumped at the constant designed rate
• dissolved oxygen (DO) measurement to check the availability of adequate DO and ensuring adequate DO supply
• Regular monitoring of biofilm growth and recycling of sludge in case a decrease of biofilm in the reactor is observed.
• If combined with a chlorination unit for disinfection: control of chlorine dosing at the final outlet
• Routine check-up of electro-mechanical equipment for efficient functioning.
• Regular cleaning of screens at the inlet sump and ensuring sufficient wastewater at the inlet for pumping
• Regular draining of grits and back-washing of multi-grade filter
• Maintaining log-book records of equipment operation, maintenance, repairs, consumption of chemicals and energy
• Maintaining log-book records of manpower deployment, flow data and observations on functioning of plant.
• Maintaining overall hygiene and safety at the plant
• Monitoring the structural cracks and leakages. Structural examination of steel frames, pipe connection fitting, and lookout for the corrosion of the materials used.

Currently, conventional MBBRs are commonly used for wastewater treatment in India. The major drawback of these MBBRs is the fact that the media floats only in the top region of the reactor thereby not utilizes its full volume. As a result, a good biofilm growth is not observed due to which its treatment efficiency is compromised.

This hydro-dynamically improved MBBR is a novel treatment technology and is being implemented for the first time in the PAVITR project. This improved design enables media to utilize the entire volume of reactor thereby reducing dead zones inside the reactor. As a result, good biofilm growth is observed.

Currently conventional MBBRs are being used globally for wastewater treatment. Although some studies have been carried out to improvise the existing technology, they were mainly focusing on improving the carrier media and optimizing aeration and agitation. There are not many studies been conducted on improving the hydro-dynamics.

The information presented in this factsheet is based on a document provided by the authors. It is important to note that the authors did not provide citations for the information presented herein. As a result, we are unable to verify the original sources of the data. This factsheet is intended to offer a summary of the available information, and readers are encouraged to independently verify the details for accuracy.