MBBR and IFAS Attached Growth Process

Fixed film or attached growth processes have been in use for biological wastewater treatment since late 1800s. In the attached growth process micro-organisms responsible for organics (BOD, COD) and nutrient (Ammonia, TKN) removal from wastewater are allowed to grow on specific support medium or carrier material which provides habitat in the form of surface for the growth of microorganisms on it.

Though attached growth process have same metabolic pathways for pollutant removal as compared to attached growth activated sludge process, they offer distinct advantages over suspended growth activated sludge process such as:

  • Smaller footprint
  • Minimize needs for secondary settling units
  • Operational simplicity
  • Protection Against Toxic Shock loads
  • Reduced operating and energy costs.

One of the first applications of attached growth processes involved use of gravel media as support mechanism in biological filters developed as early as 1890. Over the years due to continuous research and innovation, various types of media and process configurations have been developed. These different media types include simple wood sheets, blast furnace slag, coarse sand, rocks and pebbles, cords, textile materials and asbestos sheets. These media have been incorporated into different process configurations like biological filters, contact beds, Trickling Filter, Rotating Biological Contactor (RBC), Biological Aerated Filters (BAF) and Submerged Aerated Fixed Film Filter (SAFF).

Further, with more understanding and knowledge about attached growth processes and significance of media for microbial growth, there has been a trend towards developing attached growth process utilizing free floating media for biological growth in the reactors. This variant termed as MBBR (Moving Bed Bio Reactor) or IFAS (Integrated Fixed Film Activated Sludge) utilizes tiny floating carrier media which are kept in suspension just like the floc particles of suspended growth process. These tiny media or carriers are made of different materials like Poly Propylene, HDPE, LDPE, PU foam and have different shape and structure which allows growth of biomass responsible for the degradation of target pollutants.

The free moving variant of attached growth configuration commonly known as MBBR media enhances the advantages of traditional attached growth processes overcoming some of the limitations present in the traditional attached growth processes.

Fee floating MBBR media based attached growth process solutions have been successfully implemented for various wastewater treatment applications like BOD removal, COD removal, treatment of industrial effluent from different industries, Nitrogen removal and upgradation of existing Sewage Treatment Plant and Industrial effluent treatment plants based on activated sludge process for higher capacity and better removal efficiencies.

Advantages of MBBR attached growth process:

  • Simplicity of design
  • Flexibility of operation and ease of maintenance
  • Can be configured with variety of settling equipment like Lamella and Dissolved Air Flotation systems
  • Smaller footprint
  • Higher volumetric loading rates and removal efficiencies