MABRs and MBBRs
Both the MABR (a membrane-aerated biofilm reactor) and the MBBR (moving bed bioreactor) are examples of fixed film/media processes. As such, they are both based on a biofilm attached to a substratum whose properties to some extent determine both the biomass concentration and the microbial ecology in the bioreactor. Both processes can be distinguished from the MBR, which is a suspended growth process where the membrane is used to retain the mixed liquor in the process bioreactor.
The characteristics and applications of the three different processes are given below.
|Membrane aerated-biofilm reactor
|Intensive (low-footprint) biological treatment using a membrane both as the biofilm substrate and for molecular (‘bubbleless’) aeration
|Moving bed bioreactor
|Controllable biological treatment at relatively low energy demand using agitated media as the biofilm substrate
|Intensive (low-footprint) biological treatment using a membrane for clarification and substantial disinfection
Of the two media processes, the MBBR is the simpler, being based on relatively inexpensive suspended plastic media particles on which the biofilm grows. The oxygen for maintaining the biofilm is provided by air bubbles generated by conventional fine-bubble diffusers. In the case of the MABR, the biofilm grows on the membrane surface, and the oxygen is fed directly into the biofilm in ‘bubbleless’ molecular form via the membrane.