Technology of membrane biofilm reactors operated under periodically changing process conditions

Biological treatment of problematic wastewaters requires the application of specialized reactor systems and operation strategies. Two novel approaches to meet the specific requirements are discussed: (1) application of gas permeable membranes as a means to transfer oxygen into the reactor, and to provide surface area for biofilm growth, and (2) operation of biofilm reactors in a fill and draw mode (Sequencing Batch Biofilm Reactor (SBBR) Technology). Membrane oxygenation and biofilm SBR technology can be favourably combined to treat wastewaters which contain volatile organics, organics in low concentration (e.g. contaminated groundwater) or organics which are degraded only by selected, slow growing microorganisms. The current state of reactor development is summarized. Examples for reactor design are given.