Highly effective membrane filtration process as an alternative to the conventional activated sludge process

operational area | usage

  • Use in municipal and industrial wastewater treatment as a space-saving concept with high cleaning capacity
  • Phase separation by membranes instead of settling process – therefore high total solids in the activated sludge, compact design and solution without secondary settlement tank possible

Technology | Process

In the MBR process the membrane module replaces secondary settlement. Plant structure volume can be saved due to increased total solids in the aeration tank. The aeration tank is combined with a membrane filter to separation water and activated sludge. The biologically treated wastewater is drawn in through the membrane. The biomass remains in the aeration tank or in the filter chamber and must be removed separately. The process engineering design of the MBR plant is carried out as optimisation between the design of the aeration tank (tank volume, total solids, sludge age, air requirement, etc.) and design of the membrane filtration (membrane area, number of filtration units, filtration volume, permeate flux, etc.). Various process steps are necessary for the membrane cleaning: Backwashing with filtrate, creation of turbulences at the membrane surface through air flow (cross flow), chemical intermediate and intensive cleaning with substances such as sodium hypochlorite or citric acid or similar.

Total solids in the activated sludge: 8–15 kg/m³
Membrane pore size: 0.1–0.4 μm

Process Engineering Components

  • Extremely fine screens for mechanical precleaning
  • Aeration tank, if applicable with filtration units (integrated MBR system)
  • Membrane filtration tank (for separate MBR system)
  • Permeate / backwashing pumps, return activated sludge pumps (with downstream filtration tanks), surplus sludge removal
  • Cross-flow blower
  • Chemical metering for membrane cleaning


  • Compact volume due to high biomass content in the activated sludge stage and doing without a secondary settlement tank
  • Easily extendable
  • Outstanding treatment capacity with regard to carbons and nutrients as membranes are partially permeable structures, which retain organic and inorganic solids, bacteria and substances attached to solids (solids 0 mg/l, COD < 30 mg/l)
  • Extensive disinfection of the treated wastewater (bathing water quality, water reuse as non-potable water, key water reuse technology)
  • High degree of operating reliability due to the formation of parallel lines, no sludge output through bulking or floating sludge; independent of the settling properties of sludge
  • Very good usability in upgrades / extensions to existing wastewater treatment plants, if applicable can be used for partial flows only
  • Membrane filtration plants run fully automatically, no operator intervention required in normal operation

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