The expenses for the disposal of industrial and municipal wastewater are increasing strongly due to more stringent governmental legislation ordering lower discharge limits and higher discharge taxes. Moreover, the intake of ground water is being limited to prevent a dehydration of the soil having a destructive influence on nature's flora and fauna. The call for a closed water cycle is becoming louder and more efficient wastewater treatment techniques have been developed, such as the membrane bio-reactor (MBR).

An MBR is a compact-built purification system combining the biological degradation step with a membrane separation step. The influent is fed to the aerated bio-reactor where the organic components are oxidised by the activated sludge. Next, the aqueous activated sludge solution passes through a membrane filtration unit separating the water from the sludge. The latter returns to the bio-reactor, while the permeate is discharged or re-used as particle-free effluent.

The combination of biological treatment with membrane filtration offers several significant advantages over a conventional activated sludge system as presently being used for industrial wastewater, such as less surplus sludge and particle free-effluent.

A smaller surplus sludge results in a higher average age of the activated sludge leading to more component-specific bacteria and not only to fast-growing bacteria. Therefore, a MBR is very suitable to treat more heavily polluted industrial waste streams. The particle-free effluent is suitable for direct reuse or can be upgraded further by means of reverse osmosis for high-grade application as process water.
 

Norit Crossflow MBR systems are used for:

• very high mixed liquor suspended solids (MLSS) streams, up to 40,000 mg/l.

Main references are found in:

• food, beverage and dairy industry;
• landfill leachate treatment.
  
   

The Norit Crossflow system uses X-Flow modules:

• 3 m long 8” modules with COMPACT 8.0 mm ultrafiltration membranes;
• high flux membranes having excellent anti-fouling behaviour.
  
  
   

In a crossflow system the feed flows parallel to the membrane surface, controlling the cake-layer formation of retained particles by adjusting the cross-flow velocity. Together with an optimal Cleaning-in-Place (CIP) procedure the Norit CrossFlow MBR process is an efficient solution for industrial wastewater treatment.





 

Norit Crossflow MBR systems are available as standardised, modular skids. The modules are placed horizontally resulting in very reliable and compact installations.

If desired customer-built systems can be supplied.