Purac AB

Biological Treatment

Biological Treatment Of Wastewater By Anaerobic Or Aerobic Processes

Wastewater can be treated anaerobically (ANAMET) followed by an activated sludge stage, or by a biofilm aerobic method alone or in combination with an activated sludge stage.

Local conditions – sludge disposal costs and potential utilization of biogas – together with the organic load determine the choice between anaerobic and biofilm aerobic treatment.

Biofilm technology means that the biomass - micro-organisms - grows as a film on a surface in contact with liquid. The best technical solution proved to be use of mobile carriers in the form of small plastic elements, free-floating in liquid and with a large specific surface. The process, which requires minimal space, is today a proved and well-documented method with about 100 reference installations in the pulp and paper industry.

The suspended carrier biofilm process offers many benefits compared with traditional biological treatment:

• Increased treatment capacity in existing plants
• Flexible design adaptable to existing basin volumes
• Less sensitivity to load increases and toxic discharges
• A more stable treatment process
• Unaffected by sludge age