Belebungs

Belebung, or the activated sludge process, is a biological wastewater treatment method used to remove organic matter and nutrients from municipal and some industrial effluents. It relies on a suspended microbial community that oxidizes organic pollutants in aerobic conditions.

The core principle involves aerating and mixing wastewater in an aeration tank to keep microorganisms in suspension and supply oxygen for their metabolism. The resulting mixed liquor flows to a secondary clarifier, where solids settle as activated sludge. A portion of this sludge is returned to the aeration tank to maintain the microbial population, while excess sludge is withdrawn for stabilization and disposal or digestion. The clarified effluent is then discharged or subjected to additional treatment.

Key parameters for operation include the mixed liquor suspended solids (MLSS), sludge age (mean residence time), dissolved oxygen, and aeration rate. The process typically achieves substantial reduction of biochemical oxygen demand (BOD) and chemical oxygen demand (COD), often with removal efficiencies between 85% and 95%, and can be configured for nitrification and denitrification in plants with anoxic zones.

Configurations and variants include conventional activated sludge, extended aeration for further stabilization, and processes that integrate nitrification/denitrification. Sequencing batch reactors (SBRs) and other adaptations offer flexible operation in smaller plants or variable flows. Sludge management is a critical part of the process, involving thickening, digestion, and dewatering, with energy use concentrated in the aeration stage.

History and context: the activated sludge concept was developed in the early 20th century, with pioneering work by Arden and Lockett in the United Kingdom in 1914. Today it remains a widely used, flexible method for achieving high-quality effluent in many wastewater treatment plants.