Aerobic COD removal

In an aerobic treatment system, air is injected which is used by aerobic bacteria to convert BOD to carbon dioxide and water.

Organic components + O2 are converted to H2O + CO2 + BIOMASS

Primary treatment for solids removal and anaerobic treatment are usually followed by aerobic treatment.

Paques offers different solutions the aerobic post treatment, such as

  • Activated sludge for surface water discharge quality
  • Flash aeration for oxidation of odorous compounds
  • CIRCOX® airlift technology for situations with a very limited space available
  • BIOPAQ®UBOX for the compact combination of anaerobic and aerobic treatment

Activated sludge system

The activated sludge system consists of an aeration stage - and an anoxic/oxic compartment if nitrogen has to be removed - and secondary sedimentation with sludge return. Options are first quality surface aeration, fine bubble aeration and jet aeration.

After secondary clarification, further treatment can consist of filtration, de-nitrification (for achieving very low nitrogen concentrations) or effluent softening. For nitrogen removal at higher concentrations and filtration, see ANAMMOX® and ASTRASAND®.

Flash aeration

When treated water will be reused or if water will pass through a sewer, flash aeration is often required. The main reason is odour control, but it will also remove some additional COD, especially when the aeration tank is followed by solids removal such as DAF (Dissolved Air Flotation).


Read more at the CIRCOX® product page.


Read more at the BIOPAQ®UBOX product page.

Aerobic COD removal cases