Biological Treatment System, Type FBR

The FBR is a compact built continuous biological wastewater treatment system. After pre-treatment (screening), the wastewater flows into a reactor tank with aerator. The reactor tank is filled with a mix of active sludge and water. Active sludge consists of biomass (bacteria flocks) that converts pollutants in the presence of oxygen.

The required oxygen is transferred to the water by means of a fine bubble bottom diffuser system or floating surface aerator.

In general pollutants in contaminated water consist of organic compositions of carbon, hydrogen and nitrogen. The aeration system is designed to create an optimal environment for converting pollutants in the wastewater.

Ultimately all pollutants are converted into carbon dioxide, nitrogen, water and surplus active sludge. The feed pump pumps the total wastewater stream from the reactor tank to a purposely designed Dissolved Air Flotation system for the separation of the active sludge from the purified water. This flotation unit is designed for the treatment of wastewater with a high concentration of non-dissolved solids and for the dewatering of the surplus active sludge to a dry solids content of 3-5%.

Micro air-bubbles adhere to the active sludge particles, that through conditioning with polyelectrolyte, obtained optimal dewatering characteristics. The sludge particles float to the water surface of the flotation unit, from where it is removed by means of a scraper system and transported to the sludge hopper of the flotation unit.


  • Continuous disposal of purified water over 24 hours.
  • High reliability as separation of active sludge from purified water through flotation is barely sensitive to variations in sludge quality with regard to sludge mass. This property provides for a stable process.
  • Small dimensional construction of the reactor tank in comparison to conventional treatment systems with same capacity.
  • The flotation unit for active sludge is considerable smaller than a conventional clarifier.
  • The dry solids (d.s.) content of the separated sludge from the FBR is 3-5%. This is much higher than the d.s. of the sludge from a conventional clarifier or a FBR system that have a d.s. content of approx. 1%. This results in 75% less sludge volume from the FBR and a considerable saving in sludge disposal costs and capital expenditure for an additional dewatering system should this be required.
  • A relative high COD / BOD reduction, up to 99.9%, depending on pollution load and source (industry) of wastewater.