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Extended Aeration Activated Sludge Treatment Plants

Description of System.

Gazebo produces Extended Aeration Activated Sludge Treatment Plants for small and large communities:

  • MINIBIOXY/BCS (with two compartment tanks – produced with one monolithic tank) a system to treat wastewater from residential communities with a population equivalent of between 10 and 350.
  • MINIBIOXY/BSP (with separate tanks – produced with several monolithic tanks) system to treat wastewater from residential communities with a population equivalent of between 400 and 2,500/3,000.

In compliance with Italian Legislative Decree No. 152 of 03.04.06 regarding discharge into surface waters and the soil.

How the MINIBIOXY Gazebo systems work

In this kind of system, the activated sludge produced after the organic substance is transformed by specific bacteria, separated and collected on the bottom of the hopper of the final sedimentation tank, is continuously recirculated as it is aerated by means of a hydropneumatic ejector, while one part, the excess, consisting of the surplus produced daily, is removed on a regular basis.

The following treatment stages take place in the plant:

  • pre-treatment: an Imhoff-type tank is used to separate the coarsest parts of the incoming sewage which settle on the bottom and then degrade due to “anaerobic digestion” inside the tank. Alternatively, automatic sieve systems can be used,
  • accumulation/equalisation: submersible motor pumps are installed in a prefabricated tank which work to keep the water and organic load entering the biological system constant,
  • wastewater denitrification: a submerged mixer is fitted in a prefabricated tank where the nitrates (formed during the following nitrification stage and recirculated upstream with the aerated mix), are transformed into nitrogen gas by bacteria,
  • wastewater nitrification/organic oxidation: the organic substance of the sewage is completely broken down in a prefabricated tank by insufflation of the air as micro bubbles,
  • final sedimentation: the sludge is separated and it settles on the bottom of the prefabricated tank. As the clarified water overflows, it is conveyed to the outlet,
  • final disinfection: in a prefabricated tank fitted with internal dividing walls to create a labyrinth for contact between the wastewater and the chemical reagent (usually sodium hypochlorite or peracetic acid). Alternatively, bacteria can be removed from the water using ultra-violet systems,
  • sludge accumulation: the surplus sludge which is produced daily thickens in a prefabricated tank.

Supplied as standard

Gazebo Extended Aeration Activated Sludge Treatment Plants are fitted with:

  • reinforced concrete dividing walls,
  • blowers to produce compressed air,
  • electric control panel,
  • air distribution manifold,
  • fine bubble air diffusers with EPDM membrane,
  • airlift type hydropneumatic pump and/or submersible motor pump for sludge and/or aerated mix recirculation,
  • clarified water outlet channel in AISI 304 stainless steel.


  • special coatings on the internal and external surfaces of the tank,
  • pedestrian/vehicle covers,
  • manhole covers in ductile iron/galvanised metal sheet /stainless steel,
  • can be installed in the presence of groundwater,
  • spare machinery.


Urban and rural communities, artisan and commercial businesses, detached houses, camp sites, tourist villages, hotels, shopping centres.

Gazebo for professionals.

Gazebo helps designers, plant engineers, building contractors. It offers free design services, technical support, promptly drawn up projects, on-site visits and inspections, technical assistance up to installation and short lead times.

Free design services
Technical support
Promptly drawn up projects
On-site visits and inspections
Technical assistance up to installation
Short lead times

Technical documentation.

Professionals interested in specifications, diagrams, tables, technical drawings, dwg and pdf files can access the technical documentation after registering or can fill in the form below for further information.

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