Deep-aeration was opted for the Dendermonde treatment plant and thanks to the injector-aerator it is ensured a very fine air diffusion. Due to the depth of the basin (17 meters), a high water pressure on the bed is obtained so that the bubbles will cover a longer distance. Thus, together with the diffusion of the bubbles, this leads to optimum oxygen absorption. Practically, the plug flow is run continually, so untreated water and return sediment go through different compartments in succession.
In this way, the mixture covers the longest possible distance. The level of the mixed liquid in the aerator arrives below the rim of the overflow gullies, so that the sediment water mixture flows first upwards and then downwards through all compartments. The air feed is intermittent, so that nitrifying and denitrifying processes alternate with one another. Then the water flows to the post-sedimentation tanks.
Three Robuschi Blowers (type S 125/4P, 132 kW each with a capacity of 3,750 m3/h at 750 mbarg service pressure) are also located in the part upgraded in 2005 of the biological water treatment plant. All blowers are controlled by frequency control, according to the oxygen demand of the water basins.