The biorulli® biological oxidation system makes use of one or more rotating contact cylinders for the reduction of the organic matter waste water contains. Each contact cylinder is composed of a shaft, onto which polypropylene discs are fitted; discs are variable in number according to the model. The shaft is rotated very slowly (1 ÷ 5 rpm, depending on the model and the effluent properties) by means of a motor-gearbox set.

The discs are partially immerged (about 40% of their diameter) in a tank through which the water to be treated passes. The contact between the sewage and the discs favours the formation of the biological slime on the latter. Thanks to the continuous rotation of the discs, the biological sludge is alternately immersed in the liquid (from where it acquires the organic matter necessary as nutriment) and brought into contact with the surrounding air (where it is saturated with oxygen, another element fundamental to the biological oxidation process).

Once its life cycle is finished, the biological slime layer detaches itself autonomously from the disc surfaces in the form of flakes, easy to settle.