The principle of functioning of the biological discs is similar to the percolator beds: instead of sewage running through a stationary system, with the bio-discs both sewage and contactor are in movement.
Turbo-disc rotors are made of flanked plastic discs (isotactic polypropylene) arranged on a horizontal shaft. The shaft rotates slowly while 40% of the rotor surface is immersed in sewage. During rotation, the set of discs is immediately covered with biomass that carries a film of effluent the moment it contacts with air. The effluent percolates on the surface of the plastic material absorbing oxygen from air.
The pattern of operation of the TURBO-DISC is designed to work within 2 or 3 serial stages where each stage works as a independent reactor and the growth of biomass and its detachment from the discs are in a dynamic balance. The treated water and the detached biomass pass through each stage and a progressive buildup of the degree of abatement of the organic matter from specific bacteria at every stage, depending on the nature of the effluent, allows depuration levels up to 85%.
A 2-3 mm. biomass layer will deposit on the discs, the amount of solids is around 70-100 gr/lt, equal to 15-20 gr/lt. of SS in the liquid mass contained in the tanks. This high concentration of sludge allows short retention times which permits smaller necessary volumes compared to traditional active sludge systems. Moreover, a third stage dimensioned with an organic superficial load lower than 8 gr. BOD/SMxg which allows a true prolonged aeration of the sludge and its stabilization that permits its manipulation in successive dehydration treatments without hygienic issues.
Since the goal is the oxidation of the sewage via ammonia nitrogen, sizing of TURBO-DISC will be carried out keeping in mind that the nitrification will be higher with a lower hydraulic superficial load ( < 50 lt/SMxg ) in order to obtain the promised nitrogen abatement higher than 85%.
The advantages of TURBO-DISC biological rotor compared to traditional systems, are a result of the fact that the rotor is made of serial discs which are in fact small rotors themselves that rotate on their own axis and on the main axis during immersion increasing agitation and absorption of oxygen of the biological film avoiding clogging due to excess of biological film. During shear, the film shall not cover the whole width of the rotor but only detach from the 15mm. discs.