Tertiary rotating biological contactors for nitrification

The addition of rotating biological contactors (RBC) to existing treatment plants for tertiary nitrification showed many advantages over conventional one-stage RBC's. Compared to tertiary trickling filters, the nitrification rates could be doubled. In extended pilot experiments, it was demonstrated that nitrification can additionally be enhanced by a periodic change of the flow direction in a series of RBC's, by filtration of the wastewater between the first and the second biological stage (pre-filtration) and by the control of the rotational speed. The experimental findings were confirmed in a full scale two-stage RBC-plant with intermediate filtration.