Extensive nitrogen removal in a new type of airlift reactor

A new type of CIRCOX(R) airlift reactor was started-up treating anaerobical ly pre-treated potato-processing waste water. This type of airlift reactor with biofilms on carrier is an airlift reactor extended with an anoxic comp artment to obtain total nitrogen removal. This type of reactor was designed in the early nineties and was tested successfully at pilot-scale on brewer y and municipal waste water. The 3 m(3) pilot reactor was scaled-up to a si ze of 130 m(3). Both the hydraulics and the biological performance were stu died. High liquid velocities and equal concentrations of sludge throughout the whole reactor, indicated that the system was well mixed. Up to 5 kg COD /m(3)/day was removed. Ammonia was almost completely removed (up to 1.0 kg NH4-N/m(3)/day in the aerated compartment). The denitrification efficiency was over 90%. The NOX-N concentration in the effluent never exceeded 6 mg/l . The biofilm layers were extremely dense: 30 g/l of VSS with a sludge volu me of 220 ml/l. Therefore the particles had high settling velocities and co uld easily be retained in the reactor. it can be concluded that this new te chnology has been scaled-up successfully With this an aerobic technology is available in which extended treatment and nitrogen removal are accomplishe d in a very compact system.