A new fixed-film mobile bed bioreactor for denitrification of wastewaters

An innovative fixed-film mobile bed bioreactor for high-rate denitrificatio n of wastewaters has been developed and tested. This reactor, called the Mi xazur(R) enables a high denitrification efficiency due to high kinetics. Th ese properties are combined with a very simple system, particularly due to the choice of a suitable mineral granular support for bacterial growth, ena bling a very low filling ratio. This low filling ratio, usually smaller tha n 5% vol., offers a sufficient surface area for fixed-film development, eas ily moved by a simple mechanical agitation with low energy consumption (< 3 0 W/m(3) of reactor). The experimental study showed that this reactor can a chieve an eliminated loading rate of 0.6 kg NOx-N/m(3) of reactor per day a t a removal efficiency more than 80% and at water temperatures between 13 a nd 20 degrees C. The separation of a denitrifying biomass in a specific pre -denitrifying bioreactor led to a development of a very active biofilm with denitrification rates as high as 10 mg NOx-N/g MLVSS.h at 18 degrees C. Th e scale-up of this system does not need any sophisticated wastewater inlet distribution system, any additional material/biomass separation device and any recirculation loop for maintaining a constant fluidization velocity. Mo reover, the reactor is characterized by its low-cost equipment, continuous operation and by auto-regulation of both biofilm thickness and activity due to a controlled shear stress and by an overall easy operation. The first f ull-scale facility, for 1200 p.e., using this system has been operating sin ce 1996. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.