A new concept for waste water treatment based on biofilm technology is developed. Industrial waste water can be treated flexibly in a single reactor in which multiple processes can be carried out. The low cost of investment allows a cost-saving advanced treatment for the pollutants from small and medium sized factories as well as for separate streams of process waste water. The submerged reactor filled with packed material works in intermittent mode. After filling the reactor with waste water, the water is recirculated. During the recirculation phase the biofilm carriers will be fluidized to minimize the boundary layer and to maximize the reaction rate. During the last biofilm filtration phase the water will be discharged through the bed material. Suspended solids and dissolved residual pollutants are further reduced. The retention time in the reactor can be chosen depending on the effluent requirements. Results from fixed bed pilot scale experiments show that, depending on superficial water velocity, a part of the volume is not flowing through convectively. This stagnant volume has a great influence on the reaction rate and can be reduced by increasing superficial water velocity. The nitrification rate of a fixed bed depends on oxygen transfer. Increasing the superficial air velocity from 5 m/h to 15 m/h will increase the reaction rate by about 50%. The reaction in the fixed bed can be described as half order kinetic. Removal rate constants of k1/2A=0.86 (vair= 10 m/h) and 1.13 g NH4-N0.5m−0.5·d−1 (vair=15 m/h) could be achieved.

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