An airlift reactor using zeolite particles as carrier material was used for the nitrification of effluents from the aquaculture industry. During the start-up the nitrogen concentration was kept around 100 mg NH4+-N/L to develop the nitrifying population. Later it was decreased down to around 3 mg NH4+-N/L and the dilution rate was increased up to 4.8 d−1 in order to simulate the conditions in a an aquaculture waster treatment system. A nitrogen loading rate (NLR) of 535 mg NH4+-N/m2 d was fully oxidized to nitrate. Higher values of NLRs caused nitrite accumulation. A second biofilm reactor was fed with a synthetic medium containing 50 mg NH4+-N/L which simulated the effluents from anaerobic units treating domestic wastewater. A nitrogen loading rate of 400 mg NH4+-N/L d was oxidized into nitrate with an efficiency of 60% at a dilution rate of 8 d−1. Both biofilm systems allowed the development of a nitrifying population to treat the studied types of wastewaters.

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