Pilot testing and preliminary design of moving bed biofilm reactors for nitrogen removal at the FREVAR wastewater treatment plant

A moving bed biofilm reactor (MBBR) pilot plant, using Kaldnes type Kf biofilm carriers, was tested for nitrogen removal at the FREVAR wastewater treatment plant. The pilot plant was fed primary treated municipal wastewater, at temperatures from 4.8 to about 20 degrees C. The results showed that a reasonable design nitrification rate will be 190 g TKN/m(3)d, at 10 degrees C and a reactor pH greater than or equal to 7.0. Predenitrification was very dependent on the concentration of readily biodegradable organic matter and the amount of oxygen in the influent to the first anoxic MBBR. It was found that a MBBR process for nitrogen removal at FREVAR will require a total reactor volume corresponding to an empty bed hydraulic retention time of 4-5 hours at average design influent flow. This was based on an influent concentration of 25 mg total N/I, 70% annual average removal of total N and a treatment process consisting of primary treatment, MBBRs with combined pre- and post-denitrification, and followed by coagulation/flocculation and a final solids separation stage.