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35 High-rate ammonia removal using a full-scale spirally wound MABR Y.Nevo, R.Shechter, G. Yogev, N.Nathan, L. Dagai. *Fluence Corporation, Caesarea, Israel gyogev@fluencecorp.com Corresponding author: Gilad Yogev, MABR Product Manager, gyogev@fluencecorp.com, 3 HaEshel st. Caesarea, Israel, 972-4-6277555 The use of MABR (membrane a e ra t e d b i o f i lm r ea c t o r ) system removed ammon i a compounds via nitritation and partial denitritation. SUMMARY A full scaleMABR unit was installed in the Akko wastewater treatment plant to treat part of the centrate coming from its thermophilic anaerobic sludge digesters. The goal of the treatment was to removemore than90%of the ammonia load in the centrate stream, which accounts for about 20%of theammonia load in the biological process. Results from first three months of operation show exceptionally high ammonia removal rates (ARR), partly attributed to shortcut nitrogen removal. Molecular microbiology analyses show an abundance in AOBs and scarcity in NOBs, indicating that shortcut nitrogen removal is taking place. INTRODUCTION Anaerobic digester centrate contributes high total ammonia nitrogen (TAN) loads (15% to 25%) to wastewater treatment plants, despite its low daily volume (1%-2% of inlet flow). To reduce nitrogen loads and improve the energy efficiency of the entireplant, anMABRpilot unit was installed on the dewatering supernatant line of the Akko WWTP in northern Israel, in cooperation with GES who operate the plant. This paper will present treatment results, including TAN removal rates, which reached up to 6 gN/m2d during the first three months of operation. METHODS The MABR pilot system was based on two full size spirally wound modules with a total surface area of 1,800 m2, installed in a 26 m3 steel tank. An airlift pump provided an internal circulation stream in order to maintain near- CSTR conditions in the reactor. The process was acclimated to favor nitritation (AOB) over nitrification (NOB) by adding nitrite during the first couple of weeks, and thereon operated in biofilmmode without sludge circulation. Centrate from an anaerobic thermophilic sludge digestion processwas fed to the system at a flow rate in the range 8-10 m3/d. Water temperature was 30-40°C, TAN concentration 1300-1800mg/l, pH6.8-7.8 andalkalinity about 4400 mg/l as CaCO3. During operation, effluent TAN concentration waskept in the rangeof 150-200mg/l tosupport high removal rates and produce an acceptable return stream to the plant. RESULTS AND DISCUSSION The nitrite fraction of the oxidized nitrogen species, or NO2/NOx ratio, increased gradually during the inoculation period, reaching more than 80%. This high ratio indicates that conditions were preferable for selection of AOB over NOB in the process.