High-strength nitrogenous wastewater treatment in biofilm and granule anammox processes

Abstract

Biofilm and granule reactors were employed to remove nitrogen via an anammox reaction applying synthetic nitrogen wastewater, whose concentration was in the range of 20 to 1,400 mg N/L as total nitrogen. A biofilm reactor was packed with non-woven fabric and a granule reactor was filled with anaerobic granular sludge taken from the brewery wastewater treatment plant. Both reactors were seeded with Planctomycetes KSU-1 and operated for 450 days. The biofilm reactor showed high NH4+-N and NO2--N removal efficiencies of over 88% and 94%, respectively, until total nitrogen concentration was reached at 800 mg N/L. However, the biofilm reactor showed severe inhibition at over 1,000 mg N/L of total nitrogen due to nitrogen overloading. The granule reactor revealed better nitrogen removal performance than the biofilm reactor, showing high NH4+-N and NO2--N removal efficiencies of over 90%, even at a total nitrogen concentration of 1,400 mg N/L. However, aggregation of anammox bacteria grown in the sludge bed after long-term operation resulted in the deterioration of nitrogen. The removal ratio of NH4+-N and NO2--N was close to 1:1, suggesting other reactions related to ammonium oxidation could occur simultaneously. Free ammonia inhibition as well as NO2--N could be significant when high-strength nitrogenous wastewater was applied.