Enrichment of high activity nitrifers to enhance partial nitrification process

Partial nitrification (PN) process is an essential pre-treatment to Anammox process for nitrogen removal from ammonium-rich wastewaters. High activity nitrifiers (HANs) are considered as the key to high-rate PN process. The HANs could be successfully enriched at free ammonia (FA) concentrations of 10–20 mg NH3–N L−1, which differed significantly from those enriched at FA concentrations of 1–3 mg NH3–N L−1. The maximum specific ammonium conversion rate, half saturation constant, half inhibition constant, cell yield and decay rate were 2.87 g N g−1 VSS d−1, 5.82 mg N L−1, 8218.8 mg N L−1, 0.15 g VSS g−1 NH 4 + –N and 0.09 d−1 for HANs at 30 °C, respectively, which endowed the PN process a volumetric conversion rate (VCR) as high as 2.22 ± 0.33 kg N m−3 d−1. The cultivation mode of HANs was workable and the HANs were promising as inoculum for the PN process.