Effect of concentration on anammox nitrogen removal rate in a moving bed biofilm reactor

Abstract

Anammox biomass enriched in a moving bed biofilm reactor (MBBR) fed by actual sewage sludge reject water and synthetically added was used to study the total nitrogen (TN) removal rate of the anammox process depending on bicarbonate () concentration. MBBR performance resulted in the maximum TN removal rate of 1100 g N m−3 d−1 when the optimum concentration (910 mg L−1) was used. The average reaction ratio of removal, production and removal were 1.18/0.20/1. When the concentration was increased to 1760 mg L−1 the TN removal rate diminished to 270 g N m−3 d−1. The process recovered from bicarbonate inhibition within 1 week. The batch tests performed with biomass taken from the MBBR showed that for the concentration of 615 mg L−1 the TN removal rate was 3.3 mg N L−1 h−1, whereas for both lower (120 mg L−1) and higher (5750 mg L−1) concentrations the TN removal rates were 2.3 (±0.15) and 1.6 (±0.12) mg N L−1 d−1, respectively. PCR and DGGE analyses resulted in the detection of uncultured Planctomycetales bacterium clone P4 and, surprisingly, low-oxygen-tolerant aerobic ammonia oxidizers. The ability of anammox bacteria for mixotrophy was established by diminished amounts of nitrate produced when comparing the experiments with an organic carbon source and an inorganic carbon source.