High nitrogen removal performance of anaerobically treated fish processing wastewater by one-stage partial nitritation and anammox process with hydroxyapatite (HAP)-based syntrophic granules and granule structure

The one-stage partial nitritation and anammox process with the hydroxyapatite (HAP)-based syntrophic granules was studied for the ammonium nitrogen removal from the effluents of a self-agitated anaerobic baffled reactor treating the fish processing wastewater. When the ammonium in the influent was 1140 mg N center dot L-1, a high nitrogen removal rate and nitrogen removal efficiency of 1.51 +/- 0.10 kg N center dot m(-3)center dot d(-1) and 88.2% were obtained, respectively. Anammox bacteria of Candidatus Kuenenia stuttgartiensis and ammonium oxidizing bacteria of Nitrosomonas were the two most predominant bacteria, while nitrite oxidizing bacteria activity was low and could be neglected during the treatment. The inorganic element properties of the sludge were analyzed by several methods to confirm the existence of HAP granules. Optical microscopic observation and scanning electron microscopy analysis revealed the structure of the granular sludge. This study supports the feasibility and potential of this process for high-efficiency nitrogen removal from fish processing wastewater. [GRAPHICS] .

Automated summary

The study successfully demonstrated high-efficiency removal of ammonium nitrogen from fish processing wastewater using a one-stage partial nitritation and anammox process with hydroxyapatite-based syntrophic granules. The dominant bacteria were Candidatus Kuenenia stuttgartiensis and Nitrosomonas, with low activity of nitrite oxidizing bacteria during treatment.