The anammox process, as an alternative to conventional nitrogen removal technologies, has abstracted much attention in recent years. In this study, one column-type reactor using a novel support material—net type acrylic fiber (Biofix)—was used for anammox treatment. The Biofix reactor was operated at 25°C (peak summer temperature, 31.5°C). Over 330 days of operation for synthetic wastewater treatment, the nitrogen loading rates of the reactor were increased to 3.6 kg-N/m3/d and T-N removal efficiencies reached to 81.3%. For the practical anaerobic sludge digester liquor treatment, the average TN removal efficiency of 72% was obtained. A protein substance was shown to be the most abundant extracellular polymeric substances (EPS) in the granular sludge with almost two times more in the attached sludge of the Biofix reactor. Considering the EPS levels and observation by scanning electron microscopy, the anammox granules in the Biofix reactor were showing dense state. Results of DNA analyses indicated that the KSU-1 strain might prefer relatively low nutrient levels, while the KU2 strain might be better suited for the high media concentration. Other kinds of bacteria were also identified with the potentials for consuming the dissolved oxygen in the influent and facilitating anammox bacteria surviving under aerobic conditions.

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