Four materials were prepared as carriers for immobilizing anaerobic ammonium-oxidizing sludge. Nitrogen removal performance by these immobilized gel bead groups was evaluated. The removal ratios of ammonium and nitrite by CMC anammox-immobilized beads were 100% and 95.3% in 48 hours, respectively. The removal efficiencies of ammonium and nitrite by SA, PVA-SA and PVA anammox-immobilized beads were lower than the CMC beads. Subsequently, the physical properties of the beads were studied. PVA-SA was found to be the best support material among the four by comparing the case of the immobilization procedure, nitrogen removal efficiencies, and the costs of materials. PVA-SA gel entrapment was optimized by an orthogonal experiment. The SEM micrographs displayed that the surface structure of PVA-SA immobilized beads is loose and finely porous, which facilitates diffusion of the nitrogen. The SEM micrographs also clearly showed that anammox bacteria existed in the gel beads. All results clearly demonstrate that immobilizing anammox sludge in gel carriers is feasible and exhibit good performance. This research provided a new route to maintain sufficient amount of anammox sludge in a practical anammox reactor.

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