| Summary: | 碩士 === 國立中興大學 === 生物產業機電工程學系所 === 95 === Gel entrapped nitrifiers and denitrifiers may be used in wastewater treatment plants as the main N-removal system, or as an additive to existing biofilm or sludge system. In any case, gel entrapped nitrifiers and denitrifiers may be stored for safety measures and added in cases of a collapse of the activity in the plant. Different preservation techniques; freezing and drying, were evaluated as means to optimize the conservation of the nitrification and denitrification activity immobilized in PVA-sodium alginate gel beads during storage. Glycerol, sucrose and trehalose were added in various amounts as cryoprotectants. After 2-5 months of storage, the nitrifiers and denitrifiers were reactivated in 1000 ml CSTR using a synthetic medium with excess TKN and ammonium. We also got the nitrifying and denitrifying activity of immobilized beads by batch experiments. Beads frozen without any additives or in 15% glycerol maintained 70% of the orginal nitrification and denitrification rate they had before conservation, respectively. After preservation by drying, 20% or less of the activity was recovered. In the case of drying, addition of 15% glycerol improved the initial nitrification activity significantly. It is concluded that for long time storage at a wastewater treatment plant, freezing without any additives should be the preferred preservation technique.
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