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Study on Isolation, Identification and Immobilization of Denitrifying Polyphosphate-accumulating Organisms

Author: HongWuLin
Tutor: LiuJianSheï¼›XieXueHui
School: Donghua University
Course: Environmental Science
Keywords: denitrifying polyphosphate-accumulating organisms (DNPAOs) isolation identification immobilization
CLC: X172
Type: Master's thesis
Year: 2012
Downloads: 185
Quote: 0
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Abstract


Surface water pollution has been serious in China recently, and the eutrophication of lakes and reservoirs has been also observable. There are various kinds of nutrients leading to eutrophication, such as nitrogen and phosphorus which are still not effecttively removed by municipal wastewater treatment. Therefore, we should focus on how to remove nitrogen and phosphorus in the prevention of eutrophication. In anoxic condition, denitrifying polyphosphate accumulating organisms (DNPAOs) can simultaneously denitrify and excessively remove phosphorus by using nitrate as terminal electron acceptor. From the microbiological view, it is essential to isolate and screen DNPAOs which can improve nitrogen and phosphorus removal in the wastewater treatment.In this study, DNPAOs P1-1 was screened from the water sample in a lake of Inner Mongolia, by using traditional plate screening techniques, phosphate uptake experiment, where nitrates were denitrified to gas and inspection of metachromatic and polyphydroxybutyrate (PHB) granules. According to its morphological and physiological characteristics, Biolog identification and the analysis of its 16S rRNA sequence, it was identified as a strain of Pseudomonas fluorescens. Under the various conditions including culture temperature, inocula-tion amount, pH, rotation speed and carbon source, the strain P1-1 was studied on growth characteristics and the effects of denitrification and phosphorus removal. In the end, the best condition of growth and nitrogen and phosphorus removal was achieved. Moreover, with sodium alginate and polyvinyl alcohol (PVA) as embedded vector, with zeolite as adsorbent, immobilized microorganisms retained double characteristics of embedding and adsorption. By orthogonal experiment, the optimal condition of immobilized microorgan-isms was 5mL of concentrated bacterial liquid, sodium alginate 1.0%, PVA 10% and zeolite 2% for the phosphorus removal. In the conditions of high salinity or heavy mental, it was better for immobilized microorganisms than free ones in phosphorus removal.In the end, synthetic wastewater was treated in the stimulant reactor by immobilized and free microorganisms respectively. After 24 hours of treatment, phosphorus removal was 86.4% and nitrogen removal was 94.0% by immobilized microorganisms; phosphorus removal was 71.4% and nitrogen removal was 92.2%.

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