Studies On The Adsorption Of Phosphorus By Polyvinyl Alcohol-sodium Alginate Immobilized Microcystis Aeruginosa

With a series of experiments on Microcystis aeruginosa growth characteristicsand on phosphorus removal by immobilized Microcystis aeruginosa, together withanalysis of the experimental results, the study concluded the optimum embeddingcondtion for immobilization and factors which had effects on phosphorus removal.Besides, mechanism of phosphorus removal by immobilized algae was generallypresented in this dissertation．The results demonstrated that the growth rhythm of immobilized Microcystisaeruginosa was similar to that of free one. Both of them conform to Logistic growthcurve. Immobilization caused adaptive changes of the algea’s habitat so thatMicrocystis aeruginosa could remain active and the final yield was higher than freecells. Therefore, the influence of immobilization to Microcystis aeruginosa waspositive.After an orthogonal experiment, the optimal preparation conditions ofimmobilized microbes pellets were finally concluded as following: the mass fractionof polyvinyl alcohol and sodium alginate were6%and0.5%respectively and theconcentration of Microcystis aeruginosa was approximately2×107cells/mL. Underthis condition, the adsorption rate of immobilized microbes pellets could reach74.17%，which was1.34times higher than that of PVA-SA gel ball. The quality ofsodium alginate has the greatest impact on phosphorus removal and the mass fractionof polyvinyl alcohol ranked the second.The optimal range of initial pH for dephosphorization by immobilized microbespellets was from6to8, and the best pH value was7. Compared with the free algae,Immobilized algae can tolerate the more wide range of pH. In the preliminary stage ofthe experiment （from first to second days）, phosphorus removal of immobilized ballwas mainly depended on adsorption of carriers, and three days later Microcystisaeruginosa begin to take use of the phosphorus from sewage to synthesis of nucleicacid to meet themselves, at the same time can store the phosphorus of surroundingenvironment. The tolerance of immobilized algae on phosphorus concentration rangefrom0.10to1.00mg L^-1, which was more suitable for advanced treatment of thesewage treatment. Microcystis aeruginosa plays a key role in the process ofphosphorus removal. During the investigations, the auther found that the micro-structure in the carrierof consists of complex network channels which was very helpful for the absorption ofnutrition with phosphorus by the algae cells. Infrared spectral analysis shows that,compared to the PVA-SA gel the ball, the main groups and structure of immobilizedMicrocystis aeruginosa had not changed. The concentration of-COO^-and PO₄^-3ofimmobilized algae were both increased after absorption, which showed that theassimilation of phosphorus by Microcystis aeruginosa was the critical factor on thephosphorus removal.Preliminary mechanism research on removal of phosphorus by immobilized algaewas also presented in the dissertation.