Bioremediation Of Eutrophic Lake Water By Immobilized Bacteria-algae Microspheres

The removal efficiencies of total nitrogen(TN), total phosphorus(TP) and chemicaloxygen demand (COD) in the simulated Lake water by chlorella, scenedesmus, microcysticaeruginosa and synechococcus were inspected to choose the dominant algae species. Theeffects of initial cell densities of dominant algae on removal rate of total nitrogen, totalphosphorus and chemical oxygen demand were studied. Furthermore, the algae-bacteriasymbiotic system was made up of the dominant species and actived sludge, and the bestmicrobial ratio was also studied. The preparation conditions of algae-bacteriaco-immobilized microspheres were optimized using orthogonal test, and the beads preparedunder optimized conditions were characterized. The removal efficiencies of TN, TP andCOD in the simulated Lake water by suspended algae, immobilized algae, immobilizedactived sludge as well as co-immobilized algae-bacteria were compared, and theremediation efficiency of Zhenjiang Jinshan lake water by co-immobilized algal-bacterialbeads was investigated.The results show that Chlorella was the bominant specie, and achieved the highestremoval efficiency of TN, TP and COD with initial cell density of5×106/mL. The optimumratio of algae to sludge within algae-bacteria symbiotic system is determined as1:2.The orthogonal test results demonstrated that the optimum conditions for preparation ofimmobilized algal-bacterial beads are: the amount of PVA was10%(m/v), microorganismembedding capacity was15mL, sodium alginate was0.6%(m/v), calcium chlorideconcentration2%(m/v).The characterization results prove that the prepared beads have larger specific surfacearea and appear internal reticular structure, their pore size distribution are uniform,mesopore accounts for the majority, are suitable for the growth of Chlorella andmicroorganisms.The results showed that the removal efficiencies of algae-bacteria co-immobilizedmicrospheres on TN and COD is obviously higher than that of immobilized algae,suspended algae and immobilized actived sludge, but suspended algae shows slightadvantage over algae-bacteria co-immobilized microspheres on the removal of TP.The algal-bacteria co-immobilized beads can effectively remedy polluted Jinshan Lakewater. The beads can be used repeatedly3~4cycle, in the first4cycles, each cycle lasted for 96h, the average TN removal rate was above80%; the average TP removal rate was above90%; the average COD removal rate reached more than85%, showed that the immobilizedbacteria-algae beads have potential application value in the remediation of eutrophic lakewater.