Screening,Flocculating Mechanism And Application Of Algal Bioflocculant

4 strains(Synechocystis minuscule,Tetraedron pusillumKlebsormidium,scopulinum and Chlamydomonas reinhardtii)produced bioflocculants were selected after screening among 100 species based on their greater flocculating efficiencies(>90%)of the bioflocculants they produced.They were mass cultured outdoors,and then collected for their algal bioflocculants(extracellular metabolites).Compositions of the algal bioflocculants were then analyzed,and the involving flocculating mechanisms and their application were investigated.The optimum conditions for mass culture of these for species are as follows:culture temperature,illumination intensity and the frequency of aeration were 22?33 ?,610?7000 lux and 30 min per 10 min,respectively.The inoculum volumn should be kept at half of the total volume,and the original algac density must bc more than 106 individuals per mL.The best time of inoculation was 8-10 a.m.The culture period would take 20 days.At the same time,the culturing algae was sampled and observed under a microscope to ensure the purity every other day.Studies were made on the qualitative and quantitative analysis of the composition.All the algae bioflocculants were composed by polysaccharides,proteins and a small percentage of lipids.The results of thermal stability analysis showed that the polysaccharides and proteins play the leading role in the flocculation.Solubility tests showed that the algae bioflocculants were anionic flocculant and were soluble in acidic but not in organic solvents.They are of high molecules and have uronic acid contents containing-COO-and-OH.The results also showed that the acting force between algae bioflocculant and kaolin suspension is ionic bond.Therefore,the mechanisms invold was inferred that bridges occure during flocculation.In exploring the practical application of algae bioflocculants,their effect on cationic dye-Alcian blue and Fe2O3 suspension were tested in this research.It is found that S.minuscule flocculant performed pretty better.The most removal rate of dye reached 50.23%when the optimum conditions were met as follows:pH=10,the dosages of the bioflocculant was 20 mg/L,T=25 ? and t=8 h.The most removal rate of Fe2O3 suspension reached 50.5%when the optimum conditions were as follows:pH=6.82,T=18?,and t=30 min.When using S.minuscule flocculant together with other flocculants(Polymerization aluminium,Polymerization ferric,Cationic cellulose,Polysilicate and CaCl2),the results showed that the most removal rate would reach 68.43%with CaCl2 If using kind of inorganic flocculant with Polymerization aluminium,Polymerization ferric,or Polysilicate,the most removel rate would be reduced by 25%,33.3%,33.3%,respectively.Hence,the toxic effects of such inorganic flocculants to the environment can be also alleviated.If using with Cationic cellulose,the effect of Cationic cellulose could be enhanced effectively with a 14.42%greater of the most removal rate.In the final,these results could be greatly meaningful to the selection and using of bioflocculants in water pollution treatments.