Study Of Composite Flocculant Flocculation Characteristics

Bioflocculants are polymers produced by microorganisms during their growth, their obvious advantages are non-poisonous, readily biodegradable and without pollution to the environment. With the enhancement of people’s environmental consciousness, more and more attentions have been paid to the studies of bioflocculants.In this paper, the compound bioflocculant with high flocculating efficiency were constructed by 4 strains of bacteria named DG2, DN1, H8, and H13, they were isolated from activated sludge and bio-reaetor for low temperature sewage treatment, and with ability to produce bioflocculants. The flocculating activity of 4 strains performed high efficiently even at relatively low temperature (10℃～20℃). The flocculating rates reached to 95% to kaolin cay suspension. DG2, DN1, H8, and H13 had been indentified as Pseudomonas mandelii, Bacillus aerophilus, Zooglea sp.and Pseudomonas fragi by morphological and physiological characteristics and 16SrRNA sequencing method.The analysis results showed that the compound bioflocculant were composed of DG2, DN1, H8, and H13. The microbial population reached stable states after continuous culturing of 13 generations. During the different growth period, it kept invariable in component DG2≥DN1>H8>H13, the biggest population numbers were at 48h.In order to improve the flocculating activity of compound bioflocculant, the flocculating conditions were optimized. The results showed that the best flocculating condition was: pH6.0, adding dosage of culturing liquid is 4%, sendimental time is 5 mins, the additions of CaCl2 were able to increase the flocculating rate and the optimal amount was proved to be 0.05%.The distribution of flocculants produced by compound bioflocculant were tested, and the results indicated that the effective flocculants were evenly distributed in supernatant. The ethanol was used to precipitate the flocculant and the extracting product was about 0.9073 g·L-1, the dosage to kaolin suspension 0.016 g·L-1. The best extract program was: first, supersonic at 100Hz for 10min, then centrifugate at 6000r·min-1 for 10min, precipitate the supernatant by 1.5X ethanol centrifugateat at 6000 r·min-1 for 15min, at last the pellet was dried at 60℃.The chemical components of compound bioflocculants were detected by the methods of qualitative analysis and quantitive analysis. The results showed that the major components were polysaccharide and protein, with 25.5% and 23.4% respectively, also there were amino sugar 1.58 % and glucuronide 6.39 %.