Dissertation > Environmental science, safety science > Processing and comprehensive utilization of waste > General issues > Wastewater treatment and utilization > Additives

Screening of Flocculating-producing Strains and Study on Their Flocculation Characteristics

Author QuZuoJuan
Tutor LiRiQiang
School Shanxi University
Course Ecology
Keywords Microbial flocculant flocculanting activity culture condition optimize flocculation characteristic complexation
CLC X703.5
Type Master's thesis
Year 2009
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Microbial flocculants are good for human health and environmental protection as a new type of flocculant.For they have the properties of high flocculating efficiency, without toxicity and second pollution.The research on MBF have been a focus at home and abroad in recent years.This paper summarized the flocculation method of water treatment,the flocculant classification and each characteristic.Meanwhile it introduced the development of MBF, species of flocculant-producing bacterias,flocculating mechamism,factors affecting production and flocculating activity,applications and so on in detail.Based on the mentioned above,the contents of this paper are as follows:getting effective strains, optimizing culture conditions of the strains,studying the flocculation characteristics of MBF and the complexation of MBF and chemical flocculant.In this research,2 effective strains PY-M3 and PY-F6 were screened from soil by means of common bacteria screening and Kaolin suspension method.The flocculation activity of the two strains were 92.5%and 95.95%.The culture conditions of the two strains were optimized,the results are as follows:for strain PY-M3 the most suitable carbon source was glucose,nitrogen source was complex nitrogen,glucose content 2g/50mL and C/N 45.And the optimum conditions of MBF synthesizing were initial pH 7.0,30℃,agitation rate 180r/min,inoculation quantity 2%and culture time 72h,then the flocculation activity increased to 94.43%;for strain PY-F6 the optimum carbon source was also glucose,but nitrogen source was yeast extract,glucose content 0.5g/50mL and C/N 30,the optimum conditions of MBF synthesizing were initial pH 7.0,30℃,agitation rate 140r/min,inoculation quantity 3%and culture time 72h.,the flocculation activity increased to 98.61%.The active ingredient distribution test showed that:main active ingredient both existed in the supematant and the amount of flocculant by PY-M3 was 0.87g/L,PY-F6 1.51g/L.The two strains were suitable for industrial production because of their large harvest.Themal stability of the two kinds MBFs were investigated,as a result,the flocculant produced by PY-M3 had a bad themal stability,its main component maybe protein or nucleic acid,on the contrary,flocculant produced by PY-F6 which thermal stability was superordinary,the main component maybe polysaccharide.The dosage of MBF,concentration and pH of Kaolin suspension,the addition of metal ion and its amount,and idle time on flocculating activity were studied.The results showed that:suitable pH of Kaolin suspension were high than 7.0,both had high flocculating rate in small dosage;univalent metal ion had no effect to flocculating rate but divalent greatly promote the flocculation,especially Ca2+;both almost cannot improved the flocculating rate without Ca2+;terralent could promote the flocculation in a low concentration.During the flocculation,many large flocks were engerdered and sank fast, after 15mins the Kaolin suspension almost clarificition.The complexation of MBF and organic flocculant were studied.The results showed that,complexation of MBFPY-F6 and AlCl3 or PAC decreased their dosage,increased flocculating rate and decreased the cost of flocculating.Without the assistant of CaCl2 the compound flocculant also had a good effect.L9(34) orthogonal test were carried out to research the complex flocculant MBFPY-F6 and PAC in fluorescent whitening agent wastewater,as a result,effect was better when using compound flocculant than using each only.The strain PY-F6 was identified by modality observation as well as 16S rRNA sequence homology comparison.Its similarity sequence compared with Streptomyces flavotricini strain HBUM174933(EU841670)、Streptomyces flavotricini strain HBUM174888(EU841607) and Streptomyces flavotricini strain HBUM175089 (FJ532404) are 99%,so it belongs to genus Streptomyces sp.

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