Screening Of Flocculating-producing Strains And Study On Their Culture Optimize

Organic and inorganic focculants have been used widely due to their low prices and good effect. However, their disadvantages have drawn people's attention. Aluminium remaining in drinking water easily leads to senile dementia. The monomer of polyacrylamide (PAA) can't be degraded and it's both neurotoxic and oncogenic for human body.Thus, safe biodegradable focculants that are both environment-friendly and effective are urgently needed.Bioflocculant is a kind of macromolecular flocculant secreted by microorganisms. These kinds of microbial polymers are expected to be useful in flocculating wastewater due to their bio-degradability and the harmlessness of their degradation products toward humans and the environment. However, the bioflocculants identified so far in laboratories have not yet practically applied in industry because of their high cost and low productivity. In this study the screening of new flocculant-producing strains which could produce bioflocculant, the optimize culture medium composition and proportion, the optimize culture condition, flocculating capability, flocculating properties and application were carried out.This research screened 9 strains of bioflocculant-producing microorganisms with a flocculating rate over 60% from activated sludge from a municipal wastewater treatment plant in zhuzhou, soil sample from paddyfield where around zhuzhou smelt factor and sludge beside Xian Jiang River by conventional methods. After reselecting, 2 of them were obtained with higher flocculating activity and better stability, named as B212, B233 respectively.Taking the B212 and B233 as the subject investigated. Find the inoculability fountain have the certain influence to the flocculant production, The time of strain produce flocculant is different, the time of when the inoculability fountain is incline culture medium is longer than take the liquid medium about one day,its reason probably is that it needs the adjustment time of one day when take the incline culture medium; to B212,the optimal dosage is 1mL/100 mL, the best pH vaule is 7,the culture time is 29 hours; to B233, the optimal dosage is 2mL/100mL,the best pH vaule is 8,the culture time is 35 hours. Cultivation conditions for flocculant production were optimized using"one-variable-at-a-time" method. The the optimize of culture medium composition for strain were:to B212, the best carbon fountain is urea,the best nitrogen fountain is carbamide, inorganic salts adopts NaCl; to B233, the best carbon fountain is dextrose,the best nitrogen fountain is (NH4)2SO4, Inorganic salts adopts CaCl2. The optimium component proportion of medium (p/gL-1) obtained according to the orthogonal experiment was:urea 25, carbamide 0.8, NaCl 0.2, FeSO40.01.The optimiun cultural conditions was:pH 5,25℃,160 r/min, inoculability fountain is B212's starch medium culture liquid, the optimal inoculability capacity is 3.3%(v/v),cultivated for 36 hours in flakes.The factors that affect efficiency of flocculation were also tested systematically. The flocculant produced by strain B212 was found to be effective for flocculation of kaolin suspension when the dosage was 1.2mL/100mL, the optimal dosage of without addition of positive ions (CaCl2)was 5mL/100mL and the temperature was 20℃, the manner of mill is repeat mill.For B212, the growth dynamic curves of flocculating microbial were correlate with the production dynamic curves of microbial-flocculants.The experimental results showed that the flocculants produced by B212 strain mainly exist in the supernatant and they were synthesized during the cell growth.B212 had a very high thermal, stability.