Study On Isolation Of Flocculant Producing Strain And Its Performance In Brewery Wastewater Treatment

Brewery wastewater,with high level fatty acid,amino acid and lower alcohol,is recylable.The chemical flocculant was widely used to treat brewery wastewater.However,it will cause a potential hazard during the recovery byproduct of brewery wastewater treatment because of toxicity and unbiodegradabilty.Mricrobial flocculant,a natural macromolecular compound with flocculation ability,consisting of polysaccharides,proteins,and lipids,are produced by various microorganisms.Because of its nontoxicity and biodegradability,mirobial flocculant is considered as an alternative to traditional chemical flocculant.This research aimed to screen a flocculant-producing strain and to study flocculation performance of the microbial flocculant.A microbial flocculant-producing strain,with high flocculation efficiency to kaolin clay suspension,was isolated from activated sludge by pure culture technique.It was identified as Bacillus siamensis CQ-1 by colony morphology,physiological biochemical charateristics and 16s rDNA sequence.Singl factor and response surface experiments were conducted to optimize Bacillus siamensis CQ-1 fermentation condition.The result showed the maximum flocculation efficiency of 88.04%was achived when lactose concentration was 17.60g/L,urea concentration was 1.30g/L,the initial pH of culture medium was 7.3 and rotation speed was 183rpm.Logistic equation and Luedeking-Piret equation was employed to build kinetic models on growth and microbial flocculant production.The models with high fitting level?R²>0.95?can reflected the relationship among dry weight of Bacillus siamensis CQ-1,microbial flocculant production and fermentation time.The microbial flocculant,which was named as MBF-CQ,was extracted and purificated from fermentation broth of Bacillus siamensis CQ-1.The contents of carbohydrate and protein in MBF-CQ were measured by phenol-sulfuric acid method and Coomassie brilliant blue method.The result indicates that the contents of carbohydrate and protein were 67.31%and 23.50%,respectively.The analysis of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy showed the presence of Hydroxyl group,carboxyl group and amino group in MBF-CQ.The Zeta potential pre-flocculation and post-flocculation were measured.It can be inferred that the bridging was the main mechanism in flocculation process.The result of stability research showed that MBF-CQ remained high flocculation efficiency at low and high temperature.Single factor method was employed to study the influence of MBF-CQ dosage,pH and CaCl₂ dosage on flocculation characteristic.Then flocculation conditions were optimized by response surface experiments.It was found that the maximal flocculation efficiency was 94.81%at the MBF-CQ dosage 1.60mg/L,the pH of flocculation system 6.20,CaCl₂ dosage 18.00mL/L.The results indicated that MBF-CQ is valuable to treat wastewater.The fermentation broth of Bacillus siamensis CQ-1 was used to treat brewery wastewater and the treatment condition was optimized.The maximal COD removal efficiency was achieved at the fermentation broth dosage of 40mL/L,pH of 5 and CaCl₂dosage of 25mL/L.Under the optimal conditions,the removal efficiencies of the total nitrogen,total phosphorous,COD,suspension solid of was 50.27%,69.21%,70.32%,78.73%,respectively,and the flocculation efficiency was 72.89%.The removal efficiency of total phosphorous and suspension solid were higher than that of cationic polyacrylamide and polyaluminium chloride.The concentrations of total phosphorous and suspension solid in treated brewery wastewater was up to the emission standard of GB27631-2011.The levels of total nitrogen and COD were slightly higher than emission standard.