A compound bioflocculant CBF,produced by mixed culture of Rhizobium radiobacter F2 and Bacillus sphaeicus F6, was investigated with regard to its production and flocculating properties. The optimization of the culture...A compound bioflocculant CBF,produced by mixed culture of Rhizobium radiobacter F2 and Bacillus sphaeicus F6, was investigated with regard to its production and flocculating properties. The optimization of the culture medium constituents including carbon source,nitrogen source and C / N ratio,metal ions and ionic strength on CBF production were studied. Flocculating properties of CBF were examined by a series of experiments and CBF had good flocculating activities in kaolin suspension with divalent cations and stable over wide range of p H. Studies of the flocculating properties revealed that the flocculation could be stimulated by cations Ca2+,Mg2+,Fe2+,Al3+and Fe3+. In addition,it was stable at 4-30 ℃ in the presence of Ca Cl2. It was found to be effective for flocculation of a kaolin suspension under neutral and weak alkaline conditions( p H 7. 0- 9. 0),and flocculating activities of higher than 95% were obtained when the CBF concentrations among 6- 14 mg / L at p H 8. 0. The results of this study indicate that CBF is a potential replacement of conventional synthetic flocculants and is widely applied in water treatment and downstream processing of food and fermentation industries.展开更多
To elucidate the phosphorus removal and metabolism under various COD / P ratio,a sludge highly enriched in PAOs was used to investigate the impacts of COD / P in batch tests under different carbon supply conditions. A...To elucidate the phosphorus removal and metabolism under various COD / P ratio,a sludge highly enriched in PAOs was used to investigate the impacts of COD / P in batch tests under different carbon supply conditions. Acetate,propionate and a mixture of acetate and propionate at a ratio of 3 ∶ 1( COD basis) was used as carbon sources with the COD / P of 20,15,10 and 5. 0 g COD /gP,respectively. The minimum COD / P ratios for complete P removal were found to be 8. 24 g COD /gP for acetate,11. 40 g COD /gP for propionate and9. 10 g COD /gP for the 3 ∶ 1 mixture of acetate and propionate. Converted to a mass basis,all three cases had a very similar ratio of 7. 7 g VFA /gP,which represented a useful guide for operation of EBPR plants to identify possible shortages in VFAs. The trend in PHV accumulation during the anaerobic period along with the decrease of COD / P ratios suggested that,PAOs may use the TCA pathway for anaerobic VFA uptake to maintain the required NADH production with reduced glycogen degradation. During the aerobic phase,the glycogen pool was reduced but remained enough compared to the requirement for anaerobic VFA uptake,and the synthesis and degradation of glycogen was not the inhibition factor of PAOs.展开更多
基金Sponsored by the National High Technology Research and Development Program of China(Grant No.2009AA062906)the"Twelfth Five-Year Plan"National Key Technology R&D Program of China(Grant No.2012BAD14B06-04)+2 种基金the National Natural Science Foundation of China(Grant No.51478140&51408200)State Key Laboratory of Urban Water Resource and Environment(Harbin Institute of Technology)(Grant No.2015DX06)Promising Youngsters Training Program of Heilongjiang University of Science and Technology(Grant No.Q20120201)
文摘A compound bioflocculant CBF,produced by mixed culture of Rhizobium radiobacter F2 and Bacillus sphaeicus F6, was investigated with regard to its production and flocculating properties. The optimization of the culture medium constituents including carbon source,nitrogen source and C / N ratio,metal ions and ionic strength on CBF production were studied. Flocculating properties of CBF were examined by a series of experiments and CBF had good flocculating activities in kaolin suspension with divalent cations and stable over wide range of p H. Studies of the flocculating properties revealed that the flocculation could be stimulated by cations Ca2+,Mg2+,Fe2+,Al3+and Fe3+. In addition,it was stable at 4-30 ℃ in the presence of Ca Cl2. It was found to be effective for flocculation of a kaolin suspension under neutral and weak alkaline conditions( p H 7. 0- 9. 0),and flocculating activities of higher than 95% were obtained when the CBF concentrations among 6- 14 mg / L at p H 8. 0. The results of this study indicate that CBF is a potential replacement of conventional synthetic flocculants and is widely applied in water treatment and downstream processing of food and fermentation industries.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51278143,51408162)the Postdoctoral Foundation of China(Grant No.2013M530161)
文摘To elucidate the phosphorus removal and metabolism under various COD / P ratio,a sludge highly enriched in PAOs was used to investigate the impacts of COD / P in batch tests under different carbon supply conditions. Acetate,propionate and a mixture of acetate and propionate at a ratio of 3 ∶ 1( COD basis) was used as carbon sources with the COD / P of 20,15,10 and 5. 0 g COD /gP,respectively. The minimum COD / P ratios for complete P removal were found to be 8. 24 g COD /gP for acetate,11. 40 g COD /gP for propionate and9. 10 g COD /gP for the 3 ∶ 1 mixture of acetate and propionate. Converted to a mass basis,all three cases had a very similar ratio of 7. 7 g VFA /gP,which represented a useful guide for operation of EBPR plants to identify possible shortages in VFAs. The trend in PHV accumulation during the anaerobic period along with the decrease of COD / P ratios suggested that,PAOs may use the TCA pathway for anaerobic VFA uptake to maintain the required NADH production with reduced glycogen degradation. During the aerobic phase,the glycogen pool was reduced but remained enough compared to the requirement for anaerobic VFA uptake,and the synthesis and degradation of glycogen was not the inhibition factor of PAOs.
