Two artificial intelligence techniques, artificial neural network and genetic algorithm, were applied to optimize the fermentation medium for improving the nitrite oxidization rate of nitrite oxidizing bacteria. Exper...Two artificial intelligence techniques, artificial neural network and genetic algorithm, were applied to optimize the fermentation medium for improving the nitrite oxidization rate of nitrite oxidizing bacteria. Experiments were conducted with the composition of medium components obtained by genetic algorithm, and the experimental data were used to build a BP (back propagation) neural network model. The concentrations of six medium components were used as input vectors, and the nitrite oxidization rate was used as output vector of the model. The BP neural network model was used as the objective function of genetic algorithm to find the optimum medium composition for the maximum nitrite oxidization rate. The maximum nitrite oxidization rate was 0.952 g 2 NO-2-N·(g MLSS)-1·d-1 , obtained at the genetic algorithm optimized concentration of medium components (g·L-1 ): NaCl 0.58, MgSO 4 ·7H 2 O 0.14, FeSO 4 ·7H 2 O 0.141, KH 2 PO 4 0.8485, NaNO 2 2.52, and NaHCO 3 3.613. Validation experiments suggest that the experimental results are consistent with the best result predicted by the model. A scale-up experiment shows that the nitrite degraded completely after 34 h when cultured in the optimum medium, which is 10 h less than that cultured in the initial medium.展开更多
The effects of chitosan characteristics including the degree of deacetylation, molecular weight, particle size, pH pretreatment and immobilization time on the immobilization of nitrite-oxidizing bacteria （NOB） on bi...The effects of chitosan characteristics including the degree of deacetylation, molecular weight, particle size, pH pretreatment and immobilization time on the immobilization of nitrite-oxidizing bacteria （NOB） on biopolymeric chitosan were investigated. Nitrite removal efficiency of immobilized NOB depended on the degree of deacetylation, particle size, pH pretreatment on the surface of chitosan and immobilization time. Scanning electron microscope characterization illustrated that the number of NOB cells attached to the surface of chitosan increased with an increment of immobilization time. The optimal condition for NOB immobilization on chitosan was achieved during a 24-hr immobilization period using chitosan with the degree of deacetylation larger than 80% and various particle size ranges between 1-5 mm at pH 6.5. In general, the NOB immobilized on chitosan flakes has a high potential to remove excess nitrite from wastewater and aquaculture systems.展开更多
The concept of anaerobic ammonium oxidation(ANAMMOX) is presently of great interest. The functional bacteria belonging to the Planctomycete phylum and their metabolism are investigated by microbiologists. Meanwhile,th...The concept of anaerobic ammonium oxidation(ANAMMOX) is presently of great interest. The functional bacteria belonging to the Planctomycete phylum and their metabolism are investigated by microbiologists. Meanwhile,the ANAMMOX is equally valuable in treatment of ammonium-rich wastewaters. Related processes including partial nitritation-ANAMMOX and completely autotrophic nitrogen removal over nitrite(CANON) have been developed,and lab-scale experiments proved that both processes were quite feasible in engineering with appropriate control. Successful full-scale practice in the Netherlands will ac-celerate application of the process in future. This review introduces the microbiology and more focuses on application of the ANAMMOX process.展开更多
Nitrite accumulation in shrimp ponds can pose serious adverse effects to shrimp production and the environment.This study aims to develop an effective process for the enrichment of ready-to-use nitrite-oxidizing bacte...Nitrite accumulation in shrimp ponds can pose serious adverse effects to shrimp production and the environment.This study aims to develop an effective process for the enrichment of ready-to-use nitrite-oxidizing bacteria（NOB）inocula that would be appropriate for nitrite removal in brackish shrimp ponds.To achieve this objective,the effects of nitrite concentrations on NOB communities and nitrite oxidation kinetics in a brackish environment were investigated.Moving-bed biofilm sequencing batch reactors and continuous moving-bed biofilm reactors were used for the enrichment of NOB at various nitrite concentrations,using sediment from brackish shrimp ponds as seed inoculum.The results from NOB population analysis with quantitative polymerase chain reaction（q PCR）show that only Nitrospira were detected in the sediment from the shrimp ponds.After the enrichment,both Nitrospira and Nitrobacter coexisted in the reactors controlling effluent nitrite at 0.1 and 0.5 mg-NO2^--N/L.On the other hand,in the reactors controlling effluent nitrite at 3,20,and 100 mg-NO2^--N/L,Nitrobacter outcompeted Nitrospira in many orders of magnitude.The half saturation coefficients（Ks）for nitrite oxidation of the enrichments at low nitrite concentrations（0.1 and 0.5 mg-NO2^--N/L）were in the range of 0.71–0.98 mg-NO2^--N/L.In contrast,the Ksvalues of NOB enriched at high nitrite concentrations（3,20,and 100 mg-NO2^--N/L）were much higher（8.36–12.20 mg-NO2^--N/L）.The results suggest that the selection of nitrite concentrations for the enrichment of NOB inocula can significantly influence NOB populations and kinetics,which could affect the effectiveness of their applications in brackish shrimp ponds.展开更多
基金Supported by the National Natural Science Foundation of China (21076090)
文摘Two artificial intelligence techniques, artificial neural network and genetic algorithm, were applied to optimize the fermentation medium for improving the nitrite oxidization rate of nitrite oxidizing bacteria. Experiments were conducted with the composition of medium components obtained by genetic algorithm, and the experimental data were used to build a BP (back propagation) neural network model. The concentrations of six medium components were used as input vectors, and the nitrite oxidization rate was used as output vector of the model. The BP neural network model was used as the objective function of genetic algorithm to find the optimum medium composition for the maximum nitrite oxidization rate. The maximum nitrite oxidization rate was 0.952 g 2 NO-2-N·(g MLSS)-1·d-1 , obtained at the genetic algorithm optimized concentration of medium components (g·L-1 ): NaCl 0.58, MgSO 4 ·7H 2 O 0.14, FeSO 4 ·7H 2 O 0.141, KH 2 PO 4 0.8485, NaNO 2 2.52, and NaHCO 3 3.613. Validation experiments suggest that the experimental results are consistent with the best result predicted by the model. A scale-up experiment shows that the nitrite degraded completely after 34 h when cultured in the optimum medium, which is 10 h less than that cultured in the initial medium.
基金supported by the Ratchadaphiseksomphot Endowment Fund
文摘The effects of chitosan characteristics including the degree of deacetylation, molecular weight, particle size, pH pretreatment and immobilization time on the immobilization of nitrite-oxidizing bacteria （NOB） on biopolymeric chitosan were investigated. Nitrite removal efficiency of immobilized NOB depended on the degree of deacetylation, particle size, pH pretreatment on the surface of chitosan and immobilization time. Scanning electron microscope characterization illustrated that the number of NOB cells attached to the surface of chitosan increased with an increment of immobilization time. The optimal condition for NOB immobilization on chitosan was achieved during a 24-hr immobilization period using chitosan with the degree of deacetylation larger than 80% and various particle size ranges between 1-5 mm at pH 6.5. In general, the NOB immobilized on chitosan flakes has a high potential to remove excess nitrite from wastewater and aquaculture systems.
基金Project supported by the National Hi-Tech Research and Develop-ment Program (863) of China (No. 2006AA06Z332)the Scienceand Technology Foundation for Key Project of Zhejiang Province (No2003C13005), China
文摘The concept of anaerobic ammonium oxidation(ANAMMOX) is presently of great interest. The functional bacteria belonging to the Planctomycete phylum and their metabolism are investigated by microbiologists. Meanwhile,the ANAMMOX is equally valuable in treatment of ammonium-rich wastewaters. Related processes including partial nitritation-ANAMMOX and completely autotrophic nitrogen removal over nitrite(CANON) have been developed,and lab-scale experiments proved that both processes were quite feasible in engineering with appropriate control. Successful full-scale practice in the Netherlands will ac-celerate application of the process in future. This review introduces the microbiology and more focuses on application of the ANAMMOX process.
基金supported by the National Research University Project,Office of Higher Education Commission(No.WCU-014-FW-57)
文摘Nitrite accumulation in shrimp ponds can pose serious adverse effects to shrimp production and the environment.This study aims to develop an effective process for the enrichment of ready-to-use nitrite-oxidizing bacteria（NOB）inocula that would be appropriate for nitrite removal in brackish shrimp ponds.To achieve this objective,the effects of nitrite concentrations on NOB communities and nitrite oxidation kinetics in a brackish environment were investigated.Moving-bed biofilm sequencing batch reactors and continuous moving-bed biofilm reactors were used for the enrichment of NOB at various nitrite concentrations,using sediment from brackish shrimp ponds as seed inoculum.The results from NOB population analysis with quantitative polymerase chain reaction（q PCR）show that only Nitrospira were detected in the sediment from the shrimp ponds.After the enrichment,both Nitrospira and Nitrobacter coexisted in the reactors controlling effluent nitrite at 0.1 and 0.5 mg-NO2^--N/L.On the other hand,in the reactors controlling effluent nitrite at 3,20,and 100 mg-NO2^--N/L,Nitrobacter outcompeted Nitrospira in many orders of magnitude.The half saturation coefficients（Ks）for nitrite oxidation of the enrichments at low nitrite concentrations（0.1 and 0.5 mg-NO2^--N/L）were in the range of 0.71–0.98 mg-NO2^--N/L.In contrast,the Ksvalues of NOB enriched at high nitrite concentrations（3,20,and 100 mg-NO2^--N/L）were much higher（8.36–12.20 mg-NO2^--N/L）.The results suggest that the selection of nitrite concentrations for the enrichment of NOB inocula can significantly influence NOB populations and kinetics,which could affect the effectiveness of their applications in brackish shrimp ponds.
