Pollution by polycyclic aromatic hydrocarbons（PAHs） is widespread due to tmsuitable disposal of industrial waste. They are mostly defined as priority pollutants by environmental protection authorities worldwide. Phe...Pollution by polycyclic aromatic hydrocarbons（PAHs） is widespread due to tmsuitable disposal of industrial waste. They are mostly defined as priority pollutants by environmental protection authorities worldwide. Phenanthrene, a typical PAH, was selected as the target in this paper. The PAH-degrading mixed culture, named ZM, was collected from a petroleum contaminated river bed. This culture was injected into phenanthrene solutions at different concentrations to quantify the biodegradation process. Results show near-complete removal of phenanthrene in three days of biodegradation if the initial phenanthrene concentration is low. When the initial concentration is high, the removal rate is increased but 20%-40% of the phenanthrene remains at the end of the experiment. The biomass shows a peak on the third day due to the combined effects of microbial growth and decay. Another peak is evident for cases with a high initial concentration, possibly due to production of an intermediate metabolite. The pH generally decreased during biodegradation because of the production of organic acid. Two phenomenological models were designed to simulate the phenanthrene biodegradation and biomass growth. A relatively simple model that does not consider the intermediate metabolite and its inhibition of phenanthrene biodegradation cannot fit the observed data. A modified Monod model that considered an intermediate metabolite （organic acid） and its inhibiting reversal effect reasonably depicts the experimental results.展开更多
This paper reports a comparative evaluation between 2 kinetic models for predicting nitrification and biodegradable organics(BOD5)removal rates in 5 vertical flow(VF)wetland systems,that received strong wastewaters(i....This paper reports a comparative evaluation between 2 kinetic models for predicting nitrification and biodegradable organics(BOD5)removal rates in 5 vertical flow(VF)wetland systems,that received strong wastewaters(i.e.tannery,textile and municipal effluents).The models were formulated by combining first order and Monod kinetics,with continuous-stirred tank reactor(CSTR)flow approach.The performance of the 2 models had been evaluated with3 statistical parameters:coefficient of determination(R2),relative root mean square error(RRMSE),and model efficiency(ME).The statistical parameters indicated better performance of the Monod CSTR model(over first order CSTR approach),for correlating ammoniacal nitrogen(NH4+—N)and BOD5removal profiles across VF systems.Higher Monod coefficient values(from Monod CSTR model)coincided with greater input NH4+—N and BOD5loading,and experimentally measured removal rate(g/(m2·d))values.Such trends indicate that NH4+—N and BOD5removals in the VF systems were mainly achieved via biological routes.On the other hand,the rate constants(from the first order CSTR model)did not exhibit such correlations(of Monod coefficients),elucidating their inefficiencies in capturing overall removal mechanisms.The interference of organics removal on nitrification process(in VF wetlands)was identified through Monod coefficients.The deviation between NH4+—N and BOD5Monod coefficients imply incorporation of both coefficients,for calculating the area of a single VF bed.Overall,closer performance of the Monod CSTR model for predicting NH4+—N and BOD5removals indicate its potential application,as a design tool for VF systems.展开更多
Short_term batch cultures were used to measure the phosphate_dependent growth kinetics for a marine microalga, Tetraselmis subcordiformis (Wille) Hazen, and a marine macroalga, Ulva pertusa Kjellm. Results wer...Short_term batch cultures were used to measure the phosphate_dependent growth kinetics for a marine microalga, Tetraselmis subcordiformis (Wille) Hazen, and a marine macroalga, Ulva pertusa Kjellm. Results were fitted to the Monod model. U. pertusa had a lower half_saturation constant and maximum growth rate, which were 0.016 μmol/L and 0.16 d -1 respectively, while the growth kinetics of T. subcordiformis were 0.021 μmol/L and 0.83 d -1 . Long_term semicontinuous nutrient competition experiments were performed between T. subcordiformis and U. pertusa under phosphate limitation in laboratory. Loss rates were manipulated to get the same or different resource requirement values ( R * ) of the two species. Comparison between the theoretical predictions derived from Monod kinetics and the outcome of competition experiments indicated that the Monod model could predict the results only when the R * values of the two species were significantly different, and T. subcordiformis displaced U. pertusa when they had the same resource requirements. The Monod model can only partly predict the competition results between microalga and macroalga.展开更多
基金The National Natural Science Foundation of China （No. 50178040） the Royal Society of UK and the Hi-Tech Research and Development Program（863） of China（No. 2003AA601080）
文摘Pollution by polycyclic aromatic hydrocarbons（PAHs） is widespread due to tmsuitable disposal of industrial waste. They are mostly defined as priority pollutants by environmental protection authorities worldwide. Phenanthrene, a typical PAH, was selected as the target in this paper. The PAH-degrading mixed culture, named ZM, was collected from a petroleum contaminated river bed. This culture was injected into phenanthrene solutions at different concentrations to quantify the biodegradation process. Results show near-complete removal of phenanthrene in three days of biodegradation if the initial phenanthrene concentration is low. When the initial concentration is high, the removal rate is increased but 20%-40% of the phenanthrene remains at the end of the experiment. The biomass shows a peak on the third day due to the combined effects of microbial growth and decay. Another peak is evident for cases with a high initial concentration, possibly due to production of an intermediate metabolite. The pH generally decreased during biodegradation because of the production of organic acid. Two phenomenological models were designed to simulate the phenanthrene biodegradation and biomass growth. A relatively simple model that does not consider the intermediate metabolite and its inhibition of phenanthrene biodegradation cannot fit the observed data. A modified Monod model that considered an intermediate metabolite （organic acid） and its inhibiting reversal effect reasonably depicts the experimental results.
文摘This paper reports a comparative evaluation between 2 kinetic models for predicting nitrification and biodegradable organics(BOD5)removal rates in 5 vertical flow(VF)wetland systems,that received strong wastewaters(i.e.tannery,textile and municipal effluents).The models were formulated by combining first order and Monod kinetics,with continuous-stirred tank reactor(CSTR)flow approach.The performance of the 2 models had been evaluated with3 statistical parameters:coefficient of determination(R2),relative root mean square error(RRMSE),and model efficiency(ME).The statistical parameters indicated better performance of the Monod CSTR model(over first order CSTR approach),for correlating ammoniacal nitrogen(NH4+—N)and BOD5removal profiles across VF systems.Higher Monod coefficient values(from Monod CSTR model)coincided with greater input NH4+—N and BOD5loading,and experimentally measured removal rate(g/(m2·d))values.Such trends indicate that NH4+—N and BOD5removals in the VF systems were mainly achieved via biological routes.On the other hand,the rate constants(from the first order CSTR model)did not exhibit such correlations(of Monod coefficients),elucidating their inefficiencies in capturing overall removal mechanisms.The interference of organics removal on nitrification process(in VF wetlands)was identified through Monod coefficients.The deviation between NH4+—N and BOD5Monod coefficients imply incorporation of both coefficients,for calculating the area of a single VF bed.Overall,closer performance of the Monod CSTR model for predicting NH4+—N and BOD5removals indicate its potential application,as a design tool for VF systems.
文摘Short_term batch cultures were used to measure the phosphate_dependent growth kinetics for a marine microalga, Tetraselmis subcordiformis (Wille) Hazen, and a marine macroalga, Ulva pertusa Kjellm. Results were fitted to the Monod model. U. pertusa had a lower half_saturation constant and maximum growth rate, which were 0.016 μmol/L and 0.16 d -1 respectively, while the growth kinetics of T. subcordiformis were 0.021 μmol/L and 0.83 d -1 . Long_term semicontinuous nutrient competition experiments were performed between T. subcordiformis and U. pertusa under phosphate limitation in laboratory. Loss rates were manipulated to get the same or different resource requirement values ( R * ) of the two species. Comparison between the theoretical predictions derived from Monod kinetics and the outcome of competition experiments indicated that the Monod model could predict the results only when the R * values of the two species were significantly different, and T. subcordiformis displaced U. pertusa when they had the same resource requirements. The Monod model can only partly predict the competition results between microalga and macroalga.
