Both a theoretical and an empirical model were developed for predicting the formation of soluble microbial products （SMP） during drinking water biofiltration. Four pilot-scale biofilters with ceramsite as the medium...Both a theoretical and an empirical model were developed for predicting the formation of soluble microbial products （SMP） during drinking water biofiltration. Four pilot-scale biofilters with ceramsite as the medium were fed with different acetate loadings for the determination of SMP formation. Using numerically simulated and measured parameters, the theoretical model was developed according to the substrate and biomass balance. The results of this model matched the measured data better for higher SMP formation but did not fit well when SMP formation was lower. In order to better simulate the reality and overcome the difficulties of measuring the kinetic parameters, a simpler empirical model was also developed. In this model, SMP formation was expressed as a function of fed organic loadings and the depth of the medium, and a much better fit was obtained.展开更多
The effects of feed strength, hydraulic residence time （HRT）, and operational temperatures on soluble microbial product （SMP） production were investigated, to gain insights into the production mechanism. A carrier...The effects of feed strength, hydraulic residence time （HRT）, and operational temperatures on soluble microbial product （SMP） production were investigated, to gain insights into the production mechanism. A carrier anaerobic baffled reactor （CABR） treating dilute wastewater was operated under a wide range of operational conditions, namely, feed strengths of 300-600 mg/L, HRTs of 9- 18 h, and temperatures of 10-28℃. Generally, SMP production increased with increasing feed strength and decreasing temperature. At high temperature （28℃）, SMP production increased with decreasing HRT. As the temperature was decreased to 18 and 10℃, the SMP production was at its peak for 12 h HRT. Therefore, temperature could be an important determinant of SMP production along with HRT. A higher SMP to soluble chemical oxygen demand （SCOD） ratio was found at high temperature and long HRT because of complete volatile fatty acid degradation. SMP accounted for 50%-75% of the SCOD in the last chamber of the CABR. As a secondary metabolite, some SMP could be consumed at lower feed strength.展开更多
Membrane fouling is a major problem in membrane bioreactors(MBRs).In this study,membrane fouling caused by membrane rejection and adsorption was study.Filtration tests indicated that membrane rejected SMP,causing memb...Membrane fouling is a major problem in membrane bioreactors(MBRs).In this study,membrane fouling caused by membrane rejection and adsorption was study.Filtration tests indicated that membrane rejected SMP,causing membrane pore blockage and then forming a gel layer.Batch adsorption experiments showed that adsorption of SMP onto PVDF membrane was a spontaneous physical adsorption process.Meanwhile,the absolute valueΔG of adsorption of SMP onto D3520 was higher than that of adsorption of SMP onto PVDF membrane,so SMP preferentially adsorbed onto D3520 rather than PVDF membrane.Thus,the effect of ARs on reducing the SMP concentration was investigated.It was found that,6 g of D3520 was suitable for adsorption of SMP.This physical adsorption involved external film diffusion,intra-particle diffusion,and surface adsorption.The Redlich–Peterson isotherm model performed best in terms of describing this equilibrium data.The mechanism of membrane fouling mitigation was verified by MBR simulation system.A case study of AR–MBR system was conducted.The results showed that addition of D3520 can effectively alleviate the development of membrane fouling.展开更多
Soluble microbial products(SMPs),dissolved organic matter excreted by activated sludge,can interact with antibiotics in wastewater and natural water bodies.Interactions between SMPs and antibiotics can influence antib...Soluble microbial products(SMPs),dissolved organic matter excreted by activated sludge,can interact with antibiotics in wastewater and natural water bodies.Interactions between SMPs and antibiotics can influence antibiotic migration,transformation,and toxicity but the mechanisms involved in such interactions are not fully understood.In this study,integrated spectroscopy approaches were used to investigate the mechanisms involved in interactions between SMPs and a representative antibiotic,trimethoprim(TMP),which has a low biodegradation rate and has been detected in wastewater.The results of liquid chromatography-organic carbon detection-organic nitrogen detection indicated that the SMPs used in the study contained 15% biopolymers and 28% humic-like substances(based on the total dissolved organic carbon concentration)so would have contained sites that could interact with TMP.A linear relationship of fluorescent intensities of tryptophan protein-like substances in SMP was observed(R^(2)>0.99),indicating that the fluorescence enhancement between SMP and TMP occurred.Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy indicated that carboxyl,carbonyl,and hydroxyl groups were the main functional groups involved in the interactions.The electrostatic andπ-πinteractions were discovered by the UV-vis spectra and 1H nuclear magnetic resonance spectra.Structural representations of the interactions between representative SMP subcomponents and TMP were calculated using density functional theory,and the results confirmed the conclusions drawn from the 1H nuclear magnetic resonance spectra.The results help characterize SMP–TMP complexes and will help understand antibiotic transformations in wastewater treatment plants and aquatic environments.展开更多
This study aimed to explore a new degradation method-photocatalysis technology to polish membrane bioreactor(MBR) effluent, using 2,6-di-tert-butylphenol(2,6-DTBP) as a model soluble microbial product(SMP).2,6-DTBP is...This study aimed to explore a new degradation method-photocatalysis technology to polish membrane bioreactor(MBR) effluent, using 2,6-di-tert-butylphenol(2,6-DTBP) as a model soluble microbial product(SMP).2,6-DTBP is one of the predominant SMPs in MBR effluent, which is refractory and difficult to biodegrade.This study developed a novel carboxylated graphene oxide/titanium dioxide/silver(GO-COOH/TiO2/Ag) nanocomposite to photodegrade 2,6-DTBP.GO-COOH/TiO2/Ag was successfully synthesized, using L-cysteine as the linker bonding TiO2/Ag to GO-COOH.The structural, morphological and optical properties of the GO-COOH/TiO2/Ag nanocomposite were characterized using various techniques.Owing to synergistic effects, the GO-COOH/TiO2/Ag nanocomposite exhibited enhanced photocatalytic degradation performance under solar light irradiation when compared to TiO2, Ag and GO-COOH.To remove 25 mg/L 2,6-DTBP, the reaction time for GOCOOH/TiO2/Ag was only 30 min, faster than the 90 min required for pure TiO2 or Ag.In addition, the 200 mg/L GO-COOH/TiO2/Ag nanocomposite aqueous solution showed the best performance under solar light, with 99% removal of 2,6-DTBP.This enhanced capability is likely due to the surface plasmon resonance(SPR) effect contributed by Ag nanoparticles(NPs) doped onto the TiO2.In addition, GO-COOH had a high effective surface area, which assisted in degrading the 2,6-DTBP through improved adsorption.The stability study showed that the photocatalytic activity of the GO-COOH/TiO2/Ag was stable enough for recycling multiple times.The effective degradation performance and excellent stability demonstrates that the GO-COOH/TiO2/Ag nanocomposite can be a promising photocatalyst in the field of effluent SMP photodegradation, which solves the problem of the difficult biodegradation of highly toxic 2,6-DTBP.展开更多
A two-phase anaerobic reactor fed with glucose substrate（3 g chemical oxygen demand（COD）/L） was used to investigate the effects of toxic metals on the degradation of organics and the soluble microbial product（SMP...A two-phase anaerobic reactor fed with glucose substrate（3 g chemical oxygen demand（COD）/L） was used to investigate the effects of toxic metals on the degradation of organics and the soluble microbial product（SMP） formation. Low concentrations of Ni（II）（5 and10 mg/L） promoted the acid phase, whereas high concentrations（15, 20, and 25 mg/L）exhibited an inhibitory effect on, but did not alter the fermentative method, which mainly involved the fermentation of propionic acid. The methanogenic microorganism exhibited a strong capability adapting constantly increased Ni（II） levels. The acid phase was an accumulation stage of SMP. In the absence of Ni（II）, the high-molecular-weight material in the effluent SMP mainly contained polysaccharide, tryptophan, and casein. Methanogens metabolized most of the polysaccharide, the whole tryptophan content, and part of the casein, leading to the presence of humic acid and protein in effluent. After Ni（II） dosage, the protein and polysaccharide of the acid phase increased, and tryptophan changed, while casein remained stable. More protein than polysaccharide was produced, suggesting the prominent function of protein when addressing the negative effect of toxic metals. The analysis of DNA confirmed the change of bacterial activity.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 50408026)
文摘Both a theoretical and an empirical model were developed for predicting the formation of soluble microbial products （SMP） during drinking water biofiltration. Four pilot-scale biofilters with ceramsite as the medium were fed with different acetate loadings for the determination of SMP formation. Using numerically simulated and measured parameters, the theoretical model was developed according to the substrate and biomass balance. The results of this model matched the measured data better for higher SMP formation but did not fit well when SMP formation was lower. In order to better simulate the reality and overcome the difficulties of measuring the kinetic parameters, a simpler empirical model was also developed. In this model, SMP formation was expressed as a function of fed organic loadings and the depth of the medium, and a much better fit was obtained.
文摘The effects of feed strength, hydraulic residence time （HRT）, and operational temperatures on soluble microbial product （SMP） production were investigated, to gain insights into the production mechanism. A carrier anaerobic baffled reactor （CABR） treating dilute wastewater was operated under a wide range of operational conditions, namely, feed strengths of 300-600 mg/L, HRTs of 9- 18 h, and temperatures of 10-28℃. Generally, SMP production increased with increasing feed strength and decreasing temperature. At high temperature （28℃）, SMP production increased with decreasing HRT. As the temperature was decreased to 18 and 10℃, the SMP production was at its peak for 12 h HRT. Therefore, temperature could be an important determinant of SMP production along with HRT. A higher SMP to soluble chemical oxygen demand （SCOD） ratio was found at high temperature and long HRT because of complete volatile fatty acid degradation. SMP accounted for 50%-75% of the SCOD in the last chamber of the CABR. As a secondary metabolite, some SMP could be consumed at lower feed strength.
基金financially supported by the Inner Mongolia Natural Science Foundation of China(No.2016BS0205)the Scientific Research Foundation of the Inner Mongolia University of Technology of China(No.ZD201505).
文摘Membrane fouling is a major problem in membrane bioreactors(MBRs).In this study,membrane fouling caused by membrane rejection and adsorption was study.Filtration tests indicated that membrane rejected SMP,causing membrane pore blockage and then forming a gel layer.Batch adsorption experiments showed that adsorption of SMP onto PVDF membrane was a spontaneous physical adsorption process.Meanwhile,the absolute valueΔG of adsorption of SMP onto D3520 was higher than that of adsorption of SMP onto PVDF membrane,so SMP preferentially adsorbed onto D3520 rather than PVDF membrane.Thus,the effect of ARs on reducing the SMP concentration was investigated.It was found that,6 g of D3520 was suitable for adsorption of SMP.This physical adsorption involved external film diffusion,intra-particle diffusion,and surface adsorption.The Redlich–Peterson isotherm model performed best in terms of describing this equilibrium data.The mechanism of membrane fouling mitigation was verified by MBR simulation system.A case study of AR–MBR system was conducted.The results showed that addition of D3520 can effectively alleviate the development of membrane fouling.
基金supported by the National Natural Science Foundation of China (Nos. 51878244 and 52170032)the the Fundamental Research Funds for the Central Universities (No. B200202101)the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), China
文摘Soluble microbial products(SMPs),dissolved organic matter excreted by activated sludge,can interact with antibiotics in wastewater and natural water bodies.Interactions between SMPs and antibiotics can influence antibiotic migration,transformation,and toxicity but the mechanisms involved in such interactions are not fully understood.In this study,integrated spectroscopy approaches were used to investigate the mechanisms involved in interactions between SMPs and a representative antibiotic,trimethoprim(TMP),which has a low biodegradation rate and has been detected in wastewater.The results of liquid chromatography-organic carbon detection-organic nitrogen detection indicated that the SMPs used in the study contained 15% biopolymers and 28% humic-like substances(based on the total dissolved organic carbon concentration)so would have contained sites that could interact with TMP.A linear relationship of fluorescent intensities of tryptophan protein-like substances in SMP was observed(R^(2)>0.99),indicating that the fluorescence enhancement between SMP and TMP occurred.Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy indicated that carboxyl,carbonyl,and hydroxyl groups were the main functional groups involved in the interactions.The electrostatic andπ-πinteractions were discovered by the UV-vis spectra and 1H nuclear magnetic resonance spectra.Structural representations of the interactions between representative SMP subcomponents and TMP were calculated using density functional theory,and the results confirmed the conclusions drawn from the 1H nuclear magnetic resonance spectra.The results help characterize SMP–TMP complexes and will help understand antibiotic transformations in wastewater treatment plants and aquatic environments.
基金the financial support received from China Postdoctoral Science Foundation Funded Project(No.2018M641387).
文摘This study aimed to explore a new degradation method-photocatalysis technology to polish membrane bioreactor(MBR) effluent, using 2,6-di-tert-butylphenol(2,6-DTBP) as a model soluble microbial product(SMP).2,6-DTBP is one of the predominant SMPs in MBR effluent, which is refractory and difficult to biodegrade.This study developed a novel carboxylated graphene oxide/titanium dioxide/silver(GO-COOH/TiO2/Ag) nanocomposite to photodegrade 2,6-DTBP.GO-COOH/TiO2/Ag was successfully synthesized, using L-cysteine as the linker bonding TiO2/Ag to GO-COOH.The structural, morphological and optical properties of the GO-COOH/TiO2/Ag nanocomposite were characterized using various techniques.Owing to synergistic effects, the GO-COOH/TiO2/Ag nanocomposite exhibited enhanced photocatalytic degradation performance under solar light irradiation when compared to TiO2, Ag and GO-COOH.To remove 25 mg/L 2,6-DTBP, the reaction time for GOCOOH/TiO2/Ag was only 30 min, faster than the 90 min required for pure TiO2 or Ag.In addition, the 200 mg/L GO-COOH/TiO2/Ag nanocomposite aqueous solution showed the best performance under solar light, with 99% removal of 2,6-DTBP.This enhanced capability is likely due to the surface plasmon resonance(SPR) effect contributed by Ag nanoparticles(NPs) doped onto the TiO2.In addition, GO-COOH had a high effective surface area, which assisted in degrading the 2,6-DTBP through improved adsorption.The stability study showed that the photocatalytic activity of the GO-COOH/TiO2/Ag was stable enough for recycling multiple times.The effective degradation performance and excellent stability demonstrates that the GO-COOH/TiO2/Ag nanocomposite can be a promising photocatalyst in the field of effluent SMP photodegradation, which solves the problem of the difficult biodegradation of highly toxic 2,6-DTBP.
基金supported by the National Natural Science Foundation of China (Nos. 51178215 and 51378251)the Jiangsu Nature Science Fund (No. BK2011032)+2 种基金Open Science Foundation of Jiangsu (No. 50808121)the National Science and Technology Major Project for Water Pollution Control and Treatment (No. 2012ZX07301-005)the 2012 Scientific Research Open Found of Jiangsu Key Laboratory of Environmental Engineering
文摘A two-phase anaerobic reactor fed with glucose substrate（3 g chemical oxygen demand（COD）/L） was used to investigate the effects of toxic metals on the degradation of organics and the soluble microbial product（SMP） formation. Low concentrations of Ni（II）（5 and10 mg/L） promoted the acid phase, whereas high concentrations（15, 20, and 25 mg/L）exhibited an inhibitory effect on, but did not alter the fermentative method, which mainly involved the fermentation of propionic acid. The methanogenic microorganism exhibited a strong capability adapting constantly increased Ni（II） levels. The acid phase was an accumulation stage of SMP. In the absence of Ni（II）, the high-molecular-weight material in the effluent SMP mainly contained polysaccharide, tryptophan, and casein. Methanogens metabolized most of the polysaccharide, the whole tryptophan content, and part of the casein, leading to the presence of humic acid and protein in effluent. After Ni（II） dosage, the protein and polysaccharide of the acid phase increased, and tryptophan changed, while casein remained stable. More protein than polysaccharide was produced, suggesting the prominent function of protein when addressing the negative effect of toxic metals. The analysis of DNA confirmed the change of bacterial activity.
