Agnese Wang - Academia.edu (original) (raw)
Papers by Agnese Wang
Water research, 2009
Numerical simulation and laboratory experiments were conducted to investigate the determining fac... more Numerical simulation and laboratory experiments were conducted to investigate the determining factor and the underlying mechanism in aerobic sludge granulation in a sequencing batch reactor (SBR). In the numerical simulation, a sectional approach was used to develop a model to describe the biomass dynamics during the granulation process. The growth of different classes of the SBR sludge with different substrate uptake rates and different sludge discharge ratios was simulated. The results indicate that the selective discharge of slow-settling sludge flocs is the key determining factor for granulation. In the laboratory study, experiments were conducted with two identical 2.4-L SBRs, R1 and R2, using different sludge discharge methods - the selective discharge of slow-settling sludge flocs for R1, and mixed, unselective sludge discharge for R2. The SBRs were fed with glucose-based synthetic wastewater at a chemical oxygen demand (COD) loading rate of 1.5 kg/m(3)-d. The evolution of th...
Water research, 2008
Laboratory experiments were carried out to investigate the evolution of the bacterial community d... more Laboratory experiments were carried out to investigate the evolution of the bacterial community during aerobic sludge granulation. The experiments were conducted in three 2.4L sequencing batch reactors (SBRs) that were seeded with activated sludge and fed with glucose-based synthetic wastewater. Three different influent organic concentrations were introduced into the three SBRs, R1, R2 and R3, resulting in chemical oxygen demand (COD) loading rates of 1.5 (R1), 3.0 (R2) and 4.5 (R3)kg/m(3)d, respectively. Changes in bacterial diversity throughout the granulation process were monitored and analysed using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) techniques. The experimental results demonstrate that glucose-fed aerobic granules could be formed without significant presence of filamentous bacteria. Granules formed at different loading rates had different morphology, structural properties and bacterial species. A higher loading rate resulted in fa...
![Research paper thumbnail of [Efficiency and characteristic of biological activated carbon fluidized bed for oil-field wastewater treatment]](https://a.academia-assets.com/images/blank-paper.jpg)
](Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.], 2006
In order to find method to improve biodegradation of oil-field wastewater, the biological activat... more In order to find method to improve biodegradation of oil-field wastewater, the biological activated carbon fluidized bed (BAC-FB) process for oil-field wastewater treatment in aerobic condition is studied. The results show that the process demonstrated highest removal rate with hull activated carbon (AC) as carrier and carrier concentration of 15%. The optimized HRT of the process is 5 h. COD, UV254, UV410, organic acid and organic compounds (GC/MS) were detected as the index to indicate the efficiency of oil-field wastewater treatment by this process. The results show that the removal rate of COD range from 25% to 45%. The average removal rate of UV254, UV410, organic acid is 85.9%, 73.6%, 51.5% respectively. The removal rate of oil content is almost 100%. However, alkane is difficult to remove from wastewater. Furthermore, high concentration inorganic materials such as calcium, chlorine were found to accumulate on activated carbon during treatment process, which is harm to adsorpt...
Aerobic sludge granulation is an attractive new technology for biological wastewater treatment. H... more Aerobic sludge granulation is an attractive new technology for biological wastewater treatment. However, the instability of aerobic granules caused by fungal growth is still one of the main problems encountered in granular bioreactors. In this study, laboratory experiments were conducted to investigate the fate and transformation of aerobic granules under different organic loading conditions. Bacterial granules (2-3 mm) in a poor condition with fungi-like black filamentous growth were seeded into two 1-L batch reactors. After more than 100 d of cultivation, the small seed granules in the two reactors had grown into two different types of large granules (> 20 mm) with different and unique morphological features. In reactor R1 with a high organic loading rate of 2.0 g COD L-1 d-1 , the black filaments mostly disappeared from the granules, and the dominance of rod-shaped bacteria was recovered. In contrast, at a low loading of 0.5 g COD L-1 d-1 in reactor R2, the filaments eventually became dominant in the black fungal granules. The bacteria in R1 granules had a unique web-like structure with large pores of a few hundred µm in size, which would allow for effective substrate and oxygen transport into the interior of the granules. DNA-based molecular analysis indicated the evolution of the bacterial population in R1 and that of the eukaryal community in R2. The experimental results suggest that a high loading rate can be an effective means of helping to control fungal bloom, recover bacterial domination and restore the stability of aerobic granules that suffer from fungal contamination.
2,4-Dichlorophenoxyacetic acid (2,4-D) degrading aerobic granular sludge, obtained through plasmi... more 2,4-Dichlorophenoxyacetic acid (2,4-D) degrading aerobic granular sludge, obtained through plasmid pJP4 mediated bioaugmentation, was used for the degradation of a mixture of 2,4-D, 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP) in a sequencing batch reactor. The removal rate of 2,4-D always stabilized at above 99%, indicating that the granules were still active in the presence of chlorophenols. The 2,4-D fed granules demonstrated a faster adaptation and higher degradation ability to 4-CP and 2,4-DCP than to 2,4,6-TCP. Nearly complete removals of 2,4-D and chlorophenols were achieved at the initial concentrations of approximately 400 mg/L of 2,4-D, 45 mg/L of 4-CP, 25 mg/L of 2,4-DCP, and 20 mg/L of 2,4,6-TCP and a hydraulic retention time (HRT) of 6 h. Each chlorophenol could be biodegraded and mineralized by the granules as the sole carbon source and the biodegradation followed Haldane inhibition model. The granules maintained a good settling ability and a dominant granular morphology as evidenced by the low sludge volume index (SVI) value (20-70 mL/g) and large granule size (400-610 m) during the long-term operation (420 days). The finally obtained granules showed a different microbial community compared to the granule seeds, and were mainly composed of Novosphingobium sp., Aquincola tertiaricarbonis, Xanthomonas sp. and Pseudorhodoferax caeni.
Separation and Purification Technology, 2011
Aerobic sludge granulation is rather difficult or impossible for the treatment of low-strength wa... more Aerobic sludge granulation is rather difficult or impossible for the treatment of low-strength wastewater. In this study, a novel technique involving granular activated carbon (GAC) was developed for rapid aerobic granulation under a low organic loading condition. Laboratory experiments were conducted with two sequencing batch reactors (SBRs) running side by side. One reactor had fine GAC added to the sludge mixture, and the other had no GAC added. A low-strength organic wastewater with a chemical oxygen demand (COD) concentration of only 200 mg/L was used as the influent to the SBRs. The morphology, 2 physical properties, and bacterial community structure of the sludge in the two reactors were characterized and compared throughout the experiments. The results showed that granules could not be formed in the SBR without added GAC. However, complete granulation was achieved in the SBR with GAC addition. Selective discharge of slow settling sludge was also essential to the granulation process. Adding GAC to the seed sludge mixture, together with the selective discharge of small and loose sludge flocs, facilitated the retention and growth of bacterial cells on GAC in attached-growth mode, leading to complete granulation. In addition, the use of GAC produced aerobic granules with strong cores to help maintain the long-term stability of mature granules. With granulation, the solid-liquid separation property of the sludge was greatly improved. Once granules were formed, the granules were quite stable and GAC addition was no longer needed. Therefore, adding GAC is a simple and effective strategy to initiate granule formation for complete sludge granulation in bioreactors treating low-strength organic wastewater.
Process Biochemistry, 2011
Laboratory experiments were carried out to investigate the effect of the sludge loading, or the f... more Laboratory experiments were carried out to investigate the effect of the sludge loading, or the food-to-microorganism (F/M) ratio, on the rate of aerobic granulation and the size of the granules in biological wastewater treatment. Four column batch reactors were used with a similar sludge suspended solids (SS) concentration of around 2000 mg/L. The reactors were fed with a glucose-based wastewater at different chemical oxygen demand (COD) concentrations, resulting in F/M ratios from 0.3 to 1.1 g COD/g SS-d. A higher F/M ratio appeared to promote faster formation of larger granules and a lower F/M ratio led to slower 2 formation of smaller granules. Upon complete granulation, the granules became rather stable in size, and the mean diameter of the granules in different reactors increased from 1.2 to 4.5 mm linearly with the F/M ratio applied. Molecular analysis of the sludge did not show the domination of any particular bacterial species during the granulation process. In is apparent that applying different F/M ratios in different granulation stages, e.g., a higher F/M in the early stage and a reduced F/M in the later stage, can be an effective start-up strategy to facilitate rapid granule formation and sustain small and healthy granules in bioreactors.
Chemical Engineering Journal, 2010
This study was carried out to investigate the effects of seed sludge properties and the selective... more This study was carried out to investigate the effects of seed sludge properties and the selective sludge discharge method on aerobic granulation in biological wastewater treatment. Small-loose flocs and larger-denser flocs were separated from raw activated sludge by sedimentation in a settling column. The two types of sludge were used as seed biomass in two laboratory batch reactors for the granulation experiment. A fixed daily sludge discharge ratio of around 10% of slow-settling sludge was applied to the two reactors. The results showed that aerobic granules could be formed in the reactors from both seed sludge of different structural and settling properties. The initial washout of small-loose sludge flocs during the start-up of the bioreactors did not appear to be a crucial factor for granulation. The key operating parameter was the daily discharge of relatively slow-settling biomass from the reactors. PCR-DGGE analysis showed insignificant differences between the bacterial communities of the mature granular sludge in the two reactors. It implied that continuous discharge of small and slow-settling flocs removed these competitors for substrate uptake from the system and hence made the substrate more available for large and compact flocs and granules. This selective sludge discharge facilitated the growth and accumulation of denser sludge in the reactor, leading to complete granulation.
Aerobic sludge granulation is an attractive new technology for biological wastewater treatment. H... more Aerobic sludge granulation is an attractive new technology for biological wastewater treatment. However, the instability of aerobic granules caused by fungal growth is still one of the main problems encountered in granular bioreactors. In this study, laboratory experiments were conducted to investigate the fate and transformation of aerobic granules under different organic loading conditions. Bacterial granules (2-3 mm) in a poor condition with fungi-like black filamentous growth were seeded into two 1-L batch reactors. After more than 100 d of cultivation, the small seed granules in the two reactors had grown into two different types of large granules (> 20 mm) with different and unique morphological features. In reactor R1 with a high organic loading rate of 2.0 g COD L-1 d-1 , the black filaments mostly disappeared from the granules, and the dominance of rod-shaped bacteria was recovered. In contrast, at a low loading of 0.5 g COD L-1 d-1 in reactor R2, the filaments eventually became dominant in the black fungal granules. The bacteria in R1 granules had a unique web-like structure with large pores of a few hundred µm in size, which would allow for effective substrate and oxygen transport into the interior of the granules. DNA-based molecular analysis indicated the evolution of the bacterial population in R1 and that of the eukaryal community in R2. The experimental results suggest that a high loading rate can be an effective means of helping to control fungal bloom, recover bacterial domination and restore the stability of aerobic granules that suffer from fungal contamination.
Water research, 2009
Numerical simulation and laboratory experiments were conducted to investigate the determining fac... more Numerical simulation and laboratory experiments were conducted to investigate the determining factor and the underlying mechanism in aerobic sludge granulation in a sequencing batch reactor (SBR). In the numerical simulation, a sectional approach was used to develop a model to describe the biomass dynamics during the granulation process. The growth of different classes of the SBR sludge with different substrate uptake rates and different sludge discharge ratios was simulated. The results indicate that the selective discharge of slow-settling sludge flocs is the key determining factor for granulation. In the laboratory study, experiments were conducted with two identical 2.4-L SBRs, R1 and R2, using different sludge discharge methods - the selective discharge of slow-settling sludge flocs for R1, and mixed, unselective sludge discharge for R2. The SBRs were fed with glucose-based synthetic wastewater at a chemical oxygen demand (COD) loading rate of 1.5 kg/m(3)-d. The evolution of th...
Water research, 2008
Laboratory experiments were carried out to investigate the evolution of the bacterial community d... more Laboratory experiments were carried out to investigate the evolution of the bacterial community during aerobic sludge granulation. The experiments were conducted in three 2.4L sequencing batch reactors (SBRs) that were seeded with activated sludge and fed with glucose-based synthetic wastewater. Three different influent organic concentrations were introduced into the three SBRs, R1, R2 and R3, resulting in chemical oxygen demand (COD) loading rates of 1.5 (R1), 3.0 (R2) and 4.5 (R3)kg/m(3)d, respectively. Changes in bacterial diversity throughout the granulation process were monitored and analysed using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) techniques. The experimental results demonstrate that glucose-fed aerobic granules could be formed without significant presence of filamentous bacteria. Granules formed at different loading rates had different morphology, structural properties and bacterial species. A higher loading rate resulted in fa...
Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.], 2006
In order to find method to improve biodegradation of oil-field wastewater, the biological activat... more In order to find method to improve biodegradation of oil-field wastewater, the biological activated carbon fluidized bed (BAC-FB) process for oil-field wastewater treatment in aerobic condition is studied. The results show that the process demonstrated highest removal rate with hull activated carbon (AC) as carrier and carrier concentration of 15%. The optimized HRT of the process is 5 h. COD, UV254, UV410, organic acid and organic compounds (GC/MS) were detected as the index to indicate the efficiency of oil-field wastewater treatment by this process. The results show that the removal rate of COD range from 25% to 45%. The average removal rate of UV254, UV410, organic acid is 85.9%, 73.6%, 51.5% respectively. The removal rate of oil content is almost 100%. However, alkane is difficult to remove from wastewater. Furthermore, high concentration inorganic materials such as calcium, chlorine were found to accumulate on activated carbon during treatment process, which is harm to adsorpt...
Aerobic sludge granulation is an attractive new technology for biological wastewater treatment. H... more Aerobic sludge granulation is an attractive new technology for biological wastewater treatment. However, the instability of aerobic granules caused by fungal growth is still one of the main problems encountered in granular bioreactors. In this study, laboratory experiments were conducted to investigate the fate and transformation of aerobic granules under different organic loading conditions. Bacterial granules (2-3 mm) in a poor condition with fungi-like black filamentous growth were seeded into two 1-L batch reactors. After more than 100 d of cultivation, the small seed granules in the two reactors had grown into two different types of large granules (> 20 mm) with different and unique morphological features. In reactor R1 with a high organic loading rate of 2.0 g COD L-1 d-1 , the black filaments mostly disappeared from the granules, and the dominance of rod-shaped bacteria was recovered. In contrast, at a low loading of 0.5 g COD L-1 d-1 in reactor R2, the filaments eventually became dominant in the black fungal granules. The bacteria in R1 granules had a unique web-like structure with large pores of a few hundred µm in size, which would allow for effective substrate and oxygen transport into the interior of the granules. DNA-based molecular analysis indicated the evolution of the bacterial population in R1 and that of the eukaryal community in R2. The experimental results suggest that a high loading rate can be an effective means of helping to control fungal bloom, recover bacterial domination and restore the stability of aerobic granules that suffer from fungal contamination.
2,4-Dichlorophenoxyacetic acid (2,4-D) degrading aerobic granular sludge, obtained through plasmi... more 2,4-Dichlorophenoxyacetic acid (2,4-D) degrading aerobic granular sludge, obtained through plasmid pJP4 mediated bioaugmentation, was used for the degradation of a mixture of 2,4-D, 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP) in a sequencing batch reactor. The removal rate of 2,4-D always stabilized at above 99%, indicating that the granules were still active in the presence of chlorophenols. The 2,4-D fed granules demonstrated a faster adaptation and higher degradation ability to 4-CP and 2,4-DCP than to 2,4,6-TCP. Nearly complete removals of 2,4-D and chlorophenols were achieved at the initial concentrations of approximately 400 mg/L of 2,4-D, 45 mg/L of 4-CP, 25 mg/L of 2,4-DCP, and 20 mg/L of 2,4,6-TCP and a hydraulic retention time (HRT) of 6 h. Each chlorophenol could be biodegraded and mineralized by the granules as the sole carbon source and the biodegradation followed Haldane inhibition model. The granules maintained a good settling ability and a dominant granular morphology as evidenced by the low sludge volume index (SVI) value (20-70 mL/g) and large granule size (400-610 m) during the long-term operation (420 days). The finally obtained granules showed a different microbial community compared to the granule seeds, and were mainly composed of Novosphingobium sp., Aquincola tertiaricarbonis, Xanthomonas sp. and Pseudorhodoferax caeni.
Separation and Purification Technology, 2011
Aerobic sludge granulation is rather difficult or impossible for the treatment of low-strength wa... more Aerobic sludge granulation is rather difficult or impossible for the treatment of low-strength wastewater. In this study, a novel technique involving granular activated carbon (GAC) was developed for rapid aerobic granulation under a low organic loading condition. Laboratory experiments were conducted with two sequencing batch reactors (SBRs) running side by side. One reactor had fine GAC added to the sludge mixture, and the other had no GAC added. A low-strength organic wastewater with a chemical oxygen demand (COD) concentration of only 200 mg/L was used as the influent to the SBRs. The morphology, 2 physical properties, and bacterial community structure of the sludge in the two reactors were characterized and compared throughout the experiments. The results showed that granules could not be formed in the SBR without added GAC. However, complete granulation was achieved in the SBR with GAC addition. Selective discharge of slow settling sludge was also essential to the granulation process. Adding GAC to the seed sludge mixture, together with the selective discharge of small and loose sludge flocs, facilitated the retention and growth of bacterial cells on GAC in attached-growth mode, leading to complete granulation. In addition, the use of GAC produced aerobic granules with strong cores to help maintain the long-term stability of mature granules. With granulation, the solid-liquid separation property of the sludge was greatly improved. Once granules were formed, the granules were quite stable and GAC addition was no longer needed. Therefore, adding GAC is a simple and effective strategy to initiate granule formation for complete sludge granulation in bioreactors treating low-strength organic wastewater.
Process Biochemistry, 2011
Laboratory experiments were carried out to investigate the effect of the sludge loading, or the f... more Laboratory experiments were carried out to investigate the effect of the sludge loading, or the food-to-microorganism (F/M) ratio, on the rate of aerobic granulation and the size of the granules in biological wastewater treatment. Four column batch reactors were used with a similar sludge suspended solids (SS) concentration of around 2000 mg/L. The reactors were fed with a glucose-based wastewater at different chemical oxygen demand (COD) concentrations, resulting in F/M ratios from 0.3 to 1.1 g COD/g SS-d. A higher F/M ratio appeared to promote faster formation of larger granules and a lower F/M ratio led to slower 2 formation of smaller granules. Upon complete granulation, the granules became rather stable in size, and the mean diameter of the granules in different reactors increased from 1.2 to 4.5 mm linearly with the F/M ratio applied. Molecular analysis of the sludge did not show the domination of any particular bacterial species during the granulation process. In is apparent that applying different F/M ratios in different granulation stages, e.g., a higher F/M in the early stage and a reduced F/M in the later stage, can be an effective start-up strategy to facilitate rapid granule formation and sustain small and healthy granules in bioreactors.
Chemical Engineering Journal, 2010
This study was carried out to investigate the effects of seed sludge properties and the selective... more This study was carried out to investigate the effects of seed sludge properties and the selective sludge discharge method on aerobic granulation in biological wastewater treatment. Small-loose flocs and larger-denser flocs were separated from raw activated sludge by sedimentation in a settling column. The two types of sludge were used as seed biomass in two laboratory batch reactors for the granulation experiment. A fixed daily sludge discharge ratio of around 10% of slow-settling sludge was applied to the two reactors. The results showed that aerobic granules could be formed in the reactors from both seed sludge of different structural and settling properties. The initial washout of small-loose sludge flocs during the start-up of the bioreactors did not appear to be a crucial factor for granulation. The key operating parameter was the daily discharge of relatively slow-settling biomass from the reactors. PCR-DGGE analysis showed insignificant differences between the bacterial communities of the mature granular sludge in the two reactors. It implied that continuous discharge of small and slow-settling flocs removed these competitors for substrate uptake from the system and hence made the substrate more available for large and compact flocs and granules. This selective sludge discharge facilitated the growth and accumulation of denser sludge in the reactor, leading to complete granulation.
Aerobic sludge granulation is an attractive new technology for biological wastewater treatment. H... more Aerobic sludge granulation is an attractive new technology for biological wastewater treatment. However, the instability of aerobic granules caused by fungal growth is still one of the main problems encountered in granular bioreactors. In this study, laboratory experiments were conducted to investigate the fate and transformation of aerobic granules under different organic loading conditions. Bacterial granules (2-3 mm) in a poor condition with fungi-like black filamentous growth were seeded into two 1-L batch reactors. After more than 100 d of cultivation, the small seed granules in the two reactors had grown into two different types of large granules (> 20 mm) with different and unique morphological features. In reactor R1 with a high organic loading rate of 2.0 g COD L-1 d-1 , the black filaments mostly disappeared from the granules, and the dominance of rod-shaped bacteria was recovered. In contrast, at a low loading of 0.5 g COD L-1 d-1 in reactor R2, the filaments eventually became dominant in the black fungal granules. The bacteria in R1 granules had a unique web-like structure with large pores of a few hundred µm in size, which would allow for effective substrate and oxygen transport into the interior of the granules. DNA-based molecular analysis indicated the evolution of the bacterial population in R1 and that of the eukaryal community in R2. The experimental results suggest that a high loading rate can be an effective means of helping to control fungal bloom, recover bacterial domination and restore the stability of aerobic granules that suffer from fungal contamination.