Field and column studies of biocolloid transport in porous media have yielded a large body of inf... more Field and column studies of biocolloid transport in porous media have yielded a large body of information, used to design treatment systems, protect water supplies and assess the risk of pathogen contamination. However, the inherent ''black-box'' approach of these larger scales has resulted in generalizations that sometimes prove inaccurate. Over the past 10-15 years, pore scale visualization techniques have improved substantially, allowing the study of biocolloid transport in saturated and unsaturated porous media at a level that provides a very clear understanding of the processes that govern biocolloid movement. For example, it is now understood that the reduction in pathways for biocolloids as a function of their size leads to earlier breakthrough. Interception of biocolloids by the porous media used to be considered independent of fluid flow velocity, but recent work indicates that there is a relationship between them. The existence of almost stagnant pore water regions within a porous medium can lead to storage of biocolloids, but this process is strongly colloid-size dependent, since larger biocolloids are focused along the central streamlines in the flowing fluid. Interfaces, such as the air-water interface, the soil-water interface and the soil-water-air interface, play a major role in attachment and detachment, with significant implications for risk assessment and system design. Important research questions related to the pore-scale factors that control attachment and detachment are key to furthering our understanding of the transport of biocolloids in porous media.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Development of superhydrophobic materials is in constant evolution due to their multiple applicat... more Development of superhydrophobic materials is in constant evolution due to their multiple applications. Recent investigations have shown that a stable and reliable superhydrophobic performance requires the use of hierarchical structures. In this work, we have engineered superhydrophobic copper surfaces using an innovative solution-free procedure to fabricate hierarchical structures. First, sequential cycles of O 2-and Ar-plasma etching were performed on the copper substrate to generate microtexture. Secondly, a fluoropolymer was deposited on top of the metal via initiated chemical vapor deposition (iCVD). The organic layer conformally coated the copper substrate maintaining the previously etched geometry. Moreover, the polymer displayed a very characteristic and unique structure with small protuberances arising out from the film in a nanoworm-like morphology. These nanofeatures together with the microroughness, induced by plasma etching, resulted in a hierarchical structure that confers superhydrophobic properties to copper. Water contact angle (WCA) as high as 168°and WCA hysteresis of 2°were measured for the treated samples. The superhydrophobic iCVD polymer was tested as an antifouling coating. Samples were exposed to Pseudomonas fluorescens for 24 h and the attachment of the microorganisms was reduced by 57% compared to uncoated copper.
A moving bead biofilm reactor (MBBR) pilot plant was implemented as a partial nitrification proce... more A moving bead biofilm reactor (MBBR) pilot plant was implemented as a partial nitrification process for pre-treatment of ammonium-rich liquors (676 ± 195 mg L(-1)), and studied for 479 days under variations in hydraulic retention time. The main purpose of this work, was the study of dynamics abundance of total bacteria and single-cells nitrifying bacteria belonging to ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in biofilms and mixed liquor of the plant. The microbial monitoring was successfully achieved using fluorescence in situ hybridization combined with flocs disaggregation protocol as a useful microbial monitoring tool. A partial nitrification process with a N-NH4(+) removal rate of about 38.6 ± 14.8% was successfully achieved at 211 days after start-up, with a clear dominance of AOB, which accounted for 11.3 ± 17.0% of total bacterial cells compared with only 2.1 ± 4.0% of NOB. The effluent obtained was subsequently supplied to an Anammox reactor for complete ammonium treatment.
Field and columns studies of biocolloid transport in porous media have yielded a large body of in... more Field and columns studies of biocolloid transport in porous media have yielded a large body of information, used to design treatment systems, protect water supplies and assess the risk of pathogen contamination. However, the inherent “black-box” approach of these larger scales has resulted in generalizations that sometimes prove inaccurate. Over the past 10 to 15 years, pore scale visualization techniques have improved substantially, allowing the study of biocolloid transport in saturated and unsaturated porous media at a level that provides a very clear understanding of the processes that govern biocolloid movement. For example, it is now understood that the reduction in pathways for biocolloids as a function of their size leads to earlier breakthrough. Interception of biocolloids by the porous media used to be considered independent of fluid flow velocity, but recent work indicates that there is a relationship between them. The existence of almost stagnant pore water regions withi...
The microfauna communities present in the mixed liquor and biofilm of an Anoxic/Oxic Shortcut Bio... more The microfauna communities present in the mixed liquor and biofilm of an Anoxic/Oxic Shortcut Biofilm Nitrogen Removal moving-bed biofilm process were characterised in order to optimise process control through the use of bioindicators. The system operated at high ammonium concentrations, with an average of 588 ± 220 mg N-NH4(+) L(-1) in the influent, 161 ± 80 mg L(-1) in the anoxic reactor and 74 ± 71.2 mg L(-1) in the aerobic reactor. Up to 20 different taxa were identified, including ciliates (4), flagellates (11), amoebae (4) and nematodes (1). Compared to conventional wastewater treatment processes (WWTPs), this process can be defined as a flagellates-predominant system with a low diversity of ciliates. Flagellates were mainly dominant in the mixed liquor, demonstrating high tolerance to ammonium and the capacity for survival over a long time under anoxic conditions. The data obtained provide interesting values of maximum and minimum tolerance ranges to ammonium, nitrates and nitrites for the ciliate species Cyclidium glaucoma, Colpoda ecaudata, Vorticella microstoma-complex and Epistylis cf. rotans. The last of these was the only ciliate species that presented a constant and abundant population, almost exclusively in the aerobic biofilm. Epistylis cf. rotans dynamics showed a high negative correlation with ammonium variations and a positive correlation with ammonium removal efficiency. Hence, the results indicate that Epistylis cf. rotans is a good bioindicator of the nitrification process in this system. The study of protozoan communities in unexplored WWTPs sheds light on species ecology and their role under conditions that have been little studied in WWTPs, and could offer new biological management tools.
Polybrominated diphenyl ethers (PBDEs) are persistent organic pollutants that can arrive to water... more Polybrominated diphenyl ethers (PBDEs) are persistent organic pollutants that can arrive to water bodies from their use as flame retardants in a wide range of applications, such as electric and electronic devices or textiles. In this study, the photodegradation of PBDEs in water samples when applying UV-LED radiation was studied. Irradiation was applied at three different wavelengths (255 nm, 265 nm and 285 nm) and different exposure times. The best degradation conditions for spiked purified water samples were at 285 nm and 240 min, resulting in degradations between 67% and 86%. The optimized methodology was applied to real water samples from different sources: river, marine, wastewater (effluent and influent of treatment plants) and greywater samples. Real water samples were spiked and exposed to 4 hours of irradiation at 285 nm. Successful photodegradation of PBDEs ranging from 51% to 97% was achieved for all PBDE congeners in the different water samples with the exception of the ...
Infiltration percolation (IP) is an extensive technology to treat primary or secondary effluents ... more Infiltration percolation (IP) is an extensive technology to treat primary or secondary effluents of small and middle size communities before reuse or disposal to sensitive receiving bodies. Thirteen years of implementation of IP in Spain has highlighted the necessity to abide by defined design and construction rules and operation conditions in order to achieve consistently the treatment objectives and guarantee a long lasting treatment capacity. From this experience, high care should be taken of (i) the characteristics of the sand constituting the filter, (ii) the drainage conditions, (iii) the influent spreading over the infiltration surface and (iv) the risks related to recurrent overloading. Simple monitoring measures are suggested in order to improve the reliability of IP plants.
Si tenemos en cuenta el importante papel que juega la reutilización de aguas residuales en el cic... more Si tenemos en cuenta el importante papel que juega la reutilización de aguas residuales en el ciclo del agua, la búsqueda de tecnologías que nos permitan obtener agua de calidad para su reutilización toma cada vez más relevancia. En este sentido, los reactores biológicos de membrana (MBR) suponen una alternativa a los sistemas tradicionales de fangos activos, en los que la separación biomasa/agua tratada se efectúa por filtración mediante membranas en lugar de por decantación. En el presente trabajo se estudió el comportamiento y rendimiento de los sistemas de membrana en la obtención de agua residual regenerada para su posterior reutilización. Para ello se utilizó una planta piloto MBR con una línea de fibra hueca y una de membrana plana, dispuestas en paralelo. Se realizó una caracterización del agua de entrada y permeada en cuanto a parámetros habituales en el control de depuración (demanda química de oxígeno, nitrógeno, fósforo, patógenos, etc.) y a microcontaminantes específico...
1] Colloidal dispersion in porous media is a consequence of the different paths and velocities ex... more 1] Colloidal dispersion in porous media is a consequence of the different paths and velocities experienced by the colloids. We examined at the pore scale the effect of particle and pore size on colloid dispersion using water-saturated micromodels. The micromodels were produced with polydimethylsiloxane (PDMS), using a soft photolithography technique that allows creating transparent patterns that have dimensions in the range of those existing at the pore space. Four sizes of colloids were transported at several total pressure differences, and image analysis was used to determine particle trajectories, residence times, and dispersion coefficients through the micromodels. The magnitude of the dispersion at any given flow rate was found to be controlled by the pore-space geometry and the relative size of colloids with regards to pore channels. Dispersion coefficient and dispersivity decrease with increasing colloid size. Dispersivity is thus not just a function of pore geometry but depends on colloid characteristics. Because of their size, larger colloids travel in the center streamlines, leading to faster velocities, less detours, and thus lower range of transit times. These findings emphasize the role of particle and pore size on colloidal dispersion and have significant implications for predicting the movement of colloids through saturated porous media.
Infiltration-percolation is an extensive technique used to remove microorganisms from secondary e... more Infiltration-percolation is an extensive technique used to remove microorganisms from secondary effluents. It consists in intermittently infiltrating wastewater in unsaturated sand beds. Biomass expansion is managed through alternate operation and drying periods. Secondary effluent infiltration tests were performed on sand columns. Operation schedules were 4 days operation and 1 to 5 days drying. Organic matter, faecal coliforms and enterococci were monitored. Drying periods were shown to highly affect the elimination of enteric bacteria. Alternating operation and drying periods commands organic matter availability, biomass development and enteric bacteria removal. It was demonstrated that bacteria elimination was not solely related to water retention times and oxygen availability. Other factors, physical or biological, have also a key role in removal performances.
Colloid dispersion in porous media is a consequence of the different paths and velocities experie... more Colloid dispersion in porous media is a consequence of the different paths and velocities experienced by the colloids. This work represents a number of studies at the pore and column scales, as well as comparisons to field scale studies. At the pore scale we examined the effect of particle and pore size on colloid dispersion using water-saturated micromodels. Four sizes of colloids were transported at several pressure differences. Image analysis was used to determine particle trajectories, residence times and dispersion coefficients through the micromodels. The magnitude of the dispersion at any given flow rate was found to be controlled by the pore-space geometry and the relative size of colloids with regards to pore channels. Dispersion coefficient and dispersivity decrease with increasing colloid size. Dispersivity is thus not just a function of pore geometry, but depends on colloid characteristics. We corroborated these results with column-scale experiments to observe the effect...
Size exclusion is a mechanism affecting the transport of colloidal contaminants in porous media. ... more Size exclusion is a mechanism affecting the transport of colloidal contaminants in porous media. We developed polydimethylsiloxane (PDMS) micromodels to examine at the pore scale the effect of particle and pore size on saturated colloid transport. The micromodels were generated using a novel soft photolithography technique developed by Quake and Scherer (2000). This easy and inexpensive technique allows us to rapidly generate patterns that have dimensions in the range of those existing at the pore space. Three patterns were designed: two regular networks with 10-æm and 20-æm constant channel widths, respectively and a network combining two different channel widths, 10 and 20 æm. Four sizes of colloids were transported through the micromodels at different pressure gradients. The transparency of the cured PDMS allowed optical microscopy observations of the transport and dispersion of the colloids within the pores. Particle trajectories, residence times and dispersion coefficients were...
Field and column studies of biocolloid transport in porous media have yielded a large body of inf... more Field and column studies of biocolloid transport in porous media have yielded a large body of information, used to design treatment systems, protect water supplies and assess the risk of pathogen contamination. However, the inherent ''black-box'' approach of these larger scales has resulted in generalizations that sometimes prove inaccurate. Over the past 10-15 years, pore scale visualization techniques have improved substantially, allowing the study of biocolloid transport in saturated and unsaturated porous media at a level that provides a very clear understanding of the processes that govern biocolloid movement. For example, it is now understood that the reduction in pathways for biocolloids as a function of their size leads to earlier breakthrough. Interception of biocolloids by the porous media used to be considered independent of fluid flow velocity, but recent work indicates that there is a relationship between them. The existence of almost stagnant pore water regions within a porous medium can lead to storage of biocolloids, but this process is strongly colloid-size dependent, since larger biocolloids are focused along the central streamlines in the flowing fluid. Interfaces, such as the air-water interface, the soil-water interface and the soil-water-air interface, play a major role in attachment and detachment, with significant implications for risk assessment and system design. Important research questions related to the pore-scale factors that control attachment and detachment are key to furthering our understanding of the transport of biocolloids in porous media.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Development of superhydrophobic materials is in constant evolution due to their multiple applicat... more Development of superhydrophobic materials is in constant evolution due to their multiple applications. Recent investigations have shown that a stable and reliable superhydrophobic performance requires the use of hierarchical structures. In this work, we have engineered superhydrophobic copper surfaces using an innovative solution-free procedure to fabricate hierarchical structures. First, sequential cycles of O 2-and Ar-plasma etching were performed on the copper substrate to generate microtexture. Secondly, a fluoropolymer was deposited on top of the metal via initiated chemical vapor deposition (iCVD). The organic layer conformally coated the copper substrate maintaining the previously etched geometry. Moreover, the polymer displayed a very characteristic and unique structure with small protuberances arising out from the film in a nanoworm-like morphology. These nanofeatures together with the microroughness, induced by plasma etching, resulted in a hierarchical structure that confers superhydrophobic properties to copper. Water contact angle (WCA) as high as 168°and WCA hysteresis of 2°were measured for the treated samples. The superhydrophobic iCVD polymer was tested as an antifouling coating. Samples were exposed to Pseudomonas fluorescens for 24 h and the attachment of the microorganisms was reduced by 57% compared to uncoated copper.
A moving bead biofilm reactor (MBBR) pilot plant was implemented as a partial nitrification proce... more A moving bead biofilm reactor (MBBR) pilot plant was implemented as a partial nitrification process for pre-treatment of ammonium-rich liquors (676 ± 195 mg L(-1)), and studied for 479 days under variations in hydraulic retention time. The main purpose of this work, was the study of dynamics abundance of total bacteria and single-cells nitrifying bacteria belonging to ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in biofilms and mixed liquor of the plant. The microbial monitoring was successfully achieved using fluorescence in situ hybridization combined with flocs disaggregation protocol as a useful microbial monitoring tool. A partial nitrification process with a N-NH4(+) removal rate of about 38.6 ± 14.8% was successfully achieved at 211 days after start-up, with a clear dominance of AOB, which accounted for 11.3 ± 17.0% of total bacterial cells compared with only 2.1 ± 4.0% of NOB. The effluent obtained was subsequently supplied to an Anammox reactor for complete ammonium treatment.
Field and columns studies of biocolloid transport in porous media have yielded a large body of in... more Field and columns studies of biocolloid transport in porous media have yielded a large body of information, used to design treatment systems, protect water supplies and assess the risk of pathogen contamination. However, the inherent “black-box” approach of these larger scales has resulted in generalizations that sometimes prove inaccurate. Over the past 10 to 15 years, pore scale visualization techniques have improved substantially, allowing the study of biocolloid transport in saturated and unsaturated porous media at a level that provides a very clear understanding of the processes that govern biocolloid movement. For example, it is now understood that the reduction in pathways for biocolloids as a function of their size leads to earlier breakthrough. Interception of biocolloids by the porous media used to be considered independent of fluid flow velocity, but recent work indicates that there is a relationship between them. The existence of almost stagnant pore water regions withi...
The microfauna communities present in the mixed liquor and biofilm of an Anoxic/Oxic Shortcut Bio... more The microfauna communities present in the mixed liquor and biofilm of an Anoxic/Oxic Shortcut Biofilm Nitrogen Removal moving-bed biofilm process were characterised in order to optimise process control through the use of bioindicators. The system operated at high ammonium concentrations, with an average of 588 ± 220 mg N-NH4(+) L(-1) in the influent, 161 ± 80 mg L(-1) in the anoxic reactor and 74 ± 71.2 mg L(-1) in the aerobic reactor. Up to 20 different taxa were identified, including ciliates (4), flagellates (11), amoebae (4) and nematodes (1). Compared to conventional wastewater treatment processes (WWTPs), this process can be defined as a flagellates-predominant system with a low diversity of ciliates. Flagellates were mainly dominant in the mixed liquor, demonstrating high tolerance to ammonium and the capacity for survival over a long time under anoxic conditions. The data obtained provide interesting values of maximum and minimum tolerance ranges to ammonium, nitrates and nitrites for the ciliate species Cyclidium glaucoma, Colpoda ecaudata, Vorticella microstoma-complex and Epistylis cf. rotans. The last of these was the only ciliate species that presented a constant and abundant population, almost exclusively in the aerobic biofilm. Epistylis cf. rotans dynamics showed a high negative correlation with ammonium variations and a positive correlation with ammonium removal efficiency. Hence, the results indicate that Epistylis cf. rotans is a good bioindicator of the nitrification process in this system. The study of protozoan communities in unexplored WWTPs sheds light on species ecology and their role under conditions that have been little studied in WWTPs, and could offer new biological management tools.
Polybrominated diphenyl ethers (PBDEs) are persistent organic pollutants that can arrive to water... more Polybrominated diphenyl ethers (PBDEs) are persistent organic pollutants that can arrive to water bodies from their use as flame retardants in a wide range of applications, such as electric and electronic devices or textiles. In this study, the photodegradation of PBDEs in water samples when applying UV-LED radiation was studied. Irradiation was applied at three different wavelengths (255 nm, 265 nm and 285 nm) and different exposure times. The best degradation conditions for spiked purified water samples were at 285 nm and 240 min, resulting in degradations between 67% and 86%. The optimized methodology was applied to real water samples from different sources: river, marine, wastewater (effluent and influent of treatment plants) and greywater samples. Real water samples were spiked and exposed to 4 hours of irradiation at 285 nm. Successful photodegradation of PBDEs ranging from 51% to 97% was achieved for all PBDE congeners in the different water samples with the exception of the ...
Infiltration percolation (IP) is an extensive technology to treat primary or secondary effluents ... more Infiltration percolation (IP) is an extensive technology to treat primary or secondary effluents of small and middle size communities before reuse or disposal to sensitive receiving bodies. Thirteen years of implementation of IP in Spain has highlighted the necessity to abide by defined design and construction rules and operation conditions in order to achieve consistently the treatment objectives and guarantee a long lasting treatment capacity. From this experience, high care should be taken of (i) the characteristics of the sand constituting the filter, (ii) the drainage conditions, (iii) the influent spreading over the infiltration surface and (iv) the risks related to recurrent overloading. Simple monitoring measures are suggested in order to improve the reliability of IP plants.
Si tenemos en cuenta el importante papel que juega la reutilización de aguas residuales en el cic... more Si tenemos en cuenta el importante papel que juega la reutilización de aguas residuales en el ciclo del agua, la búsqueda de tecnologías que nos permitan obtener agua de calidad para su reutilización toma cada vez más relevancia. En este sentido, los reactores biológicos de membrana (MBR) suponen una alternativa a los sistemas tradicionales de fangos activos, en los que la separación biomasa/agua tratada se efectúa por filtración mediante membranas en lugar de por decantación. En el presente trabajo se estudió el comportamiento y rendimiento de los sistemas de membrana en la obtención de agua residual regenerada para su posterior reutilización. Para ello se utilizó una planta piloto MBR con una línea de fibra hueca y una de membrana plana, dispuestas en paralelo. Se realizó una caracterización del agua de entrada y permeada en cuanto a parámetros habituales en el control de depuración (demanda química de oxígeno, nitrógeno, fósforo, patógenos, etc.) y a microcontaminantes específico...
1] Colloidal dispersion in porous media is a consequence of the different paths and velocities ex... more 1] Colloidal dispersion in porous media is a consequence of the different paths and velocities experienced by the colloids. We examined at the pore scale the effect of particle and pore size on colloid dispersion using water-saturated micromodels. The micromodels were produced with polydimethylsiloxane (PDMS), using a soft photolithography technique that allows creating transparent patterns that have dimensions in the range of those existing at the pore space. Four sizes of colloids were transported at several total pressure differences, and image analysis was used to determine particle trajectories, residence times, and dispersion coefficients through the micromodels. The magnitude of the dispersion at any given flow rate was found to be controlled by the pore-space geometry and the relative size of colloids with regards to pore channels. Dispersion coefficient and dispersivity decrease with increasing colloid size. Dispersivity is thus not just a function of pore geometry but depends on colloid characteristics. Because of their size, larger colloids travel in the center streamlines, leading to faster velocities, less detours, and thus lower range of transit times. These findings emphasize the role of particle and pore size on colloidal dispersion and have significant implications for predicting the movement of colloids through saturated porous media.
Infiltration-percolation is an extensive technique used to remove microorganisms from secondary e... more Infiltration-percolation is an extensive technique used to remove microorganisms from secondary effluents. It consists in intermittently infiltrating wastewater in unsaturated sand beds. Biomass expansion is managed through alternate operation and drying periods. Secondary effluent infiltration tests were performed on sand columns. Operation schedules were 4 days operation and 1 to 5 days drying. Organic matter, faecal coliforms and enterococci were monitored. Drying periods were shown to highly affect the elimination of enteric bacteria. Alternating operation and drying periods commands organic matter availability, biomass development and enteric bacteria removal. It was demonstrated that bacteria elimination was not solely related to water retention times and oxygen availability. Other factors, physical or biological, have also a key role in removal performances.
Colloid dispersion in porous media is a consequence of the different paths and velocities experie... more Colloid dispersion in porous media is a consequence of the different paths and velocities experienced by the colloids. This work represents a number of studies at the pore and column scales, as well as comparisons to field scale studies. At the pore scale we examined the effect of particle and pore size on colloid dispersion using water-saturated micromodels. Four sizes of colloids were transported at several pressure differences. Image analysis was used to determine particle trajectories, residence times and dispersion coefficients through the micromodels. The magnitude of the dispersion at any given flow rate was found to be controlled by the pore-space geometry and the relative size of colloids with regards to pore channels. Dispersion coefficient and dispersivity decrease with increasing colloid size. Dispersivity is thus not just a function of pore geometry, but depends on colloid characteristics. We corroborated these results with column-scale experiments to observe the effect...
Size exclusion is a mechanism affecting the transport of colloidal contaminants in porous media. ... more Size exclusion is a mechanism affecting the transport of colloidal contaminants in porous media. We developed polydimethylsiloxane (PDMS) micromodels to examine at the pore scale the effect of particle and pore size on saturated colloid transport. The micromodels were generated using a novel soft photolithography technique developed by Quake and Scherer (2000). This easy and inexpensive technique allows us to rapidly generate patterns that have dimensions in the range of those existing at the pore space. Three patterns were designed: two regular networks with 10-æm and 20-æm constant channel widths, respectively and a network combining two different channel widths, 10 and 20 æm. Four sizes of colloids were transported through the micromodels at different pressure gradients. The transparency of the cured PDMS allowed optical microscopy observations of the transport and dispersion of the colloids within the pores. Particle trajectories, residence times and dispersion coefficients were...
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