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Hydrodynamic Changes in Sand due to Biogrowth on Naphthalene and Decane
Abstract and Figures
Biological activity in zones of chemical contamination changes the pore characteristics that control the flow of water and transport of dissolved chemicals in soils. To further the understanding of these processes, column experiments were performed to evaluate the effect of biomass growth on decane or naphthalene dissolved in simulated groundwater on the hydraulic conductivity and dispersivity of sand. The effect of grain size, groundwater flowrate, and nitrogen limitation were investigated. Given the low carbon loading resulting from the solubility of decane and naphthalene, sparse and discontinuous biomass growth reduced the hydraulic conductivity of the sand by 2 to 3 orders of magnitude after 35 to 63 days. This biogrowth initially increased dispersivity of the sand, but after longer periods of growth dispersivity, decreased to stable values near that of the clean sand. The results indicate that biogrowth can have significant effects in natural systems with low carbon loading and nitrogen availability, and should be taken into account when using models to predict contaminant transport in the field.
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... This can be explained by a relatively high initial value of η im for C1, which we attribute to the presence of organic matter and an active biofilm (Figure 3b) that acted as a pool for diffusion of the tracer, as noted in other studies. 73,74 In columns C1 and C2 (both columns with OS), η im tended to diminish with time (i.e., β increases), indicating that SOM was leached or consumed. This was only partially compensated by biofilm production, which should have resulted in an increase in η im , as observed in C3 and in other studies. ...
... 74,75 In our case, however, we could not observe such a clear positive trend, and for C1 there even seemed to be a decrease. This unexpected behavior, also noticed by other authors, 23,73,76 might have been caused by an increase in the mass transfer coefficient between the mobile and immobile phase (ω), revealing enhanced non-Fickianity and thus a higher model complexity, which does not allow for such direct comparisons. ...
... The exception was C2, where β = 1 for the second and third tracer tests implies an evolution to Fickian conditions, which can be explained by the presence of NaN 3 and thus the inhibition of biofilm growth. In this context, it should also be noted that most of the studies describing bioclogging and changes in the transport behavior of porous media have been conducted with glass beads 71 or quartz sand, 23,25,73,75,77 substrates neither containing SOM nor variations in surface properties. Our results seem to reveal a complex interaction of processes for natural soils. ...
Contamination of groundwater with pharmaceutical active compounds (PhACs) increased over the last decades. Potential pathways of PhACs to groundwater include techniques such as irrigation, managed aquifer recharge, or bank filtration as well as natural processes such as losing streams of PhACs-loaded source waters. Usually, these systems are characterized by redox-active zones, where microorganisms grow and become immobilized by the formation of biofilms, structures that colonize the pore space and decrease the infiltration capacities, a phenomenon known as bioclogging. The goal of this work is to gain a deeper understanding of the influence of soil biofilms on hydraulic conductivity reduction and the fate of PhACs in the subsurface. For this purpose, we selected three PhACs with different physicochemical properties (carbamazepine, diclofenac, and metoprolol) and performed batch and column experiments using a natural soil, as it is and with the organic matter removed, under different biological conditions. We observed enhanced sorption and biodegradation for all PhACs in the system with higher biological activity. Bioclogging was more prevalent in the absence of organic matter. Our results differ from works using artificial porous media and thus reveal the importance of utilizing natural soils with organic matter in studies designed to assess the role of soil biofilms in bioclogging and the fate of PhACs in soils.
... Si l'espace poral est utilisé pour l'écoulement de l'eau, il constitue aussi, et surtout, la zone d'expansion du biofilm se formant à l'interface solide-liquide. Plusieurs études ont montré que l'épaisseur du biofilm augmente avec la taille de pores (Torbati et al., 1986 ;Cunnigham et al., 1991 ;Vayenas et al., 2002 ;Bielefeldt et al., 2002). Torbati et al. (1986) attribuent la colonisation préférentielle des pores de grandes dimensions par les microorganismes à la différence de flux de masse (nutriments) traversant les pores. ...
... Directement relié à cette réduction du volume poral, de nombreuses études ont montré une diminution de la perméabilité lors de la croissance du biofilm dans des études en colonnes (Mitchell et Nevo, 1964 ;Torbati et al., 1986 ;MacLeod et al., 1988 ;Taylor et Jaffé, 1990a ;Cunningham et al., 1991 ;Vandevivere et Baveye, 1992a ;Kim et Fogler, 2000 ;Bielefeldt et al., 2002 ;Seifert et Engesgaard, 2007 ;Chatelier, 2010 ;Karrabi et al., 2011). La perméabilité peut être réduite de plusieurs facteurs, trois à quatre en général dans la plupart des études en milieu saturé. ...
... Les observations expérimentales restent cependant encore contradictoires. Bielefeldt et al. (2002), par exemple, ont observé une augmentation suivie d'une diminution de la dispersion du milieu avec la croissance microbienne. Ils ont attribué ce résultat au fait que la faible charge en substrat conduit initialement à un biofilm discontinu, i.e. : occupant préférentiellement quelques pores. ...
Un dispositif expérimental a été développé pour l'étude du couplage de la croissance d'un biofilm de Shewanella oneidensis MR-1 et du transport conservatif de l'Erioglaucine. La croissance du biofilm a été suivie par mesure de conductivité hydraulique et par acquisition d'images à l'aide d'une caméra digitale. La fraction volumique du biofilm a été caractérisée par des essais d'élution d'une macromolécule (i.e. : le Bleu Dextran) par analogie avec les méthodes de chromatographie d'exclusion ou de filtration sur gel. Ainsi au bout de 29 jours, un biofilm quasi-homogène sur l'ensemble de la cellule d'écoulement (0,1×0,1×0,05m3) et équivalent à 50% du volume poral a été formé. L'influence de la croissance du biofilm sur les propriétés de transport du milieu a été évaluée. Les essais de transport conservatif de l'Erioglaucine effectués pour deux vitesses d'injection et à deux stades de croissance du biofilm (17 et 29 jours) ont montré l'influence d'hétérogénéités locales sur les paramètres de transport (i.e. : la porosité, la perméabilité et la dispersion hydrodynamique). Ainsi après 17 jours de culture quand le biofilm occupe partiellement le milieu poreux (moitié inférieure) un modèle à deux équations ou double milieu permet de caractériser le transport conservatif. A contrario après 29 jours de culture où le biofilm occupe tout le milieu poreux, un comportement fickien classique caractérise le transport. Les valeurs théoriques du coefficient de dispersion longitudinale prédites par la méthode de prise de moyenne volumique ont permis de reproduire de manière satisfaisante le comportement observé expérimentalement
... The problem arises when biofilm growth at the surface of porous media (mud, sand and gravel as well as any artificial substrate), also known as biofouling, clogs the porous medium filter, reducing its filtration rate and compromising water purification, as seen in Figure 4 [73][74][75][76][77][78]. Microbial growth increases notable changes in the effective porosity, hydraulic conductivity and dispersivity [79][80][81][82]. Soil bioturbation is associated with the production of soil macropores as burrows or gallery networks that influence numerous physical properties of the substrate such as water infiltration [83]. ...
... Microbial growth increases notable changes in the effective porosity, hydraulic conductivity and dispersivity [79][80][81][82]. Soil bioturbation is associated with the production of soil macropores as burrows or gallery networks that influence numerous physical properties of the substrate such as water infiltration [83]. ...
Theoretical and functional ecology is a source of useful knowledge for ecological engineering. The better understanding of the natural service of water quality regulation is now inspiring for optimization of water resource management, restoration and bioremediation practices. This transfer with a biomimicry approach applies particularly well in the urban, rural and agricultural areas, but is yet underexplored for water quality purposes. This natural service intensely involves the benthic boundary layer as a biogeochemical hot spot with living communities. A selection of processes related to the bioturbation phenomena is explored because of their influence on properties of the aquatic environment. The applications are valuable in a range of fields, from water treatment technology to management of ecosystems such as constructed and natural wetlands, streams, rivers, lagoons and coastal ecosystems. This paper gathers the more obvious cases of potential applications of bioturbation research findings on the biomimicry of natural services to water practices. These include pollution pumping by bioturbated sediment, water column oxygen saving during early diagenesis of deposits under conveyors transport and conservation of macroporous as well as fine sediment. Some applications for constructed devices are also emerging, including infiltration optimization and sewage reduction based on cross-biological community involvement.
... When possible, we cross-validate the results obtained via microimage analysis with those obtained via direct bulk measurements. Numerous studies conducted on bioclogging in porous media under various conditions have reported significant reductions in hydraulic conductivity, often up to 2-3 orders of magnitude or more ( Bielefeldt et al., 2002;Cunningham et al., 1991;Seifert and Engesgaard, 2007;Thullner, 2010;Vandevivere and Baveye, 1992 ). Due mainly to limitations in measuring or imaging the spatial distribution of biomass, however, only a few reports have attempted to associate changes in pore morphology with changes in hydraulic conductivity in 3D, mostly indirectly or via destructive sampling. A number of authors have observed that a majority of the biomass and associated clogging occurred within the first several centimeters of the experimental apparatus (e.g. ...
... Although the volume fraction and associated porosity of this type of local growth is small, it can impose a dominant impact on effective permeability. Similar results have been reported by Bielefeldt et al. (2002) where decreases in hydraulic conductivity of up to 3 orders of magnitude were observed despite a mere 3-8 percent decrease in porosity due to biofilm growth. ...
We explore how X-ray computed microtomography can be used to generate highly-resolved 3D biofilm datasets on length scales that span multiple pore bodies. The data is integrated into a study of the effects of flow rate on three-dimensional growth of biofilm in porous media. Three flow rates were investigated in model packed-bed columns. Biofilm growth was monitored during an 11-day growth period using a combination of differential pressure and effluent dissolved oxygen measurements. At the end of the growth period, all columns were scanned using X-ray computed microtomography and a barium sulfate-based contrast agent. The resulting images were prepared for quantitative analysis using a novel image processing workflow that was tailored to this specific system. The reduction in permeability due to biofilm growth was studied using both transducer-based pressure drop measurements and image-based calculations using the Kozeny-Carman model. In addition, a set of structural measures related to the spatial distribution of biofilms were computed and analyzed for the different flow rates. We generally observed 1 to 2 orders of magnitude decrease in permeability as a result of bioclogging for all columns (i.e, across flow rates). The greatest average permeability and porosity reduction was observed for the intermediate flow rate (4.5 ml/hr). A combination of results from different measurements all suggest that biofilm growth was oxygen limited at the lowest flow rate, and affected by shear stresses at the highest flow rate. We hypothesize that the interplay between these two factors drives the spatial distribution and quantity of biofilm growth in the class of porous media studied here. Our approach opens the way to more systematic studies of the structure-function relationships involved in biofilm growth in porous media and the impact that such growth may have on physical properties such as hydraulic conductivity.
... Two major limitations to MICP in porous media have been suggested: first, the pore size of the medium (> 0.5 µm), through which bacteria can move freely, and second, the need for the removal of residual products of MICP from the porous media or their conversion to neutral products such as water, CO 2 , or nitrogen 18 . For decades, research groups have tried to apply this technology for permeability reduction 19,20 ; however, the mechanisms and effects of MICP in porous media are unknown 17,21 . The objective of this study was to understand the microscale mechanisms of MICP and the response of hydraulic conductivities in different sand columns. ...
Microbially induced CaCO3 precipitation (MICP) is a natural process which has recently been applied as a technique for soil solidification and hydraulic conductivity reduction. In the present study, laboratory-based MICP tests were carried out in four columns containing sand with different particle sizes together with cultures of Sporosarcina pasteurii. A calcium solution was supplied continuously to the columns at a speed of 0.97 ml/min to mimic underground seepage. Hydraulic conductivities in the columns were monitored by hydraulic tests before and during MICP. Results showed that the reduction in conductivity values could be as high as 97% after 24 h of MICP. Columns clogged with calcite precipitates were examined by environmental scanning electron microscopy and energy dispersive X-ray spectroscopy. Calcite precipitation was shown to be the reason for hydraulic conductivity reduction. The calcium precipitation rates and amounts were quantified and verified. © 2017, Science Society of Thailand under Royal Patronage. All rights reserved.
Loess is widely used as a construction material in engineering projects on the Loess Plateau of China but is regarded as one of the most problematic soils due to water sensitivity. Hydraulic conductivity (K) is an essential parameter in assessment of water transfer in porous media. However, the influence of bacterial activity on the saturated permeability of remolded loess is still unclear and rarely being studied. We systematically studied the effects of Gram-negative bacterial activity (a common bacteria in the loess region) on the hydraulic properties of remolded loess, with the aim to better understand water flow through loess. A series of laboratory experiments were conducted to identify the variation in hydraulic conductivity under various bacterial inoculation and carbon constraint conditions. The results indicated that the K was relatively stable (0.14–0.16 m/d) at the initial phase and decreased by 81–93% reaching 0.01–0.05 m/d at the end of the experiments. The variation of hydraulic conductivity can be divided into the unaffected stage, linear reduction stage and stable stage. The growth of bacteria and the accumulation of extracellular polymeric substances occupied the pores between soil particles in the sample, which reduced the porosity and lead to the decrease of K. Higher available carbon contents and greater initial inoculum sizes speeded up the process of hydraulic conductivity reduction. The delayed effect was observed between rapid decline of hydraulic conductivity and exponential growth of bacteria. It should be highlighted that the reduction of hydraulic conductivity in the soil columns was mainly dependent on clogging in the inlet layer. Our findings provide a better insight into the change of hydraulic conductivity related to bacterial activities, and promote the reorganization of water cycle uncertainty and the prevention of engineering geological disasters in loess areas.
Bioremediation of groundwater is a widely applied method for remediation of contaminated groundwater. Microbial growth and biogenic gas accumulation are common during anaerobic bioremediation. These two processes can alter groundwater flow patterns and affect the ability to deliver electron donors or acceptors to target zones through changes in subsurface permeability, porosity, and dispersivity. In this study we analyzed three tracer tests conducted in an anaerobic two-dimensional sand-filled cell inoculated with a methanogenic culture. The ability of models to predict changes in porosity, permeability, and dispersivity during microbial growth and methane generation were evaluated. Microbial growth increased spatially averaged dispersivity by a ratio of 1.67. Biomass growth coupled with biogenic gas increased the spatially averaged dispersivity by a ratio of 2.46. In contrast with biomass measurements from confocal laser scanning microscopy, the model of Taylor and Jaffe (1990b) predicted a dispersivity increase by a factor of 10–1300. For water saturations greater than 0.5, the model of Sato et al. (2003) provided estimates of the effect of gas on dispersivity similar to values fit from modelling of the tracer tests.
Enhanced In situ Biodenitrification (EIB) is a capable technology for nitrate removal in subsurface water resources. Optimizing the performance of EIB implies devising an appropriate feeding strategy involving two design parameters: carbon injection frequency and C:N ratio of the organic substrate nitrate mixture. Here we model data on the spatial and temporal evolution of nitrate (up to 1.2 mM), organic carbon (ethanol), and biomass measured during a 342 day-long laboratory column experiment (published in Vidal-Gavilan et al., 2014). Effective porosity was 3% lower and dispersivity had a sevenfold increase at the end of the experiment as compared to those at the beginning. These changes in transport parameters were attributed to the development of a biofilm. A reactive transport model explored the EIB performance in response to daily and weekly feeding strategies. The latter resulted in significant temporal variation in nitrate and ethanol concentrations at the outlet of the column. On the contrary, a daily feeding strategy resulted in quite stable and low concentrations at the outlet and complete denitrification. At intermediate times (six months of experiment), it was possible to reduce the carbon load and consequently the C:N ratio (from 2.5 to 1), partly because biomass decay acted as endogenous carbon to respiration, keeping the denitrification rates, and partly due to the induced dispersivity caused by the well-developed biofilm, resulting in enhancement of mixing between the ethanol and nitrate and the corresponding improvement of denitrification rates. The inclusion of a dual-domain model improved the fit at the last days of the experiment as well as in the tracer test performed at day 342, demonstrating a potential transition to anomalous transport that may be caused by the development of biofilm. This modeling work is a step forward to devising optimal injection conditions and substrate rates to enhance EIB performance by minimizing the overall supply of electron donor, and thus the cost of the remediation strategy.
Uncontrolled microbial growth in oil and gas reservoirs may lead to microbiologically influenced formation damage (MIFD), including but not limited to (i) reservoir souring due to H2S production, which can also cause health issues and downstream pipeline and equipment corrosion, and (ii) reservoir permeability decrease due to clogging with biofilm. In this paper, we present results from studies which illustrate the negative impact of biofouling in laboratory-scale porous media bioreactors and the impact of biocide treatments on the prevention and mitigation of the effects of MIFD. Porous media bioreactors without biocide treatment were found to develop high levels of planktonic bacterial growth and biofilm buildup, with concurrent generation of H2S and deposition of iron sulfide. Biomass plugging of the porous media resulted in decreased permeability, as measured by an increase in backflow pressure and flow interruption. In comparison, bioreactors which received biocide treatments exhibited good or extended bacterial control, had no or low biofilm growth, and maintained higher permeability as compared to untreated controls. In addition to biofouling prevention, it was also found that porous media systems with biofilm plugging could be remediated via biocide treatment, with reduction of bacterial growth and backflow pressure after treatment. These experimental results in porous media bioreactor systems suggest that microbial control within the reservoir is essential to maintaining high injectivity and productivity for the duration of the well lifetime.
Longitudinal dispersion and permeability tests were performed in the Darcy flow regime using uniform porous media consisting either of spheres or sand grains.
Studies were conducted using sand-packed column reactors for which variations in piezometric head, substrate concentration, and biomass measured as organic carbon were monitored in space and time. Methanol was used as a growth substrate. Permeability reductions by factors of order 10 -3 were observed. The data show that a limit on permeability reduction exists, having a magnitude of 5 × 10 -4 in the present study. The limit on permeability reduction and the existence of high densities of bacteria in substrate depleted zones are explained with an open pore model. Permeability reduction was observed to correlate well with biomass density for values less than about 0.4 mg/cm 3, and exhibited independence at higher densities. -from Authors
An experimental investigation was conducted to quantify the permeability reduction caused by enhanced biological growth in a porous medium. Studies were conducted using sand-packed column reactors for which variations in piezometric head, substrate concentration, and biomass measured as organic carbon were monitored in space and time. Methanol was used as a growth substrate. Permeability reductions by factors of order 10−3 were observed. The data show that a limit on permeability reduction exists, having a magnitude of 5 × 10−4 in the present study. The limit on permeability reduction and the existence of high densities of bacteria in substrate depleted zones are explained with an open pore model. Permeability reduction was observed to correlate well with biomass density for values less than about 0.4 mg/cm3, and exhibited independence at higher densities.
The design of biofilm processes can be based on the mechanistically rigorous steady-state biofilm model and can also be simple to do when normalized loading curves are employed. A family of normalized loading curves is developed from principles of biofilm kinetics. The significance of the three dimensionless design parameters- $S_{{\rm min}}^{\ast}$ , L, and $J/J_{R}$ -is discussed. Finally, the design approach is illustrated by an example for completely mixed and segmented reactors removing soluble BOD in a biofilm reactor.
The recent literature contains conflicting claims about the characteristics of attached bacteria in subsurface porous media and how these characteristics affect permeability reduction. Some claim that the bacteria form continuous biofilms that restrict the pore size, while others claim that bacteria are attached in patchy aggregates that accumulate in pore throats. This contribution applies a recently developed tool from biofilm kinetics, the normalized surface loading, to interpret a wide range of experimental data from porous media experiments and biological filtration. The normalized surface loading is the actual substrate flux (i.e., rate of removal per unit surface area) divided by the minimum flux capable of supporting a deep biofilm. The analyses show that biofilms are continuous for normalized surface loadings greater than 1.0, but appear to become discontinuous for values less than about 0.25. For the low-load situation, distinguishing between continuous and discontinuous biofilms is not important when the modeling goal is prediction of substrate removal. However, the distinction is more critical when the modeling goal is to describe the spatial distribution of attached biomass and permeability loss.
A numerical model links the build-up of mineral precipitate (primarily CaC03) and the anaerobic activity of biofilms, which occur m granular material permeated with leachate from a municipal solid waste landfill. The model represents the porous-media flow system as a collection of elements m which each element acts as a separate, fixed-film reactor. The model represents biofilm growth for microorganisms carrying out acetogenesis of propionate and methanogenesis of acetate. It also directly links substrate utilization to mineral precipitation and accounts for the accumulation of inert biomass on the porous media at any time or position along the length of the column. Thus, the model describes the ecological interactions among fermenters, methanogens, inert biomass, and mineral precipitate. Although substrate utilization by the active microorganisms drives the entire system, mineral precipitate becomes a dominant component in the biofilm.
Growth of a biofilm in a porous medium reduces the total volume and the
average size of the pores. The change in the pore size distributions is
easily quantified when certain geometric assumptions are made. Existing
models of permeability or of relative permeability can be manipulated to
yield estimates of the resulting reduction in permeability as a function
of biofilm thickness. The associated reductions in porosity and specific
surface can be estimated as well. Based on a sphere model of the medium,
the Kozeny-Carman permeability model predicts physically realistic
results for this problem. Using a cut-and-random-rejoin-type model of
the medium, the permeability model of Childs and Collis-George yields
qualitatively reasonable results for this problem, as does a
generalization of the relative permeability model of Mualem.
Permeability models of Kozeny-Carman and of Millington and Quirk lead to
unrealistic results for a cut-and-random-rejoin-type medium. The Childs
and Collis-George and the Mualem models predict that the permeability
reduction for a given volume of biomass is greatest when the porous
medium has uniform pore sizes.