Bioclogging Research Articles

Clogging of landfill tyre and aggregate drainage layers by methanogenic leachate and implications for practice

This paper reports the results of pilot scale tests carried out to investigate the clogging of shredded and baled tyres in comparison with aggregates when percolated by leachates representative of those generated by methanogenic stage landfills. Realistic lifetime loading rates of methanogenic leachate were applied, and clogging was not generally apparent in any of the drainage media studied. This is in apparent contrast to many other studies that have demonstrated the susceptibility of all forms of drainage media to biological and chemical clogging when percolated with high strength organic and calcium rich leachates. The reasons for this difference are identified, the implications for landfill drainage system design are discussed and some suggestions for operational practice are presented for discussion.

Reduction in Saturated and Unsaturated Hydraulic Conductivities of an Andisol by Vinasse Application

With the increase in the production of bioethanol, it has become urgent to establish a sustainable system for recycling vinasse that includes its application to land. The purpose of this study was to determine the impact of vinasse application on the hydraulic properties of the soil. An incubation experiment was conducted to investigate the biological effects. Temporal changes in both saturated and unsaturated hydraulic conductivities [Ks and K(ψ), respectively] after applying vinasse were measured by the falling‐head method and the steady‐state flux control method, respectively. After vinasse application, the number of bacteria increased by one order of magnitude, whereas the number of fungi increased by two orders of magnitude compared with a test with deionized water. A remarkable reduction in Ks was observed within the fourth day after vinasse was applied instead of deionized water. The reduction in Ks was due to both biological and physical clogging. We attempted to determine what factors contributed to these effects on the Ks reduction and found that 73 to 92% of the Ks reduction was caused by physical clogging due to suspended solids. The temporal reduction in K(ψ) was within one order of magnitude; however, the values of K(ψ) dropped by two orders of magnitude for the same matric potential (ψ) value at the end of each column experiment. Moreover, 91% of the increase in the total amount of organic matter came from vinasse. From the experimental results, we concluded that the reductions in both Ks and K(ψ) occurred during vinasse application and the main reason for the reductions was the physical clogging due to suspended solids.

Tomato Yield and Quality and Emitter Clogging as Affected by Chlorination Schemes of Drip Irrigation Systems Applying Sewage Effluent

Chlorination has been recognized as an efficient and economically favorable method for treating clogging in drip emitters caused by biological growth during sewage application. Further important criteria for determining an optimal chlorination scheme are the different responses of crops to the chloride added into the soil through chlorination. During two seasons in 2008 and 2009, field experiments were conducted in a solar-heated greenhouse with drip irrigation systems applying secondary sewage effluent to tomato plants to investigate the influences of chlorine injection intervals and levels on plant growth, yield, fruit quality, and emitter clogging. Injection intervals ranging from 2 to 8 wk and injection concentrations ranging 2–50 mg L−1 of free chlorine residual at the end of the laterals were used. For the 2008 experiments, the yield from the treatments of sewage application with chlorination was 7.5% lower than the yield from the treatment of sewage application without chlorination, while the yields for the treatments with and without chlorination were similar for the 2009 experiments. The statistical tests indicated that neither the chlorine injection intervals and concentrations nor the interactions between the two significantly influenced plant height, leaf area, or tomato yield for both years. The qualities of the fruit in response to chlorination were parameter-dependent. Chlorination did not significantly influence the quality of ascorbic acid, soluble sugar, or soluble acids, but the interaction between the chlorine injection interval and the chlorine concentration significantly influenced the levels of soluble solids. It was also confirmed that chlorination was an effective method for reducing biological clogging. These results suggested that chlorination is safe for a crop that has a moderate sensitivity to chlorine, like tomato, and can maintain a high level of performance in drip irrigation systems applying sewage effluent.

Monitoring of clogging evolution in the stormwater infiltration system and determinant factors

Infiltration is widely used to manage stormwater in cities and their suburbs. Despite its advantages, questions remain about its long-term performance, in particular the potential for clogging. To address this problem, a field study was undertaken to assess the evolution of clogging over time by means of hydraulic resistance (R) measurements. The experiment was carried out on an infiltration basin continuously monitored for 7 years from 2004 to 2010. The work shows that clogging takes place progressively and can be slowed down by the growth of vegetation. It also showed that the variation from one event to another presented high variability. The variation of successive R-values per time unit has been statistically explained by the variation per time unit of two groups of factors: one linked to physical aspects (water volume and particle load), and more interestingly one linked to biological clogging (solar energy and air temperature), which is generally not considered for these systems. L’infiltration est aujourd’hui largement utilisée dans la gestion des eaux pluviales en milieu urbain. Malgré ses avantages, son efficacité sur le long terme pose encore problème en particulier leur aptitude au colmatage. Pour traiter ce problème, des observations de terrain ont été menées de manière à évaluer l’évolution du colmatage au cours du temps à l’aide de mesures de résistance hydraulique (R). L’observation a été menée sur un bassin d’infiltration suivi en continu sur 7 ans de 2004 à 2010. Le travail montre que le colmatage est très progressif est peut être ralenti par la croissance de végétation. Il montre également une grande variabilité d’un évènement à l’autre. La variation entre deux valeurs de R par unité de temps a pu être expliquée statistiquement par les variations par unité de temps de deux groupes de facteurs : l’un lié à des aspects physiques (volume d’eau et charge particulaire) et de manière plus intéressante à des facteurs biologiques (énergie solaire et température d’air) non considérés habituellement.

Validation of a Relative Permeability Model for Bioclogging in Unsaturated Soils

Biological clogging of unsaturated soils is an important process that can lead to the development of a biomat and failure of biofilters used to treat various wastewater streams. Several conceptual models have been developed to simulate clogging in saturated soils; however, efforts to develop similar models for unsaturated soils have been limited. Recently, Mostafa and Van Geel proposed three conceptual models to simulate bioclogging in unsaturated systems. These models included the impact of biomass growth on the relative permeability term for unsaturated flow. The models were incorporated into a one‐dimensional unsaturated flow and transport numerical model that simulates biological clogging in which microbial growth was simulated using Monod kinetics. The conceptual models have not been validated with experimental data. In this study, column experiments were conducted to study the clogging process in three different sand soils; filter media sand, concrete sand, and septic bed sand. Monod kinetic parameters were also evaluated in a separate experiment for the same feed solution used in the column study. The aim of this study was to validate the conceptual models proposed by Mostafa and Van Geel. Significant improvements to the flow and transport numerical model were required to accommodate the laboratory conditions. Improvements included implementing a minimum relative permeability of the biomat layer and a more detailed description of the biomass structure, which includes active biomass, extracellular polymeric substances (EPS), and an inert fraction. Comparisons between experimental data and numerical simulations indicated that the improved conceptual model for relative permeability appears to be appropriate for modeling bioclogging in the experiments considered in this study.

Water quality requirements for sustaining aquifer storage and recovery operations in a low permeability fractured rock aquifer

A changing climate and increasing urbanisation has driven interest in the use of aquifer storage and recovery (ASR) schemes as an environmental management tool to supplement conventional water resources. This study focuses on ASR with stormwater in a low permeability fractured rock aquifer and the selection of water treatment methods to prevent well clogging. In this study two different injection and recovery phases were trialed. In the first phase ∼1380 m3 of potable water was injected and recovered over four cycles. In the second phase ∼3300 m3 of treated stormwater was injected and ∼2410 m3 were subsequently recovered over three cycles. Due to the success of the potable water injection cycles, its water quality was used to set pre-treatment targets for harvested urban stormwater of ≤0.6 NTU turbidity, ≤1.7 mg/L dissolved organic carbon and ≤0.2 mg/L biodegradable dissolved organic carbon. A range of potential ASR pre-treatment options were subsequently evaluated resulting in the adoption of an ultrafiltration/granular activated carbon system to remove suspended solids and nutrients which cause physical and biological clogging. ASR cycle testing with potable water and treated stormwater demonstrated that urban stormwater containing variable turbidity (mean 5.5 NTU) and organic carbon (mean 8.3 mg/L) concentrations before treatment could be injected into a low transmissivity fractured rock aquifer and recovered for irrigation supplies. A small decline in permeability of the formation in the vicinity of the injection well was apparent even with high quality water that met turbidity and DOC but could not consistently achieve the BDOC criteria.

Impact of chemical clogging on de-watering well productivity: numerical assessment

Among the processes leading to a decrease in productivity, chemical clogging is often mentioned as one of the major features. De-watering of a confined aquifer caused by an unsuitable pumping scheme produces a phenomenon involving the diffusion of oxygen in the aquifer which disturbs the geochemical conditions in the initial system. Coupled chemical and transport processes are proposed in an assessment of the impact of de-watering on the precipitation of carbonate and iron oxide. The reactions are studied for waters showing low dissolved iron concentrations such as commonly observed in drinking water supplies. The quantity and distribution of precipitated iron oxide and calcium carbonate are used in a permeability model to calculate the productivity loss. For the conditions used in the simulations, the carbonate precipitate can be neglected compared to iron deposits which remain weak. The spatial distribution is heterogeneous and quite similar to the patterns observed in the field. This shape is mainly caused by a competition between the diffusion of oxygen due to the de-watering process and the rate of precipitation of iron oxide. However, the loss of well productivity remains moderate. It is clearly shown that de-watering of the well and the associated chemical incrustations that this induces cannot alone explain field data. More complex processes involving biological clogging and accurate hydrodynamic behaviour in the closest part of the well remain to be included in the modelling approach in order to provide valuable insights into the problem of well ageing.

The Effect of Toluene‐Substrate Concentration on Biological Clogging and Sloughing in Porous Media

One‐dimensional flow experiments on biological clogging were carried out by biostimulating columns packed with glass beads, sterilized, and inoculated with toluene‐utilizing bacteria. Biostimulation consisted of continuously injecting toluene at four concentrations (3.0 ± 0.9, 6.1 ± 0.8, 8.7 ± 1.6, and 11.3 ± 0.8 mg/L). The results of column flow experiments indicated that a threshold concentration of toluene exists below which the total biomass in the column can be kept at a steady‐state level. The column cores were extruded and segmented to determine the biomass distribution throughout the column at clogging. Clogging resulted in a significant buildup of filamentous bacteria close to the inlet end. Based on the nucleotide sequence of 16S rRNA genes, the dominant filamentous bacteria were identified as Nocardia farcinica. A 235‐d column experiment demonstrated that the clogging near injection points can be controlled by keeping the influent concentration of toluene below the threshold.

Determination of groundwater flow regimes in underground storage caverns using tritium and helium isotopes

Understanding groundwater flow and chemical transport is crucial for operating underground storage caverns. Groundwater flow in the study area is mainly affected by cavern operating conditions, and groundwater chemistry in the study area is modified by disinfection activities for removing possible biological clogging and by mixing with cement pore water. It is significant to discern these two effects because wells affected by the disinfection activities, in particular, may have hydrological connections with water curtains in which disinfectant water was injected to remove the biological clogging. Concentration of tritium (3H) and helium isotopes (4He), and groundwater chemical compositions were used to confirm that there are hydrological connectivities between the water curtain and the well. Groundwater along the fault areas contains low total dissolved solid (TDS) and high 3H, suggesting that the faults may act as fast flow conduits, which is not inconsistent with previous studies. Certain diagnostic conditions (high concentrations of Na+, Cl− and TDS and high pH) are presumed by the effect of disinfection activity, indicating that there are hydrological connections between the water curtain and the wells. This hypothesis is valid in YK2U and YK2L, but is not in YK12L, implying a closed system or an immobile water to explain the isotopic results.

Biofilm morphology as related to the porous media clogging

Aquifer recharge for the wastewater reuse has been considered and studied as a promising process to cope with the worldwide water scarcity. Soil clogging by an excessive growth of bacteria is often accompanied with the aquifer recharge. In this study, biofilm morphology and hydraulic conductivity were concurrently characterized at two flow rates and two levels of substrate concentrations. The experiments were conducted using a biofilm flow cell that was filled with glass beads. The biofilm images taken by confocal laser scanning microscopy (CLSM) were quantified by textural, areal, and fractal parameters. Hydraulic conductivity was monitored during the experiments. The flow velocity influenced the superficial morphology of biofilms and initial clogging time, while the substrate concentration affected biofilm density and clogging rate. Three different clogging mechanisms were suggested depending on the flow rate and substrate concentration: (1) clogging at a high flow rate can be accelerated by entrapped and accumulated biofilms, and can be easily eliminated by high shear force, (2) clogging at a low flow rate can be delayed for the time of local biofilm growths in the narrow pore necks, but the biofilm is rigid enough not to be sloughed, and (3) clogging in a solution with high substrate concentrations cannot be easily eliminated because of the growth of dense biofilms. The depicted biological clogging mechanisms will play a role in supporting studies about aquifer recharge.

Towards optimum permeability reduction in porous media using biofilm growth simulations

While biological clogging of porous systems can be problematic in numerous processes (e.g., microbial enhanced oil recovery-MEOR), it is targeted during bio-barrier formation to control sub-surface pollution plumes in ground water. In this simulation study, constant pressure drop (CPD) and constant volumetric flow rate (CVF) operational modes for nutrient provision for biofilm growth in a porous system are considered with respect to optimum (minimum energy requirement for nutrient provision) permeability reduction for bio-barrier applications. Biofilm growth is simulated using a Lattice-Boltzmann (LB) simulation platform complemented with an individual-based biofilm model (IbM). A biomass detachment technique has been included using a fast marching level set (FMLS) method that models the propagation of the biofilm-liquid interface with a speed proportional to the adjacent velocity shear field. The porous medium permeability reduction is simulated for both operational modes using a range of biofilm strengths. For stronger biofilms, less biomass deposition and energy input are required to reduce the system permeability during CPD operation, whereas CVF is more efficient at reducing the permeability of systems containing weaker biofilms.

Modeling of biological clogging in unsaturated porous media

A two-dimensional unsaturated flow and transport model, which includes microbial growth and decay, has been developed to simulate biological clogging in unsaturated soils, specifically biofilters. The bacterial growth and rate of solute reduction due to biodegradation is estimated using the Monod equation. The effect of microbial growth is considered in the proposed conceptual model that relates the relative permeability term for unsaturated flow to the microbial growth. Two applications of the model are presented in this study. Using the model, the clogging mechanism in different soils has been simulated. The results of the model indicate that the time to reach a clogged state is influenced by the hydraulic properties of the soil. Clogging is delayed in soils with higher saturated hydraulic conductivities, and higher porosities. For the relative permeability model proposed, higher van Genuchten n values lead to a delay in clogging. The model was also used to simulate the progressive clogging of a septic bed as the biomat initially forms at the up-gradient end of the distribution pipe, displacing wastewater infiltration and biomat formation further down-gradient over time.

Multivariate statistical analysis of underground gas storage caverns on groundwater chemistry in Korea

AbstractAn understanding of groundwater flow and chemistry is important to operate underground storage caverns. Groundwater flow is mainly affected by cavern operating conditions. Groundwater chemistry is modified by disinfection activities for removing possible biological clogging and by mixing with cement pore water. It is important to discern these two effects, because wells affected by the disinfection activities may have hydrological connections with water curtains used to inject the disinfectant. However, it is difficult to separate these two effects using graphical methods because of their similar chemical characteristics. Instead, multivariate statistical analysis, such as principal component analysis (PCA) and factor analysis (FA), can be used. Groundwater samples for chemical analysis were obtained from four surveys in 1999–2000. Based on the results from PCA and FA, it appears that there were temporal variations of seepage water into the propane area when the cavern operation fluctuated, but we could not observe such variation in the butane area. These changes may occur mainly at depth, where water flow is slow and water renewal in the cavern surrounding is limited. Copyright © 2008 John Wiley & Sons, Ltd.

論文 多孔質媒体における生物的目詰りを考慮した生物学的処理モデルの開発1カラムスタディへのモデルの適用

論文 多孔質媒体における生物的目詰りを考慮した生物学的処理モデルの開発1カラムスタディへのモデルの適用

A study on biological clogging of nonwoven geotextiles under leachate flow

This paper presents results of long-term permittivity tests using leachate to evaluate biological clogging of nonwoven geotextiles. Three types of geotextiles with varying masses per unit area were used in the tests. The identification and quantification of microorganisms in the geotextile were carried out as well as microscopic investigations. The accuracies of semi-empirical models to evaluate the kinetics of bacteria growth and to correlate hydraulic properties and microbiological parameters were examined. Permittivity tests under increasing water heads were also performed on the geotextile samples already subjected to long-term leachate flow in order to evaluate the values of water heads required to wash the biofilms out of the geotextile pores. The results of the tests showed the marked reduction of geotextile permeability due to biological clogging and that the results of the predictions by semi-empirical methods were consistent with the biological mechanisms observed.

Development of a vertical TDR probe to evaluate the vertical moisture profile in peat columns to assess biological clogging

Time domain reflectometry (TDR) is used to monitor the moisture content in soils including peat. The objective of this study was to develop a TDR-based method to measure the vertical moisture profile in a peat biofilter operating in the field, where access to the filter is limited to the top surface. The moisture profile with depth can then be used to infer or assess the operating status of a filter in terms of clogging. The successful application of water content measurement using horizontal TDR probes has been demonstrated by many researchers. In this study, a single TDR probe was sequentially advanced into a peat column to estimate the vertical moisture profile and the results were compared to horizontal TDR and gravimetric measurements. The experiment was carried out in six peat columns during a drainage process and two columns during a clogging process. Water contents by the vertical and horizontal probes agreed very well, although the data was slightly more scattered in the columns subject to clogging due to signal attenuation. Total signal attenuation was observed with longer probes in clogged peat soils. However, there was a consistent discrepancy between the TDR measured water contents and those determined gravimetrically, which is believed to be caused by a systematic error, possibly error with the calibration curve.

Coupled moisture and microbial dynamics in unsaturated soils

A continuum‐scale mathematical model which couples water flow and bacterial dynamics explores the process of biological clogging in unsaturated soils. The impact of biomass dynamics on soil water flow is assumed to take place through the changes in porosity and the structural properties of the medium by suitable modifications of the pore size distribution, water retention, and hydraulic conductivity functions. The feedback of soil moisture on biomass is taken into account by including the effect of water stress on microbial growth. The model is calibrated against existing laboratory experimental data for an artificial porous medium in saturated conditions, and it is used to analyze the hydraulic behavior of unsaturated soils when subject to biological clogging and plant water uptake. The results of this analysis show that this feedback may have a substantial impact on the net water flow, the soil water‐holding capacity, and the soil moisture and biomass space‐time distributions.

Conceptual Models and Simulations for Biological Clogging in Unsaturated Soils

Biological clogging in unsaturated soils is an important concern in the design of biofilters that are used to treat wastewater in rural areas. Several conceptual models have been developed to simulate biological clogging in saturated flow systems but limited research has been performed to develop similar conceptual models in unsaturated soils. This study developed three conceptual models for biological clogging in unsaturated soils. The model formulations varied from microscale to macroscale and from analytically derived to empirical equations. They were all formulated based on the approaches proposed by Burdine and Mualem to estimate the relative permeability based on the effective water saturation and the soil moisture curve. A one‐dimensional unsaturated flow and transport code was developed, which incorporates Monod kinetics to simulate the biodegradation of an organic substrate. The three conceptual models that were developed relate the relative permeability to the microbial growth term in the unsaturated flow equation. The models were implemented in a numerical model to illustrate the impact of microbial growth on the biological clogging of unsaturated soils. Also the effect of continuous loading versus pulse loading was simulated to illustrate the difference between the loading scenarios on the clogging process within biofilters.

Removal of manganese and zinc from Kahrizak landfill leachate using daily cover soil and lime

The possibility of in situ removal of heavy metals found in leachate generated at municipal solid waste landfills was studied through amendment of daily cover soil. Kahrizak landfill, which receives the waste generated at Tehran, was selected as the source of leachate and soil samples. Manganese and zinc were selected in this study. The soil sample taken from the Kahrizak site contained about 17% clay, which was presumed to have significant capability for removing manganese and zinc. This capability was assumed to be enhanced further through the addition of lime and consequently to improve the potential for chemical precipitation of the selected metals. The in situ removal experiment was accomplished through a set of seven columns filled with the sampled soil with varying contents of lime (i.e., from 0% to 6% by dry weight). Fresh leachate of low pH was added to the columns on a daily basis. Concentrations of manganese and zinc were measured in the influent and effluent during 40 days when biological clogging resulted in a condition of almost no outflow in the columns. The results indicated a substantial increase in removal efficiency through the addition of lime to the daily cover soil. Desorption resulting from the low pH of fresh leachate occurs at later stages compared to the column with no lime addition.

Dynamics of cells attachment, aggregation, growth and detachment in trickle-bed bioreactors

Excessive biomass formation in two-phase flow trickle-bed bioreactors induces biological clogging and leads to the progressive obstruction of the bed that is accompanied with a build-up in pressure drop and flow channeling. One of the important aspects during biological clogging in trickle-bed bioreactors is the aggregation of cells and the detachment of cells and aggregates from pore bodies within the porous bed. Current theoretical models describing the transient behaviour of biomass accumulation and the biological clogging in trickle-bed bioreactors for wastewater treatment neglect the cell aggregation process and the aggregates detachment. An attempt has been made with this contribution in which the authors strived to develop an Euler–Euler two-fluid dynamic model based on the volume-average mass, momentum equations, species balance equations, biomass dynamics equation, filtration equations for the cells and the aggregates and discrete population balance equations for the cells agglomeration to describe two-phase flow and space-time evolution of biological clogging in trickle-bed bioreactors for wastewater treatment. Phenol biodegradation by Pseudomonas putida as the predominant species immobilized on activated carbon was chosen as a case study to illustrate the consequences of formation of excessive amounts of biomass. Cells aggregation was described by the rate at which a certain size aggregate is being formed by smaller aggregates minus the rate at which the aggregate combines to form a larger aggregate. The detachment of the cells or aggregates from the collector surface was supposed to be induced by the colloidal forces in the case of Brownian cells/aggregates or by the hydrodynamic forces in the case of non-Brownian aggregates.