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Urea-hydrolysing biofilms are crucial to applications in medicine, engineering, and science. Quantitative information about ureolysis rates in biofilms is required to model these applications. We formulate a novel model of urea consumption in a biofilm that allows different kinetics, for example either first order or Michaelis–Menten. The model is fit to synthetic data to validate and compare two approaches, Bayesian and nonlinear least squares (NLS), commonly used by biofilm practitioners. The shortcomings of NLS motivate the Bayesian approach where a simple Markov Chain Monte Carlo (MCMC) sampler is applied. The model is then fit to real data of influent and effluent urea concentrations from experiments with biofilms of Escherichia coli. Results from synthetic data aid in interpreting results from real data, where first-order and Michaelis–Menten kinetic models are compared. The method shows potential for general applications requiring biofilm kinetic information. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Selenium (Se) discharged into natural waterbodies can accumulate over time and have negative impacts on the environment. Se‐laden wastewater streams can be treated using biological processes. However, the presence of other electron acceptors in wastewater, such as nitrate (NO3‐) and sulfate (SO42‐), can influence selenate (SeO42‐) reduction and impact the efficiency of biological treatment systems. RESULTS: SeO42‐ removal by biofilms formed from an anaerobic sludge inoculum was investigated in the presence of NO3‐ and SO42‐ using drip flow reactors operated continuously for 10 days at pH 7.0 and 30 °C. The highest total Se (∼60%) and SeO42‐ (∼80%) removal efficiencies were observed when the artificial wastewater contained SO42‐. A maximum amount of 68 μmol Se cm‐2 was recovered from the biofilm matrix in SO42‐ + SeO42‐ exposed biofilms and biofilm mass was 2.7‐fold increased for biofilms grown in the presence of SO42‐. When SeO42‐ was the only electron acceptor, biofilms were thin and compact. In the simultaneous presence of NO3‐ or SO42‐, biofilms were thicker (> 0.6 mm), less compact and exhibited gas pockets. CONCLUSION: The presence of SO42‐ had a beneficial effect on biofilm growth and the SeO42‐ removal efficiency, while the presence of NO3‐ did not have a significant effect on SeO42‐ removal by the biofilms. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The model for microbially induced calcite precipitation (MICP) published by Ebigbo et al. (2012) has been improved based on new insights obtained from experiments and model calibration. The challenge in constructing a predictive model for permeability reduction in the underground with MICP is the quantification of the complex interaction between flow, transport, biofilm growth, and reaction kinetics. New data from Lauchnor et al. (2015) on whole-cell ureolysis kinetics from batch experiments were incorporated into the model, which has allowed for a more precise quantification of the relevant parameters as well as a simplification of the reaction kinetics in the equations of the model. Further, the model has been calibrated objectively by inverse modeling using quasi-1D column experiments and a radial flow experiment. From the postprocessing of the inverse modeling, a comprehensive sensitivity analysis has been performed with focus on the model input parameters that were fitted in the course of the model calibration. It reveals that calcite precipitation and concentrations of [ABSTRACT FROM AUTHOR]

Microbially-induced calcium carbonate (CaCO3) precipitation (MICP) is a widely explored and promising technology for use in various engineering applications. In this review, CaCO3precipitation inducedviaurea hydrolysis (ureolysis) is examined for improving construction materials, cementing porous media, hydraulic control, and remediating environmental concerns. The control of MICP is explored through the manipulation of three factors: (1) the ureolytic activity (of microorganisms), (2) the reaction and transport rates of substrates, and (3) the saturation conditions of carbonate minerals. Many combinations of these factors have been researched to spatially and temporally control precipitation. This review discusses how optimization of MICP is attempted for different engineering applications in an effort to highlight the key research and development questions necessary to move MICP technologies toward commercial scale applications. [ABSTRACT FROM PUBLISHER]

The use of microbiologically induced mineralization to plug pore spaces is a novel biotechnology to mitigate the potential leakage of geologically sequestered carbon dioxide from preferential leakage pathways. The bacterial hydrolysis of urea (ureolysis) which can induce calcium carbonate precipitation, via a pH increase and the production of carbonate ions, was investigated under conditions that approximate subsurface storage environments, using a unique high pressure (∼7.5MPa) moderate temperature (32°C) flow reactor housing a synthetic porous media core. The synthetic core was inoculated with the ureolytic organism Sporosarcina pasteurii and pulse-flow of a urea inclusive saline growth medium was established through the core. The system was gradually pressurized to 7.5MPa over the first 29 days. Concentrations of NH4 +, a by-product of urea hydrolysis, increased in the flow reactor effluent over the first 20 days, and then stabilized at a maximum concentration consistent with the hydrolysis of all the available urea. pH increased over the first 6 days from 7 to 9.1, consistent with buffering by NH4 +. Ureolytic colony forming units were consistently detected in the reactor effluent, indicating a biofilm developed in the high pressure system and maintained viability at pressures up to 7.5MPa. All available calcium was precipitated as calcite. Calcite precipitates were exposed to dry supercritical CO3 +H+. Ureolytic colony forming units were consistently detected in the reactor effluent, indicating a biofilm developed in the high pressure system and maintained viability at pressures up to 7.5MPa. All available calcium was precipitated as calcite. Calcite precipitates were exposed to dry supercritical CO2 (scCO2), water-saturated scCO2, scCO2-saturated brine, and atmospheric pressure brine. Calcite precipitates were resilient to dry scCO2, but suffered some mass loss in water-saturated scCO2 (mass loss 17±3.6% after 48h, 36±7.5% after 2h). Observations in the presence of scCO2 saturated brine were ambiguous due to an artifact associated with the depressurization of the scCO2 saturated brine before sampling. The degassing of pressurized brine resulted in significant abrasion of calcite crystals and resulted in a mass loss of approximately 92±50% after 48h. However dissolution of calcite crystals in brine at atmospheric pressure, but at the pH of the scCO2 saturated brine, accounted for only approximately 7.8±2.2% of the mass loss over the 48h period. These data suggest that microbially induced mineralization, with the purpose of reducing the permeability of preferential leakage pathways during the operation of GCS, can occur under high pressure scCO2 injection conditions. [ABSTRACT FROM AUTHOR]

Abstract: In order to develop subsurface CO2 storage as a viable engineered mechanism to reduce the emission of CO2 into the atmosphere, any potential leakage of injected supercritical CO2 (SC-CO2) from the deep subsurface to the atmosphere must be reduced. Here, we investigate the utility of biofilms, which are microorganism assemblages firmly attached to a surface, as a means of reducing the permeability of deep subsurface porous geological matrices under high pressure and in the presence of SC-CO2, using a unique high pressure (8.9MPa), moderate temperature (32°C) flow reactor containing 40millidarcy Berea sandstone cores. The flow reactor containing the sandstone core was inoculated with the biofilm forming organism Shewanella fridgidimarina. Electron microscopy of the rock core revealed substantial biofilm growth and accumulation under high-pressure conditions in the rock pore space which caused >95% reduction in core permeability. Permeability increased only slightly in response to SC-CO2 challenges of up to 71h and starvation for up to 363h in length. Viable population assays of microorganisms in the effluent indicated survival of the cells following SC-CO2 challenges and starvation, although S. fridgidimarina was succeeded by Bacillus mojavensis and Citrobacter sp. which were native in the core. These observations suggest that engineered biofilm barriers may be used to enhance the geologic sequestration of atmospheric CO2. [Copyright &y& Elsevier]

A common problem faced by drinking water studies is that of properly characterizing the corrosion products (CP) in iron pipes or synthetic Fe (hydr)oxides used to simulate the iron pipe used in municipal drinking-water systems. The present work compares the relative applicability of a suite of imaging and analytical techniques for the characterization of CPs and synthetic Fe oxide thin films and provide an overview of the type of data that each instrument can provide as well as their limitations to help researchers and consultants choose the best technique for a given task. Crushed CP from a water distribution system and synthetic Fe oxide thin films formed on glass surfaces were chosen as test samples for this evaluation. The CP and synthetic Fe oxide thin films were analyzed by atomic force microscopy (AFM), scanning electron microscopy (SEM), energy-dispersive spectroscopy, time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray powder diffractometry (XRD), grazing incident diffractometry (GID), transmission electron microscopy (TEM), selected area electron diffraction, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared, Mössbauer spectroscopy, Brunauer–Emmett–Teller N2 adsorption and Fe concentration was determined by the ferrozine method. XRD and GID were found to be the most suitable techniques for identification of the mineralogical composition of CP and synthetic Fe oxide thin films, respectively. AFM and a combined ToF-SIMS–AFM approach proved excellent for roughness and depth profiling analysis of synthetic Fe oxide thin films, respectively. Corrosion products were difficult to study by AFM due to their surface roughness, while synthetic Fe oxide thin films resisted most spectroscopic methods due to their limited thickness (118 nm). XPS analysis is not recommended for mixtures of Fe (hydr)oxides due to their spectral similarities. SEM and TEM provided great detail on mineralogical morphology. [ABSTRACT FROM AUTHOR]

Highlights: [•] Microalgal biofilm formation at lab- and field-scale. [•] Biofilm composition and orientation influence photosynthesis and respiration. [•] Decrease in localized O2 may improve photosynthetic biofilm technologies. [•] Biofilm systems produced biofuel precursor molecules. [•] Nitrogen depletion did not result in drastic triacylglycerol accumulation. [ABSTRACT FROM AUTHOR]

Abstract: Noninvasive measurements of hydrodynamic dispersion by nuclear magnetic resonance (NMR) are made in a model porous system before and after a biologically mediated precipitation reaction. Traditional magnetic resonance imaging (MRI) was unable to detect the small scale changes in pore structure visualized during light microscopy analysis after destructive sampling of the porous medium. However, pulse gradient spin echo nuclear magnetic resonance (PGSE NMR) measurements clearly indicated a change in hydrodynamics including increased pore scale mixing. These changes were detected through time-dependent measurement of the propagator by PGSE NMR. The dynamics indicate an increased pore scale mixing which alters the preasymptotic approach to asymptotic Gaussian dynamics governed by the advection diffusion equation. The methods described here can be used in the future to directly measure the transport of solutes in biomineral-affected porous media and contribute towards reactive transport models, which take into account the influence of pore scale changes in hydrodynamics. [ABSTRACT FROM AUTHOR]

Abstract: Supercritical CO2 has been shown to act as a disinfectant against microorganisms. These organisms have most often been tested in vegetative or spore form. Since biofilm organisms are typically more resilient to physical, chemical, and biological stresses than the same organisms in planktonic form, they are often considered more difficult to eradicate. It is therefore hypothesized that supercritical CO2 (SC–CO2) induced inactivation of biofilm organisms would be less effective than against planktonic (suspended) growth cultures of the same organism. Six-day old biofilm cultures as well as suspended planktonic cultures of Bacillus mojavensis were exposed to flowing SC–CO2 at 136atm and 35°C for 19min and slowly depressurized after treatment. After SC–CO2 exposure, B. mojavensis samples were analyzed for total and viable cells. Suspended cultures revealed a 3log10 reduction while biofilm cultures showed a 1log10 reduction in viable cell numbers. These data demonstrate that biofilm cultures of B. mojavensis are more resilient to SC–CO2 than suspended planktonic communities. It is hypothesized that the small reduction in the viability of biofilm microorganisms reflects the protective effects of extracellular polymeric substances (EPS) which make up the biofilm matrix, which offer mass transport resistance, a large surface area, and a number of functional groups for interaction with and immobilization of CO2. The resistance of biofilm suggests that higher pressures, longer durations of SC–CO2 exposure, and a quicker depressurization rate may be required to eradicate biofilms during the sterilization of heat-sensitive materials in medical and industrial applications. However, the observed resilience of biofilms to SC–CO2 is particularly promising for the prospective application of subsurface biofilms in the subsurface geologic sequestration of CO2. [Copyright &y& Elsevier]