Particle release and permeability reduction in a natural zeolite (clinoptilolite) and sand porous medium

Effect of Produced Sand Particles and Fines on Scale Inhibitor: A Review

Application of scale inhibitors in oil and gas production is aimed at mitigating scale blockage during production. Many experimental, mathematical, and numerical simulation modeling works have been carried out to evaluate behavior, performance, and interaction of the scale inhibitor chemicals within porous media in relation to their efficiency in solving scale problem. However, the mechanisms underpinning scale inhibitors performance are not well published. Some research works have shown theoretically that not all scale inhibitors pumped into the formation adsorb onto the formation rock. Some of the inhibitors may adsorb on produced loose sand grains or colloidal fine sand particles which float and flow within the pore spaces along with the scale inhibitor mostly in unconsolidated reservoirs This paper provides a review of research work on the effect of produced loose sand or colloidal fine particles flow on polyphosphonates and polyphosphinopolymer scale inhibitors performances during crude production.

Zeolite favours propionate syntrophic degradation during anaerobic digestion of food waste under low ammonia stress

Zeolite addition has been widely suggested for its ability to overcome ammonia stress occurring during anaerobic digestion. However little is known regarding the underlying mechanisms of mitigation and especially how zeolite influences the microbial structuration. The aim of this study was to bring new contributions on the effect of zeolite on the microbial community arrangement under a low ammonia stress. Replicated batch experiments were conducted. The microbial population was characterised with 16S sequencing. Methanogenic pathways were identified with methane isotopic fractionation. In presence of ammonia, zeolite mitigated the decrease of biogas production rate. Zeolite induced the development of Izimaplasmatales order and preserved Peptococcaceae family members, known as propionate degraders. Moreover methane isotopic fractionation showed that hydrogenotrophic methanogenesis was maintained in presence of zeolite under ammonia low stress. Our results put forward the benefit of zeolite to improve the bacteria-archaea syntrophy needed for propionate degradation and methane production under a low ammonia stress.

Natural zeolite permeable treatment wall for removing Sr-90 from groundwater

Experimental and modeling studies were completed to investigate the potential performance of a sorbing permeable treatment wall (PTW) comprised of natural zeolite for removal of strontium-90 (Sr-90) from groundwater at the West Valley Demonstration Project (WVDP) near Buffalo, NY. Multiple column tests were performed at the University at Buffalo (UB) and WVDP for periods ranging from 6 months to 2 years; UB columns were supplied with synthetic groundwater referenced to anticipated field conditions, while radioactive groundwater obtained on site was used for the WVDP columns. The primary focus was on quantifying the competitive cation reactions among five cations (Na(+), K(+), Ca(2+), Mg(2+), Sr(2+)) and Sr-90 with data obtained from the column studies used to estimate Gaines-Thomas (GT) selectivity coefficients. The resulting six-solute transport model provided flexibility to explore the influence of PTW parameters on long-term PTW performance, including variations in Sr-90 concentrations and groundwater geochemistry. The natural zeolite PTW is a viable method for in situ removal of Sr-90 from groundwater and potentially applicable to other sites contaminated by Sr-90.

Evaluation of sorbent amendments for in situ remediation of metal-contaminated sediments

The present study evaluated sorbent amendments for in situ remediation of sediments contaminated with two divalent metals. A literature review screening was performed to identify low-cost natural mineral-based metal sorbents and high-performance commercial sorbents that were carried forward into laboratory experiments. Aqueous phase metal sorptivity of the selected sorbents was evaluated because dissolved metals in sediment porewater constitute an important route of exposure to benthic organisms. Based on pH-edge sorption test results, natural sorbents were eliminated due to inferior performance. The potential as in situ sediment amendment was explored by comparing the sorption properties of the engineered amendments in freshwater and saltwater (10 PPT salinity estuarine water) matrices. Self-assembled monolayers on mesoporous supports with thiols (Thiol-SAMMS) and a titanosilicate mineral (ATS) demonstrated the highest sorption capacity for cadmium (Cd) and lead (Pb), respectively. Sequential extraction tests conducted after mixing engineered sorbents with contaminated sediment demonstrated transfer of metal contaminants from a weakly bound state to a more strongly bound state. Biouptake of Cd in a freshwater oligochaete was reduced by 98% after 5-d contact of sediment with 4% Thiol-SAMMS and sorbed Cd was not bioavailable. While treatment with ATS reduced the small easily extractable portion of Pb in the sediment, the change in biouptake of Pb was not significant because most of the native lead was strongly bound. The selected sorbents added to sediments at a dose of 5% were mostly nontoxic to a range of sensitive freshwater and estuarine benthic organisms. Metal sorbent amendments in conjunction with activated carbon have the potential to simultaneously reduce metal and hydrophobic contaminant bioavailability in sediments.

Microbially mediated clinoptilolite regeneration in a multifunctional permeable reactive barrier used to remove ammonium from landfill leachate contamination: laboratory column evaluation

This study focuses on multifunctional permeable reactive barrier (multibarrier) technology, combining microbial degradation and abiotic ion exchange processes for removal of ammonium from landfill leachate contamination. The sequential multibarrier concept relies on the use of a clinoptilolite-filled buffer compartment to ensure a robust ammonium removal in case of temporary insufficient microbial activities. An innovative strategy was developed to allow in situ clinoptilolite regeneration. Laboratory-scale clinoptilolite-filled columns were first saturated with ammonium, using real landfill leachate as well as synthetic leachates as feed media. Other inorganic metal cations, typically present in landfill leachate, had a detrimental influence on the ammonium removal capacity by competing for clinoptilolite exchange sites. On the other hand, the metals had a highly favorable impact on regeneration of the saturated material. Feeding the columns with leachate deprived from ammonium (e.g., by microbial nitrification in an upgradient compartment), resulted in a complete release of the previously sorbed ammonium from the clinoptilolite, due to exchange with metal cations present in the leachate. The released ammonium is then available for microbial consumption in a downgradient compartment. The regeneration process resulted in a slightly increased ammonium exchange capacity afterward. The described strategy throws a new light on sustainable use of sorption materials for in situ groundwater remediation, by avoiding the need for material replacement and the use of external chemical regenerants.

Probe for measuring groundwater velocity at the centimeter scale

A novel method of measuring small-scale groundwater velocities in unconsolidated noncohesive media uses the travel time of a tracer pulse between an injection port and two detectors located on the surface of a cylindrical probe, called a point-velocity probe (PVP), as the basis for velocity estimation. The direction and magnitude of the water velocity vector were determined to within +/- 9% of magnitude and +/- 8 in direction, on average, in ten laboratory tank tests conducted with the PVP, when the velocities were between 5 and 98 cm/ day. Numerical simulations supported the accuracy of the underlying theory for interpretation of the PVP data and indicated that the technology is capable of measuring velocity at a very fine scale (0.5 cm around the circumference). The benchtop and modeling investigations indicated that the probe is moderately sensitive to the condition of the porous medium immediately next to the cylinder surface, suggesting that challenges exist for the deployment of the instrument in the field.

Performance assessment of a zeolite treatment wall for removing Sr-90 from groundwater

Laboratory and modeling studies were conducted to assess the potential performance of a permeable reactive barrier constructed of a natural zeolite material at the West Valley Demonstration Project in western New York State. The results of laboratory column tests indicated that the barrier material would be effective at removing strontium from groundwater under natural gradient conditions. Two one-dimensional contaminant transport models were developed to interpret the data. A single-solute retardation factor model provided good agreement with the column test data, but time-consuming extraction and analysis of the zeolite material was required to parameterize the model. A preliminary six-solute model was also developed based on the assumption of competitive cation exchange as the primary removal mechanism. Both models yielded similar predictions of the long-term performance of the barrier, but the cation exchange model predicted higher effluent concentrations during the first 1000 pore volumes of operation. The cation exchange framework has several advantages, including the ability to calibrate the model using only data from column effluent samples, and the ability to account for site-specific differences in the groundwater cation composition. However, additional laboratory work is needed to develop a suitably robust model.

Influence of media characteristics on energy dissipation in filter backwashing

Effective cleaning of granular filters during backwashing processes needs maximum turbulence and maximum shear in the fluid particle field. The energy dissipation in a backwashed filter as a particulate fluidized bed arises due to the suspending and random motions of particles and turbulent fluctuations in the bed. Size, density, and sphericity of the filter materials greatly influence the fluidization behavior of the media. In this study, a new model is proposed for predicting the energy dissipation parameters namely the hydrodynamic shear stress (tau(a)), the velocity gradient (G(a)), the turbulence dissipation coefficient (C(a)), and the turbulence parameter (C(a)0.5/Re) in backwashing of filters for different types of filter materials (sand, anthracite, and glass ball). The hydrodynamic shear stress is the dominant mechanism of filter cleaning and appears to increase with increasing the density and size of the filter media particles. Using the basic set of data, a step by step procedure is developed to compute the velocity gradient G(a), the turbulence dissipation coefficient C(a), the hydrodynamic shear stress tau(a), and the turbulent parameter (C(a)0.5/ Re).