Enriched Stream Research Articles

The interaction between warming and enrichment accelerates food-web simplification in freshwater systems.

Nutrient enrichment and climate warming threaten freshwater systems. Metabolic theory and the paradox of enrichment predict that both stressors independently can lead to simpler food-webs having fewer nodes, shorter food-chains and lower connectance, but cancel each other's effects when simultaneously present. Yet, these theoretical predictions remain untested in complex natural systems. We inferred the food-web structure of 256 lakes and 373 streams from standardized fish community samplings in France. Contrary to theoretical predictions, we found that warming shortens fish food-chain length and that this effect was magnified in enriched streams and lakes. Additionally, lakes experiencing enrichment exhibit lower connectance in their fish food-webs. Our study suggests that warming and enrichment interact to magnify food-web simplification in nature, raising further concerns about the fate of freshwater systems as climate change effects will dramatically increase in the coming decades.

Weathering Incongruence in Mountainous Mediterranean Climates Recorded by Stream Lithium Isotope Ratios

AbstractLithium isotope ratios (δ7Li) of rivers are increasingly serving as a diagnostic of the balance between chemical and physical weathering contributions to overall landscape denudation rates. Here, we show that intermediate weathering intensities and highly enriched stream δ7Li values typically associated with lowland floodplains can also describe small upland watersheds subject to cool, wet climates. This behavior is revealed by stream δ7Li between +22.4 and +23.5‰ within a Critical Zone observatory located in the Cévennes region of southern France, where dilute stream solute concentrations and significant atmospheric deposition otherwise mask evidence of incongruence. The water‐rock reaction pathways underlying this behavior are quantified through a multicomponent, isotope‐enabled reactive transport model. Using geochemical characterization of soil profiles, bedrock, and long‐term stream samples as constraints, we evolve the simulation from an initially unweathered granite to a steady state weathering profile which reflects the balance between (a) fluid infiltration and drainage and (b) bedrock uplift and soil erosion. Enriched stream δ7Li occurs because Li is strongly incorporated into actively precipitating secondary clay phases beyond what prior laboratory experiments have suggested. Chemical weathering incongruence is maintained despite relatively slow reaction rates and moderate clay accumulation due to a combination of two factors. First, reactive primary mineral phases persist across the weathering profile and effectively “shield” the secondary clays from resolubilization due to their greater solubility. Second, the clays accumulating in the near‐surface profile are relatively mature weathering byproducts. These factors promote characteristically low total dissolved solute export from the catchment despite significant input of exogenous dust.

Parametric study and optimization of an acid gas enrichment plant with outlet streams and energy usage consideration

Acid gas enrichment (AGE) is a new method to increase the H2S conversion in conventional Clause process. In this paper effect of methyl diethanolamine (MDEA) flow rate, MDEA temperature, acid gas flow rate, and AGE tower pressure on the outlet H2S and CO2 concentration and energy consumption have been studied. A novel procedure based on enthalpy of combustion in the reaction furnace and incinerator is conducted for energy consumption calculations. By changing MDEA and inlet acid gas flow rates, a maximum H2S concentration in the enriched stream could be attainable. Increasing MDEA temperature will decrease maximum H2S concentration and enriched acid flow rate; also, CO2 concentration in off-gas will be decreased. By increasing AGE pressure, maximum H2S concentration in the enriched stream will be diminished. At higher MDEA flow rates, lower AGE pressures will bring higher H2S concentration in enriched acid gas stream. According to flame temperature simulation in the reaction furnace, energy consumption is directly related to H2S concentration in the sulfur recovery unit (SRU) feed stream. Results show that maximum H2S concentration in the enriched acid gas stream has the best conditions from energy point of view. At optimum conditions, H2S concentration in enriched acid gas is 62.45 mol%, which has been increased by 24.8%, compared with existing plant conditions, and energy consumption has been decreased by 25.05 GJ/h, and CO2 concentration in off-gas is 94.94 mol%.

Regeneration of coked catalysts via ozonation: Experimental study of diffusion–reaction mechanisms at pellet and reactor scales

This work focuses on regeneration of coked catalysts using ozonation as an alternative process to typical coke combustion with oxygen. Different samples of coked ZSM-5 zeolites obtained during catalytic pyrolysis of polyethylene at 450 °C were exposed to an ozone enriched stream in a fixed-bed reactor. The influence of main operating parameters (time of exposure, temperature, O3 inlet concentration and gas volumetric flowrate) were studied by evaluating coke removal efficiency and by observing regeneration behavior both at pellet and reactor scales. These experimental results led to a better insight of the diffusion–reaction phenomena occurring during the process. Diffusion limitations were illustrated thanks to an innovative method, the analytical acquisition of carbon radial profiles on catalyst pellets, while the apprehension and quantification of competing reactivity (thermal, catalytic and oxidation) gave a better understanding of the ozonation process. Time of exposure and temperature were found to significantly affect carbon removal efficiency, while inlet ozone concentration and flowrate influence were respectively moderate and null in the investigated range. Similarly to combustion, coke ozonation is driven by a balance between diffusion and reactivity, leading to the appearance of a mix of known regeneration regimes depending on the operating conditions: homogeneous and shrinking-core.

Clarification of the phosphorus release mechanism for recovering phosphorus from biofilm sludge in alternating aerobic/anaerobic biofilm system

A novel wastewater treatment plant process was constructed to overcome the challenge of simultaneous nitrate removal and phosphorus (P) recovery. The results revealed that the P and nitrate removal efficiency rose from 39.0 % and 48.4 % to 92.8 % and 93.6 % after 136 days of operation, and the total P content in the biofilm (TPbiofilm) rose from 15.8 mg/g SS to 57.8 mg/g SS. Moreover, the increase of TPbiofilm changed the metabolic mode of denitrifying polyphosphate accumulating organisms (DPAOs), increasing the P concentration of the enriched stream to 172.5 mg/L. Furthermore, the acid/alkaline fermentation led to the rupture of the cell membrane, which released poly-phosphate and ortho-phosphate of cell/EPS in DPAOs and released metal‑phosphorus (CaP and MgP). In addition, high-throughput sequencing analysis demonstrated that the relative abundance of DPAOs involved in P storage increased, wherein the abundance of Acinetobacter and Saprospiraceae rose from 8.0 % and 4.1 % to 16.1 % and 14.0 %. What's more, the highest P recovery efficiency (98.3 ± 1.1 %) could be obtained at optimal conditions for struvite precipitation (pH = 7.56 and P: N: Mg = 1.87:3.66:1) through the response surface method (RSM) simulation, and the precipitates test analysis indicated that P recovery from biofilm sludge was potentially operable. This research was of great essentiality for exploring the recovery of P from biofilm sludge.

Recovering phosphorus and lithium separately from wastewater and brine using a novel coupled biofilm-precipitation system

Phosphorus (P) and lithium (Li) are scarce resources. To address the situation of resource scarcity, a novel coupled biofilm-precipitation system was proposed to recover P and Li separately from wastewater and brine. The results indicated the denitrifying polyphosphate accumulating organisms (DPAOs) suitable for this operating process promoted their denitrifying phosphorus removal (DPR) capabilities at the aerobic phase, increasing the total P content in the biofilm (TPbiofilm) to 60.7 ± 2.7 mg/g SS. Moreover, the DPAOs performed a metabolic shift from glycogen accumulation metabolism (GAM) to polyphosphate accumulation metabolism (PAM) when TPbiofilm increased, which caused more P being released by DPAOs, and the P concentration of the enriched stream to rise to 185.8 ± 3.4 mg/L. Furthermore, the quadratic regression model was suitable for the struvite crystallization (R2 = 0.87–0.88) in the P recovery stage, and the pure struvite was obtained with a P recovery efficiency was 96.3–97.2 %. The pure lithium carbonate crystals were created with a Li recovery efficiency was 93.3–97.2 % in the Li recovery stage. Additionally, the enriched P stream was applied to natural brine, and pure struvite and lithium carbonate crystals were produced with the P and Li recovery efficiency was 94.7 % and 93.5 %, respectively. In general, using enriched P stream as P source to separate magnesium from brine and thus recover Li was a feasible option. This study provided support for the recovery of P and Li.

Simultaneous phosphorus recovery from wastewater and sludge by a novel denitrifying phosphorus removal system

A novel process was proposed for simultaneous denitrification and phosphorus (P) recovery. The increased nitrate concentration facilitated the activity of denitrifying P removal (DPR) in P enrichment, which stimulated P uptake and storage, making P more readily accessible for release into the recirculated stream. The total P content in the biofilm (TPbiofilm) rose to 54.6 ± 3.5 mg/g SS as the nitrate concentration increased from 15.0 to 25.0 mg/L, while the P concentration of the enriched stream reached 172.5 ± 3.5 mg/L. Moreover, the abundance of denitrifying polyphosphate accumulating organisms (DPAOs) increased from 5.6% to 28.0%, and the increased nitrate concentration facilitated the process of carbon, nitrogen, and P metabolism due to the rise in the genes involved in critical functions of metabolism. Acid/alkaline fermentation analysis indicated that the EPS release was the primary P-release pathway. Additionally, pure struvite crystals were obtained from the enriched stream and fermentation supernatant.

Water distillation for coolant purification system of DEMO water-cooled lithium lead breeding blanket

During the DEMO pre-concept design phase, a review of existing and under development technologies suitable for the Coolant Purification System (CPS) of the Water-Cooled Lithium Lead (WCLL) Breeding Blanket (BB) was carried out and two tritium recovery strategies were individuated, named on-line and off-line. The on-line concept relies on the continuous by-pass and treatment of a certain primary coolant fraction into CPS whereas the off-line scheme foresees the discharge of the whole primary water inventory after one year of DEMO operation, that will be treated in an external facility inside the tritium plant. Among these, the on-line strategy has been recently recommended as the most suitable for lowering the tritium inventory within BB and Primary Heat Transfer System (PHTS). Furthermore, such solution does not need high decontamination factor since treated water is not discharged in the environment, but it is redirected again into PHTS. In such condition, Water Distillation (WD) could be a promising technology with intrinsic simplicity and safety. The present work deals with the feasibility assessment of WD for DEMO WCLL BB CPS, investigating its capability to meet water CPS duty. A parametric study has been preliminary carried out, analysing the effect of selected parameters (i.e., tritium concentration at CPS inlet, tritium concentration in the enriched stream, efficiency of anti-permeation barriers, and operative conditions) on the WD sizing and operation. Then, a preliminary reference design has been individuated and verified with a dynamic model developed in MATLAB environment. Finally, the process flow diagram of the system has been derived and a preliminary sizing of auxiliary components is provided.

Natural β-Carotene Production by Blakeslea trispora Cultivated in Spanish-Style Green Olive Processing Wastewaters.

In the current research, the potential of Spanish-style green olive processing wastewaters (lye and washing waters) exploitation toward natural β-carotene production by Blakeslea trispora was tested for the first time. Mating culture generated by the joint cultivation of the heterothallic fungal strains ATCC 14271 and 14272 in the non-sterile lye and washing waters was able to grow, achieving the phytotoxic hydroxytyrosol degradation by 57.3% and 66.8%, respectively. However, the low sugar and nitrogen content of the streams did not favor carotenogenesis. Alternatively, in the nutrient-enriched effluents, a notable quantity of β-carotene was produced, accounted for 61.2 mg/L (lye) and 64.1 mg/L (washing waters) (82–88% of total carotenoid content). Above all, enriched streams had a noteworthy stimulating effect on the β-carotene synthesis, because both the maximum β-carotene yield per volume of enriched effluents and specific β-carotene production rate were higher when compared with the respective values obtained from trials with synthetic reference medium without added effluents. Hydroxytyrosol and tyrosol showed high stability during the non-sterile process for β-carotene production by B. trispora grown in the enriched effluents. This finding strengthens the potential toward the generation of multiple high-value products, which could lower the natural β-carotene production costs.

Development of a sustainable bioprocess based on green technologies for xylitol production from corn cob

In this work, a sustainable and environmental friendly strategy for the biotechnological production of xylitol was proposed and optimized. For this purpose, corn cob was hydrothermally pretreated at high solid loadings (25%) for an efficient solubilization of xylan in hemicellulose derived compounds, xylooligosaccharides and xylose. Xylose enriched streams were obtained from the enzymatic saccharification of the whole slurry (solid and liquid fraction) resulting from the autohydrolysis pretreatment. The xylitol production in a simultaneous saccharification and fermentation (SSF) process, by the recombinant Saccharomyces cerevisiae PE-2-GRE3 strain, was optimized using different enzyme and substrate (pretreated corn cob solid) loadings by an experimental design. This study demonstrated a significant effect of substrate loading on the production process achieving a maximal concentration of 47 g/L with 6.7 % of pretreated corn cob and 24 FPU/g of enzyme loading, with partial detoxification of the hydrolysate. Furthermore, the 1.42-fold increase in xylitol titer and 1.56-fold increase in productivity achieved in a SSF using an acetic acid free-hydrolysate evidenced the negative effect of acetic acid on the yeast-based xylitol production process. The combination of these green technologies and the optimization of the proposed strategy enhanced the overall xylitol production through the valorization of corn cob.

110th Anniversary: High Performance Carbon Molecular Sieve Membrane Resistance to Aggressive Feed Stream Contaminants

Carbon molecular sieve (CMS) membranes show high performance for various critical gas pair separations with excellent scalable manufacturability. For practical applications it is important to evaluate such membranes for resistance to contaminants possibly present in feed streams related to an onboard inert gas generation system (OBIGGS) for aerospace applications. Here we report the performance of CMS membranes prepared by optimized dual temperature secondary oxygen doping (DTSOD) in the presence of aggressive contaminants, potentially in the bleed air of aircraft. Such feed can be used to eliminate the need for a separate compressor in membrane systems to create nitrogen enriched stream for fuel tank inerting, and we considered this case using simulated engine bypass air. Our CMS membranes were exposed to different humidity levels, combinations of gaseous contaminants (denoted as Class ‘A’), and ozone to study the membrane performance for O2/N2 separation with time at high temperatures. The CMS shows a r...

Practical techniques to homogenize the feed gas mixture and enhance the laser-jet interaction time in laser assisted aerodynamic separation studies.

Laser assisted aerodynamic separation not only suffers from lengthy homogenization time of the feed gas mixture but also dilution of the enriched stream when the duration of the pulsed gas jet stream far exceeds that of the emission of the pulsed laser. We report here practical techniques to overcome the former and alleviate the latter by imposing forced circulation of the feed gas prior to affecting aerodynamic separation and the rim gas during the separation process, respectively. The forced circulation of the feed gas comprising the process gas and the buffer gas resulted in drastic reduction in the time required for their thorough mixing. The recirculation of the rim gas, on the other hand, back to the pulsed nozzle through the feed vessel allowed its increased interaction with the laser beam, thereby reducing the dilution of enrichment to a certain extent.

Design and Parameter Study of Integrated Microfluidic Platform for CTC Isolation and Enquiry; A Numerical Approach.

Being the second cause of mortality across the globe, there is now a persistent effort to establish new cancer medication and therapies. Any accomplishment in treating cancers entails the existence of accurate identification systems empowering the early diagnosis. Recent studies indicate CTCs’ potential in cancer prognosis as well as therapy monitoring. The chief shortcoming with CTCs is that they are exceedingly rare cells in their clinically relevant concentration. Here, we simulated a microfluidic construct devised for immunomagnetic separation of the particles of interest from the background cells. This separation unit is integrated with a mixer subunit. The mixer is envisioned for mixing the CTC enriched stream with lysis buffer to extract the biological material of the cell. Some modification was proposed on mixing geometry improving the efficacy of the functional unit. A valuation of engaged forces was made and some forces were neglected due to their order of magnitude. The position of the magnet was also optimized by doing parametric study. For the mixer unit, the effect of applied voltage and frequency on mixing index was studied to find the optimal voltage and frequency which provides better mixing. Above-mentioned studies were done on isolated units and the effect of each functional unit on the other is not studied. As the final step, an integrated microfluidic platform composed of both functional subunits was simulated simultaneously. To ensure the independence of results from the grid, grid studies were also performed. The studies carried out on the construct reveal its potential for diagnostic application.

Integrated UF–NF–RO route for gold mining effluent treatment: From bench-scale to pilot-scale

This study focused on the performance of an UF–NF–RO integrated system treating a gold mining effluent from the pressure-oxidation stage in order to concentrate metals, and recover acid and water. Aspects such as the most suitable cross-flow velocity, cleaning procedure, and water recovery fraction were evaluated. For cross-flow velocities, a threshold value of 1.5 × 10−2 m/s was found for NF and RO stages. Besides, the system had its best performance while operating at recovery fractions of 90%, 40–50%, and 50% for UF, NF, and RO, respectively. Concentration factors of 2.0 and 2.7 were found in metals from the NF retentate and sulfuric acid from the RO retentate respectively. For cleaning purposes, hydrochloric and oxalic acid demonstrated the best cost-benefit. A long-term operation inside the mining company was assessed and the results confirmed that NF and RO association allowed for the recovery of a purified acid stream, which may be reused in the ore processing; the production of a metal enriched stream, that can be transferred to a subsequent metal recovery stage; and the generation of high quality reuse water. The total cost of the proposed route was US$ 1.137/m3 of effluent, including UF and NF concentrate neutralisation.

Lithium capturing from geothermal water by hybrid capacitive deionization

We demonstrate a novel mode for hybrid capacitive deionization, HCDI, that allows selective extraction of lithium ions from geothermal water. The HCDI cell was comprised with cathode made of lithium selective material and anode consisting of activated carbon coated with anion-exchange membrane. To confirm ion-exchange character of the process, based on ions diffusion/migration into electrodes, impedance spectroscopy and cyclic voltammetry were applied. By optimizing the process mode it was possible to obtain lithium enriched stream and remove up to 73% of lithium captured by the electrode. The process was characterized by an extremely high salt adsorption capacity of 800 mg/g and total energy consumption on the level of 0.183 Wh per 1 g of adsorbed salt.

Light Cycle Oil Upgrading to Benzene, Toluene, and Xylenes by Hydrocracking: Studies Using Model Mixtures

The regular use of light cycle oil (LCO) for diesel fuel production by hydrotreatment (HDT) procedures has been facing difficulties of complying with the currently stricter environmental regulations due to the low quality of this middle distillate with high sulfur, nitrogen, and aromatic contents. An interesting alternative is to obtain valuable petrochemicals from this feedstock. LCO presents a high percentage of diaromatic hydrocarbons (naphthalene derivatives). To facilitate the study of the effect of the experimental conditions, a review regarding the hydrogenation-hydrocracking (HYD-HCK) procedures for obtaining enriched streams containing benzene, toluene, and xylene (BTX) from model mixtures (naphthalene, methylnaphthalenes, and tetralin) is presented. In addition to the economic advantages of using a middle distillate of reduced marketability, this research work opens the door to the development of technologies for obtaining valuable chemicals such as BTX from oil sources. The focus on model mixtu...

Sub-ambient air separation via Li+ exchanged zeolite

In this study, we extend the concept of adsorptive air separation using zeolites to sub-ambient temperature conditions. Sub-ambient temperature conditions investigated in this study (210–270 K) enable larger swing capacities for solid adsorbents under significantly milder conditions than those required by cryogenic distillation systems. Experimental O2 and N2 isotherms—measured in a wide range of temperatures (150 K–300 K)—were utilized to construct multicomponent isotherms (IAST) and estimate the temperature-dependent separation performances of Li+-exchanged type X zeolite (Si/Al ratio ∼1) under synthetic air mixture (22 mol% O2 and 78 mol% of N2). As temperature decreases from ambient conditions, the IAST selectivity (N2/O2) increases. Sorption breakthrough tests at 240 K with synthetic air mixtures further validated the enhanced swing capacity and selectivity provided by sub-ambient conditions. Dual-bed vacuum pressure swing adsorption (VPSA) experiments at sub-ambient temperatures were compared to standard VPSA experiments at room temperature. The sub-ambient temperature (240 K) application of VPSA process using synthetic air mixture produced O2 with a purity over 99% and recovery over 56%, surpassing the VPSA performance at ambient temperature conditions (298 K). The separation process investigated in this study could potentially be coupled to certain cryogenic air separation units to reduce the overall energy cost of the unit by supplying O2 enriched stream into the distillation system.

Effects of Oxygen Vacancy Order–Disorder Phase Transition on Air Separation by Perovskite Sorbents

Perovskite oxide sorbents offer promise for adsorption-based separation of air to produce an oxygen enriched stream. The oxygen desorption rate however should be further improved. This work studies the oxygen sorption properties of three La1–xSrxCo1–yFeyO3-δ (LSCF) perovskite oxides with and without oxygen vacancy disorder–order phase transition. The LSCF with lower iron content [La0.1Sr0.9Co0.9Fe0.1O3-δ (LSCF1991)] shows the highest sorption capacity in 500–800 °C. The material with disorder–order phase transition during desorption also exhibits enhanced oxygen desorption rate during the TGA measurement. However, in the fixed-bed desorption process, no obvious rate enhancement resulting from the disorder–order phase transition in oxygen desorption is observed for the LSCF1991 sorbent. The LSCF1991 sample in the fixed-bed quenched at 600 °C after 2 h of desorption shows occurrence of disorder–order phase transition for the perovskite sorbent in the fixed-bed environment. The difference in oxygen desorptio...

The metabolic versatility of PAOs as an opportunity to obtain a highly P-enriched stream for further P-recovery

The effects of two sequencing batch reactor operation strategies for phosphorus stream enrichment over the biological phosphorus removal performance have been studied. The objective of both strategies is of performing an extraction cycle in order to obtain a new stream highly enriched with phosphorus. In the 1st strategy the amount of influent volatile fatty acids (VFAs) is the same in each cycle; while in the 2nd strategy the influent VFAs concentration is increased during phosphorus extraction experiments. Despite the strong decrease of the stored poly-P inside the cells in both strategies after the recovery cycles, the ability of the systems to remove phosphorus was not affected. The Prelease/HAcuptake ratio (changing from 0.73 to 0.21mmolPmmolC−1) together with FISH analyses (around 85% of Accumulibacter through the experimental period) confirmed that a shift from PAM to GAM occurred after phosphorus enrichment in the 2nd strategy experiments. These results suggest that energy required for VFA uptake by polyphosphate-accumulating organisms (PAOs) was not only derived from polyphosphates degradation, but also from glycogen degradation. FISH also revealed that Type II Accumulibacter species are responsible of the metabolic shift. The strategy based on increasing influent VFAs concentration during phosphorus extraction experiments showed a higher extraction efficiency (from 46% to 76%), as higher phosphorus concentration within supernatant can be achieved (from 113.9 to 198.7mgPl−1). Following this strategy, it is possible to concentrate up to 81% of the incoming phosphorus in a single enriched stream. This suggests that, despite the extra addition of carbon source needed (9%), this strategy is more appropriate if phosphorus recovery for reuse purposes is required.

Stream nutrient enrichment has a greater effect on coarse than on fine benthic organic matter

Nutrient enrichment affects bacteria and fungi associated with detritus, but little is known about how biota associated with different size fractions of organic matter respond to nutrients. Bacteria dominate on fine (<1 mm) and fungi dominate on coarse (>1 mm) fractions, which are used by different groups of detritivores. We measured the effect of experimental nutrient enrichment on fungal and bacterial biomass, microbial respiration, and detrital nutrient content on benthic fine particulate organic matter (FPOM) and coarse particulate organic matter (CPOM). We collected FPOM and CPOM from 1 reference and 1 enriched stream. CPOM substrates consisted of 2 litter types with differing initial C:nutrient ratios (Acer rubrum L. and Rhododendron maximum L.). Fungal and bacterial biomass, respiration, and detrital nutrient content changed with nutrient enrichment, and effects were greater on CPOM than on FPOM. Fungal biomass dominated on CPOM (∼99% total microbial biomass), whereas bacterial biomass dominated on FPOM (∼95% total microbial biomass). These contributions were unchanged by nutrient enrichment. Bacterial and fungal biomass increased more on CPOM than FPOM. Respiration increased more on CPOM (up to 300% increase) than FPOM (∼50% increase), indicating important C-loss pathways from these resources. Microbial biomass and detrital nutrient content were positively related. Greater changes in nutrient content were observed on CPOM than on FPOM, and changes in detrital C:P were greater than changes in detrital C:N. Threshold elemental ratios analyses indicated that enrichment may reduce P limitation for shredders and exacerbate C limitation for collector-gatherers. Changes in CPOM-dominated pathways are critical in predicting shifts in detrital resource quality and C flow that may result from nutrient enrichment of detritus-based systems.