Effect Of Hydrodynamic Conditions Research Articles

Optimization of photocatalytic ceramic membrane filtration by response surface methodology: Effects of hydrodynamic conditions on organic fouling and removal efficiency

The effects of the operating conditions, including the applied pressure, feed organic concentration, and recirculation flowrate along the TiO2-coated ceramic membrane, on the normalized membrane permeability and organic removal efficiency were systematically investigated by operating a photocatalytic membrane reactor (PMR). Response surface methodology (RSM) was conducted to better understand the interactive effect of operational conditions as well as their individual and combined effects to control membrane performance. Our results showed that the applied pressure and feed organic concentration, as single parameter, affected the normalized membrane permeability and organic removal efficiency more dominantly than the recirculation flowrate. The polynomial performance equations generated by RSM successfully predicted the membrane performance of the PMR. The responses to the normalized membrane permeability and organic removal efficiency with respect to the operational conditions were less sensitive to any combination of operational conditions than to their individual impacts. The combined effects of the operating conditions were less pronounced in promoting the catalytic performance of organic contaminants on the TiO2 surface. Our RSM analysis based on experimental observations designed by Box–Behnken Design (BBD) suggested that 1.3 bar of applied pressure, 44 mg/L of feed organic dye concentration and 0.8 L/min as recirculation flowrate as optimum conditions achieved more than 98% of organic removal efficiency and less than 5% of decline in normalized membrane permeability. This research shows that the RSM provides effective tool to optimize operational conditions to determine fouling rate and organic removal in PMR.

Effects of transient flow conditions on colloid-facilitated release of decabromodiphenyl ether: Implications for contaminant mobility at e-waste recycling sites

Polybrominated diphenyl ethers (PBDEs) are ubiquitous contaminants, especially in the soil and groundwater of contaminated sites and landfills. Notably, 2,2′,3,3′,4,4′,5,5′,6,6′-decabromodiphenyl ether (BDE-209), one of the most frequently and abundantly detected PBDE congeners in the environment, has recently been designated as a new pollutant subject to rigorous control in China. Colloid-facilitated transport is a key mechanism for the release of PBDEs from surface soils and their migration in the aquifer, but the effects of hydrodynamic conditions, particularly transient flow, on colloid-facilitated release of PBDEs are not well understood. Herein, we examined the effects of typical transient flow conditions on the release characteristics of colloids and BDE-209 from surface soil collected from an e-waste recycling site by undisturbed soil core leaching tests involving multiple dry–wet cycles (with different drying durations) and freeze–thaw cycles. We observed significant positive correlations between BDE-209 and colloid concentrations in the leachate in both the dry–wet and freeze–thaw leaching experiments, highlighting the critical role of colloids in facilitating BDE-209 release. However, colloids mobilized during the dry–wet cycles contained higher contents of BDE-209 than those in the freeze–thaw cycle tests, and the difference was primarily due to the more intensive disintegration of soil aggregates and elution of newly formed inorganic colloidal particles (mainly primary silicate minerals such as quartz and albite) with low BDE-209 content during the freeze–thaw process. These findings underscore the necessity of considering transient flow conditions when assessing the fate and risks of PBDEs at contaminated sites.

Effects of Hydrodynamic Conditions on Algal Organism Growth

Effects of Hydrodynamic Conditions on Algal Organism Growth

Effect of Hydrodynamic Conditions During Coking on the Structure of the Resulting Coke

Effect of Hydrodynamic Conditions During Coking on the Structure of the Resulting Coke

Improved eutrophication model with flow velocity-influence function and application for algal bloom control in a reservoir in East China

Improving hydrodynamic conditions is considered an effective method for facilitating the eutrophication management. However, the effect of hydrodynamic conditions on algal growth has rarely been quantified. In this work, a eutrophication model was developed and flow velocity was introduced into the algae growth kinetic formula to simulate the dynamics of algae growth in a drinking water source reservoir in East China. Based on the previous research and model calibration, the flow velocity-influence function f(v) and its parameters were determined. Accordingly, the optimal flow velocity for the dominant algae growth and critical flow velocity for algal growth inhibition were presented to be 0.055 m/s and 0.200 m/s for the study reservoir. Modeled results considering f(v) agreed with better with observations and reproduced the algal overgrowth process more accurately. The spatial-temporal differences in chlorophyll a (Chl a) concentration distribution during the algal proliferation period were analyzed on the basis of simulation results, which corroborated the significant influence of flow velocity on algal growth. The established model was applied to investigate the effect of improvement in hydrodynamic conditions on algal bloom control in the reservoir, and the scenario simulation of the additional sluice was conducted. Results showed that the additional sluice operation inhibited algal overgrowth effectively, resulting in an average decrease of 24.8%, 3.3%, 43.0%, and 37.5% in modeled Chl a concentration upstream north, upstream south, midstream and downstream, respectively. The established model might serve as a practical tool for eutrophication management in the study reservoir and other water bodies with similar hydrological characteristics and geographical features.

Experimental study on the effect of hydrodynamic conditions on flocculation and settling properties of fine-grain sediment

The flocculation of cohesive sediment particles is a function of the collision efficiency of sediment particles, which is mainly influenced by local flow hydrodynamics. A detailed study on local hydrodynamic characteristics in a novel stirred tank was done to measure the flow field of a turbulent flow. Instantaneous flow velocity fields were obtained and processed, and the average flow field was computed. Particle image velocimetry (PIV) results measuring the hydrodynamic characteristics (expressed as turbulent kinetic energy (TKE), local dissipation rate of TKE, velocity gradient or shear rate, turbulent shear stress, etc.) were analyzed and discussed. Particle tracking and automated image processing techniques were utilized to analyze the impact of the hydrodynamic conditions on the floc and settling properties. The differences in floc properties under the two turbulent shear states (i.e., steady-state (SS) and unsteady-state (US)) hydrodynamic conditions were examined. The results show that floc size and floc size distribution (FSD) of pure kaolin clay flocs are significantly influenced by the local dissipation rate of TKE and the turbulent intensity states. The floc size, df, 84, at local dissipation rate of TKE of 11 × 10−4, 29 × 10−4, 44 × 10−4, 83 × 10−4, and 142 × 10−4 m2/s3 is 97, 108, 107, 124, and 150 μm, respectively. It was found that by increasing the local dissipation rate of TKE, the FSD was skewed left. The US shear condition generated larger flocs (and in higher proportions) relative to the SS condition. The settling velocity and flux settling velocities of flocs formed under SS conditions are higher than those formed under US conditions. The fractal dimension of SS flocs also is higher than the fractal dimension of US flocs. These results highlight a significant impact of the states of hydrodynamics on floc properties such as floc size and FSD as well as the settling and morphological properties of flocs.

Kinetic modeling of xylonic acid production by Gluconobacter oxydans: effects of hydrodynamic conditions

In this study, the synthesis of xylonic acid from xylose by Gluconobacter oxydans NL71 has been investigated. According to the relationship between oxygen transfer rate and oxygen uptake rate, three different kinetic models of product formation were established and the nonlinear fitting was carried out. The results showed that G. oxydans has critical dissolved oxygen under different strain concentrations, and the relationship between respiration intensity and dissolved oxygen conformed to the Monod equation [Formula: see text]. The maximum reaction rate per unit cell mass and the theoretical maximum specific productivity of G. oxydans obtained by the kinetic model are 0.042mol/L/h and 6.97g/gx/h, respectively. These results will assist in determining the best balance between the airflow rate and cell concentration in the reaction and improve the production efficiency of xylonic acid.

Effects of Mud Supply and Hydrodynamic Conditions on the Sedimentary Distribution of Estuaries: Insights from Sediment Dynamic Numerical Simulation

Estuaries are important sediment facies in the fluvial-to-marine transition zone, are strongly controlled by dynamic interactions of tides, waves, and fluvial flows, and show various changes in depositional processes and sediment distribution. Deep investigations on the sediment dynamic processes of the sand component of estuaries have been conducted; however, the understanding of how mud supply affects estuaries’ sedimentary characteristics and morphology is still in vague. Herein, the effects of mud concentration, mud transport properties, fluvial discharge, and tidal amplitude on the sedimentary characteristics of an estuary were systematically analyzed using sedimentary dynamic numerical simulation. The results show that the mud concentration has significant effects on the morphology of tidal channels in estuaries, which become more braided with a lower mud concentration, and straighter, with reduced channel migration, with a higher mud concentration. The mud transport properties, namely, setting velocity, critical bed shear stress for sedimentation, and erosion, mostly affect the ratio between the length and width (RLW) of the sand bar; a sheet-like sand bar with a lower RLW value develops in the lower settling velocity, while there are obvious strip shaped bars with a high RLW value in the higher settling velocity case. Moreover, the effects of hydrodynamic conditions on sedimentary distribution were analyzed by changing the tidal amplitudes and fluvial discharges. The results show that a higher tidal amplitude is often accompanied by a stronger tidal energy, which induces a more obvious seaward progradation, while a higher fluvial discharge usually yields a higher deposition rate and yields a greater deposition thickness. From the above numerical simulations, the statistical characteristics of tidal bars and mud interlayers were further obtained, which show good agreement with modern sedimentary characteristics. This study suggests that sedimentary dynamic numerical simulation can provide insights into an efficient quantitative method for analyzing the effects of mud components on the sediment processes of estuaries.

Effects of hydrodynamic conditions on the composition, spatiotemporal distribution of different extracellular polymeric substances and the architecture of biofilms

Microbial biofilms are common on abiotic and biotic surfaces, especially in rivers, which drive crucial ecosystem processes. The microorganisms of biofilms are surrounded by a self-produced extracellular polymeric substance (EPS). In this study, we investigated the effects of different hydrodynamic conditions on the composition, spatiotemporal distribution of different extracellular polymeric substances, and the architecture of biofilms. Multidisciplinary methods offer complementary insights into complex architecture correlations in biofilms. The biofilms formed in turbulent flow with high shear force were thin but dense. However, the biofilms formed under laminar flow conditions were thick but relatively loose. The thickness and compactness of the biofilms formed in the transitional flow were different from those of the other biofilms. The compact structure of the biofilm helped to resist shear forces to minimize detachment. Under the turbulent flow condition, bacteria, exopolysaccharides, and extracellular proteins permeated through the biofilm, and more extracellular polysaccharides enveloped bacteria and extracellular proteins. However, under the transitional flow condition, the extracellular polysaccharides and proteins were fewer than those under the turbulent flow condition; bacteria and algae were seen more prominently in the upper layer of the biofilm. Under the laminar flow condition, the distribution of extracellular polysaccharides, extracellular proteins, and bacteria was relatively uniform throughout the biofilm. The number of extracellular polysaccharides was greater than that of extracellular proteins. The total number of EPS in the biofilm was the largest under turbulent flow condition, followed by that under transitional flow condition and then under laminar flow condition. This study also observed that soluble EPS (S-EPS) were secreted first, followed by loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS). In particular, the adhesion of LB-EPS and flocculation capability of TB-EPS play some role in regulating biofilm formation. This study would help to perfect the five-stages theory of biofilm formation.

Effect of hydrodynamic conditions on seagrass ecosystems during Cyclone Lehar in the South Andaman Islands, India

The physical disturbances of hydrodynamic conditions in shaping the seagrass meadows were studied in the vicinity of seagrass meadows over the south of Port Blair in the Andaman and Nicobar Islands (ANI) during the lifetime of Cyclone Lehar using spatial and temporal metrological - oceanic parameters and in-situ measurements. A cyclonic depression formed on 23 November 2013 over the west coast of the Malay Peninsula and then transformed into a severe cyclone named Lehar on 25th November 2013. It made its first landfall south of Port Blair in the ANI and caused extensive damage to life and properties. The present study made an attempt to investigate the hydrodynamic condition and their impact on the seagrass meadows during the lifetime of the cyclone. The results revealed that the floristic composition of seagrass species such as Thalassia hemperichii, Halodule pinnifolia and Halodule uninervis was badly damaged due to the effect of the high gradient of velocities in the vertical direction, turbulence, high energetic waves, and storm surge. Approximately 32.4% of the seagrass meadows were uprooted in Haddo Bay and 68% in Sesostris Bay of the South Andaman Islands. A year after the cyclone passage (December 2014), 13% (∼0.70 ha) of the seagrass meadow in Haddo Bay and 44.5% (∼0.30 ha) of the seagrass in Sesostris Bay had recovered. This study emphasises that the morphometric features of the most dominant species, T. hemperichii, were regulated by the physical hydrodynamic mechanisms and led to substantial destruction in the study sites. This study is very useful to understand the impact of hydrodynamic conditions on seagrass ecosystems during a cyclone and brings attention to the real-time monitoring of seagrass ecosystems. Monitoring of the seagrass ecosystem can be further improved by predicting the behavioural dynamics of the marine ecosystem under the various scenarios of extreme weather conditions using high-resolution numerical models. It also helps to determine the appropriate management policy during extreme natural events.

Effect of hydrodynamic condition on algae control based on montmorillonite modified lime-ceramic sand-lake sediments

Abstract Montmorillonite modified lime-ceramic sand-lake sediment (LC-sediments) was synthesized and its algae removal efficiency was investigated in this study. Montmorillonite not only improved the morphology and surface area of original LC-sediments, but also promoted the algal removal rate due to its inherent properties such as accumulating an electric charge, acting as a flocculant, and displaying a local bridging effect. Based on parameter optimization including the ratio of raw materials, agent dosage, initial algae density, pH and a determination of overlying water, the effect of hydrodynamic conditions on the algal removal process was researched. Under the optimal condition, the removal rates of turbidity, algae density and chlorophyll a could reach 86, 88 and 68%, respectively. As verified with a response surface model, it was shown that low disturbance (stirring) of the algae could promote algal removal by montmorillonite modified LC-sediment. Furthermore, a water column was utilized to approximatively simulate the flocculation and algae control in shallow lakes. This study solved the problem of reducing the dosage of lake sediment and improving the removal efficiency of algae without causing secondary pollution to the environment. It was expected to provide a certain theoretical basis for clay flocculation-based algae control in a real environment.

Effect of Hydrodynamic Conditions on Micromixing in Impinging-Jets Microreactors

Effect of Hydrodynamic Conditions on Micromixing in Impinging-Jets Microreactors

Production of Urea/Acetylated-lignin Sulfonate Matrix as SRFs and an Investigation on the Effect of Hydrodynamic Conditions on Release Rate Using the Biot Number

Background: This study aimed to investigate the effect of hydrodynamic conditions on the release rate of urea/acetylated lignin sulfonate (Ac-LS) matrix as slow-release fertilizers (SRFs). Therefore, two models were developed using the mass transfer balance for the determination of finite/infinite volume of fluids and solving finite integral transformation/separation of a variable. The Biot number, validating the hydrodynamic condition, was found in these models. Methods: In this study, the urea/Ac-LS matrix fertilizer was prepared. The morphological, thermal, chemical, and mechanical properties of the LS, Ac-LS, urea, and urea/Ac-LS matrix were analyzed using Fe-SEM, TGA, XRD, and SANTAM. Finally, the nitrogen release of the matrix fertilizer was investigated at 25°C for different impeller speeds. The models were also validated using the experimental data. Results: The results showed that the thermal and mechanical resistance of urea/Ac-LS due to strong interaction increased compared to pure urea or Ac-LS. The results further showed that the external resistance on the mass transfer decreased as the impeller speed increased, and the nitrogen release rate increased as the Biot number increased in both the states, i.e., finite and infinite. Conclusion: It was also observed that the release rate in the finite environment was less than that of the infinite one in the given hydrodynamic condition initially; however, the type of environment did not affect the release rate after a while.

Исследование подвижности дисперсных гелей полимерно-гелевой системы "Темпоскрин"

The article describes the method of optical-electronic observation of the process of sedimentation of gel particles in the polymer-gel system. The analysis of hydrodynamic movement of gel particles in laminar and turbulent modes during the implementation of the Temposcreen technology in oil production is carried out. The effect of hydrodynamic conditions on the mobility of the polymer-gel system in well and reservoir conditions, as well as on the distribution of the dispersal gel phase in the reservoir, is considered. On the basis of the graph theory, the model of fluid flow management in the oil layer by the Temposcreen mobile polymer-gel system is presented.

Effect of hydrodynamic conditions on the formation and structure of aerobic granular sludge performing enhanced biological phosphorus removal

AbstractThe study investigated the effect of hydrodynamic conditions on the formation of enhanced biological phosphorus removal (EBPR) granular sludge without losing the EBPR capacity, and its structure. The effect of hydrodynamic conditions on the formation of EBPR granular sludge was evaluated by using the minimum settling velocity, (Vs)min, and superficial air velocity. The application of (Vs)min strategy was proved to be beneficial in maintaining granular biomass without losing the EBPR capacity. Microscale structure, the chemical composition and chemically stored phosphorus of the matured EBPR granular sludge were determined by using ESEM‐EDX and cold perchloric acid (PCA) analyses. The results of both the ESEM‐EDX and PCA analyses proved that the poly‐P granules were stored extracellular in EPS structure of EBPR granular sludge. Therefore, the EBPR granular sludge has a high potential for both removal and recovery of phosphorus from wastewater, which needs to be investigated in future studies.

Characteristics of adsorption kinetics and isotherms of Cu(II) by sediment under different hydrodynamic of the Ganjiang river, China

Abstract Discharges from industrial and agricultural processes into water bodies can result in the accumulation of heavy metals such as Cu(II) in the sediment via various physical and chemical interactions. While there are many studies of the adsorption of heavy metals by sediment, few have considered the effects of hydrodynamic conditions. Here, the adsorption of Cu(II) by sediments under different hydrodynamic conditions was studied using a particle entrainment simulator. The sediment samples were obtained from the Poyang Lake basin in China. Models describing pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion kinetics and the Langmuir, Freundlich, Temkin and Dubin Radushkevich adsorption isotherms were used to evaluate the adsorption of Cu(II) by the sediments under different hydrodynamic conditions. The results showed that adsorption equilibrium for Cu(II) by the sediment was attained within 4 hours and increased with increasing shear stress; the kinetics were consistent with pseudo-second-order and Elovich models, indicating that chemical processes were involved in adsorption; the adsorption isotherms could be described by the Langmuir and Freundlich models. Changes in the sediment shear stress had little effect on the maximum adsorption capacity and values ranged from 0.9425 to 1.0634 mg/g. The results indicated that the adsorption sites for Cu(II) in soil were heterogeneous.

Effect of hydrodynamic conditions on the water quality in urban landscape water

Abstract In this study, a 2D hydrodynamic and water quality model was built based on MIKE 21 to investigate the relationship between hydrodynamic condition and water quality, and then applied in an urban landscape lake in Tianjin, China. Moreover, an engineering experiment was carried out to confirm the comprehensive degradation coefficients of chemical oxygen demand (COD), total phosphorus (TP), nitrogen ammonia (NH4+-N), and total nitrogen (TN) (0.014 d−1, 0.024 d−1, 0.019 d−1, and 0.005 d−1, respective). Circulation system was the main force that expedited water changes and pollutant movement, increased the lake average water speed from 0.003 m/s to 0.008 m/s, and could effectively reduce the COD, NH4+-N and TN concentration nearly by 35, 32, and 5%. The high concentrations nitrogen and phosphorus in the reclaimed water would accelerate the deterioration of water quality, and the concentrations of TP, NH4+-N, and TN in the lake increased from 0.080 mg/L, 0.53 mg/L, and 1.53 mg/L to 0.090–0.096 mg/L, 0.71–0.81 mg/L, and 1.89–2.08 mg/L, respectively. The circulation system could slow the water quality deterioration but cannot eliminate the eutrophication risk. Improving the hydrodynamic conditions was proposed for enhancing water quality in urban landscape lakes.

The Effect of Hydrodynamic Conditions on the Selective Flotation of Fully Liberated Low Grade Copper-Nickel Ore

Low grade sulfide ores are difficult to process due to their composite mineralogy and their fine grained dissemination with gangue minerals. Therefore, fine grinding of such ores becomes essential to liberate valuable minerals. In this research, selective flotation was carried out using two pitched blade turbine impellers with diameters of 6 cm and 7 cm to float copper and nickel. The main focus of this research was to generate optimum hydrodynamic conditions that can effectively separate nickel and copper from gangue minerals. In addition, we investigated the effects of superficial gas velocity, impeller speed, bubble size distribution, and bubble surface area flux on the flotation recovery and rate constant. The results demonstrated that a 7 cm impeller comparatively produced optimum hydrodynamic conditions that improved Cu-Ni recovery and the rate constant. The maximum copper and nickel recoveries in the 7 cm impeller tests were observed at 93.1% and 72.5%, respectively. However, a significant decrease in the flotation rate of nickel was observed, due to entrainment of nickel in copper concentrate and the slime coating of gangue minerals on the nickel particle surfaces.

Effect of Hydrodynamic Conditions in an Impinging-Jet Microreactor on the Formation of Nanoparticles Based on Complex Oxides

The effect of the hydrodynamic situation (mainly conditions of mixing of the solutions of the reagents) on the composition and sizes of the nanoparticles being formed in an impinging-jet microreactor (IJMR) upon the impinging of the jets of the reagents—aqueous solutions of lanthanum nitrate and ammonium dihydrogen phosphate—is studied. Unique conditions are generated in the IJMR providing a short-term contact of the jets of the solutions that move at a high velocity (of about 10–20 m/s). The characteristics of turbulence in the IJMR are calculated. It is shown that the rate of dissipation of turbulent kinetic energy in the zone of impinging of the jets may reach 107–109 W/kg, which is comparable to the level of dissipation of energy in ultrasonic baths and is several orders of magnitude higher when compared to almost any other type of reactor. The effect of the region that has a size of the minimum Kolmogorov turbulence scale, i.e., a self-organizing “nanoreactor,” on the size of the particles being formed upon the deposition of particles with a complex composition is determined. Comparing the results of the calculation with the experimental data shows that, in some cases, the volume of the nanoreactor, taking into account the concentration of the solutions, determines the weight and size of the particles being formed. An explanation for the effect of a different influence of the velocity of impingement of the jets on the size of the nanoparticles being formed during the microreactor mixing of the reagents, depending on the characteristic features of the mechanisms of chemical reactions under the conditions of “soft” chemistry, is provided.

Efecto de antiincrustantes y variables de operación en la eficiencia de desalinización por destilación por membranas por contacto directo (DMCD)

The effect of hydrodynamic conditions (feed and permeate flow rates) and the action of six different types of antiscalants on desalination of seawater from the Gulf of Mexico by direct contact membrane distillation (DCMD) was studied. The effect of feed temperature during the DCMD process was also evaluated on performance of two microfiltration membranes (0.5 µm) having different thickness (300 and 250 µm). Results showed more than 100 % increments on water vapor flux by raising feed temperature from 50 to 70 oC and feed flow rates up to 7 L·min-1. No significant effect on process performance was determined by raising permeate flow rates in the range tested. Choosing the type and concentration of antiscalants is critical during seawater desalination by DCMD. Performance of this process increased by up to 49.2 % during desalination of real seawater by adding the KMRO S-516 antiscalant designed to disperse iron, silica and calcium carbonate salts. During DCMD no important water vapor flux decay and no increase on conductivity of the distillate was observed by antiscalants’ dosage. In addition, scanning electron microscopy (SEM) from the membrane surface after DCMD desalination of seawater treated with the KMRO S-516 antiscalant confirmed the absence of scaling.