Continuous Water Flow Research Articles

Can Microcavitated Slippery Surfaces Outperform Micropillared and Untextured?

Surface features' morphology is crucial in designing lubricant-infused slippery surfaces (LIS). Microcavities were hypothesized to provide lower physical pinning, reduced droplet normal adhesion, and superior lubricant retention as compared to micropillars and untextured surfaces. Micropillars and microcavities (h = 10 ± 3 μm, d = 8 ± 1 μm, p = 17 ± 3 μm, rw = 1.4 ± 0.2) were replicated on polydimethylsiloxane from Lotus leaf and were coated with 1000 cSt silicone oil films (530 nm-27 μm thick). Water wetting, water-oil thermodynamic stability, droplet's normal adhesion and oil shear drainage properties were investigated to evaluate the relative performance of microcavitated, micropillared and untextured LIS. For ≤7 μm thick oil films, cavitated and untextured LIS displayed superior slippery properties than micropillared LIS (16 ± 1°, 7 ± 1°, 30 ± 4° slide-off angles respectively). Also, normal adhesion is of the order: cavities < untextured < pillars, and smaller than their dry counterparts. Furthermore, the oil retention efficiency under the action of centrifugal forces and continuous shear flow of water is of the order: pillars > cavities > untextured. Thus, it can be concluded that microcavitated LIS can outperform micropillared and untextured LIS.

Processable CMP aerogel with Ag nanocatalysts for the treatment of combined pollutant containing p-NP&MO in continuous flow

It is challenging to produce soft polymer materials with high surface area and nanoscale morphology that can be used for continuous flow water treatment in a processable, versatile, and stable manner. Here, we manufactured a processable Ag@CMPA-bph and used it to treat pollutants in wastewater at continuous flow conditions. The aerogel was prepared by a simple reduction method of CMP matrix and Ag metal precursors. Thermogravimetric analysis and electron microscopy showed that the aerogel had excellent thermal stability and distribution of fine Ag nanoparticles. The synthesized aerogel inherits the controllable properties of the CMP matrix and can be tailored to a specific shape for installation into the water treatment unit. In continuous flow conditions, this aerogel shows excellent catalytic activity to efficiently treat the combined pollutant containing p-nitrophenol and methyl orange (p-NP&MO), which can reach a removal rate of more than 99 % at the flow rate of 0.6 L h-1. Furthermore, the Ag@CMPA-bph can also be used for continuous flow treatment of pollutants in river water sample and shows robust anti-pollution load capacity and catalytic activity.

Supplemented prebiotics in the feeding of Arapaima gigas juveniles raised in water-boxes with continuous mechanical aeration and water-boxes flow

The study aimed to evaluate the effect on zootechnical performance and survival of pirarucu juveniles (Arapaima gigas) submitted to prebiotic supplementation in their diet. Were 120 juveniles of A. gigas acquired, acclimated in water-boxes with continuous aeration and water flow, and fed ad libitum four times a day, with a diet containing 55% crude protein. The 25.5 ± 3.5 g fish were distributed in 12 water-boxes of 500L (3 water-boxes/treatment and 10 fish/water-box). Juveniles were subjected to control (without prebiotics) and also subjected to three treatments A, B and C. The parasites found were observed under optical and scanning electron microscopy (SEM). Fish were distributed in completely randomized design water-boxes. The data obtained were evaluated by the Shapiro-Wilk and Bartlett’s tests (α=0.05). Then, they were submitted to ANOVA, and contrasted by the Tukey’s test (α=0.05). While the treatments were contrasted with each other by Dunn's test (α=0.05). The water quality parameters were kept adequate for A. gigas cultivation. In treatments, zootechnical performance and survival rate differed from each other, and were better than the control (p&lt;0.05). Treatment A expressed the highest final weight 77.32 ± 10.23g (p&lt;0.05), and the control had the lowest final weight 20.08 ± 6.64g. The average weight gain was different between treatments (p&lt;0.05), which presented better results than the control (p&lt;0.05). Treatments A and C expressed the highest mean weight gain 49.90 ± 8.95 and 54.17 ± 4.12 g (p&lt;0.05), respectively. The final biomass was different between treatments, which showed better results than the control group (p&lt;0.05). Survival rate was not different between treatments (p&gt;0.05). However, the control presented the lowest rate of 13.33%, due to trichodinid infestation. Supplemented prebiotics were beneficial for weight gain, final biomass, apparent feed conversion and survival of pirarucu juveniles.

Fibrous Solar Evaporator with Tunable Water Flow for Efficient, Self‐Operating, and Sustainable Hydroelectricity Generation

AbstractConvenient and green hydroelectricity generation (HG) systems are widely studied to cope with the energy crisis. Electricity can be generated through streaming potential with merely water droplets. Nevertheless, the operational requirement of persistent water supply restricts the durability and practicality of HG. Solar‐driven steam generation with continuous and sufficient water flow has become a promising integration way to enhance HG sustainability. However, most evaporation‐accelerated hydroelectricity generators are threatened by excessive wetting decay and ionic erosion damage, which significantly impair charge accumulation and operational durability. To address this issue, a carbon black/polypyrrole decorated Tencel framework (CPF) with tunable water flow is fabricated through twisting and braiding technology. The modified water flow rate, height, and content ensure rapid ion migration, appropriate wetting boundary, and sufficient brine circulation, respectively. The aqueous flow and ion strength are optimized through the evaporation‐accelerated and desalination‐integrated HG. Hence, the CPF evaporator shows an efficient, self‐operating, and sustainable output of 0.73 V, 0.6 µA, and 2.38 kg m−2 h−1 in 3.5 wt.% brine under 1 sun radiation without salt deposition. The scalable, prolonged, and adaptable outdoor operation throughout the daytime ensures the clean production of electricity and freshwater.

Nonchemical Aquatic Weed Control Methods: Exploring the Efficacy of UV-C Radiation as a Novel Weed Control Tool.

Aquatic weeds, including invasive species, are a worldwide problem. The presence of aquatic weeds poses several critical issues, such as hindering the continuous flow of water in irrigation channels and preventing the proper distribution of adequate water quantities. Therefore, effective control measures are vital for agriculture and numerous downstream industries. Numerous methods for controlling aquatic weeds have emerged over time, with herbicide application being a widely used established method of weed management, although it imposes significant environmental risks. Therefore, it is important to explore nonchemical alternative methods to control existing and emerging aquatic weeds, potentially posing fewer environmental hazards compared with conventional chemical methods. In this review, we focus on nonchemical methods, encompassing mechanical, physical, biological, and other alternative approaches. We primarily evaluated the different nonchemical control methods discussed in this review based on two main criteria: (1) efficiency in alleviating aquatic weed problems in location-specified scenarios and (2) impacts on the environment, as well as potential health and safety risks. We compared the nonchemical treatments with the UV-C-radiation-mediated aquatic weed control method, which is considered a potential novel technique. Since there is limited published literature available on the application of UV-C radiation used exclusively for aquatic weed control, our review is based on previous reports of UV-C radiation used to successfully control terrestrial weeds and algal populations. In order to compare the mechanisms involved with nonchemical weed control methods, we reviewed respective pathways leading to plant cell death, plant growth inhibition, and diminishing reemergence to justify the potential use of UV-C treatment in aquatic habitats as a viable novel source for aquatic weed control.

Growth performance and intestinal histology of juvenile pirarucu fed with increasing levels of soybean meal

The aim of this study was to evaluate the inclusion of different levels of soybean meal in pirarucu’s diet. 200 pirarucu juveniles (152.15 ± 0.8 g) were distributed in 20 polyethylene tanks with a continuous water flow system. A completely randomized experimental design was used, with five treatments (n = 4) containing 0, 10, 20, 30 and 40% of soybean meal inclusion levels. Growth performance was measured as specific growth rate, feed conversion, weight gain and survival. Body composition, protein retention rate and histopathological changes in the intestine were analyzed. The different treatments did not affect weight gain, specific growth rate and survival. The body composition of the fish was affected by treatments for ash and ether extract and the IHS was also affected. The diet with 40% soybean meal compromised feed conversion rate. Additionally, the distal intestine of fish fed with the same diet showed a reduction in the height of mucosal folds and a loss of supranuclear vacuolation in enterocytes. Based on these results, the inclusion of up to 30% of soybean meal in the diet of juvenile pirarucu is possible without negative effects on performance and enteric morphology.

Biofloc technology in aquaculture: Advantages and disadvantages from social and applicability perspectives – a review

Abstract The world aquaculture industry seeks sustainable production strategies to respond to the needs of the growing world population for valuable food. Biofloc technology (BFT) is accepted as a novel sustainable method that reduces the pollution load on receiving water resources with its zero-water-discharge approach, eliminates extra water treatment costs with its biological cycles, and supports the growth performance of reared animals and thereby reduces feed costs. However, each BFT system has its own set of difficulties and obstacles. This review focuses on the advantages and disadvantages of BFT systems in terms of economy, sociability and applicability. The BFT shows more effective results in the conversion of toxic nitrogenous compounds to nontoxic compounds compared with the technologies based on nitrification processes. In addition, the growth performance and health of the cultured animals are generally better in BFT systems than those in conventional rearing systems (continuous water flow). The risk of common diseases occurrence due to pathogenic microorganisms appears to be lower in BFT systems compared to conventional aquaculture. It is also noteworthy that the immune system, biochemical stress indicators and antioxidant activities of organisms held in BFT systems are positively affected. In BFT systems based on microbial activity, the high water temperature demanded by bacteria is a limiter for the system. Moreover, a higher aeration/energy requirement is the case in BFT to meet the oxygen demand of all organisms including fish, shrimp, heterotrophic bacteria, nematodes, rotifers and others inside. There is also another concern about the acceptability potential of the cultured organism in BFT systems for consumption. Finally, since the high temperature demand of the system will create high energy costs, it should be considered as another restriction that forces the application. Considering the advantages and disadvantages of BFT systems as sustainable aquaculture, this review provides a guide for future studies and full-scale implementations.

A review of Enhancing Abrasion Resistance of Dry Geopolymer Ramie Fiber Composite Mortar in Hydraulic Structures

Hydraulic structures, such as dams, spillways, and tunnels, suffer from severe abrasion and erosion due to the continuous flow of water and particles carried away. Such damage will result in expensive operating and maintenance of hydraulic structures. The purpose of this review is to discuss various abrasion testing methods as well as various efforts enhancing abrasion resistance, such as adding silica fume, and fibers, improving quality, and using geopolymers. In conclusion, the development of dry geopolymer methods offers great potential for use because they are more practical than wet geopolymer systems, however, the brittle nature of geopolymers is a weak point, which can be addressed by adding composite materials, such as ramie fiber. With the expectation that the matrix of composite geopolymer mortar with ramie fiber will have good abrasion resistance. Further research and development are needed to address existing challenges and establish this innovative construction material as a viable solution for sustainable hydraulic applications.

Enhancing the Antibacterial Effect of Erythrosine-Mediated Photodynamic Therapy with Ethylenediamine Tetraacetic Acid

This study evaluated the additive impact of ethylenediamine tetraacetic acid (EDTA) on erythrosine-mediated photodynamic therapy (PDT) against &lt;i&gt;Streptococcus mutans&lt;/i&gt; (&lt;i&gt;S. mutans&lt;/i&gt;) biofilm by measuring colony-forming units and applying confocal laser scanning microscopy. Fifty-six bovine incisors, free from dental caries or structural defects, were utilized in this study. Dentin specimens were created by cutting with a low-speed diamond disk under a continuous flow of water, resulting in dimensions of 6.0 mm × 3.0 mm × 2.0 mm. The specimens were categorized into 4 groups: Control, EDTA, PDT, and EDTA + PDT. &lt;i&gt;S. mutans&lt;/i&gt; ATCC 25175 was employed to establish biofilm on the dentin specimens. A 17% EDTA solution was applied for 1 min. For PDT, erythrosine served as the photosensitizer. Finally, a light-emitting diode source (385 - 515 nm) was employed in this study. The PDT group exhibited a significantly lower bacterial count than both the control and EDTA groups (&lt;i&gt;p&lt;/i&gt; &lt; 0.001). The EDTA + PDT group demonstrated a significantly reduced bacterial count compared to the other 3 groups (&lt;i&gt;p&lt;/i&gt; &lt; 0.001). This study demonstrated that EDTA enhances the antimicrobial efficacy of PDT on S. mutans biofilm. Even at a low concentration of photosensitizer, the combination of EDTA and PDT yields a significant antibacterial effect.

Start-up of biofilter for nitrification and effect of filtration rate on the ammonium removal efficiency in drinking water treatment on pilot plant

ABSTRACT Biological filtration is a process that can be used for ammonium removal from water. The removal of ammonium is based on the nitrification process. Nitrification depends on many factors, such as water quality and filtration process parameters. To investigate the influence of filtration rate on the nitrification efficiency, nitrifying biofilters were formed at the pilot plant in the industry for drinking water production from surface water. The new biological filters were started under optimal conditions for biofilm formation. After the biofilm formation, the influence of the filtration rate on nitrification was examined over 3 months (from November to January). The time required for the spontaneous growth of nitrifying bacteria on the new filters was around 70 days. The operating conditions at the start-up period were the continuous flow of water containing γ(NH4+) ≈ 1mg/L, dissolved oxygen in a concentration &amp;gt;9 mg/L, filtration rate &amp;lt;1 m/h, inlet water temperature &amp;gt;12 °C and pH from 7.8 to 8. After the complete formation of the nitrifying biofilm, the percentage of NH4+ removal was greater than 95% for all tested filtration rates, from 0.5 to 8.4 m/h, at γ(NH4+) from 1 to 2.5 mg/L and raw water temperature from 13 to 7°C.

Evaluation of Growth Parameters in Post Larvae Catfish in Relation to Feed Types

The aim of this research is to evaluate growth parameters in post larvae catfish in relation to feed types. This study will analyze the trend for length of Claria gariepinus fed on commercial feed, maggot and zooplankton; analyze the trend of weight of Claria gariepinus fed on commercial feed, maggot and zooplankton; analyze the relationship between length and weight and; make forecasts for the length and weight of the fish fed on the specified feed types. Artificial reproduction of African Catfish (C geriepinus) was carried out using the hypophysation technique. Brood stocks were selected from centrally located parent stock holding ponds. Males and females were conditioned in separate ponds. The brood stocks were fed with 20% crude protein formulated feed, acclimatized for three weeks, then transferred into the hatchery holding tanks between 240 Celsius and 270 Celsius to stimulate ovulation after injecting the females with 0.5ml of ovalin. Fertilized eggs were incubated in continuous flow of water until hatching was completed. A commercial starter feed consisting of 8% ash, 6% fiber, 12% NFE, 1.5% calcium, 1.6% sodium, 1.5% phosphorous and sufficient amount of essential vitamins was administered to the larvae. Larvae were randomly distributed into 45 plastic tanks in a flow-through system at a density of 500 fish per tank. Fifteen fries were randomly selected from each holding tank and measurements on weight and length collected daily. Time series analysis and regression analysis were applied in the study. It was found that the length and weight of post larvae fed on mixed zooplankton was consistently lower than the other treatments. The length and weight of the fish fed on the three feed types were successfully modeled and forecasts made for future five periods while the relationship between length and weight was found to be significant on a linear regression model. This certainly adds value as the weight of post larvae catfish is measure with less difficulty and without causing injury or stress to the fish than measurement of length.

Rapid continuous aqueous production of copper indium sulfide quantum dots via a microwave-assisted microfluidic technique.

Ternary copper indium sulfide (CIS) quantum dots (QDs) have been emerging as attractive alternatives to Cd- and Pb-based QDs in various applications owing to their favorable optical properties and low toxicity. However, methods allowing continuous production of CIS QDs in an easy-to-perform and/or organic-solvent-free way are yet to be realized. Here, we report a facile, rapid, continuous, and aqueous synthetic approach for CIS QDs based on a microwave-assisted microfluidic (MAM) technique with easy scale-up of production. Typically, CIS QDs and CIS@ZnS QDs are continuously produced with a flow rate of 30 mL h-1 at a moderate temperature (∼95 °C) in an open-air system with a continuous flow of water as the reaction medium. This continuous synthesis process circumvents the requirements of batch operation, a degassed/inert atmosphere, high temperatures, organic solvents, and complex/expensive equipment. The resulting water-soluble CIS@ZnS QDs show a photoluminescence quantum yield of 44%. This work provides an efficient and green synthetic route for the scalable production of fluorescent nanomaterials.

TRATAMENTOS NATURAIS DE LESÕES EM REPRODUTORES DE PEIXES

The aim of this research was to test the use of natural operating as prophylaxis for the treatment of injuries and diseases during fish reproduction at aquaculture stations as an alternative treatment to allopathic medicines. The main objective was to analyze the mastic bark (Schinus terebenthifolius), garlic bark (Allium sativum), and sodium chloride (NaCl) regarding their antimicrobial properties for prophylactic use. The broodstocks of the species pirapitinga Piaractus brachypomus were kept confined in water tanks with a capacity of 1000 L, with a continuous water flow for oxygenation and renewal. The stock density was 3 fish/m³, due to the fish being the breeding season why it becomes territorial. A confrontation between males occurred, causing the loss of scales in one of the specimen, mainly above the lateral line. The treatment of this injured fish lasted for 21 days, daily in the morning and afternoon; it was bathed in a 30g/L salt solution for 30 seconds, then the mastic and garlic extract were applied directly to the injury. For the mastic extract 50 mL of the concentrate was used without dilution and for the garlic extract 40 mL was diluted in 60 mL of water

Cello-MOF filters for multifaceted emerging pollutant abatement and their value addition

The current study showcases the effective utilization of Saccharum officinarum bagasse (SB), a prominent agricultural waste product, as a valuable precursor for the production of adsorptive filters. These pristine filters were subsequently augmented with MIL-88 (Fe) to incorporate functionally active sites. The fabricated filters exhibited exceptional efficacy in the removal of cationic dyes such as methylene blue, malachite green, crystal violet and rhodamine B; pharmaceutical wastes namely ciprofloxacin and paracetamol, and metal ion, chromate. The adsorption capacity for methylene blue (MB) using the MIL-88 (Fe) integrated SBF material significantly surpassed expectations, demonstrating an impressive capacity of 602 mg/g in batch adsorption mode. Furthermore, the drain-type system, equipped with stacked MIL-88(Fe)@SB filters, consistently and effectively removed organic contaminants from the continuous water flow. Additionally, they proved to be highly efficient in the separation of oil–water emulsions, serving as an effective barrier with a separation efficiency of upto ∼100 %. In addition to their primary use, the filters were repurposed as valuable electrode materials by high temperature carbonization of the filters at 800 °C for 3 h under N2 atmosphere, for the development of point-of-use energy storage devices. This secondary application demonstrated remarkable results, with the devices achieving a substantial capacitance value of 88 F/g at a current density of 0.1 A/g. This reutilization not only enhances the sustainability and economic feasibility of the filtering system but also opens promising avenues for the utilization of waste materials in the realm of energy storage. While prior studies have primarily focused on the application of metal–organic framework (MOF)-based filters for the removal of specific contaminants, our present research represents a multifaceted approach. It not only addresses the challenges of diverse pollutant removal but also delves into the transformative potential of these filters in supercapacitor devices.

Advection-based tracking and analysis of salinity movement in the Indian Ocean

The Bay of Bengal (BoB) has maintained its salinity distribution over the years despite a continuous flow of fresh water entering it through rivers on the northern coast, which is capable of diluting the salinity. This can be attributed to the cyclic flow of high salinity water (≥35 psu), coming from Arabian sea and entering BoB from the south, which moves northward and mixes with this fresh water. The movement of this high salinity water has been studied and analyzed in previous work (Singh et al., 2022). This paper extends the computational methods and analysis of salinity movement. Specifically, we introduce an advection based feature definition that represents the movement of high salinity water, and describe algorithms to track their evolution over time. This method allows us to trace the movement of high salinity water caused due to ocean currents. The method is validated via comparison with established observations on the flow of high salinity water in the BoB, including its entry from the Arabian Sea and its movement near Sri Lanka. Further, the visual analysis and tracking framework enables us to compare it with previous work and analyze the contribution of advection to salinity transport.

The Significance of Al-Jazari's Four-Bucket Water Lifting Machine in the History of Engineering and Science

The developments in the field of engineering have an eclectic structure. During ancient times, the works carried out at the School of Mechanical Engineering in Alexandria were transmitted to the Islamic world through translations at the House of Wisdom (Bayt al-Hikmah). Following this process, engineering studies became the focus of research in the Islamic world, both from theoretical and practical perspectives. Prominent researchers in this context include the Banu Musa brothers (9th century), Al-Farabi (875-950), Al-Hazini (1100s), and Al-Jazari (13th century). The renowned Turkish philosopher Al-Farabi conducted research on air and vacuum, expressing his views in the treatise "Risale li-Ebi Nasr al-Farabi fi’l-Hala" (On Vacuum). Al-Hazini's book "Mizanu’l Hikme" (The Balance of Wisdom) sheds light on the concept of balance, with Hazini turning the water balance into an extraordinary equilibrium device and creating a balance called "Mizânü'l-Câmî" (The Collector).The Banu Musa brothers presented valuable machine and mechanical system designs in their work "Kitab al-Hiyal" (The Book of Ingenious Devices). Al-Jazari, born in 1153 in Cizre, served as the chief engineer of the Artuklu palace for 32 years. During this time, he designed many mechanical and automation-based systems. Upon examining the designs in Al-Jazari's book "Kitab-ül Cami Beyn-el-İl ve'l-Amel el-Nâfi fi Sınaât el Hiyel," it becomes apparent that he elevated the designs made before him to a completely different level. Some of today's engineering designs can trace their origins to the drawings found in this book. In this study, the design features of Al-Jazari's 4-bucket water-lifting machine are examined, and its value in contemporary engineering is explored. Al-Jazari designed a mechanical timer to ensure the continuity of water flow in his design. This timer allowed each bucket to discharge water one after the other, maintaining a continuous flow of water. He achieved this through a shaft with quarter-toothed gears. This design can be considered the precursor to the eccentric and crankshafts found in modern internal combustion engines. The eccentric shaft controls the mechanical timing of valves in engines, while crankshafts ensure the continuous transmission of the force generated by four pistons in a four-stroke engine over a quarter of the cycle to the flywheel gear.

On the Flow of CO2-Saturated Water in a Cement Fracture

Cement fractures represent preferential leakage pathways in abandoned wells upon exposure to a CO2-rich fluid. Understanding fracture alteration resulting from geochemical reactions is critical for assessing well integrity in CO2 storage. This paper describes a mathematical model used to investigate the physical and the chemical changes in cement properties when CO2-saturated water is injected into a wellbore. This study examines the flow of a solution of CO2-saturated water in a two-dimensional fractured cement. In this approach, a micro-continuum equation based on the Darcy–Brinkman–Stokes (DBS) equation is used as the momentum balance equation; in addition, reactive transport equations are used to study the coupled processes of reactant transport and geochemical reactions, and the model for cement porosity alteration and fracture enhancement. This paper focuses on the effects of cement porosity, fracture aperture size, and surface roughness. Mineral dissolution and precipitation mechanisms are also considered. Our simulations show that smaller initial fracture apertures tend to a high mineral precipitation self-sealing. However, a complete sealing of the fracture is not observed due to the continuous flow of CO2-saturated water. The calcite precipitation mechanism of a rough fracture (random zigzag shape) differs from that of a smooth/flat fracture surface.

Influence of organic matter on seawater battery desalination performance

A rechargeable seawater battery desalination (SWB-D) system stores energy in a battery cell while removing salts from saline water via a sodium superionic conductor membrane and an anion exchange membrane. However, the electrochemical performance often degrades owing to the organic fouling generated on the ion exchange membranes. In this study, we investigated the fouling behavior of the SWB-D system by individually dissolving three different types of organic matter—humic acid, sodium alginate, and bovine-serum-albumin. In terms of the salt-removal performance of the SWB-D system, gradual degradation was observed over three charging cycles using hydrophobic humic acid (~13 %) and bovine-serum-albumin (~18 %), whereas no degradation was caused by hydrophilic sodium alginate. Continuous water flow mitigated the fouling behavior, and a large volume of saline water enabled longer charging. The increase in the electrical resistance of the SWB-D system was measured in the presence of organic matter using electrochemical impedance spectroscopy and the four-electrode method. Additionally, the presence of fouling layer was identified using field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier-transform infrared spectrometry. In conclusion, the results demonstrated that the hydrophobic organic matter in the feed water could be unfavorable when operating the SWB-D system.

Lab- and pilot- scale evaluation of bacterial inactivation and reactivation influenced by UV-LEDs arrangements in continuous flow water disinfection reactors

In the recent years, UV-LED has emerged as an alternative UV source due to its distinguish advantages. One of the primary benefits of UV-LEDs is their ability to facilitate fine-tuned regulation of UV radiation utilization in disinfection systems, which could increase the effective UV fluence in the reactor and thus improve the disinfection efficiency compared with conventional UV disinfection devices. This study evaluated the inactivation and reactivation performance of continuous flow UV-LED (265 nm) disinfection reactor with four different designs of UV-LEDs arrangement under both lab- and pilot- scale testing conditions. Lab-scale tests showed that UV-LEDs at the outlet position delivered a much higher E.coli disinfection efficiency compared with other three arrangements (UV-LEDs at inlet, center, and separated positions) under various of UV-LED outputs and flowrates. Mechanisms analysis indicated that the improved disinfection efficiency was because UV radiation was applied to the lower velocity region in the reactor, leading to a longer effective UV exposure time and thus a higher UV fluence generated. Sub-germicidal levels of UV irradiation prior to the high UV fluence region could also improve the overall disinfection efficiency for separated and outlet arrangement, with synergy values of 0.21 log (16.6 % of overall log reduction) and 0.53 log (21.4 % of overall log reduction) generated. The reactivation experiments showed that the inlet arrangement led to the highest photo repair rates. Dark repair was not affected by the different UV-LEDs arrangement due to the relatively slow dark repair rates. The key findings in the lab-scale tests were then validated in a small-scale (Total flowrate was 13.3 L/min) recirculatory aquaculture system (RAS) system for shrimp farming. The inactivation and reactivation results under pilot-scale tests were consistent with the lab-scale testing results, showing that UV-LEDs at outlet position provided an average total bacteria disinfection efficiency of 1.84 logs in an 8 week testing period, which was more than twice of that for the inlet position. After disinfection, samples from the outlet arrangement also exhibited at least 26.5 % less photoreactivation percentage compared with that when LEDs were at the inlet position. These findings proposed an optimal design of UV-LEDs arrangement for UV disinfection reactors and verified this design in pilot-scale testing condition. This information is important for future optimizations of UV LED disinfection system design.

Modeling of a stand-alone solar photovoltaic water pumping system for irrigation

Solar photovoltaic water pumping systems have been research topics in recent decades. The purpose was to develop much more profitable and efficient systems to meet the needs of pumping water for livestock and irrigation. This paper describes the design of a stand-alone photovoltaic water pumping system. A Boost converter is used to apply the Maximum Power Point Tracking (MPPT) algorithm. Similarly, a three-phase voltage source converter (VSC) is used to supply the asynchronous motor. The installation must provide a continuous water flow during the irrigation interval. It has been verified that in adverse weather conditions (cloud transits or partly cloudy) it is necessary to incorporate a decentralized-hybrid energy storage system (based on batteries or ultracapacitors), or excessively oversize the standalone photovoltaic system, to supply the water pump. The model has been simulated in Matlab-Simulink. In this way, different simulations have been developed to verify the basic characteristics of the proposed system. The results of the simulated model and the conclusions obtained are also presented in this paper.