Recirculation System Research Articles

Dynamics Changes of Total Bacteria in the Recirculating Aquaculture System (RAS) of Koi Fish (Cyprinus rubrofuscus)

Koi fish (Cyprinus rubrofuscus) is one of the aquaculture commodities that is highly marketable because of its unique color pattern and body shape. The prevalence of parasites and pathogenic agents in Koi fish among farmers poses challenges and leads to the occurrence of numerous illnesses. Water quality management is implemented in an effort to prevent several infectious microorganisms. The application of a recirculation system is used to enhance water quality and bolster the disease resistance of Koi fish. The objective of this study was to evaluate the application of RAS technology in the koi fish culture under different filter media on bacterial density. This study used four treatments, namely treatment A (RAS with a dacron filter and pumice), B (RAS with a dacron filter and sand), C (RAS with a sand and pumice filter), and K (control without a recirculation system). The parameter observed in this study was the density of bacteria in the koi fish rearing-media. These findings demonstrated that the utilization of various filters had an impact on bacterial density. Treatment C (RAS with sand and pumice filter) exhibited the greatest bacterial density with an average value exceeding 3.4 log CFU. mL-1 from the first week to the third week. The density of nitrifying bacteria in the koi fish production system is positively influenced by the high-quality maintenance practices that are maintained under optimal conditions.

Novel SOFC system concept with anode off-gas dual recirculation: A pathway to zero carbon emission and high energy efficiency

In recent years, the potential of Solid oxide fuel cell (SOFC) technologies as energy conversion devices with high efficiency and zero‑carbon emissions has been underestimated, where high fuel utilization plays a crucial role. Although the SOFC system with anode off-gas single recirculation has received much attention as a means to increase fuel utilization, this problem is not thoroughly addressed. To overcome this limitation, this paper proposes a novel SOFC system concept featuring anode off-gas “dual” recirculation, designed to maximize fuel utilization up to the theoretical limit of 100%. This innovative approach inherently eliminates carbon dioxide emissions through an integrated carbon capture process, thereby maintaining systematic carbon balance. A comparative analysis among the novel dual recirculation system, traditional single-pass, and other anode off-gas recirculation systems, reveals that the proposed system outperforms existing configurations. It achieves electrical and overall combined heat and power efficiencies of 49.6% and 85.7%, respectively, even after accounting for the energy required for carbon capture. This represents a 21.5% increase in electric efficiency over the single recirculation system, with a six-fold increase in tail-gas CO2 concentration, reaching 26.3%. The study categorizes the four analyzed systems into “open” or “closed” based on whether the anode off-gas is directly discharged into the environment. Systematic investigations into carbon deposition potential, fuel utilization, flow rate, operating voltage, carbon capture ratio, and condensation temperature disclose distinct patterns between open and closed systems. The closed configurations exhibit superior performance, suggesting they are more suitable for SOFC applications.

Intensification of Amazon River Prawn Hatchery

The effects of the intensification on the performance of the Amazon River prawn hatchery carried out in a simple recirculation system were investigated. Newly hatched larvae were stocked in 120 L tanks at 80, 100, 120 and 140 larvae L−1 in a closed recirculating system. The experiment used a randomized block design with five replicates. An exponential equation was adjusted to express the relationship between the stocking density and productivity (postlarvae L−1). The development, larval quality, survival and postlarval (PL) dry weight did not significantly differ among the treatments (p > 0.05). When 80 larvae were stocked, the productivity (54 ± 11 PL L−1) was lower than those at higher densities (p < 0.05). Stocking 120 and 140 larvae L−1 resulted in higher productivities (75 ± 18 and 80 ± 17 PL L−1, respectively) with a lower use of Artemia nauplii to produce each postlarvae (~1200 Artemia nauplii PL−1). The maximum mean M. amazonicum postlarval production estimated by the exponential model was 93 PL L−1. This means that despite the increase in stocking density, productivity tends to stabilize. The results showed that M. amazonicum tolerates high intensification in recirculating hatchery systems based on a crushed shell bed biofilter, and the intensification optimizes Artemia use.

Leakage and loss of contact/adjustment effects on slip-joins of a jet-pump assembly of BWR nuclear reactors by dynamic fluid-structure interaction modelling

This work presents a methodology for the evaluation of self-excited vibrations of jet-pump assemblies that make up the water recirculation system of boiling water nuclear reactors. Therefore, for the analysis three different type of models were developed: finite element, computational fluid dynamics and fluid-structure interaction models of a jet-pump assembly. The models were subjected to pressurized water flow in order to analyse leakage effect in the gaps between slip-joints and the diffuser of the assembly, and how the vibrations level can affect the integrity of jet-pump assemblies were also evaluated. Analyses of loss of adjustment of structural components in the wedge system were also performed, in order to study their contribution on the vibrations level under water flow conditions, since this effect has been identified as a potential failure mechanism in jet-pump assemblies. Three different gap sizes were modelled along with two critical loss of mechanical/adjustment components conditions, and the vibrations level of the jet-pump assembly under each modelled condition was obtained. The results showed the presence of self-excited vibrations of the jet-pump assembly under water flow, however little effect of leakage occurred in the slip-joint, on the vibration levels of the jet-pump assembly. Nonetheless, for the cases of loss of adjustment/contact components in the wedge system, high natural frequencies were obtained, and the vibrations were more severe when the loss of adjustment occurred in two mechanical/adjustment components. The results were also used to identify the mechanical components that may experience accelerated material degradation in the mixing-diffuser section of jet-pump assemblies, which occurred under loss of adjustment of mechanical components.

Organosilicon elastomers of MWCNTs and nano-sized metals for heating purposes

Silicone elastomers are continuously gaining importance in a variety of industrial applications, including strain gauges, electrical heaters, electromagnetic interference, and electrostatic discharge protection coatings. But these materials have certain drawbacks such as high cost, poor resistance to solvents, low tear strength, limited high-temperature resistance, difficulty in bonding and limited abrasion resistance. Therefore, unique nanocomposites of organosilicon elastomers with metals have been prepared using MWCNTs. The prepared nanocomposites demonstrated nano-diameter structures (15–60 nm) with micron-sized fibrous structures (12–60 μm). Aluminum elongated inclusions (60 µm in size) and bronze spherical inclusions (12–30 µm) were observed in the nanocomposites. The composites containing MWCNTs, Co-Mo/Al2O3-MgO catalyst and bronze (3 wt. %) had the maximum thermal and electrical conductivity. The prepared nanocomposites were used to make the heaters. The heating of the heaters was carried out by applying a voltage of 12–24 V. The Highest temperature achieved was more than 50 °C in all the heaters. By supplying 12–24 V electricity to the heaters in the ventilation and heat recirculation system, the interior of a minibus or living space can be heated. The developed electric heater has another important economic application in temperature-controlled materials.

Partial Replacement of Fish Meal with Protein Hydrolysates in the Diet of Penaeus vannamei (Boone, 1934) during the Nursery Phase

The objective was to evaluate the effects of partial replacement of fish meal with protein hydrolysates and a commercial product in the diets of Penaeus vannamei post-larvae on zootechnical performance, proximate chemical composition, digestive enzyme activity, and total hemocyte count. The experiment was conducted in a clear water recirculation system comprising 24 experimental units, each with 30 shrimp with an average weight of 0.2 g. The treatments were control, chicken protein hydrolysate (CPH), enzymatic hydrolysate of chicken feathers, Aquabite®, CPH + maltodextrin, and CPH + yeast, with four replicates each. The inclusion level of the different protein sources evaluated was 6%. At the end of the experiment, all shrimp were counted, weighed, and measured to determine the zootechnical performance. The body and feed chemical compositions, as well as the enzymatic activities of the hepatopancreas and the total hemocyte count in the hemolymph, were analyzed. The data obtained were subjected to ANOVA and Tukey’s test. There was no statistical difference between the treatments in any of the analyzed parameters. The results showed that all the evaluated protein hydrolysates can be used as partial substitutes for fish meal in P. vannamei diets during the nursery phase, maintaining equivalent and adequate digestive enzyme activities, health, growth, and body composition of the shrimp, in addition to being ecologically sustainable ingredients.

Different Protein Hydrolysates Can Be Used in the Penaeus vannamei (Boone, 1934) Diet as a Partial Replacement for Fish Meal during the Grow-Out Phase

This study evaluated the inclusion of protein hydrolysates and a commercial product as a partial replacement for fish meals in the diet of Pacific white shrimp (Penaeus vannamei) during the grow-out phase. A recirculation system with 24 experimental units and a biological filter was used. The experimental design was completely randomized with six treatments: control; chicken protein hydrolysate (CPH); enzymatic hydrolysate of chicken feathers; Aquabite®; CPH + maltodextrin; CPH + yeast; and four replicates. After 50 days, the zootechnical performance and animal welfare parameters, centesimal carcass composition, digestive enzyme activity, and hemocyte count were evaluated. The treatments did not affect the zootechnical performance and total hemocyte count of the animals (p > 0.05). The evaluation of the antenna length indicated that all animals were in good health. The antenna length in treatment T5 was significantly greater (p > 0.05) than that in T4 and similar to that in treatments T3 and T6, demonstrating a positive influence of dietary protein hydrolysates. Concerning animal welfare, dietary protein hydrolysates influenced the length of the antenna (p < 0.05). The antenna length associated with different treatments indicated that the animals were in good welfare conditions in the production environment. With respect to body chemical composition, dry matter, ether extract, and ash were affected by the treatments (p < 0.05). Regarding the analysis of digestive enzymes, the treatments influenced the activities of amylase and trypsin (p < 0.05). The performance of the animals was satisfactory under all treatments, including enzymatic activity, demonstrating the possibility of using hydrolysates.

Juvenile production technology for tiger shrimp, Penaeus monodon, through different stocking density using a recirculation system

AbstractAquaculture recirculation technology has evolved in recent years, as it can save water use and maintain good water quality during tiger shrimp fry rearing and ultimately increase juvenile production. The recirculation technology in this experiment is expected to be adopted by small‐scale tiger shrimp seed farmers. This study aims to develop the technology for producing a juvenile tiger shrimp recirculation system to support shrimp cultivation in ponds. The recirculation system container comprises a biofiltration tank filled with oysters, seaweed, and tilapia. Containers to keep tiger shrimp larvae alive in the recirculation system use a round‐shaped container with a volume of 2 m3. Tiger shrimp larvae were cared for at; A. density of 2000 individuals/m2; B. density of 1500 individuals/m2; and C. density of 1000 individuals/m2. This study found that the survival rate of tiger shrimp in treatments C and B were high, reaching 96.800b ± 2.716% and 91.62b ± 3.432%, respectively, while survival in treatment A was the lowest, at 81.700a ± 4.715%.

Effect of augmented nutrient composition and fertigation system on biomass yield and cannabinoid content of medicinal cannabis (Cannabis sativa L.) cultivation.

Growing evidence underscores the role of nutrients and fertigation systems in soilless production, influencing medicinal cannabis biomass and secondary metabolite content. This study delves into the impact of enhanced nutrient regimes on the 'ionome' and its ramifications for biomass and cannabinoid production in medicinal cannabis, comparing two distinct fertigation systems: recirculation and drain-to-waste. Notably, we assess the optimal harvest time for maximizing profitability. In comparing the experimental variant with elevated levels of phosphorus (P), potassium (K), and iron (Fe) in the nutrient solution to the control variant, we observe distinct patterns in element composition across stems, leaves, and flowers, with significant differences between fertigation systems. Total nitrogen content was determined through the Kjeldahl method. Flame atomic absorption spectrometry (FAAS) and inductively coupled plasma optical emission spectrometry (ICP-OES) were employed for elemental analysis. Cannabinoid identification and quantification used high-performance liquid chromatography with a diode-array detector (HPLC/DAD). Followed statistical analyses included ANOVA and Tukey's HSD test. Although the augmented nutrient regimen does not substantially increase plant biomass, interesting differences emerge between the two fertigation systems. The recirculation fertigation system proves more profitable during the recommended harvest period. Nonetheless, the altered nutrient regime does not yield statistically significant differences in final inflorescence harvest mass or cannabinoid concentrations in medicinal cannabis. The choice of fertigation system influences the quantity and quality of harvested inflorescence. To optimize the balance between the dry biomass yield of flowers and cannabinoid concentration, primarily total THC yield (sum of tetrahydrocannabinolic acid, Δ9-tetrahydrocannabinol, and Δ8-tetrahydrocannabinol), we propose the 11th week of cultivation as the suitable harvest time for the recirculation system. Importantly, the recirculation system consistently outperformed the drain-to-waste system, especially after the ninth week, resulting in significantly higher total THC yields. Enriched nutrition, when compared with control, increased THC yield up to 50.7%, with a remarkable 182% surge in the recirculation system when compared with the drain-to-waste system.

Auxiliary-ejector-based hydrogen recirculation system to broaden PEMFC operating range

This study presents an auxiliary-ejector-based hydrogen recirculation system to widen the operating range of the proton exchange membrane fuel cell system (PEMFCS). An auxiliary ejector (BE) design model is presented and then an experimentally verified two-dimensional numerical-simulation model is built to study the relationships between PEMFC output power, ejector geometrical parameters, and its performance (μ) based on sensitivity analysis. Finally, the operating characteristics of the BE are clarified. The results show that the μ is highly sensitive to position (Lb), followed by width (w) and angle (A) of auxiliary port. The BE can provide satisfactory μ above 0.8 under higher power output, and a μ higher than 0.6 for lower power output with the Lb, A, and w of 1.1, 30°, and 4 mm when PEMFCS works from 17.9 to 84 kW. This proposed system can extend the operation range of PEMFCS using a single ejector, which can contribute to fuel cell development.

Energetic and economic analysis of novel cascade systems for ammonia-fed solid oxide fuel cell

This study proposes an ammonia-fed cascade recirculation system comprising: (1) two stacks connected in series and (2) an anode off-gas recirculation configuration to enhance electrical efficiency of the system. The proposed system is both energetically and economically investigated. Under energetic analysis, the effects of fuel utilization, temperature, and recirculation rate, are clarified. Information from energetic analysis is employed to investigate levelized cost of electricity (LCOE) value in the entire working range. Due to the high potential of the cascade configuration, a cascade system without recirculation is also investigated using the same methods. The results reveal that the cascade-only and cascade recirculation systems obtain electrical efficiency up to 67.78% and 68.80%, respectively. The minimum LCOEs are 0.485 and 0.486 $/kWh, respectively, which are both higher than grid electricity cost; however, compared with other ammonia-fed SOFC systems, the two cascade configuration-based systems show significant improvements in both efficiency and cost.

Effect of fermented lemon peel as a functional feed additive on growth, non-specific immune responses, and Vibrio alginolyticus resistance in whiteleg shrimp, Litopenaeus vannamei

The study evaluated the impact of lemon peel fermented with Lactobacillus plantarum (FLP) being a practical feed additive, and its effects on growth performance, non-specific immune indicators, and disease resistance for whiteleg shrimp (Litopenaeus vannamei). The FLP was incorporated into the control diet at a graded level of 0%, 1%, 2%, and 3%. Four experimental feeds were randomly assigned to 4 replicates of L. vannamei with average weight of 2.37 g in a recirculation system for 56 days. Shrimp fed the four diets revealed similar (p > 0.05) weight gain percentage (489.01%−520.25%), feed conversion rate (2.46–2.70), protein efficiency ratio (1.05–1.14), and survival (78.75%−90.00%) after the feeding trial. Total hemocyte count (THC) was higher in shrimp delivered feeds containing 1% and 2% FLP whereas the phenoloxidase (PO) activity was advanced in shrimp fed the feed containing 2% FLP comparing with the FLP-free control group. In the V. alginolyticus challenge test, final survival after 72 h injection was higher in shrimp delivered feeds containing 2% and 3% FLP (66.67%−70.00%) than that in the control group (43.33%). The findings emphasize that fermented lemon peel is a potential functional feed additive on improving immunity and disease resistance for whiteleg shrimp, and showing no negative effects on growth and hepatopancreas morphology. An inclusion rate of 2% FLP is suggested for whiteleg shrimp to maximize the THC and PO activity and resistance ability to V. alginolyticus.

Flue Gas Recirculation System for Biomass Heating Boilers—Research and Technical Applications for Reductions in Nitrogen Oxides (NOx) Emissions

The paper discusses the results of investigations of the change in thermal and emission-related parameters of a heating boiler fueled with biomass after a modification with a proprietary flue gas recirculation system made for this type of equipment. The results provide insight into the combustion process with a multistage flue gas recirculation that materially affected the boiler operation: a reduction in the mass concentration of nitrogen oxides (NOx) by reducing the combustion temperature. The authors also observed a reduction in the emission of particulate matters (PM) and carbon monoxide (CO). For the investigations, the authors used a heating boiler fitted with an automatic fuel feed (timber pellets) and a proprietary patented flue gas recirculation system (Polish patent Pat. 243395) for low power solid fuel heating boilers. Aside from the measurement of the mass concentration of the emitted pollutants, the research focused on the measurements of the temperature inside the combustion chamber, the temperature of the flue gas and the level of oxygen in the flue gas. The aim of the research was to confirm the validity of using the flue gas recirculation technique to reduce emissions of harmful substances from biomass heating boilers, as a technique not previously used for this group of devices. Moreover, the aim of the research was to test an original engineering solution, in the form of a flue gas distribution valve, and investigate its effect on reducing NOx emissions and improving other thermal and emission parameters of the boiler. The obtained research results confirm the validity of the chosen actions and provide a positive premise for the practical use of this technology in solid fuel heating boilers.

Understanding the oceanographic dynamics of the Isla Chañaral baleen whale feeding ground, (Humboldt Archipelago, Northern Chile) to extend habitat protection

Off Northern Chile, baleen whales use the area around Isla Chañaral as a feeding ground where they forage on euphausiids. Isla Chañaral is part of the highly productive Humboldt Archipelago (∼ 28°S-29°S) within the Humboldt Current System (HCS). In this study, we seek to understand the sub-mesoscale spatial distribution of fin and blue whales and their prey around Isla Chañaral using systematic and opportunistic visual sighting data of whales and systematic acoustic backscatter data of zooplankton from an Acoustic Zooplankton and Fish Profiler (AZFP); and to examine the oceanographic dynamics of the wider Humboldt Archipelago area with remote-sensing oceanographic data. We completed a total of 512.6 km of survey effort over 20 days in 2018 and 318.3 km over 16 days in 2019 collecting systematic whale sighting and backscatter data. A total of 42 fin whales, 0 blue whales and 66 unidentified whales were sighted in 2018, and 7 fin whales, 3 blue whales and 12 unidentified whales were sighted in 2019. Observed spatial distribution of backscatter and whales was strongly associated with a bathymetric feature, i.e., the submarine canyon that curves around Isla Chañaral. Generalized Additive Models showed that fin whale presence was associated with high levels of backscatter and shallow depths similar to those of the canyon. We found that long-term average geostrophic currents form a recirculation system between 28°S and 31°S that can transport nutrient-rich upwelled surface waters back towards the Humboldt Archipelago and contribute to high biological productivity in this area. However, in summer 2019 geostrophic flow occurred away from the coast and a warm low-productivity spring explained low backscatter and whale sightings around Isla Chañaral. The unique oceanographic features of Isla Chañaral and the Humboldt Archipelago that contribute to high concentrations of Endangered baleen whales and their prey justify the extension of the Isla Chañaral Marine Reserve to include the canyon between the mainland and the island, and the implementation of a Multiple Use Marine Protected Area for the entire Humboldt Archipelago area that explicitly protects this critical feature.

The scheme of liquefied carbon dioxide production by membrane separation with recirculation system

The scheme of liquefied carbon dioxide production by membrane separation with recirculation system

Optimizing JICA Tilapia Larvae Production: Effect of Egg Density in Controlled Hatching at Jambi Peatland Hatchery

Sustainable aquaculture is crucial for environmental and economic stability in tropical regions. JICA tilapia (Oreochromis sp.) aquaculture development in Sumatran peatlands requires sustainable fry. This study aimed to analyze the optimal egg density to maximize larval production in a controlled hatchery environment. Utilizing a randomized experimental approach, we obtained eggs from naturally spawned tilapia, hatched in a funnel container (top diameter 30 cm; bottom diameter 15 cm; height 50 cm; water volume 10 L) within a 5 x 10 x 1 m3 tub filled with 90 cm of water using a recirculation system. We compared two densities: 2,000 eggs/L water and 3,000 eggs/L water. The findings of our study indicate that the difference in hatching rate between egg densities of 2000 eggs/L and 3000 eggs/L was not significant at the 95% confidence level (p> 0.05). Increasing the egg density to 3000 eggs/L does not significantly reduce the hatching rate, making it possible to consider higher densities without significant risks to larval production. This offers a model that can be replicated in similar tropical peatland environments.

A recirculation system for concentrating CO2 electrolyzer products

Ethylene concentrations from electrochemical carbon dioxide reduction are increased 20-fold by using a recirculation system with a hydrogen pump.

The effect of sulphur goatfish, sesarma, and green mussel as feed on the growth and survival of mud crab (Scylla paramamosain) in recirculation systems

The effect of sulphur goatfish, sesarma, and green mussel as feed on the growth and survival of mud crab (Scylla paramamosain) in recirculation systems

Physiological and biochemical parameters of the fish organism under conditions of improved growth in recirculation systems under the influence of Southern Ukraine

Physiological and biochemical parameters of the fish organism under conditions of improved growth in recirculation systems under the influence of Southern Ukraine

Effectiveness of a nanofiltration membrane-based recirculation system on growth and survival of asian redtail catfish (Hemibagrus nemurus) under various retentate treatments

Recirculated Aquaculture Systems (RAS) is an efficient, stable, and easily controllable method of aquaculture. By utilizing nanofiltration, these systems improve water quality in the pond, which in turn promotes better fish growth. The purpose of this study is to assess the optimal management of retentate flow in rearing systems utilizing nanofiltration membrane technology, aimed at improving the growth performance and survival rate of Asian redtail catfish. The research follows a Completely Randomized Design (CRD) with one factor, five treatment levels and three repetitions. The treatment levels are as follows: P1 = discarding 40% of the retentate, P2 = discarding 50% of the retentate, P3 = discarding 60% of the retentate, P4 = discarding 70% of the retentate, and P5 = discarding 80% of the retentate. The best results were obtained in P2, with an average absolute weight growth of 6.45±0.42 g, absolute length growth of 4.79±0.19 cm, specific growth rate of 4.82±0.19%, feed efficiency of 77.35±1.08%, feed conversion ratio of 1.29±0.01, survival rate of 90.62±3.12%, and water quality within the rearing media suitable for Asian redtail catfish growth and survival. The glucose levels observed during the study ranged from 47 to 61 mg dL-1.