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Effect of seasonal variation on nitrogen transformations in aquaponics of northern China
Abstract
Aquaponics is considered to be a promising production system in the future, due to its high nitrogen utilization efficiency (NUE). In this study, lab-scale aquaponic systems with native species, common carp (Cyprinus carpio) and pakchoi (Brassica chinensis), were achieved successfully in northern China. And nitrogen transformations in aquaponics during summer and autumn were thoroughly investigated. High fish and plant yields were observed in summer because of suitable environment. However, seasonal variation has minimal effect on NUE, which was 43.8 ± 5.9% and 44.6 ± 3.7% in summer and autumn, respectively. Similar phenomenon occurred for N2O. N2O emission flux of aquaponics was 508.2 ± 80.6 ug m−2 h−1 in summer, and decreased to 218.5 ± 30.6 ug m−2 h−1 in autumn, whereas the N2O conversion ratio changed from 1.6 ± 0.2% to 1.3 ± 0.1%, correspondingly. This was mainly because of the decrease of nitrogen input at lower temperature. TAN concentration was lower in summer (0.5 mg/l) than autumn (1.0 mg/l), indicating faster nitrification occurred at higher temperature. And NO3−-N concentrations showed an obvious increase and decrease period in summer but only a slow increase in autumn, which was ascribed to the effect of seasonal variation on the balance between nitrification, denitrification and plant growth. Results of this study could provide theoretical supports of aquaponics’ seasonal performance for aquaponics’ application in northern China.
... Another benefit of hydroponics is its ability to act as a subsystem in aquaponic systems. In recent years, aquaponics has become an exciting vegetable production approach for application near urban centres with minimal water consumption [121,122]. As a combination of aquaculture and hydroponics, it provides an environmentally and economically sustainable food production system by uniting two systems that normally operate independently [123][124][125][126]. ...
... Zou et al. [121]; Love et al. [122] Better land use/irrigation water saving/nutrition control Aquaponics is an interesting combined system of hydroponics and aquaculture for the production of vegetables near urban centres with minimal water consumption. ...
... In addition, vertical production ensures a reduction in cropland [99,107]. Hydroponics, as a soilless cultivation method, can be applied in areas without arable land [41,97,98] and urban centres [108,121,122]. ...
The increasing demand for food, the lack of natural resources and arable land, and the recent restrictions on energy consumption require an immediate solution in terms of agricultural activities. This paper’s objective was to review hydroponics (a new soilless cultivation technology) and compare it with conventional agriculture (soil cultivation) regarding its environmental impact and water and energy consumption. The soil loss, the crop/soil contamination, and the greenhouse gas emissions were the criteria for the environmental comparison of conventional agriculture and hydroponics. As for resource consumption, the water consumption rates (L/kg), energy consumption rates (kWh), and energy required (kW) were the criteria for comparing conventional agriculture with hydroponics. Tomato and cannabis cultivation were used as case studies in this review. The review results showed that the advantages of hydroponics over conventional cultivation include zero-soil cultivation, land-use efficiency, planting environment cleanliness, fertilizer and resource saving, water consumption reduction, and conservation. The disadvantages of hydroponics versus conventional cultivation were found to include the high investment costs, technical know-how requirements, and higher amount of demanded energy.
... Good nitrogen absorption by plants will increase growth because it affects the length of plant life, vegetative growth of plants can provide dyes to plants, and others. 13 Based on study 18 , Pakcoy plants can absorb nitrate content better than spinach plants, lettuce and red spinach. The end result of the nitrification process is nitrate, which does not harm the plant if it does not exceed the limit. ...
... Analysis of pH In a recirculation system, one of the important things is pH, because it functions as a balance between water, fish, and microbes. 18 The observation of pH is directly measured at the sampling location, the results can be seen in Based on the observations obtained, the pH obtained at each sampling point in both aquaponic systems and modified conventional aquaculture systems meets dwith compromise water quality standards namely 6-7. 11 On aquaponic and modified conventional aquaculture systems on the 0 th day, the pH values of water were 8.9 and 8.8 respectively. ...
... However, if the pH value of the water is less or equal to 7 then ammonium (NH 4 + ) will be ionized. 13,18 Therefore pH compromises fish, plants and bacteria tend to be slightly acidic 6-7. pH values in modified conventional aquaculture systems were higher than for aquaponic systems, causes higher ammonia content in modified conventional aquaculture systems. ...
Indonesia is currently faced with a variety of problems, including relating to increasing food demand and prices, increasingly scarce clean water, and poverty. Therefore, the development of aquaponics technology has been carried out, which integrates aquaculture and hydroponics. This study was conducted to compare water quality (pH, temperature, ammonia, nitrite, and nitrate) produced from 2 different systems, namely aquaponic with modified conventional aquaculture systems. In an aquaponic system, water recirculation follows the steps: Water from a fish pond tank (FPT), flows to mechanical tanks-1(MT-1), biofilter tanks (BT), mechanical tanks-2 (MT-2), to hydroponic plants (HP), and finally back to FPT, and so on. While conventional aquaculture systems, water recirculation is only through FPT, MT, and BT. The results were obtained for aquaponic (ammonia 0.350-5.946 mg/L, nitrite 0.193-0.880 mg/L and nitrate 1.031-5.542 mg/L), and for modified conventional aquaculture systems (ammonia 0.350-9.353 mg/L, nitrite 0.114-0.880 mg/L and nitrate 0.949-1.031 mg/L). While the pH and temperature values for the two systems are the same, pH 7.18-8.9, and water temperature 26.7-30.0°C. After the t-test, both showed a significant difference where the aquaponics system was better than the modified conventional aquaculture system because the aquaponic system was supported by the presence of MT-1, BT, MT-2, HP, and FPT, while the modified conventional aquaculture systems were only supported by MT, BT, and FPT.
... Good nitrogen absorption by plants will increase growth because it affects the length of plant life, vegetative growth of plants can provide dyes to plants, and others. 13 Based on study 18 , Pakcoy plants can absorb nitrate content better than spinach plants, lettuce and red spinach. The end result of the nitrification process is nitrate, which does not harm the plant if it does not exceed the limit. ...
... Analysis of pH In a recirculation system, one of the important things is pH, because it functions as a balance between water, fish, and microbes. 18 The observation of pH is directly measured at the sampling location, the results can be seen in Based on the observations obtained, the pH obtained at each sampling point in both aquaponic systems and modified conventional aquaculture systems meets dwith compromise water quality standards namely 6-7. 11 On aquaponic and modified conventional aquaculture systems on the 0 th day, the pH values of water were 8.9 and 8.8 respectively. ...
... However, if the pH value of the water is less or equal to 7 then ammonium (NH 4 + ) will be ionized. 13,18 Therefore pH compromises fish, plants and bacteria tend to be slightly acidic 6-7. pH values in modified conventional aquaculture systems were higher than for aquaponic systems, causes higher ammonia content in modified conventional aquaculture systems. ...
... There are also reports of pak choi grown successfully in aquaponics systems between 21.6-30.4 °C [33], and in hydroponic systems under greenhouse conditions between 34 and 45 °C [36,37] of environmental temperature. This suggests that the environmental temperature during the experiment was appropriate for pak choi development. ...
... The pak choi humidity was also similar to the value reported by the US Department of Agriculture [32] (95.32%). Pak choi productivity in both treatments was higher than that reported in other aquaponics studies [33][34][35] and was within the range of 0.5 to 7 kg/m 2 for soil culture [28]. This may be because the response of different plant varieties to environmental temperature can vary [25]. ...
... This may be because the response of different plant varieties to environmental temperature can vary [25]. There are also reports of pak choi grown successfully in aquaponics systems between 21.6 and 30.4 • C [33], and in hydroponic systems under greenhouse conditions between 34 and 45 • C [36,37] of environmental temperature. This suggests that the environmental temperature during the experiment was appropriate for pak choi development. ...
This study compares the aquaponics Nile tilapia (Oreochromis niloticus)—pak choi (Brassica chinensis) system with and without a bacterial biofilter (BF and NBF) in a tropical location. The aim was to determine whether a semi-intensive aquaponics system NBF could offer a production alternative for small-scale farmers in this region, both technically and biologically. The Tilapia aquaponics culture was continuously recirculated and water was added (influent) and removed (effluent) from the plant aquaponics culture every 24 h. Total ammonia nitrogen (TAN) and nitrite nitrogen (NO2⁻-N) were analysed in the plant aquaponics culture influent and effluent. At the end of the experiment the individual fresh total weight, dry total weight, edible weight, height and diameter of the pak choi plants were measured. None of the pak choi variables showed significant differences between treatments. TAN and NO2⁻-N were higher in the NBF influent than in the BF influent. TAN and NO2⁻-N in the effluent of both treatments were similar and lower than in the influent. The plant aquaponics culture therefore works as a biofilter and the NBF aquaponics system could be used for small-scale farmers in the tropics, with easier management and less costs than a BF aquaponics system.
... Concentrations of the major macronutrients and micronutrients required for plant growth (nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), and sodium (Na)) were measured with an atomic absorption spectrophotometer (model 2380; Manasquan, NJ, USA) except for N, which was quantified by the Kjeldahl method. Although analyses were performed using the dry matter, all values were transformed to natural or humid matter (Zou et al. 2016a). ...
... Analysis of the output and accumulation of nutrients showed that the proportion of nutrients absorbed by the fish was constant. A significant percentage of surpluses were recorded, which might be associated with the accumulation of sludge in sedimentation systems (Delaide et al. 2017) and floc aggregates (Fimbres-Acedo et al. 2020) and biocycling by microorganisms (Zou et al. 2016a). Data also suggest that lettuce grown in FP was unable to efficiently absorb nutrients, in spite of the amount being increased during Cycle 2 due to fish growth and higher feed supply. ...
The aim of the present study was to evaluate the use of the technology we have named for the first time as FLOCponics (biofloc + hydroponic) (FP) and conventional aquaponics (AP) systems in producing Nile tilapia (Oreochromis niloticus) juveniles and lettuce (Lactuca sativa). The experiment was carried out for 46 days and consisted of two cycles of lettuce production (23 days each) and one cycle of juvenile production. The physical-chemical variables of the water, zootechnical performance of the fish, growth performance and visual characteristics of the plants, nutrient dynamics, and characterization of the planktonic community were evaluated in both systems. The results showed better fish productive performance in FP, with a mean final weight of 36.7 g compared with 34.9 g in AP. For plants, the Cycle 2 in the AP system showed the best plant growth and visual results (98% of the plants received the highest scores-grades A (excellent) and B (good)-on the plant quality index), whereas in FP only 37% achieved these grades in the same cycle. The results suggest that the integrated production of tilapia juveniles and lettuce using FP might be technically feasible if specific fertilization management or mechanisms are developed to refine the critical points of the system (e.g., nutrient imbalance and solids accumulation in the plant roots) to improve plant production.
... Aquaponics, which combines the aquaculture and hydroponic technologies, is regarded as an innovative and unique environment for food production in the field of environmental science (Hu, et al., 2015;Zou et al., 2016). In an aquaponics environment (as shown in Figure 2), fish waste is utilized for hydroponic plant growth, and plants benefit the fish via the water filter (Genello, Fry, Frederick, Li, & Love, 2015), indicating that a symbiotic relationship is established. ...
... In recent years, aquaponics has drawn extensive attention due to its environmental and economic benefits (Zou et al., 2016). Some previous research has probed the mechanism and function of the aquaponics system. ...
Several previous studies have emphasized the importance of situating students in authentic learning or problem‐solving contexts to enhance their learning performances. However, some challenges of situated learning have been stated, such as the lack of effective learning support or concrete objective design to improve students’ learning engagement, problem‐solving competences and their active thinking. In this study, a mobile technology‐supported experiential learning system was developed to improve students’ problem‐solving competences as well as their learning performances, attitudes and collective efficacy. Moreover, an experiment was conducted on an environmental science course in an elementary school to compare the effects of this method with those of the conventional situated mobile learning approach on students’ learning effectiveness. The experimental results display that the implemented approach can significantly enhance students’ learning achievements, environmental attitudes and collective efficacy; furthermore, the students who learned with the implemented approach showed higher problem‐solving competence than those who learned with the conventional situated mobile learning approach, implying a noticeable reference for conducting experiential learning activities in environmental science education. Furthermore, the promotion of students’ active thinking in the mobile technology‐supported experiential learning is discussed.
Practitioner Notes
What is already known about this topic The importance of situating students in authentic learning or problem‐solving contexts to enhance their learning performances has been emphasized.
Some challenges of situated learning have been stated, such as the lack of effective learning support or concrete objective design to improve students’ learning engagement, problem‐solving competences and active thinking.
Properly integrating technology into instruction is most effective in an authentic learning context.
What this paper adds A mobile technology‐supported experiential learning system was designed to conduct an authentic learning activity.
The proposed approach can significantly enhance students’ learning achievements, environmental attitudes and collective efficacy.
The students who learned with the proposed approach showed higher problem‐solving competence than those who learned with the conventional situated mobile learning approach.
The promotion of students’ active thinking while learning with the mobile technology‐supported experiential learning system is discussed.
Implications for practice and/or policy The mobile technology‐supported experiential learning system is beneficial to students in an authentic learning environment as it triggers their active thinking.
Such an approach can be designed with authentic learning activities in other courses by replacing the authentic objects and learning materials.
It would be interesting to probe students’ social interactions and learning patterns in an experiential collective learning activity.
... Nutrient loss occurs through various pathways, including sludge settlement (37% from faeces and 18% from uneaten feed) (Montanhini Neto and Ostrensky, 2015), water renewal (Eck et al., 2019), denitrification, ammonia volatilization, and water losses (Wongkiew et al., 2018). Denitrification, for instance, can lead to the loss of 25-60% of nitrogen (Hu et al., 2015;Zou et al., 2016). Nitrogen loss may also occur through anaerobic ammonium oxidation (ANAMMOX), the oxidation of ammonium into dinitrogen gas in the presence of nitrite (Hu et al., 2011). ...
More than half of the nutrients sustaining the optimal plant growth in the aquaponic system are derived from fish waste. However, the use of fish meal and nitrogen, phosphorus, potassium (NPK) fertilizer in promoting growth parameters of the plant and for some fish species in such a system is not well documented. This study aimed to examine the effect of NPK fertilizer on the growth performance of Tinfoil barb (Barbonymus shcwanefeldii), a common riverine species as well as Chinese broccoli (Brassica oleracea) in a low-tech aquaponic system. A total of ninety fingerlings of Tinfoil barb (Barbonymus shcwanefeldii) were randomly distributed into three treatment groups with three replicates. The control group had no fertilizer added while the other groups were treated either with NPK or fish meal. After a 45-day feeding trial, fish, and plants treated with NPK fertilizer demonstrated significantly higher weight gain (4.11±0.01 g) (P<0.05) and plant height (15.77±0.15 cm) (P<0.05), respectively, compared to fish meal and the control. NPK treatment also resulted in the significantly greatest number of leaves (8.33±0.33) (P<0.05), explaining good productivity. NPK fertilizer appears to be a promising growth enhancer for both Tinfoil barb and Chinese broccoli that grow in the aquaponic system.
... Por otro lado, el efecto de las condiciones climáticas sobre la productividad de los sistemas acuapónicos también ha sido estudiado. Zou et al. (2016) observaron mejor productividad animal y vegetal en verano, posiblemente porque mayores temperaturas generan aumento de la actividad microbiana y del metabolismo de los peces. ...
La acuaponía es un sistema de producción que integra la acuicultura y la hidroponía, se destaca por su capacidad de producir alimentos de forma sostenible, promoviendo el reciclaje de nutrientes, el uso eficiente del agua y generando alimentos de alta calidad e inocuidad. Por ese motivo, el objetivo de este artículo de revisión fue compilar los conceptos más relevantes y avances alcanzados en la aplicación de esta técnica productiva mediante la exploración y sistematización de investigaciones publicadas en bases de datos de revistas indexadas durante la década 2012-2022. Los resultados obtenidos se organizaron en cuatro grandes categorías: 1. La acuaponía desde una perspectiva biológica; 2. viabilidad y rentabilidad del sistema acuapónico; 3. desarrollos ingenieriles, nuevas tendencias y tecnologías en acuaponía; y 4. aspectos ambientales y sociales de la acuaponía. La información científica y tecnológica compilada permitirá conocer el potencial, la viabilidad y adaptabilidad de los sistemas acuapónicos en un contexto de cambios ambientales, sociales y económicos. En ese sentido, la bibliometría, realizada con 55 publicaciones seleccionadas, permite identificar que el año de mayor producción científica en sistemas acuapónicos fue 2020, con 23% de la producción total en la década analizada, y que el 63% de las investigaciones se publicó en los últimos cinco años (2018 a 2022). Finalmente, por área temática, se encontró que el 44% de las investigaciones realizadas corresponden a la categoría “desarrollos ingenieriles, nuevas tendencias y tecnologías”, seguido por la “perspectiva biológica” y “aspectos ambientales y sociales” con 28% y 20% respectivamente.
... The amount of ammonia produced in the system depends on several factors such as fish biomass, fish size, and the amount/nature of food fed to the fish. Environmental changes like water temperature, salinity, and oxygen levels can also affect all system components' activities and growth, including microbes, fish, and plants 11 . ...
This study investigated the utilization of fish effluents as irrigation water and nutrient sources to close the crop yield gap and increase Swiss chard productivity in a closed-loop sandponics system. The experiment was operated using desalinated water from a Reverse Osmosis plant. The study followed a completely randomized design with four variants, i.e., an aquaponic system (T1) and three sandponics systems; October (T2), Benu Suef (T3) and Fayoum (T4). Results indicated that T2 and T4 significantly recorded the highest plant heights in all cuts. The number of leaves per plant decreased with the increase in cut number. Leaf area and chlorophyll was significantly different between the treatments. T1 significantly had low biomass yields in cuts one and two, almost 40% less than T3 and T4. The various systems efficiently minimized water consumption ranging from 1.5 to 1.96 L/m2/day. The crop protein content ranged from 11.84 to 18.72 mg/100 g dry weight. Mineral composition in cut one was significantly higher compared to cuts two and three. The study recommends a novel technique for increasing crop production using fish effluents under sandponics systems while increasing water and fertilizer efficiency to close the crop yield gap.
... Fang et al. (2017) estimated that 24.9% of N input was recovered in fish biomass and a further 22.3% in the vegetable biomass, while Jaeger et al. (2019) found that only 19.3% of N in fish feed was recovered in common carp and lettuce biomasses. A cumulative fish-vegetable NUE of 48.9% has been reported in a small-scale AP system producing common carp and pakchoi (Brassica chinensis) with minimal NUE variation between summer (43.8%) and autumn (44.6%) (Zou et al., 2016a(Zou et al., , 2016b. A plant species effect on N recovery efficiency in AP has been found by Hu et al. (2015) who obtained a NUE of 41.3% and N o n -c o m m e r c i a l u s e o n l y 34.4% in tomato (Solanum lycopersicum) and pakchoi based AP systems, respectively. ...
As in any agroecosystem, also in aquaponics the nitrogen (N) balance represents an important tool to evaluate sustainability, and to identify factors that can improve N use efficiency (NUE) and reduce N losses. In this respect, fish stocking density has been little investigated, hence this research aimed to evaluate the N balance of a low technology aquaponic (AP) system managed at two fish densities in comparison with a hydroponic system (HP). In the fish tanks common carp at two initial stocking densities were reared (2.5 and 4.6 kg m–3 in low and high AP, hereafter named APL and APH, respectively) and the vegetated sector was cultivated with a leafy vegetable crop succession (Catalogna chicory, lettuce, Swiss chard). The N balance considered N input as fish feed or fertiliser, and N content in the initial water and the N output as N in the incremented fish biomass, in the harvested vegetables, in the sediments, and in the remaining water. Total N loss was estimated by difference. The total N input and the N loss through gas emission in the atmosphere were much higher in AP than in HP, particularly at high stocking density. The opposite trend was observed for the N input recovered in vegetable aboveground biomass. The N input recovered as fish biomass was slightly higher in APL compared to APH. The better results of APL than APH suggest that in low-tech AP system lower initial fish density should be adopted at the system start up to maximise both production and N recovery.
... The promotion of commercial aquaponics was performed through the system definition, market research, and economic feasibility analysis [30][31][32][33][34]. In addition, Shandong University and the University of Hawaii participated in a series of studies on the dynamic changes and distribution of nitrogen forms in aquaponics, and conducted an in-depth exploration of the influencing factors, such as pH [35], season [36], and plant species [37]. ...
As an environmentally-friendly aquaculture and planting system, aquaponics has attracted attention in various fields, such as fisheries, agriculture, and ecology. The existing review qualitatively described the development and challenges of aquaponics but lacked data support. This study selected 513 related documents (2000–2019) in the Web of Science database (WOS) to mine and quantitatively analyze its text data. The keyword co-occurrence network shows that the current aquaponics research mainly focuses on the system components, wastewater treatment, nutrient management, and system production. Research areas reflect obvious regional characteristics. China, the United States and Europe are dedicated to the application of new technologies, the optimization of system production, and the exploration of multiple roles. At present, the aquaponics development is facing many pressures from management and market. Future research requires more in-depth research in the system construction, nutrient management, and microbial community structure to provide a theoretical basis. Moreover, the identity construction within the conceptual framework of green infrastructure is a research direction worth exploring to solve low social recognition for aquaponics.
... Nitrite nitrogen in aquaculture water is directly toxic to cultures [4], affecting its growth and development, and even leading to death [5]. However, these toxic substances are good fertilizers for plants (such as aquatic vegetables) [6]. As the vegetables grow, the water is purified and the growth environment of the fish is improved, thus achieving an ecological balance between plants, animals and microorganisms [7]. ...
How to design an effective experiment system to teach computational intelligence methods is big challenge nowadays. For the computational intelligence course, we design an aquaponics system and use the project-based teaching method. The aquaponics experiment system includes PLC, LabVIEW and OPC technology. The computational intelligence teaching project has data acquisition, sensors, and model subsystems. This project-based teaching method not only allows students to easily learn the computational intelligence methods and soft measurement, but also enhances their practical skills. Finally, we provide the teaching evaluation of the proposed teaching method.
... For appropriate functioning, aquaponic systems require balancing multiple factors, including solution pH (Wongkiew et al., 2017a;Zou et al., 2016), plant and animal density (Buzby and Lin, 2014;Hussain et al., 2014Hussain et al., , 2015, solution flow rates (Hussain et al., 2015;Khater and Ali, 2015;Wongkiew et al., 2017b), economics (Quagrainie et al., 2018;Tokunaga et al., 2015), system configuration (Klemencic and Bulc, 2015;Monsees et al., 2017), and food safety considerations (Elumalai et al., 2017;Pantanella et al., 2015). Several authors have reviewed system types, management, and potential profitability of aquaponic production systems (Blidariu and Grozea, 2011;Lewis et al., 1978;Love et al., 2015). ...
The recent increased market demand for locally grown produce is generating interest in the application of techniques developed for controlled environment agriculture (CEA) to urban agriculture (UA). Controlled environments have great potential to revolutionize urban food systems, as they offer unique opportunities for year-round production, optimizing resource-use efficiency, and for helping to overcome significant challenges associated with the high costs of production in urban settings. For urban growers to benefit from CEA, results from studies evaluating the application of controlled environments for commercial food production should be considered. This review includes a discussion of current and potential applications of CEA for UA, references discussing appropriate methods for selecting and controlling the physical plant production environment, resource management strategies, considerations to improve economic viability, opportunities to address food safety concerns, and the potential social benefits from applying CEA techniques to UA. Author’s viewpoints about the future of CEA for urban food production are presented at the end of this review.
... In these studies, they reported a hydraulic loading rate of 1.28 m/day with a flow rate of 1.6 L/min as optimum for fish and plant growth together with wastewater nutrient removal. Contrary to Endut, Jusoh, Ali, Wan Nik, and Hassan (2010), Zou et al. (2016); Roosta (2014b); Hu et al. (2014); Hu et al. (2015)) reported varying results on different aquaponic systems using different crops and different flow rates in RAS. It is important to note that, though several researchers have undertaken aquaponics research, most of them have tried to optimize only one component at a time such as crop density, fish density, flow rates, etc., within the whole system, resulting in inconsistent results. ...
Namibia is the driest country in sub-Saharan Africa, with surface water being only available for very limited periods during the year. This has seen the country importing up to 70% of its food requirements which exacerbates the food security challenge in the face of climate change. This review looks at the Namib Desert, and how its unique environment can be exploited for agricultural production. The cool but sunny desert makes it possible to produce crops under controlled environments with limited evapotranspiration. However, the high cost of inorganic hydroponic fertilizers makes adoption of hydroponics by smallholder subsistence farmers a great challenge thus the potential of hydroponics fertilized by organic nutrient sources like vermicomposts is discussed; highlighting research gaps. This review also highlights the potential of utilizing fog water for irrigation, a resource that is abundant in the Namib Desert, which can be crucial in desert greening. Though mushroom production is an established technology, the potential of using seaweeds from the highly productive Atlantic Ocean as mushroom substrate amendments and their potential in improving the nutrient value of mushrooms is also explored. This review highlights that agriculture is possible in this hyper-arid desert, with research being critical in driving its success.
... Aquaculture has become one of the fastest-growing food producing sectors since 1980s and accounted for almost half (49%) of global fish consumption in 2012 and it is estimated that aquaculture would account for 62% of world's fish supply for human consumption by 2030 [1,2]. The large scale application of aquaculture, however, is restricted by land and water utilization as well as by environmental concerns, thus, aquaponics which is an integrated system that links aquaculture and hydroponic production is considered to be an innovative and sustainable solution [3,4]. ...
Aquaponics system is an innovative idea which combined both aquaculture and hydroponics systems. In this study performance of four different types of water treatment technique was investigated in cocopeat media filled grow bed aquaponics system. The techniques that had been investigated were mechanical filter, biological filter, combination of both mechanical and biological filters and grow media (cocopeat) itself as filtration media. The effectiveness these techniques were assessed through (i) water quality and nutrients level of circulated water and (ii) growth rates of plant (Gynura procumbens) and Red Nile Tilapia fish (Oreochromis niloticus) The (i) water quality (pH, temperature, total suspended solid and dissolved oxygen) (ii) nutrient level (ammonia, nitrite, nitrate) and (iii) grow rates of plant and fish were weekly measured for this study. The results revealed that cocopeat media filled grow bed only was insufficient to act as water treatment unit in the aquaponics system studied. The aquaponics system required at least a biological or mechanical filter to produce acceptable yields of fish and plant. For the long term, the combination of axial flow and biofilter with superlative ratio was suggested in order to produce the best performance of parameters studied. This integrated technique was able to maintain the water quality within the tolerance limit of fish besides supplying enough amount nutrients (especially nitrate) for the plant growth and easier maintenance work in terms of cleaning and disposal of sludge.
... Similarly, N 2 O conversion efficiencies of about 1.3-1.6% were also observed in the pak choi-based media-filled (flood-and-drain) aquaponic systems and aquaculture systems (Hu et al., 2013;Zou et al., 2016a). Moreover, studies have reported that N 2 O emission and conversion efficiency depend on several factors such as fish stocking density, pH, DO concentration, season, temperature, and water quality (e.g., ammonia, nitrite, and nitrate concentrations) (Fang et al., 2017;Hu et al., 2012;Zou et al., 2016b). ...
Aquaponics recycles nitrogen from nitrogen-rich aquaculture effluent into organic crops (fish and vegetables/fruits) in hydroponic grow beds. Fundamental understanding of nitrogen transformations in aquaponics is critically important to improve nitrogen use efficiency (NUE) within aquaponics systems and to reduce release of environmentally harmful effluent and gases. This study elucidated nitrogen transformations in floating-raft aquaponic systems using four plant species, namely lettuce (Lactuca sativa longifolia cv. Jericho), pak choi (Brassica rapa L. Chinensis), tomato (Lycopersicum esculentum), and chive (Allium schoenoprasum L.). Using nitrogen mass balance and ¹⁵N labeled nitrogen species, it was found that nitrate was the primary form of nitrogen assimilated by plants. Nitrification and denitrification occurred simultaneously in the aquaponic system, resulting in an inevitable nitrogen loss (22.3–29.3% of nitrogen input). Nitrogen loss via nitrifier denitrification (33.7–55.3%), which was stimulated by low dissolved oxygen (DO) levels (∼3.8 mg/L), and denitrification occurred simultaneously. Moreover, nitrogen loss from the aquaponic system in the form of nitrous oxide (N2O), a potent greenhouse gas, accounted up to 0.72–1.03% of the nitrogen input. Aerating biofilters to prevent the formation of anoxic zones reduced total nitrogen loss but did not affect N2O emission. This study suggests that increasing DO concentrations only by aeration does not improve NUE and reduce N2O emission simultaneously.
Objective: The study sought to analyze work related to the aquaponics system and the emission of this greenhouse gas. Initially, 143 articles were selected, resulting in 14 final articles, using the PRISMA protocol. Result and Discussion: The study concluded that further research is needed to increase the efficiency of Nitrogen use and reduce denitrification, since these variables are directly related to the emission of N2O and its consequent harmful effects on the environment. The cultivation systems evaluated had the following distribution: The Cultivation Bed system represents 60% of the studies, followed by the DWF - Deep Wather Culture system with 26.7% and the NFT - Nutrient Film Technique system with 13.3% of the samples evaluated
Aquaponic systems are an innovative production model that combines aquaculture with hydroponic (soilless)
farming systems, providing economic, ecological, and social benefits. This system enables the production of fish and
plants within the same cycle, recycling organic waste. Aquaponic systems are crucial for food security and sustainability, reducing environmental impacts while increasing efficiency and optimising waste management. They
are particularly ideal for regions facing water scarcity and soil infertility. The efficient operation of this system
requires continuous monitoring of water quality, pH balance, water temperature, dissolved oxygen, and bacterial
activity. Aquaponic systems also offer high efficiency in energy and water usage and contribute to sustainable
development goals. With significant potential in food security and safe food production, aquaponic systems minimise
the use of chemicals and enhance agricultural productivity due to their closed-loop nature. These system models,
which provide local and fresh food production, especially in urbanised areas, reduce the carbon footprint and offer
promising prospects for sustainable food production in the future.
In recent years, the rapid development of the large-scale aquaculture industry has generated substantial economic benefits, positioning it as one of the fastest-growing sectors in global agricultural production. However, improper management practices in aquaculture, including overfeeding, improper feed selection, antibiotic misuse , high stocking densities, inappropriate choice of aquaculture species, and improper discharge of aquaculture wastewater, have resulted in significant watershed pollution in agriculture and the wastage of valuable resources. To address these challenges, extensive research and application of wastewater treatment technologies have been conducted in large-scale aquaculture in China. This review provides an overview of current cases and applications of wastewater treatment in large-scale aquaculture in China, focusing on four common intensive wastewater treatment methods: constructed wetland treatment model, ecological ditch treatment model, Integrated Multi-trophic Aquaculture model, and recirculating aquaculture model. The constructed wetlands utilize plants and microorganisms to purify both organic and inorganic pollutants in water, while ecological ditches employ engineering measures such as sedimentation ponds, interception ditches, and aeration devices to achieve wastewater treatment. Additionally, other aquaculture models are highlighted, such as Integrated Multitrophic Aquaculture (IMTA), which emphasizes synergistic interactions between aquaculture species and the recycling of nutrients, and the Recirculating Aquaculture Systems (RAS), which utilize water circulation and treatment equipment for wastewater treatment. The consequences and benefits of these systems in pollution reduction are described. These treatment technologies have made significant progress, offering theoretical guidance for environmentally friendly aquaculture production and the maintenance of ecological stability in aquaculture water bodies. Each wastewater treatment model has a different function, target, and methodology. Finally, this paper proposes directions and recommendations for future pollution management in large-scale aquaculture in China, including strengthening technological research and development, the combined application of multiple treatment models, promoting industry collaboration, and achieving resource sharing. These efforts will contribute to further promoting the sustainable development of China's aquaculture industry and provide valuable experiences and references for other countries and regions.
Nitrogen, a critically important nutrient that boosts yields in agriculture and food production, is currently overused to meet the rising demand for food. Surplus nitrogen ends up in the environment in excess of the capacity of natural nitrogen cycle, thereby leading to serious environmental pollutions, such as eutrophication of water bodies and emission of nitrous oxide (a highly potent greenhouse gas) to atmosphere. Aquaponics–bioponics is an emerging soilless technology for nitrogen recovery that links organic vegetable production to aquaculture effluent remediation (aquaponics) or organic waste recycling (bioponics). This Review presents the concept of aquaponics–bioponics for nitrogen recovery. Nitrogen transformations and nitrogen mass distributions in aquaponic–bioponic systems are critically discussed, along with the nutrient availability of several organic composts that can be integrated with the systems, and the microbial communities involved. This discussion is followed by a dynamic nitrogen modeling for managing nitrogen from different wastes in aquaponics–bioponics. Various emerging engineering technologies that could improve aquaponics–bioponics are presented, including aeration with microbubbles and/or nanobubbles, cocultivation with algae, process automation with Internet of Things, and integration with indoor vertical farming (plant factory with artificial light). Overall, the Review lays out the state-of-art in aquaponics–bioponics and highlights potential approaches for developing highly efficient nitrogen recovery technologies from diverse organic waste streams.
The characteristics of dissolved organic matter (DOM) that formed during the aerobic and anaerobic incubation of drinking water treatment sludge stored at different temperatures (5 °C, 20 °C, 40 °C) for long periods (7, 14, and 21 days) were investigated. Anaerobic incubation at high temperatures with prolonged storage was found to result in higher organic content than aerobic incubation (3.6–6.8 times at 40 °C). The high temperatures caused changes in the DOM fractions, with humic-like substances mainly formed in aerobic incubation and protein-like substances in anaerobic incubation. Results showed that the fluorescence intensity of humic-like and protein-like substances increased by 45% and 22%, respectively, at the end of the anaerobic incubation period. The UV-absorbing DOM constituents in aerobic incubation had lower molecular weights and were more heterogeneous than those in anaerobic incubation.
Aquaponics is known to be a smart way of producing fish and crops simultaneously; however, there is a paucity of information about the extents of this system's efficiency over other conventional methods of food production. Thus, this study was designed to evaluate the performance of a catfish–pumpkin aquaponics system in comparison with recirculatory and static aquaculture systems (for fish performance), as well as irrigated and nonirrigated systems (for pumpkin performance). Results obtained showed that the production of fish in the aquaponics system was 29% and 75% more efficient than recirculatory and static aquaculture systems, respectively. The survival of the fish was also significantly improved probably due to better water quality in the aquaponics system. With respect to pumpkin production, yield in the aquaponics system was about five times the performance in irrigated land and eleven times those in nonirrigated land. This study gives definitive evidence to support the efficiency of the aquaponics system over other conventional food production methods.
In a recirculating aquaponic system (RAS), the heating method based on an electric heater requires considerable amounts of electrical energy to maintain the water temperature for optimal warm-water fish growth conditions. Minimizing electrical energy consumption in the RAS is a great challenge. To solve this problem, a novel heating method that uses a combination of helically coiled heat exchangers (HCHEs) and a thermal energy storage (TES) unit is proposed to replace the electric heater. Several studies on heating and cooling systems with HCHEs and TES tanks have been conducted, but their integration in RASs is very rare. In this study, the thermal energy of the water in an RAS was the research objective. A computational fluid dynamics approach was adopted for transient analysis and inspection of the HCHE model considering eight cases with four temperature levels, 55, 60, 70, and 80 °C, and three mass flow rates, 0.166, 0.249, and 0.332 kg/s. The results showed that the HCHE was compatible with the regular heat sources of the TES unit (including solar collectors and heat pump systems). The temperature distribution of the water in the fish tank, from 26.75 to 30 °C, was suitable for maintaining the health of warm-water fish. To heat 3.4 m³ of the fish tank water from 24.5 to 28 °C, case 6 (where the temperature and mass flow rate of hot water were 70 °C and 0.332 kg/s, respectively) obtained the best results during a period of 26 min, usable heat transfer rate of 31.8 kW, and thermal efficiency of 76.1%. On the contrary, the results for case 1 (where the temperature and mass flow rate of hot water were 60 °C and 0.166 kg/s, respectively) were 70 min, 11.8 kW, and 57.5%, respectively.
Aquaponics is a technology for food production (fish and vegetables/fruits) with concomitant remediation of nitrogen-rich aquaculture effluent. There is, however, a critical need to improve the nitrogen use efficiency (NUE) in aquaponics. Here, we employed quantitative polymerase chain reactions and next-generation sequencing to evaluate the bacterial communities and their links to nitrogen transformations for improving NUEs in four bench-scale plant-based floating-raft aquaponics (pak choi, lettuce, chive, and tomato) and three pH levels (7.0, 6.0, and 5.2). Low relative abundance of nitrifiers in plant roots and biofilters suggested nitrogen loss, which decreased NUE in aquaponics. Low pH level was a major factor that shifted the microbial communities and reduced the relative abundance of nitrifiers in aquaponic systems, leading to total ammonia nitrogen accumulation in recirculating water. In plant roots, the abundance of nitrite-oxidizing bacteria (e.g., Nitrospira spp.) did not decrease at low pH levels, suggesting the benefit of growing plants in aquaponics for efficient nitrification and improving NUE. These findings on microbial communities and nitrogen transformations provided complementary strategies to improve the performance of the aquaponics regarding water quality and extent of nutrient recovery from aquaculture effluent.
Aquaponics (AP), the integrated multi-trophic fish and plants production in quasi-closed recirculating system, is one of the newest sustainable food production systems. The hydroponic component of the AP directly influences water quality (in turn influencing fish growth and health), and water consumption (through evapotranspiration) of the entire system. In order to assess the role of the design and the management of the hydropon-ic component on the overall performance, and water consumption of the aquaponics, 122 papers published from 1979 to 2017 were reviewed. Although no unequivocal results were found, the nutrient film technique appears in several aspects less efficient than medium-based or floating raft hydroponics. The best system performance in terms of fish and plant growth, and the highest nutrient removal from water was achieved at water flow between 0.8 L min-1 and 8.0 L min-1. Data on water consumption of aquaponics are scarce, and no correlation between the ratio of hydroponic unit surface/fish tank volume and the system water loss was found. However, daily water loss was positively correlated with the hydroponic surface/fish tank volume ratio if the same experimental conditions and/or systems were compared. The plant species grown in hydroponics influenced the daily water loss in aquapon-ics, whereas no effect was exerted by the water flow (reciprocat-ing flood/drain cycle or constant flow) or type (medium-based, floating or nutrient film technique) of hydroponics.
Aquaponics is a promising technology combining aquaculture with hydroponics. In this study, algal-bacterial consortia were introduced into aquaponics, i.e., algal-bacterial based aquaponics (AA), to improve the nitrogen utilization efficiency (NUE) of aquaponics. The results showed that the NUE of AA was 13.79% higher than that of media-based aquaponics (MA). In addition, higher NO3(-) removal by microalgae assimilation led to better water quality in AA, which made up for the deficiencies of poor aquaponic management of nitrate. As a result of lower NO3(-) concentrations and dramatically higher dissolved oxygen (DO) concentrations caused by microalgae photosynthesis in the photobioreactor, the N2O emission of AA was 89.89% lower than that of MA, although nosZ gene abundance in MA's hydroponic bed was approximately 30 times over that in AA. Considering the factors mentioned above, AA would improve the sustainability of aquaponics and have a good application foreground.
Aquaponics is the cultivation form that integrates aquaculture with hydroponics to nurture plants and fish simultaneously. And aeration plays an important role in its sustainable operation, as well as economic and environmental feasibility. In this study, two patterns to reduce aeration intensity, i.e., semi-aeration (SA) and intermittent aeration (IA) were used to improve the economic and environmental benefits of media-based aquaponics. Results showed that SA aquaponics, in which the energy efficiencies on culturing fish and crop were improved respectively by 78.20% and 77.61% compared with Control, had the potential to obtain higher economic benefits. Although both SA and IA could save half of the aeration cost by reducing aeration flux and time respectively, the product yields in SA weren’t impaired seriously while in IA aquaponics they were. And the nitrogen utilization efficiency (NUE) of SA aquaponics was 11.3% higher than that of IA aquaponics, mainly attributed to the more stable dissolved oxygen concentration in SA. Better water quality was obtained in IA aquaponics, however, it was achieved at the cost of higher N loss (mainly in the form of N2), which subsequently reduced the potential for further improvement of NUE. Both SA and IA could considerably reduce GHG emissions from aquaponics, due to lower energy requirement. IA aquaponics showed the lowest N2O emission, but the primary source (over 97%) of greenhouse gases (GHG) emissions from aquaponics was off-site indirect CO2 emission. Taking productivity and environmental impact into consideration, semi-aeration was believed to be a better choice when reducing aeration.
Managed grasslands are known to be an important source of N2O with estimated global losses of 2.5 Tg N2O-N yr−1. Chambers are to date the most widely used method to measure N2O fluxes, but also micrometeorological methods are successfully applied. In this paper we present a comparison of N2O fluxes measured by non-steady state chambers and eddy covariance (EC) (using an ultra-sonic anemometer coupled with a tunable diode laser) from an intensively grazed and fertilised grassland site in South East Scotland. The measurements were taken after fertilisation events in 2003, 2007 and 2008. In four out of six comparison periods, a short-lived increase of N2O emissions was observed after mineral N application, returning to background level within 2–6 days. Highest fluxes were measured by both methods in July 2007 with maximum values of 1438 ng N2O-N m−2 s−1 (EC) and 651 ng N2O-N m−2 s−1 (chamber method). Negative fluxes above the detection limit were observed in all comparison periods by EC, while with chambers, the recorded negative fluxes were always below detection limit. Median and average fluxes over each period were always positive. Over all 6 comparison periods, 69% of N2O fluxes measured by EC at the time of chamber closure were within the range of the chamber measurements. N2O fluxes measured by EC during the time of chamber closure were not consistently smaller, neither larger, compared to those measured by chambers: this reflects the fact that the different techniques integrate fluxes over different spatial and temporal scales. Large fluxes measured by chambers may be representing local hotspots providing a small contribution to the flux measured by the EC method which integrates over a larger area. The spatial variability from chamber measurements was high, as shown by a coefficient of variation of up to 139%. No diurnal pattern of N2O fluxes was observed, possibly due to the small diurnal variations of soil temperature. The calculation of cumulative fluxes using different integration methods showed EC data provide generally lower estimates of N2O emissions than chambers.
Aquaponics has attracted worldwide attention in recent years and is considered as an alternative technology for conventional aquaculture. In this study, common carp (Cyprinus carpio) and pakchoi (Brassica chinensis) were cultured in lab-scale aquaponics, and attempts were conducted to enhance its nitrogen utilization efficiency (NUE) through two optimization methods, i.e., nitrifies addition (NA) and filler gradation (FG). Results showed that NA and FG could improve the NUE of aquaponics by 8.8 and 16.0 %, respectively, compared with control. The total ammonia (TAN) and nitrite (NO2 (-)) concentrations in NA and FG systems were maintained at relatively low level (TAN < 0.5 mg/L, NO2 (-) < 0.1 mg/L), which demonstrated that both the NA and FG could provide non-toxic water environment for fish culture. Nitrous oxide conversion ratio of the control, NA, and FG were 0.8, 1.2, and 1.7 %, respectively, indicating that media-based aquaponics also contributed to global warming. Although the two proposed attempts in this study caused more N2O emission, they made new breakthrough in improving the NUE of aquaponics.
Nitrate removal is essential for the sustainable operation of recirculating aquaculture system (RAS). This study evaluated the heterotrophic denitrification using poly(butylene succinate) as carbon source and biofilm carrier for RAS wastewater treatment. The effect of varied operational conditions (influent type, salinity and nitrate loading) on reactor performance and microbial community was investigated. The high denitrification rates of 0.53±0.19kgNO3(-)-Nm(-3)d(-1) (salinity, 0‰) and 0.66±0.12kgNO3(-)-Nm(-3)d(-1) (salinity, 25‰) were achieved, and nitrite concentration was maintained below 1mg/L. In addition, the existence of salinity exhibited more stable nitrate removal efficiency, but caused adverse effects such as excessive effluent dissolved organic carbon (DOC) and dissimilation nitrate reduce to ammonia (DNRA) activity. The degradation of PBS was further confirmed by SEM and FTIR analysis. Illumina sequencing revealed the abundance and species changes of functional denitrification and degradation microflora which might be the primary cause of varied reactor performance.
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In this study, we investigated effects of different feeds (live food (Artemia+Drosophila sp.), wet feed (Spleen+Liver) and commercial feed) and different water temperatures (9.10±0.85 and 15.00±0.50°C) on meat yield, Survival Rate (SR), Feed Conversion Ratio (FCR), Condition Factor (CF) and growth in Rainbow trout, Oncorhynchus mykiss (Walbaum) fingerlings. The fingerlings had 0.23±0.04 g mean initial weight. The study lasted a total of 16 weeks and carried out according to completely randomized factorial experimental design (3X3X2). At the end of the experimental period, final weights of fish having about the same initial weights showed big differences. The highest final weight was 13.05±0.21 g from the higher temperature and commercial feed group. The differences between the groups were found statistically significant (p<0.05). In terms of feed conversion ratio, very different values were observed among the groups and their differences were also statistically significant (p<0.01). At the end of research, carcass weights differences between the results of the commercial feed, wet feed and live food groups were statistically significant (p<0.05). In terms of condition factor values, the differences between the groups were insignificant. In terms of Hepatosomatic (HSI) and Viscerasomatic (VSI) indices the differences between the results of the groups were found statistically significant (p<0.05).
Abstract
The traditional pond aquaculture in northern Vietnam is a plant-based integrated aquaculture system using poor-quality pond inputs (macrophytes, farm by-products, manures). Most applied feeds are palatable solely to the grass carp (Ctenopharyngodon idella), which is the main species in traditional fish polyculture. Secondary species are malnourished as the natural food productivity is diminished by uncontrolled water flow through and high turbidity. Mass mortalities of grass carp lead to high financial losses for the farmers. To improve the fish production, researchers developed a semi-intensive pond management in stagnant water in which common carp was cultured as the main species with supplemental fertilization and pelleted feeds based mainly on locally available resources. In this study, the traditional and semi-intensive pond management was compared in six ponds for fish production, nutrient efficiencies and economic net benefit. The use of higher-quality feed and fertilizer inputs under semi-intensive pond management resulted in higher fish yields of 228 ± 42 kg × 1,000 m−2 compared to 88 ± 44 kg × 1,000 m−2 under traditional management and higher net economic benefit of 3,848,000 ± 1,469,000 VND × 1,000 m−2 under semi-intensive compared to 846,000 ± 3,753,000 VND × 1,000 m−2 under traditional management. Under semi-intensive management, 11.5 % of applied total nitrogen was transferred into fish biomass while under traditional management, 4.4 % of applied total nitrogen converted into fish biomass.
The increasing number of depleted, overexploited and recovering world marine stocks, together with increasing demand for fish and need for sustain-able management of aquatic resources has led to a gradual shift to inland intensive aquaculture with water reuse. Intensive recirculating systems are becoming a rapidly developing sector of aquacul-ture, with the objectives to increase production and minimize environmental impact. However, transfer of technologies from original sites to locations of different climate is not always success-ful. The present study evaluates the use of an open recirculating system in a temperate climate. The 3-year study showed successful production with better fish growth and feed utilization than in a flow-through facility at the same site, but pre-sented significant issues necessitating changes in technology as well as physical adaptations. A posi-tive effect of the technology with respect to the environment is possible, but systems must be adapted to temperate climatic conditions.
In this study, the dynamics of nitrogen through aquaponics recirculation system was examined by developing a nitrogen budget. The model evaluated total ammonia nitrogen (TAN) production and removal in biofilters, identifying and quantifying the fate of nitrate nitrogen ([Inline formula]-N) and determining the system maximum carrying capacity. Of the nitrogen input into the culture tank via feed, 83.8% was recovered from different pool: 39.4% as fish flesh (harvested), 2.1% as mortalities, 34.7% as dissolved inorganic forms of nitrogen and 7.6% as total organic nitrogen. The remaining 16.2% of nitrogen unaccounted for likely was lost as nitrogen gas due to passive denitrification and as volatization of ammonia. Average TAN in the culture tanks was 2.08 mg/L. Under current condition, system loading with fish biomass at average of 68.5% of the maximum predicted. The hydroponic troughs removal efficiency averaged 60.4% TAN per pass. From TAN production, 88% was removed in hydroponic troughs, 11% by passive nitrification and 1% by water exchange. Under conditions of reusing treated effluent with residual TAN, the hydroponic troughs work normally, while TAN in the systems did not increase noticeably.
The study was conducted to see the feasibility of raft aquaponics in polyculture pond. Three experimental ponds (with an area of 5.2, 3.12 and 3.12 decimal) were selected where the third one was considered as control pond. Locally available cheap materials were used in preparing rafts, e.g., bamboo splits, iron wire, plastic thread and disposable plastic water bottle. Okra (Abelmoschus esculentus), water spinach (Ipomoea aquatica), pudina (Mentha arvensis), brinjal (Solanum melongena), tomato (Lycopersicon esculentum), giant taro (Alocasia macrorrhiza) and Indian spinach-red (Basella rubra) saplings were planted in the raft. Pond 1 and 2 were found to be covered with 4.12% and 2.56% with raft vegetable respectively. The percentage of specific growth rate (SGR) per day for Pangas (Pangasius hypophthalmus) was 2.57, 1.27 and 2.36 but it was found to be 0.822, 0.795 and 0.438 for Tilapia (Oreochromis mossambicus) in ponds 1, 2 and 3 respectively. For both fishes, the highest growth was found in pond 1. The production from each raft for pudina, water spinach and okra was about 266.7, 333.3 and 66.7 g respectively. Only pudina production was well enough to get benefit from raft vegetable culture and benefit-cost ratio of pudina production was about 7.82. In the study period giant taro showed good growth. Fruits and flowers were observed in Indian spinach-red and brinjal respectively at the end of the study period. Brinjal plants was affected by disease and tomato plants did not survive in the pond condition due to algae and other fouling clog on the roots which prevented nutrients up take from the pond water.
Nitrous oxide (N(2)O) is an important greenhouse gas (GHG) which has a global warming potential 310 times that of carbon dioxide (CO(2)) over a hundred year lifespan. N(2)O is generated during microbial nitrification and denitrification, which are common in aquaculture systems. To date, few studies have been conducted to quantify N(2)O emission from aquaculture. Additionally, very little is known with respect to the microbial pathways through which N(2)O is formed in aquaculture systems. This review suggests that aquaculture can be an important anthropogenic source of N(2)O emission. The global N(2)O-N emission from aquaculture in 2009 is estimated to be 9.30 × 10(10) g, and will increase to 3.83 × 10(11)g which could account for 5.72% of anthropogenic N(2)O-N emission by 2030 if the aquaculture industry continues to increase at the present annual growth rate (about 7.10%). The possible mechanisms and various factors affecting N(2)O production are summarized, and two possible methods to minimize N(2)O emission, namely aquaponic and biofloc technology aquaculture, are also discussed. The paper concludes with future research directions.
Light compares a complex of external and ecological factors, including colour spectrum, intensity and photoperiod. Light characteristics are very specific in an aquatic environment and light is extremely variable in nature. `Receptivity' of fish to light profoundly changes according to the species and the developmental status. Specific photoreceptor cells are present in both eye and pineal. If it is easy to change the light in experimentation and to observe the effects on fish growth, it is much more difficult in nature to make such determinations. In larvae, many studies have been dedicated to the influence of intensity and photoperiod on growth: generally, species need a minimal threshold intensity to be able to develop normally and grow. This is probably related to the aptitude to localize, catch and ingest prey. Light is also indispensable for body pigmentation, an important phenomenon involved in early development and growth. Too intense light can be stressful or even lethal. A few species are able to develop and grow at very low intensities or, sometimes, in the absence of light. Generally, long daylength improves larval rearing quality. The synergistic effect of `food availability-daylength' appears to be determining at this stage. In older fish, there is very little information about the influence of light `quality' but more about intensity and much more about photoperiod. Light intensity effects are not so clear and depend on the species and the experimental procedures: it is probably not an important factor for growth stimulation. Daylength appears much more important. Many species, including both marine species and salmonids, react to photoperiod treatments and long daylength stimulates growth. The most studied species is the Atlantic salmon, which is very sensitive, both during the freshwater stage, with the parr–smolt transformation very dependent on the photoperiod, and also in sea water. In this last condition, lighting also influences early maturation. An important point is to be certain that light affects fish growth through a better food conversion efficiency and not just through stimulated food intake. Also included in this review is a discussion about the endolymph–otolith system, which is very sensitive to daylight and seasonal cycles and a review of the present knowledge on the involvement of light influence on hormone levels (melatonin, somatotropin, thyroid hormones and other hormones).
Phytoremediation of highly water soluble and volatile organic xenobiotics is often inefficient because plants do not completely degrade these compounds through their rhizospheres. This results in phytotoxicity and/or volatilization of chemicals through the leaves, which can cause additional environmental problems. We demonstrate that endophytic bacteria equipped with the appropriate degradation pathway improve the in planta degradation of toluene. We introduced the pTOM toluene-degradation plasmid of Burkholderia cepacia G4 into B. cepacia L.S.2.4, a natural endophyte of yellow lupine. After surface-sterilized lupine seeds were successfully inoculated with the recombinant strain, the engineered endophytic bacteria strongly degraded toluene, resulting in a marked decrease in its phytotoxicity, and a 50-70% reduction of its evapotranspiration through the leaves. This strategy promises to improve the efficiency of phytoremediating volatile organic contaminants.
Nitrogen transformations in aquaponics with different edible plant species, i.e., tomato (Lycopersicon esculentum) and pak choi (Brassica campestris L. subsp. chinensis) were systematically examined and compared. Results showed that nitrogen utilization efficiencies (NUE) of tomato- and pak choi-based aquaponic systems were 41.3% and 34.4%, respectively. The abundance of nitrifying bacteria in tomato-based aquaponics was 4.2-folds higher than that in pak choi-based aquaponics, primarily due to its higher root surface area. In addition, tomato-based aquaponics had better water quality than that of pak choi-based aquaponics. About 1.5% to 1.9% of nitrogen input were emitted to atmosphere as nitrous oxide (N2O) in tomato- and pak choi-based aquaponic systems, respectively, suggesting that aquaponics is a potential anthropogenic source of N2O emission. Overall, this is the first intensive study that examined the role plant species played in aquaponics, which could provide new strategy in designing and operating an aquaponic system.
The denitrification process occurring in wastewater treatment plants (WWTPs) is responsible for nitrous oxide (N2O) and nitric oxide (NO) emissions. These compounds indirectly lead to the global warming. In this study, we investigated the impact of the temperature on N2O and NO emissions. Experiments were achieved at PH 7 in a batch reactor with acetate as the carbon source. The nitrogen source was nitrates (NO3−) and the COD/N ratio was set to three. Results showed that NO and N2O emissions increased when the temperature decreased. NO emissions appeared only at 10 °C and 5 °C, with respectively 8% and 18% of the total denitrified nitrogen. N2O emissions increased from 13 to 40 then 82% of the total denitrified nitrogen, respectively at 20, 10 and 5 °C. Several hypotheses were suggested to explain these results: a general enzymatic slow down, enzymatic inhibitions, electron donor competition between the different enzymes and metabolic pathway alterations.
Abstract—The nitrogen nutrition index (NNI) is calculated
from the measured N concentration and the critical nitrogen (N)
curve. It can be used to determine the N required by a crop and
is helpful for optimizing N application in the field. Our objectives
were to validate the existing corn critical N curve for the
northwestern plain of Shandong Province and to design a more
accurate remote detection method for the NNI. For this purpose,
field measurements were conducted weekly to acquire the biomass
and N concentrations during the corn growing season of 2011.
Additionally, nearly 60 corn canopy spectra were collected during
field campaigns. First, limiting and non-limiting N points were
selected from sampled data, and they were used to validate the
existing critical N curve. Second, an NNI estimation model based
on a Principal Component Analysismethod and Back Propagation
Artificial Neural Network (PCA-BP-ANN) model was established.
The collected canopy spectra and corresponding NNI were used
to compare the performances of the above mentioned method and
other for NNI estimation. The results showed that the N curve
proposed in the literature is suitable for the study region. Among
the three remote detection methods, PCA-BP-ANN provided the
best results with highest R value and lowest root mean square
error value.
Laboratory experiments were conducted with Cladophora glomerata isolated from Lake Huron near Harbor Beach, Michigan, to determine gross and net photosynthesis and respiration as functions of temperature and light intensity. Rates of net photosynthesis and respiration were measured in three replicate cultures at all combinations of eight temperatures (1° to 35° C) and eight light levels (12 to 1235 μE/m2•sec) using oxygen electrode techniques. Maximum net photosynthesis occurred between 13 and 17° C and 300 to 600 μE/m2•sec. The data were converted to specific rates of growth and respiration for use in a mathematical model, and three-dimensional response surfaces were generated for gross and net growth and respiration over the entire range of light levels and temperatures examined.
The effects of continuous and intermittent feeding strategies on nitrogen removal and N2O emission from surface flow and subsurface flow constructed wetlands were evaluated in this study. Microcosm wetlands planted with Phragmites australis were constructed and operated with different feeding strategies for the 4-month experiment. Results showed the intermittent feeding strategy could enhance the removal of ammonium effectively in the subsurface flow constructed wetlands, although it had no significant effect for the surface flow wetlands. And the intermittent feeding mode could promote the emission of N2O. The amount of N2O–N emission from the subsurface flow constructed wetlands with intermittent feeding mode was about 5 times higher than that with continuous feeding strategy and the emission rate ranged from 0.09±0.03 to 7.33±1.49mg/m2/h. Compared with the surface flow constructed wetlands, the N2O emission in the subsurface flow constructed wetlands was affected significantly by the intermittent feeding mode.
A brackish water source containing high magnesium concentration (333 mg/L as CaCO3) for reverse osmosis (RO) was studied for silica scaling. Threshold limit for RO recovery and required silica removal were firstly determined by a removal-saturation-recovery curve. Three different ratios of lime/soda ash combination were used to test the efficiency of silica removal as well as the impact of calcium and magnesium. Higher pH was more effective for silica removal due to electrostatic attraction since H3SiO4- and H2SiO4-2 were dominant when pH > 9.9. The precipitation of Mg(OH)(2)(s) has assisted more for silica removal than that of CaCO3(s) and the ratio of 0.044 mg SiO2/Mg Mg(OH)(2)(s) and 0.027 mg SiO2/Mg CaCO3(S) were statistically determined. Moreover, the presence of high magnesium causes Mg(OH)(2)(S) to precipitate at lower pH (9.41) instead of formation of forsterite (Mg2SiO4(S)), which typically occurs at pH > 12.3. Therefore, no forsterite was observed and was verified by X-ray diffraction (XRD) analysis. Consequently, adsorption is more dominant than chemical reaction in this study. Silica removal was also enhanced by coagulation. With the addition of coagulant (PACl), highest silica removal was achieved at pH of 10, but was decreased when the pH was over 10, due to the amphoteric properties of aluminum hydroxide to reduce the electrostatic attraction to silica at higher pH. Since both softening and coagulation were effective for silica removal, seven decision-making criteria were developed to compare the pros and cons of these two processes.
Estimates of N(2)O emission based on limit measurements could be highly inaccurate because of considerable diurnal variations in N(2)O flux due to rapid transformation of nutrients and diel change of dissolved oxygen (DO). In the present study, the N(2)O fluxes, dissolved N(2)O concentrations, and the controlling variables were measured hourly for 3d and night cycles at five sites on a typically sewage-enriched river in the Taihu region. There were no significant diurnal patterns in N(2)O emissions and dissolved N(2)O saturation, with respective mean value of 56.1μg N(2)O-Nm(-2)h(-1) (range=41.1μg N(2)O-Nm(-2)h(-1) to 87.7μg N(2)O-Nm(-2)h(-1)) and 813% (range=597-1372%), though distinct diurnal patterns were observed in DO concentration and river chemistry. However, the mean N(2)O emissions and the mean dissolved N(2)O saturation during the day (61.7μgNm(-2)h(-1) for N(2)O fluxes and 0.52μgNL(-1) for dissolved N(2)O saturation) were significantly higher than those during the night (50.1μgNm(-2)h(-1)for N(2)O fluxes and 0.44μgNL(-1) for dissolved N(2)O saturation). Factors controlling the N(2)O flux were pH, DO, NH(4)(+),SO(4)(2-), air temperature, and water temperature. Sampling at 19:00h could well represent the daily average N(2)O flux at the studied river.
Water-related problems are currently second only to energy issues as threats to human society. North China is a region that is facing severe water scarcity problems. In order to provide appropriate water mitigation policies a regional study is completed. Under this circumstance, Liaoning Province, a typical heavy industrial province in north China is chosen as a case study region. The input-output analysis method is employed in order to evaluate the water footprint both from production and consumption perspectives. The results show that the total water footprint of Liaoning in 2007 was 7.30billionm(3), a 84.6% of internal water footprint and a 15.4% external water footprint. The water trade balance of Liaoning was 2.68billionm(3), indicating that Liaoning was a net water export region, although water shortages are becoming a more serious concern. The "Agriculture" and "Food and beverage production" sectors are found to have the highest water footprint, water intensity, water exports, and water trade balance. Based upon Liaoning realities policy implications and suggestions are made, including industrial and trade structure adjustment, application of water efficient technology and management measures, and appropriate capacity-building efforts. The methodology and findings may be useful for investigation of water footprints throughout various regions of the world.
We present an update of the global budget of atmospheric nitrous oxide (N2O) that accounts for recent revisions in estimates of global emissions. Most importantly, new estimates of N2O emissions from agriculture and from oceans and a surface sink of N2O have been included. Our estimates confirm that current food production is the largest anthropogenic source of N2O. However, its relative share in total anthropogenic emissions (about 60%) is smaller than in earlier studies (almost 80%). We estimate past trends in global emissions of N2O and use these as input to a simple atmospheric box model to calculate trends in atmospheric N2O concentrations for the period 1500-2006. We show that our revised estimates for global emissions of N2O are consistent with observed trends in atmospheric concentrations.
A pilot-scale constructed wetland (CW) system, combining a free water surface wetland and a subsurface wetland in series, was used to purify highly polluted river water. The concentrations of constituents varied seasonally. The effects of season-dependent parameters, such as temperature, mass loading rate and inflow salinity, on the removal of ammonia nitrogen (AN) in the wetland system were examined at a constant hydraulic loading rate, based on data from June 1998 to February 2000. AN removal of the CW varied cyclically with the seasons. The removal efficiency and the first-order volumetric removal rate constant (k(V)) increased exponentially with water temperature, yielding a high temperature coefficient (theta). However, the mass removal rate decreased exponentially as temperature increased. These contradictory results made the actual effect of temperature uncertain. The inhibition of high water salinity on AN removal was also unclear because k(V) (as well as k(V20)) and mass removal rate were inversely proportional to salinity. However, mass loading rate (MLR) predominantly affected both the removal efficiency and the mass removal rate of AN, both of which were factors that explicitly determined seasonality. A power equation, k(V20)' alpha MLR(-n), was proposed to correct the variation of the mass loading rate in estimating k(V) and thus in designing a constructed wetland.
Spring maize under plastic mulch is the staple food crop in northwest China. Studying its evapotranspiration (ET) and crop coefficient (Kc) is important for managing water-saving irrigation in the region. Eddy covariance (EC) was applied to measure spring maize ET in 2007 in northwest China, focusing on the characteristics of the maize ET and Kc processes under plastic mulch. An interesting result was that a higher Kc in this study relative to the value of FAO 56 was presented in the mid and late season, e.g. average Kc was 1.46, 1.39 and 1.22 during the heading, filling and maturity stage, respectively. This result was mainly due to that (1) the plastic mulch had an effect on anti-senescence of maize and great green leaf still existed before the harvest; (2) the FAO 56 PM model may underestimate the reference crop ET in the mid and late season of maize in the region; (3) the planting density was higher in the study, which was about 374,800 plants ha−1. Though Kc during the mid and late season was high, a high water use efficiency of 25.2 kg ha−1 mm−1 was still obtained in the study. Our study confirmed that plastic mulch has beneficial effect on improving maize water use efficiency in this severe water shortage region of northwest China.
Agricultural practices are believed to be the major anthropogenic source of enhanced nitrous oxide (N2O) gas emissions in New Zealand. Studies conducted in New Zealand generally suggest low N2O emission from pasture; however, there is little information for arable farming systems. This paper evaluates tillage and land use effects on N2O emissions using a closed chamber technique at an Ohakea silt loam (Gleyic luvisol) where winter oats (Avena sativa L.)/fodder maize (Zea mays L.) was double-cropped for 5 years. The tillage types included conventional tillage (CT) and no-tillage (NT) systems, and a permanent pasture (PP) was used as a control.
Nitrous oxide (N(2)O) is a significant greenhouse gas, and biological nitrogen removal systems have been shown to be a significant N(2)O source. To evaluate the control parameters for N(2)O emission in the wastewater treatment process, N(2)O emissions were compared in the activated sludge from anoxic-aerobic sequencing batch reactors (A/O SBRs) acclimated under different aeration rates, and fed with synthetic wastewater. Results showed that a higher aeration rate led to a smaller N(2)O emission, while reactors acclimated under mild aeration performed the best in terms of nitrogen removal efficiency. Most of the N(2)O was produced during the aerobic phase, regardless of the aeration rate. Trace studies showed that incomplete denitrification appeared to be the major process responsible for high N(2)O emission at a low aeration rate (Run 1), while incomplete nitrification was the reason for N(2)O emission at a higher aeration rate (Run 2 and Run 3). For enhancing the efficiency of nitrogen removal while lowering energy consumption and reducing N(2)O emission, the optimal aeration rate would be 2.7 L(air)/(L(reactor) . h), in terms of the synthetic wastewater used.
The paper presented an efficient integrated physicochemical process, which consists of chemical precipitation and air stripping, for the simultaneous removal of NH(3)-N, total P and COD from anaerobically digested piggery wastewater. In the integrated process, Ca(OH) (2) was used as the precipitant for NH(4)(+), PO(4)(3-) and organic phosphorous compounds, and as the pH adjuster for the air stripping of residual ammonia. The possibility of the suggested process and the related mechanisms were first investigated through a series of equilibrium tests. Laboratory scale tests were carried out to validate the application possibility of the integrated process using a new-patented water sparged aerocyclone reactor (WSA). The WSA could be effectively used for the simultaneous removal of NH(3)-N, total P and COD. 3g/L of Ca(OH) (2) is a proper dosage for the simultaneous removal. The simultaneous removal of NH(3)-N, total P and COD in the WSA reactor could be easily optimized by selecting a proper air inlet velocity and a proper jet velocity of the liquid phase. In all the cases, the removal efficiencies of the NH(3)-N, total P and COD were over 91%, 99.2% and 52% for NH(3)-N, total P and COD, respectively. The formed precipitates in the process could be easily settled down from the suspension system. Therefore, the integrated process provided an efficient alternative for the simultaneous removal of NH(3)-N, total P and COD from the wastewater.
Constructed wetlands are considered to be important sources of nitrous oxide (N(2)O). In order to investigate the contribution of nitrification in N(2)O formation, some environmental factors, plant species and ammonia-oxidizing bacteria (AOB) in active layers have been compared. Vegetation cells indicated remarkable effect of seasons and different plant species on N(2)O emission and AOB amount. Nitrous oxide data showed large temporal and spatial fluctuations ranging 0-52.8 mg N(2)O m(-2)d(-1). Higher AOB amount and N(2)O flux rate were observed in the Zizania latifolia cell, reflecting high potential of global warming. Roles of plants as ecosystem engineers are summarized with rhizosphere oxygen release and organic matter transportation to affect nitrogen transformation. The Phragmites australis cell contributed to keeping high T-N removal performance and lower N(2)O emission. The distribution of AOB also supported this result. Statistical analysis showed several environmental parameters affecting the strength of observed greenhouse gases emission, such as water temperature, water level, TOC, plant species and plant cover.
The research results clearly indicated the inhibitory effects of unionized ammonia (FA) and unionized nitrous acid (FNA) on the nitrification process. The FA and FNA concentrations, rather than total ammonia or nitrite ion concentrations, inhibit nitrification. The concentrations of FA that inhibit nitrosomonads are greater than those that inhibit nitrobacters. The ranges of FA concentrations that begin to inhibit the nitrifying organisms are: FA inhibition to nitrosomonads, 10 to 150 mg/l and FA inhibition to nitrobacters, 0.1 to 1.0 mg/l. The inhibition of nitrifying organisms was initiated at concentrations of FNA between 0.22 and 2.8 mg/l. The following may affect the inhibitory FA and FNA concentrations in a nitrification system; acclimation of the nitrifiers to FA and FNA, temperature, and the number of active nitrifying organisms. An operational chart may be used to assess the performance of nitrifying systems. Nitrification patterns may be modified by using operating procedures that increase or reduce the inhibitory effects of FA and FNA as appropriate. FA and FNA inhibition has been shown to occur with municipal, industrial, and agricultural wastes and with fertilizers in the soil.
Combining the processes of partial nitrification and anaerobic ammonium oxidation (ANAMMOX) is an attractive wastewater-treatment technology for nitrogen removal. In this study we investigated partial nitrification by implementing a closed down-flow hanging sponge (DHS) reactor operated at controlled oxygen concentrations. Basic concept of DHS process is similar to that of trickling filter, in which oxygen concentration can be easily manipulated by controlling airflow to the reactor. The closed reactor was fed with artificial wastewater containing NH(4)Cl and operated with an HRT of 1.5h at 30 degrees C. Oxygen inside the reactor was maintained below 3% (1.2mgDO x L(-1)) (DO-dissolved oxygen) except during the startup periods. Five months of continuous operation showed that there was a strong relationship between oxygen concentration and nitrite production. The ratio of nitrite produced relative to ammonium oxidized increased by decreasing oxygen concentration. Partial nitrification was satisfactorily accomplished under oxygen limitation at around 0.5% in the gas phase (0.2mgDOL(-1)). The system showed a high ammonium-removal rate, at a maximum of 1.46kg NH(4)(+)-Nm(-3)day(-1), even at limited oxygen concentration. We also found that oxygen concentration played an important role in the production of nitrous oxide, which increased with decreasing oxygen concentration.