Advances in aeration and wastewater treatment in shrimp farming: emerging trends, current challenges, and future perspectives

Urbanization and industrialization bring considerable benefits to humanity but also worsen water quality (Samage et al. 2022). The discharge of toxic industrial effluents, particularly from dyeing and heavy metal industries, into freshwater sources pollutes the environment. This pollution makes it challenging for living organisms to access clean drinking water and maintain cleanliness (Ahmad & Mirza 2018). Consequently, various techniques such as coagulation, flocculation, reverse osmosis, photodegradation, adsorption, and ion exchange are employed for wastewater treatment (Halakarni et al. 2023).

The shrimp farming industry plays a crucial role in providing food security, generating income for farmers, and contributing to national economic prosperity; however, this industry often faces some critical issues related to environmental pollution and energy consumption. In fact, ecological concerns and ensuring energy security need to be addressed for the sustainable development of the shrimp farming sector. The leading causes of environmental problems are the salinization of local land (Tho et al. 2008) and the pollution of water resources (Anh et al. 2010). The energy demand, primarily driven by the operation of aerators and water pumps, is a significant challenge. Specifically, the power usage of aerators takes up a substantial 80% of the energy, while water pumps contribute an additional 10%, leaving only 10% of the energy for other essential loads in shrimp farming operations (Peterson 2002).

The concentration of dissolved oxygen (DO) is crucial for the health and survival of the shrimp. Unlike their counterparts in natural river and sea environments, pond-reared shrimp have specific oxygen requirements, particularly in intensive aquaculture systems. Maintaining high levels of DO in the pond is paramount for the success and productivity of shrimp farming operations (Sombatjinda et al. 2011) to ensure the optimal conditions for shrimp to thrive and grow effectively. Therefore, aeration systems are essential tools in aquaculture, including shrimp farming, to enhance oxygen levels in the rearing pond (Boyd 1998; Moulick et al. 2002).

Intensive systems demand meticulous water treatment measures to maintain appropriate water quality, particularly concerning DO levels (Chamberlain 1987; Hopkins et al. 1993). The necessity for frequent water exchange to ensure good water quality is crucial, but it comes at a significant cost, both in terms of energy consumption and potential environmental impact. The reliance on energy-intensive water pumps, often powered by fossil fuels, increases production costs and environmental pollution. This underscores the need for sustainable energy solutions in shrimp farming operations. Additionally, abrupt changes in water conditions resulting from improper exchange practices can lead to stress and health issues for the shrimp, potentially causing significant losses. Furthermore, the potential transmission of pathogens through water exchange poses a considerable risk. Disease outbreaks can devastate shrimp populations, leading to mass mortalities and economic losses for farmers (Funge-Smith & Briggs 1998).

Intensive shrimp farming can lead to rapid pollution of pond water due to high stocking densities and feeding rates, resulting in a significant input of organic matter, uneaten food, shrimp feces, and other waste products into the water (Vo 2010). A Chinese research group found some of the most severe pollutants, such as inorganic nitrogen, chemical oxygen demand, and inorganic phosphorus, when investigating the impact of intensive shrimp farming on water quality in coastal creeks (Biao et al. 2004). In 2018, China utilized 35.86 × 10¹⁰ m³ of fresh water for aquaculture (Liu et al. 2021). Among different regions worldwide, Asia contributed the most aquaculture wastewater (about 37%). However, only approximately 23% of wastewater in total was treated, with 60% being reused (Kashem et al. 2023). In fact, if the wastewater is not appropriately managed, this can lead to various environmental issues. The excess nutrient content in shrimp feeds, particularly nitrogen and phosphorus, can surpass the levels in the actual culture water, resulting in eutrophication in aquaculture wastewater, potentially causing ecological imbalances and even ecosystem collapse. Shrimp feces contain a significant amount of nitrogen compounds, predominantly ammonia, which can lead to further chemical reactions in the aquatic environment, producing ammonia, urea, and carbon dioxide (Patil et al. 2021). Moreover, ammonia is highly toxic to marine organisms, including shrimp, and can significantly impact pond water quality. Besides, when dead shrimp are not promptly removed from the pond, they can have several negative consequences, including increased organic load and the potential for disease outbreaks. Therefore, shrimp farmers often apply various drugs and chemicals to prepare the culture facilities, promote growth, and treat diseases. To some extent, using chemical substances in shrimp farming, if not appropriately managed, can lead to water pollution. Managing and treating waste is crucial for maintaining productivity and ensuring high-quality shrimp production. In other words, a well-designed and adequately maintained wastewater treatment system is vital in mitigating the severe environmental consequences caused by wastewater from shrimp ponds.

Aeration systems are crucial in shrimp farming as they provide the necessary oxygen levels for the shrimp to thrive. However, they can be energy-intensive, especially in intensive farming systems with high stocking densities. This increased energy consumption leads to higher operating costs for the farm. Therefore, various significant studies on aeration systems related to design modification (Boyd & McNevin 2021), operation controlling modes (Zhu et al. 2020; Tsai et al. 2022), and renewable energy applications (Campana et al. 2019; Garavelli et al. 2022; Jamroen 2022) have been investigated to enhance aeration efficiency, operational costs, and CO₂ emission. Several reviews exist on various aeration facilities and renewable energy applications for effective aquaculture (Roy et al. 2021, 2022; Vo et al. 2021). While there have been efforts to improve aeration systems in shrimp aquaculture, a comprehensive and widely available body of reviews on this topic is still relatively limited.

There has been a concerted effort in the scientific community to develop and study various treatment technologies for wastewater from shrimp ponds. These technologies aim to mitigate the adverse environmental impacts of shrimp farming and contribute to the industry's sustainability. Some conventional methods have been applied, such as recirculating aquaculture (Zohar et al. 2005) and biological and physicochemical systems (Kumararaja et al. 2019; Aquilino et al. 2020). In addition, few review papers and research studies specifically focus on wastewater treatment technologies for aquaculture, including shrimp culture (Iber & Kasan 2021; Ahmad et al. 2022).

Addressing the challenges of aeration and wastewater management in shrimp aquaculture is critical for sustainable industrial development. By focusing on recent advanced approaches, this paper contributes to the cutting-edge knowledge and technologies that can potentially impact shrimp farming practices. Additionally, by emphasizing the review gaps, the review actively contributes to the research community's understanding of the current state of knowledge in this field. Specifically, the current state-of-the-art aeration systems and wastewater treatment methods will be outlined, followed by the proposed energy model. Besides, this study focuses on an energy model and its unique features for sustainable shrimp production, which significantly contributes to aquaculture. Lastly, concluding remarks are summarized.

The atmospheric pressure is more significant than that in the water pond; hence, oxygen from the air is driven into the water at the pond's surface and circulates over the water body in bubble form. This process, called aeration, increases the DO level in pond water. There are two main aeration types, i.e., natural aeration and artificial aeration, used in practices for shrimp aquaculture. In natural aeration, the DO level in water bodies increases during the daytime since phytoplankton and aquatic plants dwelling in the surface water produce oxygen via photosynthesis (Mahmudov et al. 2019). Consequently, the level of DO during the day is higher than the saturated concentration because the amount of DO production is greater than the respiration rates of organisms in the cultured pond.

Nonetheless, natural processes could not supply sufficient DO to shrimps because they live in the bottom and middle layers of the pond (Chunrong et al. 1994; Oberle et al. 2019). Apart from that, the intensification of shrimp farming has increased in recent years, leading to the high demand for DO in cultured ponds. Therefore, artificial aeration systems are necessary to compensate not only for the respiration of the cultivated species but, more importantly, for the decomposition of organic matter, which is significantly accumulated during the intensive or especially supper-intensive culture. In artificial aeration, the contact between water and air interfaces is increased to mix more oxygen from the atmosphere into the water body. Artificial aerators improve DO levels and alleviate DO stratification in the water columns thanks to water circulation.

Mechanical or artificial aeration systems are commonly used in aquaculture ponds as they are the most effective means of improving oxygenation in semi-intensive and intensive aquaculture productivity (Roy et al. 2021). Mechanical aerators are classified into splash, bubbling, and gravity aerators according to their design and operation modes. Each type has many subclassifications with specific configurations and functions.

Splash aerators, e.g., paddlewheel aerators, spiral aerators, pump sprayers, and vertical pumps, employ mechanical energy to break down the water into droplets. Paddlewheel aerators are the most effective surface aerators (Roy et al. 2015).

Diffused aerators, propeller-aspirators, and submersible aerators, which belong to bubbling aerators, release air bubbles into the water. A diffused aerator consists of a compressor, diffusers, and pipelines. The air containing oxygen is blown via pipelines by a compressor to diffusers with tiny pores that release bubbles to aerate the water body at the bottom or the top of the pond. The diffuse aeration system is energy efficient, saving operation costs compared to other systems (Roy et al. 2021).

When the water flows over ladder steps due to potential energy, the interfacial area between water and air increases, thus facilitating aeration (Timmons et al. 2002). This performance is called gravity or cascade aeration. There are several cascade aerators, such as stepped cascade aerators, circular stepped cascade aerators, and pooled circular stepped aerators. A pooled circular stepped aerator has a configuration similar to a circular stepped cascade one, except that the former has enclosures at the outskirt of each circular step. The barrier increases the time exposure of water droplets on steps, resulting in a high aeration transfer rate. This aeration manner could increase standard aeration efficiency (SAE) with the same power consumption, making this aerator type helpful in aquaculture (Kumar et al. 2013). The performance of aerators, based on standard oxygen transfer rate (SOTR) and SAE, and their application according to pond volumes are presented in Table 1.

The intensification of aquaculture, while providing significant benefits in increased food production and economic opportunities, can coincide with energy-related challenges. When intensified aquaculture practices are not managed sustainably, they can have various negative impacts. Rising energy prices can significantly affect food security at multiple levels (Kim & Zhang 2018).

Researchers have investigated vital factors affecting energy demand in the aquaculture industry. Some key determinants of energy intensity in aquaculture production include cultured species, farming systems, scale, technology, and local conditions (Cao et al. 2013). Energy plays a crucial role in shrimp aquaculture operations, such as aeration systems, water pumps, feeder machines, lighting systems, heating or cooling systems, monitoring and control systems, and waste management systems. The aeration system is one of the most energy-intensive components in a typical shrimp farming operation, consuming approximately 90–95% of the total energy (Marappan et al. 2020). Electric motors are commonly used to drive mechanical aerators in aquaculture operations, including shrimp farms. They are favored for several reasons: efficiency, simple operation, reliability, variable speed control, and low maintenance. In many intensive aquaculture operations, including shrimp farming, aeration systems often need to run continuously, 24 h a day, to maintain optimal oxygen levels for the aquatic organisms. This continuous operation leads to high energy consumption, and a high operational cost for aquaculture facilities. Besides, in remote or off-grid areas where access to the national power grid is unavailable, diesel generators are a common alternative for powering mechanical aeration systems in shrimp farms (Taparhudee et al. 2007). Generally, the energy demand for shrimp production is high, varying from 11.4 to 41.6 GJ/t shrimp (Boyd & McNevin 2021), accounting for about 10% of total variable costs (Ngoc et al. 2021).

Electric motors powering mechanical aerators in aquaculture, especially in systems where aeration needs to be continuous, can be significant energy consumers. This is particularly crucial in high-density farming scenarios where maintaining optimal DO levels is vital for the health and growth of aquatic organisms like shrimp. Controlling aerators effectively is an essential area of research and development in aquaculture. The goal is to balance maintaining optimal DO levels for the aquatic organisms and minimizing power consumption. Some of the strategies and technologies focusing on controlling aerators have been considered. When aerators are controlled intermittently, energy consumption is reduced (Zhu et al. 2020). Furthermore, automatic control (Tsai et al. 2022) and intelligent control (Elmessery & Abdallah 2014; Cruz et al. 2019; Deng et al. 2019) also effectively decrease the energy requirement of aeration technologies.

Besides, design modifications to mechanical aerators have been implemented to improve aeration efficiency and reduce operational costs (Boyd & McNevin 2021). In addition, a study on different configurations of impeller aerators (Adel et al. 2019) tried to achieve the highest aeration efficiency. On the one hand, research and experimentation are conducted to determine the ideal rotation speed for surface aerators in specific aquaculture systems such as paddlewheel aerators (Moore & Boyd 1992; Roy1i et al. 2015) and spiral aerators (Roy et al. 2017). On the other hand, the new generation of aerators, namely impeller (Marappan et al. 2020), centrifugal water stirrer (Itano et al. 2019), and new tube aeration device (Zhang et al. 2020), have been applied in aquaculture and enhanced oxygenation energy-saving technology with high performance (Table 1).

Moreover, aquaculture operations can reduce their reliance on fossil fuels, lower greenhouse gas emissions, and achieve significant cost savings over time by incorporating renewable energy sources. A standalone photovoltaic system with battery storage is used to power the aeration system (Jamroen 2022). Floating and floating-tracking PV systems are employed for shrimp farms in Thailand, producing energy self-sufficiency with high reliability and better competitiveness by limiting the energy storage system (Campana et al. 2019). Furthermore, combining PV and solar-thermal panels provides electrical and thermal loads for the fish farm (Ioakeimidis et al. 2013). Likewise, wind energy is solely employed for small-scale fish farms in developing countries (Mahmudov et al. 2019) or combined with a PV system to power the farm (Nguyen & Matsuhashi 2019). Renewable energy is also employed for on-shore and off-shore aquaculture, with promising results (Garavelli et al. 2022). Besides, a workboat is powered by hydrogen from water electrolysis using off-shore wind power for bluefin tuna farming (Miyoshi 2020). Notably, the local biogas waste at a shrimp farm in Vietnam is used to generate hydrogen by dry reforming methane for power generation (Shiratori et al. 2019).

Several waste sources, including suspended solids and chemicals, can impact shrimp farms' water quality and environmental sustainability. Suspended wastes, primarily composed of unconsumed feed and fecal matter, can significantly impact shrimp growth and aquaculture performance. Solid wastes, which include both suspended solids (small particles that are carried by the water) and settled solids (particles that have sunk to the bottom), can pose significant risks to water quality and aquatic life if not managed properly (Timmons & Summerfelt 1997). Suspended solids in shrimp farms can significantly impact the availability of light, which is crucial for the growth of phytoplankton. This, in turn, affects the availability of natural food sources for aquatic animals. Suspended solids, especially when they consist of fine particles, can be challenging to remove from aquaculture systems using conventional methods. Coagulation and sedimentation are particularly effective for dealing with such particles (Dauda et al. 2019). Settled solids refer to larger particles that, due to their size and weight, can sink to the bottom of a container relatively quickly (Ebeling & Timmons 2012). Excessive solid waste accumulation can lead to eutrophication, severely affecting the aquatic ecosystem, including shrimp populations.

Excessive nutrient loading, particularly of nitrogen and phosphorus, can lead to the proliferation of algae. This can have significant negative impacts on shrimp farming. The decomposition of organic matter may produce ammonia (⁠ and ⁠), and nitrite. and are harmful to fish while is non-toxic to them. The concentration of increases at higher pH and temperature (Ng et al. 2018). Ammonia oxidation produces nitrate, which is generally safe for most cultured species (Dauda & Akinwole 2015). However, nitrate and phosphorus are essential nutrients for aquatic plants and algae. However, excessive concentrations of these nutrients can lead to over-enrichment of the water, a condition known as eutrophication (Wong 2001).

Reducing the use of chemicals in aquaculture is a significant step toward more sustainable and environmentally friendly practices. Recent aquaculture has strictly reduced reliance on chemicals used for prophylaxis, curative (Ajadi et al. 2016), anesthetics, ectoparasiticides, endoparasiticides, and vaccines (Costello et al. 2001). While preparing culture facilities, growth and treatment of diseases, salt, lime, and bleaching powder are also applied. The use of these substances can contribute to pollution if not managed properly (Iber & Kasan 2021). Both salts and lime serve essential purposes in aquaculture, and when used appropriately, they can contribute to creating a healthy and suitable environment for aquatic organisms. While chemicals like salts and lime play crucial roles in aquaculture, their excessive or improper use can negatively impact the environment (Boyd & McNevin 2015). In shrimp aquaculture, it is common practice to discharge wastewater from the ponds, and this water typically flows into nearby natural water bodies, such as rivers, streams, or estuaries. The concentration of chemicals in the wastewater from a shrimp farm can be influenced by several factors, including the farm size, the types and quantities of chemicals used, and the size and capacity of the receiving water body (Dauda et al. 2019).

A few reported methods exist to remove the waste sources in shrimp aquaculture systems. Cavitation is an effective method for wastewater treatment, offering specific advantages over traditional advanced oxidation processes. During the operation, reactants and ultraviolet light are not required. This method also helps minimize by-products compared to other techniques; thus, it could reduce the contaminants in the wastewater (Joshi et al. 2019). Cavitation also plays an essential role in destroying the cell structure of bacteria and other microorganisms in wastewater.

Secondly, nanomaterials can be used in various applications, including wastewater treatment, to protect the environment. Nanomaterials such as nano adsorbents (Manyangadze et al. 2020), polymeric nano adsorbents (Thamer et al. 2020), nanomaterial-based membranes (Ng et al. 2018), and nanofiber membranes (Askari et al. 2019) are applied for wastewater treatment. This method can adsorb pollutants and significantly reduce the amount of nitrate and phosphate. The use of nanomaterials in shrimp aquaculture wastewater treatment is still an emerging technology; therefore, very little research has been done to date. The adsorption method is selected for its simplicity, efficiency, and ease of reusing adsorbents (Hegazi 2013; Nakamoto et al. 2017). Zeolites are adsorbents with high exchange ion capacity, selectivity, and compatibility (Gargiulo et al. 2018). Some metals, such as ⁠, and were treated using zeolite with fly ash and oil shale ash (Bai et al. 2022) and zeolite NaP1 (Liu et al. 2018). Besides treating heavy metals, zeolites, and their composites still have nitrate and phosphate adsorption abilities. The adsorption experiments of natural zeolites on nitrate were performed with a removal efficiency of 98% (Gaikwad & Warade 2014). The nanomaterials-based membrane is also applied to treat wastewater in shrimp aquaculture since it is permeable, has easy fouling resistance, and has mechanical and thermal stability. Membranes are known to remove viruses, sludge, and phosphorus in shrimp wastewater (Ng et al. 2018). Moreover, the nanofiber membranes have shown better efficiency with high adsorption capability of small particles in effluent since they have larger specific surface areas and greater porosity. It is reported that nanofiber reactors could efficiently remove nitrate and phosphate in aquaculture wastewater by 70.52 and 70.48%, respectively (Iber & Kasan 2021).

The third technological treatment for shrimp wastewater uses the high-rate algal pond system because it is a practical, highly profitable, and green technology. The authors simulated aquaculture wastewater and reported completely removing ammonium, nitrate, and phosphate while treating above 80% of organic matter (Kishi et al. 2018). Using aquatic plants in shrimp wastewater treatment greatly benefits the removal of pollutants. Picochlorum maculatum could uptake 57, 46.4, 89.6, and 98.5% of phosphate, nitrate, nitrite, and ammonia in shrimp wastewater treatment systems, respectively (Kumar et al. 2016).

Solid-state thermophilic aerobic fermentation is an innovative technique that has been developed for producing clean nutrients, including ammonium gas, which can be used to culture and harvest algae (Koyama et al. 2018). Nonetheless, the selection of species for aquaculture or algae cultivation requires a thorough understanding of both the biological requirements of the species and the local environmental conditions, which can limit the vast application range of this method. Because the ever-increasing and severe environmental challenges are bedeviling shrimp aquaculture farms, especially in wastewater handling, the biofloc technology has been developed. This technology uses isolated biofloc boost-up bacterium inoculums to enhance the water quality of the shrimp culture and improve shrimp growth (Kasan et al. 2018; El-Sayed 2021). This technology partially departs from the conventional biological filter that removes ammonia, nitrate, and dissolved organic solids in a recirculation aquaculture system. Bioaugmentation with nitrifying and denitrifying microbial consortia is a practical approach used in aquaculture, particularly in shrimp culture, to address the issue of nitrogenous metabolites. The incorporation of ammonia-oxidizing, nitrite-oxidizing, and denitrifying bacteria is a cutting-edge technology used to manage total ammonia nitrogen levels in shrimp culture water effectively (Shi et al. 2020; Patil et al. 2021). While systems incorporating ammonia-oxidizing, nitrite-oxidizing, and denitrifying bacteria can be highly effective in increasing farmer yield and conserving water, there can be challenges associated with the resulting wastewater. Specifically, elevated ammonia, nitrite, and nitrate levels in the wastewater can pose environmental risks and render the system less environmentally friendly. Besides each method applied to the treatment of shrimp pond wastewater, combining these solutions to increase the effectiveness of wastewater treatment is also studied and applied. Combining cavitation and biofloc technology could remove chemicals and shrimp feces and successfully feed debris from the wastewater (Kwon et al. 2021). Table 2 shows different wastewater treatment technologies for aquaculture farming.

Implementing mechanical aerators and water pumps in shrimp farms can lead to high energy consumption, elevated operational costs, and greenhouse gas emissions. Despite advancements in aerator technology and adopting green energy sources in aquaculture, conventional aeration systems can still have drawbacks, such as low aeration efficiency and high energy consumption due to atmospheric oxygenation, which accounts for 21%. Using pure oxygen instead of atmospheric air for aeration systems in aquaculture is a well-established practice that offers several advantages, such as higher DO levels, reduced energy consumption, and increased growth rates. However, there are associated costs and environmental considerations when using pure oxygen in aquaculture. Pure oxygen finds broad applications in various industrial processes due to its unique properties (Jianwei et al. 2003); few works about utilizing pure oxygen from water electrolysis for aeration systems in aquaculture were demonstrated (Nguyen et al. 2021).

Besides, pollution associated with wastewater from shrimp aquaculture is a significant concern that can negatively impact the environment and surrounding ecosystems. There are various methods to address pollution and treat sources of disease in shrimp farming environments; however, the development of a comprehensive, practical, and sustainable solution is significantly challenged. Therefore, finding effective wastewater treatment methods for shrimp ponds is critical and urgent. This is vital for maintaining the health of the shrimp, preventing pollution of the surrounding environment, and ensuring the long-term sustainability of shrimp farming operations. For the above reasons, designing an optimal sustainable energy model for shrimp farms is crucial to reducing environmental impact and ensuring long-term viability. The sustainable energy system utilizes renewable energy to power the aeration system for producing oxygen on-site, combined with an advanced wastewater treatment system for shrimp farms.

Shrimp ponds must be continuously aerated to maintain optimal water quality, oxygen levels, and overall environmental conditions for the shrimp. However, aeration intensity is higher at night than during the day. During the day, electrical energy is extracted from solar panels and wind turbines to power the aeration system. A stable amount of energy is needed for the wastewater treatment system because maintaining a steady and consistent power supply is crucial for the proper functioning of the wastewater treatment system, ensuring that the water quality in the shrimp ponds remains optimal for the health and growth of the shrimp. The excess energy is used to operate an electrolyzer for on-site oxygen production. Furthermore, the by-product hydrogen through water electrolysis is stored in a suitable container or system to generate backup power.

The pure oxygen from the electrolyzer is temporarily stored in a tank before being sent to the wastewater treatment system. The wastewater from shrimp ponds is piped to the intensive filtration unit to remove organic contaminants, such as feces, silt, large algae, and uneaten food. The filtered water discharged from the filtration system combines with pure oxygen released from the tank. The mixture of water and oxygen is sent to the bactericidal treatment unit, which applies hydrodynamic cavitation technology, ensuring that the water in the shrimp ponds remains free from harmful pathogens and is conducive to the health of the shrimp. Introducing pure oxygen into the hydrodynamic cavitation process can indeed enhance its effectiveness. Moreover, pure oxygen increases the solubility of oxygen in water; thus, shrimps can absorb oxygen more efficiently. After removing pathogenic microorganisms, the treated wastewater is sent to an adsorption system containing adsorbents such as NaX zeolite and NaP zeolite. Both could absorb ions such as ⁠, and the total phosphate, ensuring the shrimp pond water satisfies the standard QCVN 02 - 19: 2014/BNNPTNT. The treated water is transferred to a microorganism pond with substrates, probiotics, and vigorous aeration. The water from the microorganism pond is used to supply cultured ponds. Furthermore, a specific water flow creation unit is employed to achieve uniform distribution of DO and efficient waste collection for siphoning or removal in a shrimp pond.

This innovative aeration system provides pure oxygen for the shrimp ponds with high efficiency in absorbing oxygen instead of relying solely on oxygen from the air. Therefore, combining an efficient aeration system with an effective wastewater treatment system can lead to significant energy savings and reduced emissions in a shrimp farming operation compared to a traditional aeration system since a large amount of nitrogen gas is removed from the air. As a result, the amount of gas injected into shrimp ponds and energy requirements are reduced.

Implementing a well-controlled system operation in shrimp ponds can lead to significant energy savings and cost reduction. This is achieved by leveraging the natural oxygen production from photosynthesis to meet a portion of the shrimp's oxygen demand during daylight hours. As a result, the electrolyzer, which is responsible for supplemental oxygen production, can be controlled dynamically based on the oxygen concentration in the water. Monitoring DO levels in the cultured ponds is crucial for this process. Dedicated DO sensors provide real-time data on oxygen levels, which serve as feedback to adjust the electrolyzer's output. By modulating the input power of the electrolyzer between 20 and 100% of its capacity, the oxygen production rate can be finely tuned to match the shrimp ponds' oxygen requirements. During high oxygen production from photosynthesis, the electrolyzer can operate at lower power levels or be temporarily turned off, reducing energy consumption. Conversely, when oxygen levels decrease, indicating higher demand from the shrimp, the electrolyzer can ramp up its production to ensure optimal conditions for the aquatic environment.

At night, since there is no sunlight, photosynthesis does not occur. However, organisms in the pond, including plants, animals, and microorganisms, continue to respire. Respiration is using oxygen to break down glucose, release energy, and produce carbon dioxide and water as by-products. This consumes oxygen from the water, decreasing oxygen levels; hence, aeration becomes necessary. In other words, at night, only the wind turbine system cannot produce enough energy, or during the day, when renewable energy sources cannot meet the power demand due to their fluctuating behavior, electricity shortages are inevitable. When imbalances in energy supply and demand occur, the energy storage system is used to provide the necessary power to meet the energy shortage needs of the shrimp farm.

When a power shortage occurs, the by-product hydrogen stored in a tank through electrolysis is fed into the fuel cell to regenerate electrical power to supply the load at the shrimp farm. However, if the power demand exceeds the fuel cell capacity, the system is connected to the national grid to buy electricity, ensuring the system's stable operation. In addition, with the assistance of a fuel cell, this process produces pure water and a vast amount of heat. This pure water is reused for electrolysis, which saves water and forms a sustainable closed cycle. Besides, the heat generated is used to warm up grow-out ponds in the rainy season or for nursery ponds.

Many attempts have been made to alleviate the socio-economic impacts of shrimp farming owing to improper management practices. This paper reviews recent technologies for aeration and wastewater treatment management in the shrimp industry. Technological approaches for aeration and wastewater treatment systems for shrimp aquaculture have undergone numerous modifications to address specific challenges. An integrated technology of suitable solutions offers more efficiency than independent approaches to save energy and protect the environment. This integration promotes sustainability, improves shrimp growth, protects surrounding ecosystems, and complies with water discharge and quality regulations by implementing adequate aeration and wastewater management practices. Therefore, a proposed hybrid system in this paper based on the author's experience and opinion after intensive study, including an advanced aeration system combined with a multi-stage wastewater treatment system, can significantly reduce its environmental footprint, minimize energy consumption, effectively manage water quality, and promote sustainable development for shrimp aquaculture. Nonetheless, the technology has not matured and is still in progress; further study on system optimization and effective validation is needed. In the long run, the proposed sustainable energy model will be a breakthrough with the ultimate goal of achieving financial feasibility and environmental sustainability for the shrimp industry and aquaculture.

N.T.N. was funded by the Postdoctoral Scholarship Programme of Vingroup Innovation Foundation (VINIF), code VINIF.2023.STS.04.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.