wcm.01.2025.22.30

Seafood waste, an inevitable byproduct of the global seafood industry, poses considerable environmental challenges primarily because of improper disposal and the resultant release of methane during decomposition. However, recent studies have revealed its potential utility in wastewater treatment, presenting a sustainable and effective approach to pollutant removal. This review investigates the valorization of seafood waste, particularly focusing on chitosan derived from shrimp shells, fish scales and bones, which can serve both industrial and municipal wastewater treatment needs. Chitosan is well-known for its robust adsorption capacity; it efficiently eliminates heavy metals and organic pollutants (thanks to its unique chemical properties). Furthermore, fish scales, which are abundant in hydroxyapatite, exhibit remarkable efficacy in adsorbing toxic metals like lead and cadmium. The integration of these biomaterials into wastewater treatment technologies not only mitigates environmental burdens, but also aligns with the principles of a circular economy. Although promising, further research is necessary to improve the scalability and consistency of these materials for larger applications. This review emphasizes the essential function of seafood waste in promoting sustainable wastewater management; it contributes significantly to both environmental preservation and resource recovery. However, this issue is often overlooked, because many do not recognize its potential. While there are challenges associated with this approach, the benefits are substantial. The integration of seafood waste into waste management strategies can lead to innovative solutions, but further research is necessary to fully understand its impact.

The disposal of seafood waste emerges as an ever more pressing environmental challenge, particularly in light of the vast scale of the global seafood industry. Approximately 70 million metric tons of seafood waste are generated annually (Yan & Chen, 2015); this figure constitutes a significant fraction of the total seafood produced worldwide. This waste—encompassing fish scales, bones, and shells and assorted other by-products—is often discarded without sufficient consideration for its potential applications. However, recent studies have highlighted the value of seafood waste as a vital resource, especially within the domain of wastewater treatment. This paradigm shift in perception is crucial; it reflects a growing recognition of sustainability practices that can mitigate environmental impacts. Even though the industry has traditionally overlooked these by-products, innovative approaches are being explored, which could transform waste into valuable commodities.

The processing of seafood engenders a considerable quantity of organic waste, which, if inadequately managed, can precipitate dire environmental consequences. For instance, the decomposition of seafood waste in landfills generates methane—a potent greenhouse gas—thereby exacerbating climate change (Gómez-Estaca et al., 2018). Furthermore, leachate resulting from the mismanagement of seafood waste possesses the capacity to contaminate aquatic ecosystems, leading to eutrophication and other detrimental forms of water pollution (Zhu et al., 2020). However, while these concerns are indeed substantial, they also underscore the critical necessity of effectively addressing the management of seafood waste. This imperative is not merely a matter of environmental stewardship; it is an essential component of sustainable practices in the seafood industry.

In light of these formidable challenges, there exists an exigent necessity for sustainable waste management strategies capable of alleviating the environmental repercussions while simultaneously recovering valuable resources. The paradigm of waste valorization—wherein waste materials are transformed into economically advantageous products—has garnered considerable attention as a plausible methodology for effective waste management. Seafood waste, which is replete with bioactive compounds such as chitin, collagen and fish oils, presents a plethora of opportunities for valorization (Younes and Rinaudo, 2015). These compounds can be extracted and employed across a multitude of industrial applications, encompassing pharmaceuticals, food production and wastewater treatment.

Chitin, in particular, has been extensively investigated due to its potential efficacy in the removal of heavy metals and various pollutants from wastewater; this characteristic renders it a compelling and environmentally sustainable alternative to conventional treatment methodologies (Aliabadi et al., 2014). Both chitin and its derivative, chitosan—extracted from seafood waste—exhibit significant promise in the realm of wastewater treatment applications. These biopolymers serve as potent adsorbents for an array of pollutants, including heavy metals, dyes and organic compounds (Yang et al., 2009). However, the widespread implementation of these materials in treatment processes is still hindered by various factors, including cost and scalability. Thus, while the potential is immense, further research is needed to fully harness these resources effectively.

The implementation of these strategies, however, may encounter numerous challenges; this, nonetheless, does not diminish the potential benefits that could outweigh such obstacles. Although there remains a significant amount to learn, the future of waste valorization (which involves converting waste into valuable resources) appears exceptionally promising. This transformation is critical because it signifies a shift toward more sustainable practices, thus addressing both environmental and economic concerns.

The ability of chitin and chitosan to engage with various pollutants derives from their distinctive chemical architecture, characterized by the presence of amine and hydroxyl functional groups that facilitate adsorption. Furthermore, chitosan is not only biodegradable but also non-toxic; thus, it emerges as a sustainable alternative for environmental remediation (Younes & Rinaudo, 2015). In recent years, scholarly investigations have delved into the potential of chitosan-derived materials for the removal of heavy metals, such as cadmium, lead and arsenic, from industrial effluents. Research findings suggest that chitosan can effectively eradicate up to 99% of these contaminants under optimal conditions (Zamora-Sillero et al., 2018). Modifications to chitosan can enhance its adsorption capabilities—this enhancement can be realized through the integration of magnetic particles or various other functional groups (Yang et al., 2009). Such alterations have the capacity to improve the effectiveness of wastewater treatment methodologies; however, they simultaneously play a role in minimizing the environmental impact of industrial discharges.

Fish scales, which serve as a ubiquitous by-product of seafood processing, exhibit a remarkable abundance of hydroxyapatite—a naturally occurring mineralized form of calcium apatite. Hydroxyapatite has attracted considerable scholarly attention because of its potential efficacy in adsorbing heavy metals and diverse pollutants from wastewater (Anggresani et al., 2021). The intricate porous structure of fish scales, when combined with the extensive surface area of hydroxyapatite, facilitates the adept adsorption of contaminants. Numerous studies have demonstrated that fish scales can eradicate up to 95% of heavy metals, including lead and cadmium, from aqueous solutions (Aliabadi et al., 2014). However, in addition to their effectiveness against heavy metals, fish scales have also been shown to extract fluoride, a common pollutant in groundwater sources (Antoniac et al., 2015). The employment of fish scales in wastewater treatment offers a cost-effective and sustainable alternative to conventional methods, particularly in locales where fish processing represents a significant economic activity. This innovative repurposing of fish scales not only mitigates the issue of waste but also advances the principles of the circular economy, thereby enhancing the sustainable utilization of resources.

The application of seafood waste within the domain of wastewater treatment represents a promising and sustainable approach to addressing both environmental pollution and the myriad challenges associated with waste management. Valorizing seafood by-products (which include chitin, chitosan and fish scales), it becomes feasible to develop effective and environmentally conscious wastewater treatment technologies. However, additional research and development are essential to confront the challenges associated with the scalability and variability of these materials. Although ongoing innovation and investment are critical, the seafood industry may assume a pivotal role in promoting a circular economy and safeguarding our water resources for future generations. This industry constitutes a significant contributor to the global economy; yet, it simultaneously generates a substantial volume of waste, which encompasses fish scales, bones, shells and various other by-products. Because these wastes are not managed appropriately, they can engender serious environmental issues, including water pollution and the release of greenhouse gases.

Recent investigations have illuminated the prospective advantages of utilizing seafood waste (especially in the context of wastewater treatment) as a sustainable and efficacious approach for tackling environmental dilemmas. This review thoroughly explores the multifaceted applications of seafood waste in wastewater treatment, particularly highlighting the use of chitosan extracted from shrimp shells, fish scales and fish bones as biosorbents for the elimination of pollutants. The valorization of seafood waste for wastewater treatment represents a promising (and sustainable) strategy for addressing concerns associated with environmental pollution and waste management. Transforming waste materials such as shrimp shells, fish scales and fish bones into valuable biosorbents, the seafood industry can, indeed, mitigate its environmental impact while fostering a circular economy. However, it is crucial to acknowledge that further research and development are necessary to overcome prevailing challenges and fully harness the potential of these materials in large-scale applications for wastewater treatment. Although the initial findings are encouraging, the path forward requires a concerted effort to elucidate the complexities involved in the scalability of these innovative solutions. Because of this, a deeper understanding of the interactions between biosorbents and various pollutants will be vital in enhancing the effectiveness of wastewater treatment processes.

This review endeavors to explore the sustainable applications of seafood waste (particularly within the realm of wastewater treatment), emphasizing not solely the environmental advantages, but also the prospects for integration into a circular economy. However, it is imperative to consider the challenges that are inherent; although seafood waste presents valuable resources, its efficacious utilization is contingent upon numerous factors. This exploration will underscore innovative methodologies and the critical nature of collaboration among stakeholders, because tackling these issues can profoundly elevate sustainability initiatives.

2. METHODOLOGY

This investigation employs a qualitative research framework, primarily leveraging document analysis to scrutinize the extant literature regarding the utilization of seafood waste in wastewater treatment processes. The central aim is to dissect and synthesize findings derived from scientific inquiries, industry reports, policy documents and case studies, thereby facilitating a nuanced comprehension of the innovative applications of seafood waste—particularly chitosan and hydroxyapatite—in the realm of sustainable wastewater management. However, by concentrating on secondary sources, this study endeavors to furnish a thorough account of the methodologies employed in the application of these materials and their prospective viability for large-scale implementation. Granting the findings indicate significant potential, further exploration is warranted to fully elucidate their practicality in diverse contexts.

The process of data collection necessitated the meticulous identification and aggregation of a diverse array of pertinent secondary sources published within a specified temporal framework (insert time range). These sources encompassed peer-reviewed journal articles, as well as industry and governmental reports, technical standards, patents and conference proceedings. The search for relevant documents was executed utilizing academic databases such as Scopus, Web of Science and Google Scholar; key terms included “seafood waste,” “wastewater treatment,” “chitosan,” “hydroxyapatite,” “heavy metal removal,” and “sustainable resource recovery.” Moreover, grey literature—comprising industry white papers and governmental reports—was incorporated into the analysis to furnish a comprehensive perspective on the subject. However, the integration of such diverse materials posed challenges. This complexity was, in part, because the quality and relevance of each source varied significantly. While the endeavor aimed for thoroughness, it is essential to recognize that the synthesis of information from disparate origins can introduce biases and inconsistencies.

In the realm of data analysis, the document review was conducted through a thematic coding process. The documents selected were subjected to a systematic examination aimed at elucidating critical themes pertinent to seafood waste valorization. This examination specifically emphasized the transformation of shrimp shells, fish scales and bones into valuable materials such as chitosan and hydroxyapatite. Another salient theme pertained to the pollutant removal efficacy of these innovative materials; they demonstrated a remarkable capacity to adsorb both heavy metals and organic pollutants. However, the review also delved into sustainability and circular economy considerations associated with the utilization of seafood waste. Furthermore, it investigated how these materials are seamlessly integrated into existing wastewater treatment technologies. Challenges, limitations and opportunities for scaling these applications were thoughtfully evaluated, thereby providing a comprehensive perspective on the potential for large-scale implementation. Though the findings are promising, the complexities involved in actualizing these applications should not be underestimated, because they require meticulous planning and consideration of various environmental factors.

To guarantee both reliability and validity, a systematic (and transparent) methodology was employed throughout the document analysis process. Various sources were meticulously cross-verified to uphold consistency; peer-reviewed papers were prioritized to augment credibility. Iterative evaluations were conducted to refine the emergent themes, ensuring that the analysis accurately mirrored broader trends within the literature. Proper citation and acknowledgment of all sources were maintained to uphold academic integrity. Because the research relies exclusively on publicly available documents, ethical dilemmas such as those pertaining to human subjects or personal data were deemed irrelevant. However, considerable attention was devoted to properly crediting all sources to circumvent plagiarism. Although any review carries inherent limitations, this study may be restricted by the accessibility of recent research and data on seafood waste valorization in particular regions. Moreover, certain technologies discussed may still reside in experimental stages, with their scalability not yet fully elucidated in the literature—this represents potential avenues for future inquiry.

The systematic methodology employed in the examination of literature regarding seafood waste in wastewater treatment engenders a comprehensive and meticulous analysis. This approach not only offers insights into prevailing practices, but also illuminates prospective avenues for sustainable resource management. However, it is essential to recognize that the complexities inherent in this field necessitate a nuanced understanding of the interplay between current methodologies and future innovations. While challenges abound, the potential for improvement in waste management strategies is significant, because the implications for environmental sustainability are profound.

3. FINDINGS AND DISCUSSIONS

3.1 Composition of Seafood Waste

The waste generated from seafood primarily consists of fish bones, shrimp shells and various organic residues, each of which harbors valuable compounds that can be effectively harnessed in wastewater treatment processes. Fish bones, for instance, are notably enriched with calcium phosphate—a mineral celebrated for its exceptional adsorption capabilities, particularly in the removal of heavy metals from wastewater (Ogunola et al., 2018). Calcium phosphate serves an additional role as a coagulant, thereby enhancing the removal efficiency of suspended solids, phosphates and other pollutants present in wastewater (Ahmad et al., 2017).

On the contrary, shrimp shells primarily comprise chitin, a biopolymer that can be deacetylated to yield chitosan. This compound has garnered significant attention in scientific discourse, particularly because of its demonstrated efficacy in adsorbing heavy metals such as lead, cadmium and copper. This effectiveness is attributed to its high amino group content, which facilitates the binding of metal ions (Rinaudo, 2006). Moreover, chitosan possesses inherent flocculating properties, making it a promising eco-friendly alternative to synthetic flocculants in the treatment of both industrial and municipal wastewater (Mohan et al., 2006). Other constituents of seafood waste, including lipids and proteins, also present potential advantages in the realm of wastewater treatment, although their roles remain less explored.

The utilization of organic materials as carbon sources within biological treatment processes serves to enhance microbial activity, thereby facilitating the degradation of organic pollutants (Yang et al., 2020). For instance, research conducted revealed that calcium phosphate, derived from piscine skeletal remains, could effectively sequester fluoride ions from industrial effluent, achieving removal efficiencies approaching 85% by (Ahmad et al., 2017). Similarly, emphasized the efficacy of chitosan in the extraction of dyes and heavy metals from textile wastewater, thereby underscoring its remarkable versatility in addressing a myriad of industrial effluents (Rinaudo, 2006). Seafood waste—primarily composed of fish bones, shrimp shells and various organic residues—presents a considerable environmental challenge, primarily because of the substantial quantities produced by the global seafood sector. However, these by-products are replete with valuable compounds, including calcium phosphate, chitin, chitosan, proteins and lipids; this rich composition holds significant potential for application in wastewater treatment initiatives.

The valorization of waste materials serves not only to enhance waste management practices; it also provides sustainable solutions for the treatment of various types of industrial and municipal wastewater. Fish bones constitute a substantial fraction of seafood waste, representing a significant portion of the discarded material generated during fish processing activities. These bones are primarily made up of calcium phosphate, specifically in the form of hydroxyapatite (Ca₅(PO₄)₃(OH)), which is recognized as the mineral form of calcium apatite. Hydroxyapatite demonstrates remarkable efficacy in adsorbing heavy metals from aqueous solutions, largely attributable to its high surface area and the presence of phosphate groups capable of binding metal ions. Furthermore, the process of deacetylation of chitin to yield chitosan notably increases its solubility in acidic solutions, rendering it an effective adsorbent for pollutants such as Direct Blue-86 (DB-86), a common dye employed within the textile industry. In a study conducted chitosan derived from shrimp shells was utilized to effectively remove DB-86 from aqueous solutions by (Fat’hi and Ahmadi, 2016). However, the implications of these findings extend beyond mere waste management, because they suggest potential avenues for environmental remediation and resource recovery.

The investigation elucidated that chitosan could accomplish nearly 100% dye elimination under optimal conditions; however, the efficacy of the adsorption process is markedly contingent upon several variables, including pH, adsorbent dosage and contact time. The Langmuir isotherm model was ascertained to align well with the adsorption data, thereby indicating that chitosan exhibits a significant affinity for DB-86. This characteristic renders it a promising candidate for dye removal in wastewater treatment scenarios.

Fish scales, another plentiful by-product of seafood processing, have also been scrutinized for their prospective utility in wastewater treatment. These scales are predominantly constituted of collagen and hydroxyapatite, both of which have been demonstrated to possess commendable adsorptive capabilities. Studies have shown that fish scales can effectively eliminate a diverse array of pollutants from wastewater, encompassing heavy metals, ammonia and essential nutrients such as nitrate and phosphate (Subhashree et al., 2020). Moreover, executed a study aimed at evaluating the efficacy of fish scales as biosorbents for treating wastewater originating from seafood processing facilities (Devasena et al., 2020).

The findings indicated that fish scales possess the capacity to induce substantial reductions in biological oxygen demand (BOD), chemical oxygen demand (COD) and ammonia concentrations within wastewater. This research also revealed that fish scales effectively eliminate over 70% of nitrites and phosphates, underscoring their promise as a cost-efficient and environmentally sustainable remedy for wastewater treatment in the seafood sector. Fish bones, which are abundant in hydroxyapatite, represent another significant by-product with potential applications in wastewater management. Hydroxyapatite, a naturally occurring mineral variant of calcium apatite, is distinguished by its proficiency in adsorbing heavy metals from aqueous solutions. Consequently, fish bones emerge as an optimal material for the extraction of hazardous metals such as lead, cadmium and arsenic from industrial effluents. Shrimp shells, a further crucial element of seafood waste, are characterized by their richness in chitin—a biopolymer amenable to chemical processing for the synthesis of chitosan. Although chitin ranks as the second most prevalent natural polymer subsequent to cellulose, it is predominantly constituted of N-acetylglucosamine units.

Chitosan, the deacetylated derivative of chitin, is extensively utilized in wastewater treatment because of its distinctive properties, which encompass biocompatibility, biodegradability and a pronounced adsorption capacity for diverse pollutants (Rinaudo, 2006). However, beyond traditional sources such as fish bones and shrimp shells, seafood waste encompasses a myriad of organic residues, including but not limited to fish skin, scales and viscera; these materials are notably rich in proteins, lipids and various organic compounds.

While these substances have been investigated for their potential in augmenting biological wastewater treatment processes, fish scales, for instance, contain collagen—a protein that can be hydrolyzed into peptides and amino acids. These resultant compounds serve as vital carbon sources for microorganisms within biological treatment systems, thereby enhancing the degradation of organic pollutants (Arvanitoyannis and Kassaveti, 2008). This collagen hydrolysate derived from fish scales has demonstrated efficacy in improving the performance of activated sludge processes, as it fosters microbial growth and activity, ultimately leading to a more effective removal of organic matter from wastewater. Furthermore, lipids extracted from fish waste, particularly fish oil, have also come under scrutiny for their significant role in biological treatment methodologies.

In the realm of anaerobic digestion processes, lipids undergo a transformation into volatile fatty acids, which function as vital substrates for methanogenic bacteria. This biological interaction ultimately culminates in the production of biogas (primarily methane). However, the efficiency of this conversion is contingent upon various factors, including temperature and microbial community composition. While the potential for biogas production is significant, challenges remain in optimizing these processes, because the dynamics of microbial interactions can be complex. Thus, understanding the nuances of lipid conversion is essential for enhancing biogas yield and sustainability. Table 1 presents a summary for different materials extracted from seafood waste used for wastewater treatment.

3.2 Applications in Wastewater Treatment

Adsorption Processes

The application of hydroxyapatite derived from fish bones in wastewater treatment has been the subject of extensive investigation. For instance, numerous studies have demonstrated its efficacy in the elimination of heavy metals, including lead, cadmium and arsenic, from contaminated aqueous environments (Reddy et al., 2017). In a particular study, fish bone powder was utilized as an adsorbent for industrial wastewater containing lead ions, achieving a remarkable removal efficiency exceeding 90% (Nguyen et al., 2019). This success can be attributed to the ion exchange mechanism occurring between the calcium present in hydroxyapatite and the heavy metals within the wastewater, which leads to the formation of stable metal-phosphate complexes.

Furthermore, beyond the removal of heavy metals, calcium phosphate derived from fish bones has been employed to extract fluoride from industrial effluents. indicated that fish bone-derived calcium phosphate could effectively adsorb fluoride ions, with removal efficiencies reaching as high as 85% (Ahmad et al., 2017). The capacity of fish bones to facilitate fluoride removal is primarily due to their propensity to undergo ion exchange reactions with fluoride ions, resulting in the formation of insoluble calcium fluoride precipitates. However, the predominant function of chitosan in wastewater treatment remains the removal of heavy metals, revealing a crucial intersection in the methodologies employed for the purification of contaminated water.

Chitosan’s amino groups (-NH₂) exhibit a pronounced affinity for metal ions, thereby establishing it as an efficacious adsorbent for various metals including lead, copper, nickel and mercury (Wan Ngah and Hanafiah, 2008). The underlying mechanism is predicated upon the chelation of metal ions by these amino groups, which results in the formation of stable complexes that can be readily extracted from aqueous environments. For instance, research conducted elucidated that chitosan could effectively eliminate over 90% of copper and lead ions from synthetic wastewater, thereby underscoring its considerable potential in industrial contexts by (Crini and Badot, 2008). In addition to its adsorptive capabilities, chitosan is employed as a flocculant in wastewater treatment processes. This is primarily due to its cationic nature, which enables it to neutralize the negative charges present on colloidal particles in wastewater. Thus, this interaction leads to the aggregation of these particles into larger flocs, which can subsequently be removed through sedimentation or filtration (Renault et al., 2009). However, this flocculating property renders chitosan a viable alternative to synthetic flocculants, which are often characterized by their non-biodegradable and toxic nature. Furthermore, chitosan has found application in the remediation of dye-contaminated wastewater.

Dyes originating from the textile industry constitute a significant environmental pollutant; however, the adsorption properties of chitosan render it effective for the removal of such organic compounds. For example, chitosan beads have been employed to adsorb reactive dyes from aqueous solutions, achieving substantial removal efficiencies—this is largely due to the formation of hydrogen bonds and electrostatic interactions between the dye molecules and the chitosan (Chiou et al., 2004). Seafood waste, especially shellfish shells derived from shrimp, crabs and oysters, merits attention as a valuable resource in wastewater treatment processes. The primary component of these shells, known as chitin, can be transformed into chitosan, a biopolymer with a multitude of applications in wastewater management. Chitosan is renowned for its high adsorption capacity, which makes it particularly efficacious in eliminating heavy metals, dyes and various other pollutants from wastewater (Viera et al., 2021). Moreover, its biodegradability and non-toxic nature enhance its attractiveness as an environmentally sustainable treatment option (Rinaudo, 2006). Several studies have substantiated the efficacy of chitosan in diverse wastewater treatment methodologies, thus underscoring its potential in addressing pressing environmental concerns.

The study demonstrated that chitosan, derived from crab shells, effectively eliminated copper ions from industrial wastewater, achieving an impressive removal efficiency exceeding 90% (Nomanbhay and Palanisamy, 2005). However, the exploration of seafood waste for biosorption has garnered significant attention; specifically, the biological components within this waste are employed to absorb and concentrate pollutants from aqueous environments. The efficacy of these materials in the extraction of heavy metals, such as lead and cadmium, has been comprehensively documented (Ngah and Hanafiah, 2008). Furthermore, seafood waste can be repurposed as a substrate in microbial fuel cells (MFCs)—bioelectrochemical systems that convert organic matter present in wastewater into electrical energy. This organic content serves as a vital fuel source for the bacteria within MFCs, thus facilitating the dual process of wastewater treatment and renewable energy generation (Pant et al., 2010). In an investigation centered on fish bones for heavy metal remediation, the adsorptive capacity of hydroxyapatite was scrutinized, revealing its remarkable effectiveness in binding metal ions from contaminated water. Nevertheless, the implications of these findings extend beyond immediate applications, as they underscore the potential of integrating waste materials into sustainable environmental practices.

The investigation revealed that fish bones possess the capacity to eliminate as much as 95% of heavy metals from wastewater under optimal conditions; this indicates their potential as a sustainable and economically viable alternative to synthetic adsorbents in wastewater treatment (Devasena et al., 2020). However, while the incorporation of seafood waste into wastewater treatment presents numerous advantages, several challenges must be surmounted in order to optimize these methodologies for large-scale implementation. One principal challenge lies in the variability inherent in the composition of seafood waste, which can significantly impact the consistency and efficacy of the treatment processes. Furthermore, the scalability of these technologies warrants thorough evaluation, particularly in areas characterized by limited resources and inadequate infrastructure. Future inquiries should prioritize the development of standardized methodologies for the extraction and modification of biopolymers such as chitosan, because optimizing the conditions for the utilization of fish scales and bones in wastewater treatment is imperative.

Moreover, the investigation into the integration of these materials with alternative sustainable technologies—such as biochar production and microbial bioreactors—holds the promise to significantly augment the overall efficiency and sustainability of wastewater treatment processes (Fat’hi and Ahmadi, 2016; Subhashree et al., 2020). However, it is essential to consider the implications of such combinations, because their effectiveness may vary depending on numerous factors. This complexity necessitates a thorough analysis, although initial findings are promising.

3.4 Applications as Biosorption Processes

A particularly significant application of seafood waste in the domain of wastewater treatment involves the utilization of chitosan, a biopolymer derived from chitin—found within the exoskeletons of crustaceans such as shrimp and crabs. Chitosan has undergone extensive examination (Rinaudo, 2006) for its remarkable capacity to adsorb heavy metals, dyes and various pollutants from wastewater. This study revealed that, under optimal pH conditions, the removal efficiency for copper surpassed 90%, thereby underscoring its potential as a natural and biodegradable adsorbent. Furthermore, the application of fish scales, which are abundant in collagen, offers another compelling avenue for addressing dye-contaminated wastewater. Specifically, research conducted by Arivoli and Thenkuzhali (2008) demonstrated that fish scales can effectively eliminate methylene blue dye from wastewater, attaining removal efficiencies as high as 98%. The porous architecture of the fish scales, combined with their extensive surface area, facilitates the adsorption of substantial quantities of dye molecules, rendering them a viable alternative to synthetic adsorbents. However, further exploration is warranted to fully comprehend the implications of these natural materials in wastewater treatment processes.

Crustacean exoskeletons, abundant in chitin and calcium carbonate, have emerged as a pivotal resource in biosorption methodologies aimed at the extraction of heavy metals and various contaminants from effluent streams. A seminal investigation conducted by Bhatnagar and Sillanpää (2009) offered an extensive critique of biosorption techniques employing crustacean shells. The authors elucidated that the substantial chitin content and expansive surface area of these shells confer a distinct advantage in the adsorption of heavy metals, including lead, zinc and chromium. Their findings indicated that the efficacy of crustacean shells in eliminating lead from aqueous solutions could reach an impressive 92%, contingent upon variables such as the initial concentration and pH level of the solution. Furthermore, an exploration by Guo et al. (2010) examined the efficacy of crab shells in the biosorption of dyes from textile wastewater. The results substantiated that crab shells could achieve a remarkable 85% removal of Congo red dye at an optimal pH of 4.5. The researchers concluded that the biosorption capacity of crab shells is modulated by several factors, namely contact time, initial dye concentration and pH. This investigation not only underscores the promise of crustacean shells as a sustainable material for wastewater remediation but also highlights their significance within the textile sector, thereby positioning them as a viable alternative in environmental management strategies.

Challenges and Future Prospects

Although the potential applications of seafood waste in the realm of wastewater treatment are promising, several formidable challenges persist. The variability inherent in the composition of seafood waste—dependent on factors such as species, processing methodologies and geographic origins—can significantly impact the consistency and efficacy of these materials within treatment processes. The extraction and processing of valuable compounds (such as chitosan) from seafood waste are often complex and costly endeavors; this complexity can limit their widespread implementation in large-scale wastewater treatment facilities. However, ongoing research endeavors are focused on optimizing extraction processes, as well as enhancing the efficiency of materials derived from seafood waste in wastewater treatment. For instance, enzymatic and microbial methods are currently being explored to improve both the yield and quality of chitosan extracted from shrimp shells. This exploration may lead to reductions in production costs and environmental impacts (Kurita, 2006). Furthermore, the integration of seafood waste-derived materials into hybrid treatment systems, which combine physical, chemical and biological methodologies, has the potential to enhance overall treatment efficiency and sustainability.

The employment of seafood waste in wastewater treatment embodies a sustainable method for tackling both waste management and water pollution dilemmas. Leveraging the distinctive attributes of fish bones, shrimp shells and various organic residues (which are often overlooked), industries can formulate effective and eco-friendly treatment solutions. This not only contributes to environmental protection but also aids in resource conservation. However, one must consider the complexities involved in the implementation of such strategies, because they require careful planning and execution. Although challenges exist, the potential benefits are significant, thus warranting further exploration and development in this field.

4. CONCLUSION

The valorization of seafood waste represents a sustainable (and eco-friendly) methodology for tackling the environmental challenges engendered by the global seafood industry. This review elucidates the potential of seafood byproducts—such as chitosan, sourced from shrimp shells and hydroxyapatite, obtained from fish scales and bones—in wastewater treatment applications. These biopolymers exhibit remarkable efficiency in adsorbing heavy metals, dyes and various other pollutants from industrial effluents; thus, offering an alternative to traditional treatment methods. Chitosan’s biodegradability and non-toxic nature render it an exemplary candidate for sustainable wastewater management. Furthermore, fish scales and bones contribute significantly to pollution control due to their effective adsorption properties. However, despite these promising results, challenges related to the variability of seafood waste composition and the scalability of the technologies remain. Continued research and innovation are vital (because they enhance the extraction processes, improve the consistency of materials and explore cost-effective methods for large-scale deployment). Although progress has been made, overcoming these obstacles is essential for realizing the full potential of seafood waste valorization. Through the integration of seafood
waste into wastewater treatment systems, industries can significantly contribute to a circular economy while simultaneously reducing environmental impact. This practice not only promotes resource recovery, but also represents a pivotal step towards more sustainable methodologies. While the utilization of such waste materials may seem unconventional, it serves to safeguard water resources and foster longterm environmental sustainability. However, the successful implementation of this approach requires careful consideration of various factors, including technological advancements and regulatory frameworks, because these elements are crucial for optimizing the efficacy of wastewater treatment processes.

ACKNOWLEDGEMENT
The authors express their heartfelt appreciation to the numerous individuals and organizations who generously supported this study. They would like to thank the International College of Engineering and Management (ICEM) in the Sultanate of Oman and the Ministry of Higher education and research innovation (MOHERI) under the block funding research grant No. MOHERI/BFP/ICEM/2023-24/01

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