REVIEW ARTICLE

Phytoaccumulation to Nanotechnology: Hydrophytes as Sustainable Agents for Heavy Metal Bioremediation

Tarun Kumar Patel*

Department of Biotechnology, Sant Guru Ghasidas Govt. P.G. College, Kurud, Dhamtari, India

*Corresponding Author Email- tarun_rgh@yahoo.co.in

Graphical Abstract

Introduction

Heavy metal pollution represents a pervasive global environmental crisis, stemming from industrial discharges, mining operations, agricultural runoff, and urban activities, which contaminate water bodies, soils, and ecosystems worldwide (Yu et al., 2025; Piwowarska et al., 2024). Metals such as lead (Pb), cadmium (Cd), mercury (Hg), arsenic (As), chromium (Cr), copper (Cu), zinc (Zn), and nickel (Ni) are persistent, bioaccumulative, and toxic, leading to severe disruptions in aquatic ecosystems, including biodiversity loss, soil degradation, and bioaccumulation in food chains (Angon et al., 2024; Piwowarska et al., 2024). These contaminants pose significant risks to human health, causing organ damage (e.g., kidneys, liver, brain), neurological disorders, and increased cancer incidence through contaminated water and food sources (Piwowarska et al., 2024; Angon et al., 2024). Global hotspots include regions like Asia's Yangtze River Basin and India's Ganges Plain, where concentrations exceed safe thresholds due to rapid industrialization, exacerbating threats to sustainable development goals (SDGs) such as SDG 6 (Clean Water and Sanitation) and SDG 3 (Good Health and Well-being) (Yu et al., 2025).

Conventional remediation techniques, including chemical precipitation, ion exchange, and adsorption, are often energy-intensive, costly, and prone to generating secondary pollutants, highlighting the urgent need for alternatives rooted in life sciences (Angon et al., 2024; Singh et al., 2024). Phytoremediation, particularly using hydrophytes-aquatic plants adapted to submerged or wetland environments-emerges as a promising, nature-based solution (Farid et al., 2023; Ali et al., 2020). Hydrophytes like E. crassipes (water hyacinth), Lemna minor (duckweed), Pistia stratiotes (water lettuce), Typha latifolia (cattail), and submerged species such as Ceratophyllum demersum and Potamogeton pectinatus leverage biological processes including phytoaccumulation, phytostabilization, rhizofiltration, and biosorption to absorb, sequester, and detoxify heavy metals (Ali et al., 2020; Tanko et al., 2025). Their efficacy is enhanced through symbiotic interactions with metal-resistant bacteria (e.g., Pseudomonas and Bacillus spp.), which facilitate metal transformation and uptake of Cu and Zn in industrial wastewater (Bhat et al., 2022; Farid et al., 2023).

These plants exhibit unique biological capabilities, such as rapid growth, high biomass production, and tolerance to contaminated conditions, making them ideal for treating diverse pollution sources, from mining effluents to textile wastewater (Ali et al., 2020; Singh et al., 2024). For instance, E. crassipes has demonstrated significant removal of Cr and Cu in constructed wetlands, while submerged hydrophytes such as P. pectinatus are capable of removing Cd, Pb, Zn, and Mn (Farid et al., 2023; Tanko et al., 2025).

Methods

This article aims to provide a thorough examination of hydrophytes as sustainable bioremediation tools for heavy metal pollution by exploring their biological mechanisms, practical applications, challenges, and future directions. A comprehensive literature search was conducted across reputable databases, including Google Scholar, PubMed, Scopus, Web of Science, and ScienceDirect. The search focused on documents published between 2015 and 2025 to capture recent developments while including foundational studies. Keywords such as "hydrophytes," "phytoremediation," "heavy metal bioremediation," "phytoaccumulation," "phytostabilization," "microbial synergies," "nanophytoremediation," and "sustainable heavy metal removal" were used in the search strategy. The inclusion criteria centered on peer-reviewed articles, reviews, and case studies relevant to aquatic plants and heavy metal detoxification, while non-peer-reviewed sources and studies outside the scope of hydrophyte-based approaches were excluded unless they provided essential context on pollution impacts or conventional methods. The search results were systematically categorized into key areas, including physiological and biochemical mechanisms, species-specific efficacies, environmental factors, microbial interactions, applications in wastewater treatment, and emerging technologies. A critical analysis was conducted to evaluate the methodologies, results, and conclusions of the selected studies. Gaps in the literature, such as limited field-scale implementations and policy integration, and areas of consensus or disagreement were identified to inform future research directions.

Biological Mechanisms of Hydrophyte Bioremediation

To understand how hydrophytes contribute to heavy metal removal, it is essential to first examine phytoaccumulation, a key process that underpins their bioremediation potential (Figure 1).

Phytoaccumulation

Phytoaccumulation, a cornerstone of hydrophyte-based bioremediation, is the ability of aquatic plants to absorb heavy metals from water or sediment and translocate them into their tissues, effectively reducing environmental concentrations (Sukul et al., 2023). This biological process leverages the physiological and biochemical adaptations of hydrophytes, enabling them to uptake, transport, and store toxic metals such as Cd, Pb, Zn, and Hg in their roots, stems, or leaves (Barba-Brioso et al., 2023; Pelcová et al., 2022).

The mechanism of phytoaccumulation begins with metal uptake through the roots, driven by active transport processes involving specialized membrane transporters, such as those in the ZIP (Zinc-regulated, Iron-regulated transporter-like Protein) family, which regulate the influx of divalent cations like Zn and Cd (Gul et al., 2023). Once absorbed, metals are translocated to aerial tissues via the xylem, a process mediated by chelating agents like phytochelatins and metallothioneins, which bind metals to prevent cellular toxicity (Sukul et al., 2023; Quronfulah et al., 2023). For instance, L. minor can accumulate up to 1,400 mg/kg of Cd, demonstrating its high phytoaccumulation capacity (Hassan et al., 2020). Submerged hydrophytes, such as C. demersum, exhibit enhanced uptake of dissolved metals due to their direct exposure in the water column, enabling the removal of Hg in contaminated aquatic systems (Pelcová et al., 2022).

Building on the role of phytoaccumulation in metal uptake and storage, the next mechanism, phytostabilization, further enhances the stability of contaminated environments by immobilizing heavy metals in the soil.

Phytostabilization

Phytostabilization is a key bioremediation mechanism employed by hydrophytes to immobilize heavy metals in contaminated aquatic environments, preventing their migration into water bodies and food chains (Mendez & Maier, 2008). Unlike phytoaccumulation, which involves metal uptake and translocation to shoots, phytostabilization focuses on sequestering metals such as Cd, Pb, Cu, Zn, and As in roots or the rhizosphere, thereby reducing their bioavailability and environmental risk (Radziemska et al., 2017; Lacalle et al., 2023).

The process begins with metal adsorption onto root surfaces or precipitation within the rhizosphere, facilitated by root exudates such as organic acids, amino acids, and polysaccharides that bind metals into stable complexes (Egendorf et al., 2020). For example, P. australis stabilizes Pb and Zn in wetland sediments by forming insoluble metal sulfides or phosphates, reducing their mobility (Saran et al., 2020). The rhizosphere also fosters microbial activity, in which metal-tolerant bacteria stabilize metals by transforming them into less bioavailable forms (Yi et al., 2023).

Physiological adaptations in hydrophytes, including robust root cell walls and vacuolar compartmentalization, further support phytostabilization by limiting metal translocation to shoots, thereby protecting photosynthetic tissues from toxicity (Radziemska et al., 2017). Biochemical mechanisms, such as the production of metallothioneins and phytochelatins, bind metals in roots, mitigating oxidative stress caused by high metal concentrations (Lacalle et al., 2023).

Biochemical Detoxification

Complementing the physical immobilization provided by phytostabilization, biochemical detoxification mechanisms enable hydrophytes to neutralize metal toxicity at the cellular level, ensuring plant survival and sustained remediation in harsh contaminated conditions.

Figure 1: Schematic Diagram of Phytoaccumulation and Phytostabilization Mechanisms [The diagram showing metal uptake from water/sediment to roots, translocation to shoots (phytoaccumulation), or immobilization in rhizosphere (phytostabilization), with transporters, chelators, and microbial action.]

Biochemical detoxification is a critical mechanism by which hydrophytes mitigate the toxic effects of heavy metals, enabling their survival and sustained bioremediation in contaminated aquatic environments (Molina & Segura, 2021). This process involves activating enzymatic and non-enzymatic pathways that neutralize oxidative stress and sequester metals such as Cd, Pb, Zn, and Cr within plant cells, thereby preventing cellular damage (Bortoloti & Baron, 2022). Hydrophytes such as E. crassipes, T. latifolia, and P. australis (common reed) employ these mechanisms to detoxify metals, ensuring their efficacy in bioremediation (Ejaz et al., 2023).

A primary component of biochemical detoxification is the production of metal-binding compounds, such as phytochelatins (PCs) and metallothioneins (MTs), which chelate metals to reduce their toxicity (Shivappa et al., 2025). Phytochelatins, synthesized from glutathione by the enzyme phytochelatin synthase, form stable complexes with metals such as Cd and Pb, sequestering them in vacuoles to protect cellular components (Molina & Segura, 2021; Ejaz et al., 2023). For instance, E. crassipes upregulates PC production under Cd stress, binding the absorbed Cd in its roots (Bortoloti & Baron, 2022). Metallothioneins, cysteine-rich proteins, similarly bind metals such as Zn and Cu, and P. australis shows enhanced MT expression in metal-contaminated wetlands (Shivappa et al., 2025).

Antioxidant defense systems play a pivotal role in counteracting oxidative stress induced by heavy metals, which generate reactive oxygen species (ROS) that damage membranes, proteins, and DNA (Molina & Segura, 2021). Hydrophytes activate enzymes such as superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) to scavenge ROS, maintaining cellular homeostasis (Bortoloti & Baron, 2022). Studies on T. latifolia demonstrate increased SOD activity under Cr exposure, mitigating lipid peroxidation (Sekaran & Thiagarajan, 2025). Non-enzymatic antioxidants, including glutathione and ascorbic acid, further neutralize ROS, with L. minor showing elevated glutathione levels in response to Pb stress (Ejaz et al., 2023).

Microbial Synergies

Microbial synergies play a pivotal role in enhancing hydrophyte-based bioremediation of heavy metals, leveraging interactions between aquatic plants and rhizospheric microorganisms to improve metal uptake, transformation, and detoxification (Khatoon et al., 2024; Mandal et al., 2025). Hydrophytes form symbiotic relationships with metal-tolerant bacteria and fungi, including arbuscular mycorrhizal fungi (AMF), thereby enhancing remediation efficiency in contaminated aquatic environments (Hnini et al., 2024; Zheng et al., 2023).

These microorganisms enhance bioremediation through several mechanisms. First, they facilitate metal bioavailability by producing organic acids, siderophores, and biosurfactants that solubilize metals making them more accessible for plant uptake (Khatoon et al., 2024; Ejaz et al., 2023). For instance, Bacillus spp. associated with T. latifolia increase Cd solubility, boosting phytoaccumulation in wetland systems (Mandal et al., 2025). Second, microbes transform toxic metals into less harmful forms; for example, Aspergillus ruber in the rhizosphere reduces hexavalent chromium (Cr⁶⁺) to trivalent chromium (Cr³⁺), reducing toxicity and aiding phytostabilization (Sekaran & Thiagarajan, 2025; Hnini et al., 2024).

Microbial synergies also enhance plant tolerance to metal stress by promoting growth and mitigating oxidative damage. Plant growth-promoting rhizobacteria (PGPR), such as Pseudomonas fluorescens, produce phytohormones like indole-3-acetic acid (IAA) and enzymes like 1-aminocyclopropane-1-carboxylate (ACC) deaminase, which reduce ethylene levels, thereby enhancing root growth and metal uptake in P. australis  (Zheng et al., 2023; Shivappa et al., 2025). AMF, such as Glomus spp., colonize hydrophyte roots, improving nutrient uptake and stabilizing metals like Pb in the rhizosphere through fungal hyphae, resulting in a reduction in metal mobility (Hnini et al., 2024; Yi et al., 2023). For example, L. minor inoculated with PGPR shows an increase in Zn accumulation due to enhanced root biomass (Khatoon et al., 2024).

Environmental factors, such as pH and organic matter, influence these synergies, with optimal microbial activity occurring in slightly acidic to neutral conditions (Mandal et al., 2025). Challenges include microbial competition and metal toxicity, which can reduce microbial viability at high concentrations (Zheng et al., 2023). Bioaugmentation with metal-resistant strains and genetic engineering of microbes to overexpress metal-binding proteins can enhance synergy (Mandal et al., 2025; Shivappa et al., 2025). By integrating microbial biotechnology with hydrophyte physiology, these synergies significantly improve bioremediation outcomes, resulting in increased removal rates of Cu and Zn in wastewater systems (Khatoon et al., 2024; Mandal et al., 2025).

These interactions underscore the potential of hydrophytes and their microbial partners as a sustainable, life-sciences-driven approach to heavy-metal remediation. With a solid understanding of the underlying biological mechanisms and microbial contributions, attention now turns to specific hydrophyte species, evaluating their unique efficacies and applications in real-world metal remediation scenarios.

Key Hydrophyte Species and Their Efficacy

Hydrophytes are vital for the bioremediation of heavy metals due to their exceptional metal-uptake capacities, with species such as E. crassipes, L. minor, P. australis, and T. latifolia among the most effective (Farid et al., 2023; Ali et al., 2020). These species excel in removing metals such as Cd, Pb, and Hg from contaminated water and sediments, leveraging their unique physiological traits and adaptability to diverse environmental conditions (Ayaz et al., 2020). This section profiles their capabilities, compares their efficacy, and examines factors influencing their performance to guide species selection for specific contamination scenarios.

Eichhornia crassipes is renowned for its rapid growth and high biomass, enabling it to accumulate significant amounts of Cd, Pb, and Hg. Studies show it removes Cd and Pb in constructed wetlands, with root accumulation reaching 1,500 mg/kg for Cd (Farid et al., 2023; Ayaz et al., 2020). Its extensive, fibrous root system enhances phytoaccumulation and rhizofiltration, making it ideal for industrial wastewater treatment (Ali et al., 2020). However, its efficacy decreases at high metal concentrations due to toxicity, requiring optimal pH (5.5–7.0) for maximum uptake (Khan et al., 2024).

Lemna minor, a free-floating hydrophyte, excels in accumulating Hg and Cd due to its high surface area and rapid reproductive rate. It can accumulate up to 1,400 mg/kg of Cd and Hg in controlled settings, thanks to its small size, which allows dense coverage in contaminated water bodies (Farid et al., 2023; Sabreena et al., 2022). Its performance is sensitive to pH, with optimal uptake at slightly acidic conditions (pH 6.0), and its low biomass necessitates frequent harvesting to maintain efficiency (Ali et al., 2020).

Phragmites australis is highly effective for phytostabilization, immobilizing Pb and Zn in its robust root system, with studies reporting reduction in Pb mobility in wetland sediments (Ayaz et al., 2020; Sabreena et al., 2022). Its deep roots and tolerance to high metal concentrations make it suitable for large-scale applications like mining effluents, though its slower growth compared to Eichhornia limits its phytoaccumulation capacity (Khan et al., 2024). It thrives in a wide pH range (4.5–8.0), enhancing its versatility (Farid et al., 2023).

T. latifolia balances phytoaccumulation and phytostabilization, accumulating Cd and Pb in roots (up to 1,000 mg/kg) while stabilizing Zn in the rhizosphere (Ayaz et al., 2020; Ali et al., 2020). Its high biomass and tolerance to waterlogged conditions make it ideal for constructed wetlands, with high removal rates for Cd and Pb (Sabreena et al., 2022). Its efficacy is influenced by metal concentration and redox conditions, with anaerobic environments enhancing metal precipitation (Khan et al., 2024).

Thus, selecting E. crassipes or L. minor for rapid phytoaccumulation, or P. australis and T. latifolia for effective phytostabilization, enables the design of tailored bioremediation strategies (Farid et al., 2023; Ayaz et al., 2020). Building on these species-specific capabilities, the following sections examine their practical deployment in real-world environmental management, including ecosystem restoration and contributions to global sustainability goals.

Applications in Environmental Management

Hydrophytes play a transformative role in environmental management by leveraging their biological capabilities to address heavy metal pollution, aligning with ecological restoration, SDGs, and circular economy principles (Figure 2) (Ayaz et al., 2020; Rodrigo, 2021).

Restoring Ecosystems

Hydrophytes significantly improve water quality and support biodiversity in contaminated wetlands and lakes. By removing metals, they reduce toxicity and foster healthier aquatic ecosystems. For instance, P. australis in constructed wetlands can reduce Pb concentrations, enhancing water clarity and enabling the recovery of aquatic flora and fauna (Ayaz et al., 2020; Rodrigo, 2021). Eichhornia crassipes achieves over 90% removal of Cd in industrial wastewater, promoting habitat restoration in polluted lakes (Farid et al., 2023). These plants stabilize sediments, control erosion, and increase oxygen levels, creating favorable conditions for biodiversity, as seen in wetland restoration projects where the introduction of hydrophytes boosted species diversity (Rodrigo, 2021; Ali et al., 2020).

Supporting SDGs

The use of hydrophytes in wastewater treatment systems directly supports SDG 6 (Clean Water and Sanitation) by providing low-cost, eco-friendly solutions for treating industrial and municipal effluents. Constructed wetlands with T. latifolia and P. australis achieve 70–85% removal of Cd and Pb, improving water quality for human and ecological use (Ayaz et al., 2020; Zhang et al., 2023). By reducing metal exposure, hydrophytes also align with SDG 3 (Good Health and Well-being) and help mitigate health risks, such as neurological disorders caused by Pb and Cd (Piwowarska et al., 2024). Their sustainable, low-energy approach promotes responsible consumption and production (SDG 12), as it requires minimal infrastructure compared to conventional methods such as chemical precipitation (Singh et al., 2024; Ali et al., 2020).

Enabling Circular Economy

Harvested hydrophyte biomass, laden with metals, can be repurposed to support a circular economy, minimizing waste and enhancing sustainability. Biomass from E. crassipes and L. minor can be processed into bioenergy sources, such as biogas, or compost for agricultural use after safe metal extraction via phytomining (Zhang et al., 2023). This aligns with hydroponic principles of resource-efficient biomass production, enabling year-round sustainable farming and waste minimization (Patel, 2024). For example, L. minor biomass has been used to produce biogas with a yield of 200 mL/g, reducing waste and providing renewable energy (Zhang et al., 2023). Safe disposal methods, such as incineration with metal recovery, prevent secondary pollution and align with sustainable waste management practices (Sabreena et al., 2022). These applications highlight hydrophytes’ role in integrating bioremediation with resource recovery, fostering environmental and economic benefits.

Hydrophytes thus offer a versatile, life sciences-driven approach to environmental management, supporting ecosystem health and global sustainability goals. While current applications demonstrate the value of hydrophytes in real-world settings, emerging advances in life sciences, such as omics and genetic engineering, promise to further elevate their bioremediation potential.

Figure 2: Applications of Hydrophytes in Environmental Management

Advances in Life Sciences for Enhanced Bioremediation

Recent advances in life sciences are revolutionizing hydrophyte-based bioremediation, enhancing the efficiency of plants in removing heavy metals (Barathi et al., 2023; Bhat et al., 2022). Innovations in omics technologies, genetic engineering, microbial biotechnology, and nanotechnology are deepening our understanding of metal stress responses and amplifying hydrophyte performance, offering sustainable solutions for environmental management (Figure 3) (Mosa et al., 2016; Firincă et al., 2025).

Omics technologies-genomics, proteomics, and metabolomics-provide insights into the molecular mechanisms of metal uptake and detoxification in hydrophytes. Genomic studies have identified genes, such as ZIP transporters and phytochelatin synthase, in P. australis that regulate metal uptake, enabling targeted enhancements (Nosek et al., 2020; Shivappa et al., 2025). Proteomics reveals upregulation of proteins, such as superoxide dismutase, in E. crassipes under Hg stress, thereby improving antioxidant defenses (Bhat et al., 2022). Metabolomics uncovers metabolites like glutathione that mitigate oxidative stress guiding precision bioremediation strategies (Ejaz et al., 2023). These approaches allow for tailored species selection and optimization for specific contaminants (Barathi et al., 2023).

Genetic engineering significantly enhances hydrophyte efficacy in heavy metal bioremediation by modifying genes to boost metal tolerance and accumulation, enabling plants to thrive in contaminated aquatic environments. This approach involves targeted manipulation of plant genomes using techniques such as CRISPR-Cas9, Agrobacterium-mediated transformation, or gene overexpression to enhance traits critical to phytoaccumulation and phytostabilization. By altering genes involved in metal uptake, transport, and detoxification, hydrophytes like E. crassipes, T. latifolia, and P. australis  exhibit improved remediation capacities for metals such as Cd, Pb, and Zn, addressing limitations like toxicity-induced growth inhibition (Mosa et al., 2016; Shivappa et al., 2025). Key genes targeted for engineering include those encoding MTs, PCs, and ZIP (Zinc-regulated, Iron-regulated transporter-like Protein) transporters. Metallothioneins, cysteine-rich proteins, bind metals like Pb and Zn, reducing cellular toxicity by sequestering them in vacuoles. Overexpression of MT genes in T. latifolia increases Pb binding capacity, enhancing phytostabilization by limiting metal mobility in roots (Mosa et al., 2016; Nosek et al., 2020).

This modification strengthens root cell walls, preventing metal translocation to shoots and mitigating oxidative stress, thus sustaining plant growth in high-Pb environments. Similarly, phytochelatins, synthesized via glutathione by phytochelatin synthase (PCS) enzymes, form stable complexes with Cd and Pb. Engineering E. crassipes to overexpress PCS genes boosts Cd chelation, improving phytoaccumulation in wastewater systems (Barathi et al., 2023). ZIP transporters, responsible for the uptake of divalent cations (e.g., Zn²⁺, Cd²⁺), are critical for phytoaccumulation. Transgenic plants with enhanced ZIP gene expression increase Cd uptake by facilitating active transport across root cell membranes, allowing higher metal accumulation in aerial tissues (Barathi et al., 2023). Other genes, such as those encoding superoxide dismutase and catalase, enhance antioxidant defenses, countering ROS induced by metal stress. Overexpression of SOD in P. australis improves Zn tolerance, maintaining photosynthesis and biomass production under high metal loads (Shivappa et al., 2025). Mechanistically, genetic engineering involves inserting or upregulating these genes using vectors like Agrobacterium tumefaciens, which delivers DNA to plant cells or CRISPR-Cas9 for precise edits. For example, editing the Nramp (Natural resistance-associated macrophage protein) gene in L. minor enhances Hg uptake by improving metal transport to vacuoles (Ejaz et al., 2023).

These modifications reduce toxicity effects, enabling hydrophytes to thrive in high-metal environments. However, regulatory and ecological concerns, such as gene flow to wild populations or unintended ecosystem impacts, necessitate rigorous field testing and biosafety protocols (Firincă et al., 2025). By leveraging genetic engineering, hydrophytes can be tailored for specific contaminants, significantly advancing their role in sustainable bioremediation.

Microbial biotechnology, particularly bioaugmentation with metal-tolerant bacteria like Pseudomonas putida and Bacillus spp., strengthens plant-microbe synergies. Inoculation of P. australis with Pseudomonas increases Zn removal by enhancing metal bioavailability and plant growth via phytohormone production (Khatoon et al., 2024; Qurbani et al., 2025). Bioaugmentation with arbuscular mycorrhizal fungi in T. latifolia improves Cd stabilization by reducing metal mobility in wetlands (Saha et al., 2021; Sobahan et al., 2025). These synergies are critical for scaling bioremediation in complex aquatic systems (Mandal et al., 2025).

Nanotechnology, specifically nano-enhanced phytoremediation, significantly boosts hydrophyte performance in heavy metal bioremediation. Silicon dioxide nanoparticles (SiO₂ NPs) applied to E. crassipes increase Pb uptake by expanding root surface area and enhancing metal chelation, facilitating efficient phytoaccumulation (Amooaghaie et al., 2025; Joshi et al., 2025). 

Figure 3: Roadmap for Future Directions in Hydrophyte Bioremediation [A flowchart outlining steps like omics integration, microbial engineering, policy development, and climate synergies.]

Carbon nanomaterials, such as graphene oxide, improve Cd removal efficiency by boosting photosynthesis and biomass production, enabling higher metal sequestration (Wang et al., 2025). These nanoparticles enhance metal bioavailability, stimulate antioxidant defenses, and promote microbial synergies in the rhizosphere, amplifying remediation outcomes (Firincă et al., 2025). However, the potential toxicity of nanoparticles to ecosystems requires rigorous environmental risk assessments to ensure safe application (Prakash & S, 2023). Alongside omics technologies, genetic engineering, and microbial bioaugmentation, nanotechnology complements hydrophyte-based bioremediation. For instance, P. australis with Pseudomonas inoculation achieves higher Zn removal, while transgenic T. latifolia overexpressing metallothionein genes enhances Pb stabilization (Khatoon et al., 2024; Mosa et al., 2016). These life sciences innovations collectively advance sustainable solutions that align with SDG 6 (Clean Water and Sanitation) by offering scalable, eco-friendly approaches to mitigate heavy metal pollution in aquatic systems (Zhang et al., 2024; Barathi et al., 2023).

Despite these promising advancements, hydrophyte-based bioremediation faces several challenges that require targeted solutions to achieve widespread scalability and effectiveness.

Challenges and Solutions

Biological Limitations

Hydrophyte-based bioremediation faces significant biological limitations that can hinder its effectiveness in removing heavy metals from contaminated aquatic environments (Bhat et al., 2022; Ejaz et al., 2023). High metal concentrations often induce toxicity, causing oxidative stress that damages cellular structures, inhibits photosynthesis, and reduces plant growth and biomass, critical for efficient remediation (Molina & Segura, 2021). For instance, Cd levels above 50 mg/L impair L.  minor’s growth, decreasing its phytoaccumulation capacity (Farid et al., 2023). Similarly, E. crassipes exhibits reduced biomass and chlorophyll content under Pb stress, limiting its ability to sequester metals effectively (Bortoloti & Baron, 2022).

Oxidative stress from metal exposure generates ROS, which disrupt metabolic processes and damage membranes, proteins, and DNA in hydrophytes (Shivappa et al., 2025). This stress triggers physiological responses, such as reduced root elongation and nutrient uptake, further compromising remediation efficiency (Rasheed et al., 2020). Additionally, species-specific tolerance varies; P. australis tolerates higher Pb concentrations than L. minor due to its robust root system, but even it faces growth inhibition at extreme levels (Ayaz et al., 2020; Sabreena et al., 2022). Genetic variability within species also affects performance, with some E. crassipes ecotypes showing greater Cd tolerance due to enhanced antioxidant enzyme activity (Nosek et al., 2020).

Solutions to these biological constraints leverage advances in the life sciences. Enhancing antioxidant defenses through genetic engineering, such as overexpressing genes for stress-related enzymes, bioaugmentation with metal-tolerant bacteria, and application of nanoparticles to enhance root resilience and increase heavy metal accumulation by improving metal chelation and reducing oxidative stress, as previously discussed. Optimizing plant selection for specific contaminants, such as using P. australis for Pb-heavy sites, also improves outcomes (Ali et al., 2020). These strategies, combined with omics-guided insights into stress response pathways, enable tailored interventions to overcome biological limitations; ensuring hydrophytes remain effective, sustainable tools for heavy metal bioremediation (Barathi et al., 2023; Firincă et al., 2025). Beyond inherent biological constraints, environmental variability introduces additional complexities, influencing metal bioavailability and requiring adaptive strategies for optimal hydrophyte performance.

Environmental Variability

Environmental variability, including pH, temperature, and water chemistry, significantly impacts heavy metal bioavailability and hydrophyte performance in bioremediation (Piwowarska et al., 2024; Rasheed et al., 2020). These factors influence metal solubility and plant physiological processes (Farid et al., 2023). Acidic pH (5.5–6.5) enhances Cd and Pb solubility, increasing uptake, but extreme acidity (pH < 4) inhibits growth (Khan et al., 2024; Ayaz et al., 2020). Conversely, alkaline conditions reduce Zn bioavailability, limiting phytostabilization (Radziemska et al., 2017).

Temperature affects metabolic rates; optimal ranges (20–30°C) boost metal (e.g. Cd) accumulation, while temperatures above 35°C reduce biomass (Bhat et al., 2022; Barathi et al., 2023). Water chemistry, including redox potential and organic matter, also plays a role. Anaerobic conditions in wetlands promote Pb precipitation as sulfides by enhancing phytostabilization (Mendez & Maier, 2008; Zhang et al., 2023). High salinity or nutrient imbalances can suppress Hg uptake, necessitating tailored water management (Nosek et al., 2020).

Optimizing field applications involves adjusting environmental conditions. Maintaining pH at 6.0–7.0 maximizes metal uptake (Sabreena et al., 2022). Bioaugmentation with Pseudomonas spp. mitigates adverse water chemistry, improving Zn bioavailability (Khatoon et al., 2024; Qurbani et al., 2025). Nanoparticles, enhances E. crassipes’s resilience to pH fluctuations, boosting Pb removal (Amooaghaie et al., 2025; Joshi et al., 2025). These strategies ensure hydrophytes perform effectively across diverse environmental conditions (Firincă et al., 2025; Ali et al., 2020). To elucidate the environmental and biological factors influencing hydrophyte performance, Table 1 summarizes key variables such as pH, temperature, and microbial activity, their impacts on metal bioavailability and plant efficacy, and optimization strategies to enhance bioremediation outcomes. Addressing environmental factors is essential for field success, yet scaling hydrophyte systems to large sites demands further engineering and policy interventions to overcome logistical hurdles, discussed in the next section.

Scalability

Scaling hydrophyte-based bioremediation from controlled settings to large contaminated sites, such as mining effluents, presents logistical challenges requiring engineering and policy support (Ayaz et al., 2020; Piwowarska et al., 2024). Hydrophytes achieve significant removal of Cd and Pb in small-scale wetlands, but large-scale applications face issues like variable water flow, high metal loads, and site heterogeneity (Farid et al., 2023; Bhat et al., 2022).

Engineering solutions include designing hybrid constructed wetlands integrating multiple hydrophytes and microbial bioaugmentation. A case study in China’s Yangtze Basin used P. australis and Bacillus spp., achieving 85% Pb removal (Mandal et al., 2025; Zhang et al., 2023). However, limitations like clogging and maintenance costs hinder scalability (Rodrigo, 2021). Application of nanotechnology & genetic engineering enhances metal uptake, supporting large-scale systems (Amooaghaie et al., 2025; Joshi et al., 2025).

Policy support is critical, as regulatory frameworks and funding are often lacking, especially in developing regions (Bashir et al., 2024; Firincă et al., 2025). Incentives for green technologies and public-private partnerships can facilitate implementation, as seen in India’s wetland projects treating textile effluents (Barathi et al., 2023). Despite successes, long-term monitoring and adaptive management are needed to address site-specific challenges, ensuring hydrophyte systems align with SDG 6 for sustainable water management (Ali et al., 2020; Piwowarska et al., 2024). While engineering aids in expanding applications, effective post-remediation biomass management is crucial to prevent secondary pollution and maximize sustainability.

Biomass Management

Post-remediation, managing metal-laden hydrophyte biomass is critical to prevent secondary pollution, as metals like Cd and Pb in plants like E. crassipes and P. australis can re-enter ecosystems if improperly handled (Farid et al., 2023; Song & Park, 2017). Effective strategies, such as incineration and phytomining, ensure safe disposal or resource recovery, aligning with sustainable practices (Tan et al., 2023; Mukherjee et al., 2025).

Incineration reduces biomass volume and concentrates metals like Pb and Zn in ash, enabling safe disposal or metal recovery. For instance, incinerating T. latifolia biomass yields ash with 60% recoverable Cd, minimizing environmental risks (Khan et al., 2023; Vigil et al., 2022). However, high energy costs and potential emissions require controlled systems with filtration (Mukherjee et al., 2025). Phytomining extracts valuable metals from biomass, such as Zn from L. minor (Tan et al., 2023). This approach supports a circular economy by converting waste into resources (Kowalska & Biczak, 2025).

Table 1: Factors Affecting Phytoremediation Ability of Hydrophytes and Optimizing Strategies