Phytoremediation in sustainable wastewater management: an eco-friendly review of current techniques and future prospects

Water, a crucial natural resource, sustains life and environments. The two primary categories of natural water resources, surface water and groundwater, play indispensable roles in meeting various human needs. However, the escalating demands resulting from climate change, rapid population growth, overexploitation of natural resources, and accelerated industrialization have imposed immense pressure on freshwater reserves (Calzadilla et al. 2011; Connell 2018). The exacerbation of this situation is compounded by industrial activities near water bodies, agricultural runoff, and the release of untreated sewage, collectively contributing to the deterioration of water quality (Azizullah et al. 2011; Meghla et al. 2013; Weldemariam 2013). Globally, nearly 2 million metric tons of wastewater are dumped into water bodies, particularly affecting poorer nations where surface water bodies receive a significant proportion of untreated industrial effluents and raw sewage (Azizullah et al. 2011).

The repercussions of this pollution are severe, with the enrichment of wastewater by heavy metals (HMs) posing threats to human health, plants, and animals (Jeevanantham et al. 2019). It is clear from these challenges that wastewater must be treated before being released into an aquatic environment. Wastewater treatment is an essential concern in order to provide clean drinking water and preserve biodiversity. Wastewater treatment aligns with the essential components of the 2030 Sustainable Development Goals (SDGs), contributing to sustainable development by addressing poverty and illness. Traditional wastewater treatment methods, such as distillation systems or using physicochemical techniques like ion exchange, adsorption, reverse osmosis, and UV treatment, have been utilized. However, these techniques often generate sludge and are time-consuming, expensive, and inefficient (Ahila et al. 2020; Ali et al. 2020).

Certain plants, termed hyperaccumulators, exhibit the remarkable ability to accumulate substantial quantities of HMs (Andrianisa et al. 2008). These plants are suitable for remediation because they can retain HMs in their tissues without experiencing significant damage. Phytoremediation emerges as a viable, economical, and efficient cleanup technique for treating groundwater, wastewater, and contaminated soil. Plant species, namely Eichhornia sp., Salvinia sp., duckweed, Azollasp., Typha sp., Scirpus sp., Limnocharisflava, Potamogeton sp., Myriophyllum sp., Spartina sp., Cyperus sp., and Phragmites sp., have demonstrated significant potential in eliminating HMs from wastewater (Soda et al. 2012; Rodríguez & Brisson 2015).

This study provides a comprehensive analysis of phytoremediation as a sustainable wastewater treatment technique. It delves into the fundamental mechanisms, efficiency, and applications of phytoremediation in various environments. The article proceeds to illustrate the adaptability of phytoremediation through various case studies in diverse environmental contexts, highlighting its potential in addressing the contemporary challenges of water pollution.

Water bodies face contamination from numerous sources, introducing varied contaminants that impair both environmental and human well-being. The two primary types of pollutants are inorganic pollutants and organic pollutants.

Recent reports underscore the global contamination of water sources by a diverse array of organic pollutants, including pharmaceutical waste, dyes, and pesticides, precipitating severe environmental challenges. The unregulated discharge of untreated waterborne organic pollutants into water systems poses harmful effects on living organisms and ecosystems (Madima et al. 2020). Carrying carcinogenic potential, toxicity, and mutagenic properties, many waterborne organic pollutants, particularly dyes, exhibit high toxicity even at low concentrations (Yang 2011; Shanker et al. 2017). Moreover, the intricate structures of these waterborne contaminants render them extremely impervious to biodegradation and impervious to conservative physical and biological oxidation treatments.

The destiny of pesticides in the environment is intricately linked to their physicochemical properties, particularly their water solubility determined by the octanol–water partition coefficient and their mobility and persistence in the soil. Beyond inherent properties, water pollution from pesticides is influenced by numerous factors, including climatic conditions (precipitation, temperature, wind, and humidity), cultivation practices, hydrogeological characteristics, application speed, soil type (organic matter content and texture), frequency, product amounts, seasonality, and trophic status (Worrall & Kolpin 2004; Carles et al. 2019).

Pesticides, classified by target species such as fungicides, insecticides, and herbicides, are extensively used in both urban settings and agricultural farmland (De et al. 2014). Fungicides, utilized to prevent fungus infection in seeds or plants, are applied either before the presence of fungus or after infection. Insecticides, employed to control insects, and herbicides, designed to eliminate weeds, are prevalent in farmlands and other areas (Syafrudin et al. 2021). Pesticides can also be categorized on the basis of their mode of action, like agents that repel, destroy, or mitigate (Mahmood et al. 2016), and through a more scientific approach considering their chemical composition.

These chemicals, partly soluble in water, elicit more concern for their residues in foods than in drinking water. Pesticides that are synthetic and organic, such as DDT, endrin, aldrin, and chlorinated hydrocarbons like chlordane, have a tendency to build up in food chains. Even though they are extremely hazardous, organophosphorus chemicals like malathion and diazinon, which were created as alternatives to chlorinated hydrocarbon pesticides, break down quickly in the environment and lose their presence in groundwater. Since carbamate insecticides have a limited ability to bind to soil particles, they may find their way into surface waters as a substitute for chlorinated hydrocarbons (Riyaz et al. 2022).

Marine petroleum hydrocarbons have two primary sources: natural (diagenetic or biogenic) and anthropogenic (pyrogenic or petrogenic) (Adeniji et al. 2017). Diagenetic sources result from transformations in sediment, while biogenic hydrocarbons originate from living organisms. Natural seepage serves as a prevalent route for these hydrocarbons to infiltrate marine water (Kvenvolden & Cooper 2003). Anthropogenic hydrocarbons, more prevalent in the environment, result from several human activities such as urbanization, transportation, industrialization, oil operations, shipping, fishing, and storage (Sakari et al. 2008; Strother et al. 2013).

Oil industries, particularly during production, refining, transportation, and storage processes, play a substantial role in water pollution through the discharge of oily wastewater (Al-Futaisi et al. 2007). Accidental spills, frequently occurring on ships, oil platforms, and during oil transportation, result in hydrocarbon pollution in water. This leads to petroleum products forming a water-resistant film on seawater, hindering oxygen exchange, and causing harm to marine life (Obida et al. 2018). The increased use of vehicle oil, a major contributor to petroleum hydrocarbon contamination in water, results in runoff from oil drops onto the ground, eventually washing into water streams (Mfarrej et al. 2023).

The formidable presence of inorganic pollutants, specifically HM ions, constitutes a severe threat to organisms, influenced by both anthropogenic and geological factors (Tarannum & Khan 2020). The escalation of harmful pollutants in water results directly from the increasing social, agricultural, industrial, and domestic activities. There are several ways that inorganic contaminants enter natural ecosystems. Non-point contributors, including agriculture plant wastewater, and point sources like treatment centers located across the city, pharmaceutical, cosmetics, and sanitary industries contribute to contamination. Groundwater pollution is influenced by interactions involving leaching from agricultural fields, rivers, and sewage networks (Ebele et al. 2017).

Inorganic pollutants encompass industrial waste, nutrients, HM, and sediments (Zhang et al. 2020), out of which HM and nutrients are discussed in a subsequent section. Although many of these pollutants exist naturally, human activities like agriculture, mining, and industrial processes have escalated their amounts in the environment (Madima et al. 2020). Most inorganic pollutants are not biodegradable, and when they build up in the body, they can cause serious health problems (Lu & Astruc 2018). The global prevalence of inorganic pollutants, especially HM such as zinc (Zn), lead (Pb), iron (Fe), cadmium (Cd), chromium (Cr), arsenic (As), cobalt (Co), and nickel (Ni), represents an urgent environmental concern affecting both developing and developed nations (Baruah et al. 2016; Bashir et al. 2019; Malik et al. 2019). These carcinogenic, non-biodegradable, and highly toxic metals necessitate prompt removal from water before release into the environment (Malik et al. 2017; Talaiekhozani & Rezania 2017; Abdi et al. 2018).

Categorized among the most perilous substances due to their deadly nature (Järup 2003), HM infiltrates water from several industrial sources, including mining, metal plating, painting, tanneries, fertilizers, and batteries (Javadian 2014; Mahmud et al. 2016). Whether directly or indirectly, metals like Co, As, mercury (Hg), Pb, Cu, Cd, Zn, Ni, and Cr enter water bodies and persist in various oxidation states for extended periods (Yadav et al. 2019). Urban pollution contributes HM through polluted air, dust, and sediment, with these contaminants traveling over long distances in both non-biological and biological forms. The biological form is particularly significant, posing heightened risks to humans and ecosystems. Therefore, the imperative remains for the elimination of HM ions from contaminated wastewater before discharge into water bodies (Yadav et al. 2019).

The excessive loading of nutrients, particularly nitrogen (N) and phosphorus (P), stands as a critical ecological concern and a prominent water quality issue in contemporary surface water bodies (Badruzzaman et al. 2012). While these nutrients are vital for the persistence of aquatic organisms, their excessive loading can have adverse effects on the designated usage of water (Freeman et al. 2009). Nutrient enrichment in water bodies results from a combination of natural and anthropogenic sources, with several factors influencing the loading process, including bioavailability, source output, loading mode, location, seasonal variation, specification, and concentration (Withers & Jarvie 2008).

The primary catalyst for the increased loading of nutrients into water resources is linked to the production of agricultural food (Han & Allan 2012). Multiple sources contribute to the excess nutrient loading in water bodies, including potential influence from climate change, inappropriate land usage and management, and intensive and poor farming practices (Wang et al. 2010; Castillo et al. 2014; Giri et al. 2014). Significantly, the primary sources of N and P pollution in water bodies are the result of sewage effluents originating from detergents and human waste and excess agricultural nutrients (Bayram et al. 2013).

By understanding and harnessing the capabilities of plants, phytoremediation emerges as a promising approach to mitigate the diverse range of contaminants threatening water ecosystems. A profound understanding of the intricate interactions between these contaminants and water ecosystems is essential for formulating effective remediation strategies. Phytoremediation, grounded in plant-mediated processes, emerges as a promising and sustainable approach to water purification. The upcoming section delves into how plants actively engage in improving water pollution, emphasizing a nature-centric strategy that holds considerable promise for transforming environmental remediation methodologies.

The initiation of phytoremediation involves the absorption of pollutants by plant roots, functioning as natural filters that selectively draw pollutants from the surrounding water (Abdel-Shafy & Mansour 2018). This process engages physiological mechanisms facilitating the transport of contaminants from water into plant tissues. A thorough examination of factors influencing uptake efficiency becomes crucial for judiciously selecting plant species across phytoremediation applications (Kvesitadze et al. 2015).

Subsequent to the absorption of contaminants, plants undergo biochemical processes for the transformation and detoxification of pollutants (Singh & Jain 2003). This involves metabolic activities within plant cells, leading to the conversion of toxic substances into less harmful forms. A thorough investigation into the enzymatic pathways governing this transformation provides insights into the potential of different plant species to detoxify specific contaminants (Jabeen et al. 2009).

The rhizosphere, influenced by root secretions, plays a pivotal role in the phytoremediation process. Microorganisms within this zone actively contribute to contaminant degradation and nutrient cycling. A detailed exploration of interactions between plant roots and rhizospheric microbes offers valuable insights into microbial-assisted mechanisms that enhance the overall efficiency of phytoremediation (Agarwal et al. 2020).

Understanding these fundamental phytoremediation mechanisms is vital for the development of sustainable and effective wastewater treatment strategies. Subsequent sections will explore specific phytoremediation types and explore case studies demonstrating the application of these mechanisms in diverse environmental contexts.

Phytoremediation, an innovative plant-based method for in-situ elimination of HMs from contaminated environments, has gained global attention (Liu et al. 2020; Yang et al. 2020). As an application of plant sciences, phytoremediation seeks to harness the natural capabilities of plants to improve living conditions for humans. This approach utilizes the symbiotic relationship between rhizosphere organisms and plant physiology to eliminate persistent or hazardous contaminants from soils and waterways, particularly in regions with limited waterway pollution treatment (Schwitzguébel et al. 2011).

Phytoextraction, a technique involving the cultivation of plants in polluted areas with the ability to accumulate HMs, facilitates the harvesting of metal-enriched biomass upon maturity (Pajević et al. 2016). This method aids in removing contaminants from the soil. The efficacy of phytoextraction as an environmentally friendly approach depends on the ability of plants to absorb and store metals in their aerial parts, considering metal availability for absorption. Typically, the collected biomass is either composted or incinerated, with limited recycling for further use (Prasad & De Oliveira Freitas 2003; Bhargava et al. 2012). Several essential plant characteristics contribute to successful phytoextraction, including the ability to cover a broad area, rapid growth, substantial biomass production, flexibility in harvesting, and the capacity to accumulate various HMs in their harvestable sections (Jabeen et al. 2009; Seth 2012).

Phytoextraction processes are generally categorized as induced or continuous. Continuous phytoextraction involves using plants that accumulate toxins throughout their entire life cycle, while induced phytoextraction employs chelators to increase toxin growth at specific stages of plant development (Starck 2005; Mukhopadhyay & Maiti 2010; Materac et al. 2015). Table 1 provides insights into various researchers utilizing phytoextraction technology for toxin removal, employing diverse plant species and methodologies.

The effectiveness of phytoextraction is determined by the plant's growth rate, biomass production, and root depth. Alyssum species, for example, have been demonstrated to efficiently reduce the amounts of soil metals (Dehghani et al. 2021). It is efficient; up to a 60–70% reduction in soil metal concentrations which can be achieved by hyperaccumulator plants such as Alyssum. A high output of biomass is essential; certain species, such as Indian mustard (Brassica juncea), may generate 20–30 tons of biomass yearly per hectare (Farooq & Khanday 2020). Depending on pollution levels, the process can take multiple growing seasons to accomplish considerable metal reduction; this can take up to five years. Phytoextraction can be used on a wide scale, particularly in agricultural and industrial areas where there is lot of soil pollution (DalCorso et al. 2019; Bhat et al. 2022).

Phytoextraction is a widely recommended green remediation approach, however it still has a lot of practical limits and needs further study. It takes a lot of time and administrative work, which prevents it from being quickly installed in hotspots with high levels of contamination. The ability of HMs to accumulate is hampered by insect attacks and diseases they cause. The efficiency of phytoextraction is influenced by various environmental factors, including pollutant distribution irregularities, soil pH, temperature variations, and moisture content (Prasad et al. 2022). Large-scale soil disposal raises environmental concerns even when the cleanup is completed quickly and all pollutants are eliminated (Robinson et al. 2015). Another significant challenge linked to the phytoextraction approach is the potential for food chain contamination due to the direct introduction of accumulated metals from plant biomass into the environment, if not managed appropriately (Mahar et al. 2016). Addressing these issues requires continued research and development to optimize phytoextraction methods and ensure safe and effective remediation.

Recent technological advancements in the last several years have brought new, creative, and effective ways to maximize the potential of phytoextraction. Genetic engineering and selective breeding can introduce or overexpress genes for metal tolerance, translocation, hyperacuumulation, and detoxification in plants with rapid growth and high biomass production (Prasad et al. 2022). As a result, phytoextraction's practical usefulness is much improved. There have been encouraging findings about HM accumulation in a number of genetically modified plants. For example, owing to the overexpression of the γ-glutamylcysteine synthetase enzyme, Silene cucbalus, Populas angustifolia, and Nicotiana tabacum have shown excessive accumulation of HMs (Fulekar et al. 2009). It has also been observed that overexpressing Saccharomyces cerevisiae's YCF1 vacuolar transporter increases the absorption of complexes containing As, Cd, and Hg. According to Yadav et al. (2010), transgenically modified Arabidopsis thaliana exhibited a four-fold increase in Cd absorption when compared to wild-type plants. These advancements show how genetic alterations may greatly increase the efficacy and efficiency of phytoextraction, making it a more practical choice for extensive environmental rehabilitation.

Phytodegradation involves harnessing the enzymatic activity of plants and their associated microbes to convert organic contaminants into simpler molecules (Lakshmi et al. 2017). This process relies on plants' capacity to produce necessary enzymes that initiate the breakdown of xenobiotics (Alkio et al. 2005). The accomplishment of phytodegradation hinges on collaborative interactions among soil, water, microbes, and plants, with the plant's role being pivotal in providing a surface area for bacteria colonization around the shoot and root. This, in turn, enhances microbial activity, facilitating the breakdown of carbon substrates (Lakshmi et al. 2017).

Researchers suggest that phytodegradation is applicable in various habitats, encompassing surface and groundwater, soil, as well as river sediments and sludges (Edwards & Dixon 2004; Malecka & Tomaszewska 2005; Materac et al. 2015). Table 1 succinctly presents key findings from several studies, highlighting the adaptability and efficiency of phytodegradation in addressing challenges posed by organic pollution in diverse environmental contexts. The versatility of phytodegradation as a method for breaking down organic contaminants underscores its potential in addressing environmental pollution concerns across different scenarios.

Plants with broad root systems and quick growth, such as poplar (Populus spp.) and willow (Salix spp.), are frequently employed. For some organic pollutants, such as polycyclic aromatic hydrocarbons, phytodegradation can reach a degradation efficiency of up to 90% (Alagić et al. 2015). Large regions of soil and water polluted by organic pollutants, such as industrial waste sites and agricultural runoff areas, respond well to this treatment approach. Although phytodegradation is a promising method for treating wastewater, there are a number of limitations that prevent its widespread use. The heterogeneity in plant species' capacities to absorb and decompose certain pollutants is a significant problem that can lead to uneven treatment results. Climate variables like pH, temperature, and the availability of nutrients have a big influence on how well phytodegradation works (Qadir et al. 2020; Ullah et al. 2023). Depending on the pollution and the surrounding circumstances, the process might take months or years, and it is comparatively slow. When severe or mixed metal contamination occurs, its applicability is more constrained (He et al. 2022).

The efficacy and applicability of this green remediation strategy have been greatly increased by developments in phytodegradation methods. Among the most recent developments is the use of genetically engineered plants that express enzymes that more efficiently degrade a variety of organic contaminants (Rai et al. 2020). For example, plants are able to break down complex organic pollutants like pesticides, medicines, and industrial chemicals since genes encoding for enzymes like laccases, peroxidases, and cytochrome P450 monooxygenases have been inserted into the plants (Takkar et al. 2022). Further research has demonstrated that the creation of symbiotic plant–microbe systems in which some microorganisms aid in the process of degradation can accelerate the rate at which pollutants decompose (Padhan et al. 2021). These developments in biotechnology, along with the improvement of growing conditions and plant species selection, have strengthened and increased the viability of phytodegradation as a wastewater treatment and pollution mitigation technique.

Phytostabilization relies on plants' exceptional ability to absorb and store pollutants, leading to their immobilization or solidification (Chandekar & Godboley 2015). This approach effectively hinders the dispersion of pollutants through precipitation runoff, inhibiting their entry into groundwater and migration to surface soil. Plants selected for phytostabilization exhibit desirable characteristics, such as a robust root system that promotes the adsorption and accumulation of pollutants in tissues. The absorption of pollutants and their conversion into less soluble composites in the rhizosphere further enhances the efficacy of phytostabilization (Segura & Ramos 2013; Materac et al. 2015).

By employing plants to stabilize pollutants and impede their movement via wind or water, phytostabilization aims to reduce the bioavailability of toxins (Lakshmi et al. 2017). This method becomes particularly valuable when an extended phytoextraction process is impractical, making phytostabilization an economical and ecologically benign restoration technique. It proves especially suitable for soils with high metal content and widespread pollution (Wong 2003; Alkorta et al. 2010; Dary et al. 2010).

Researchers have implemented phytostabilization techniques to address various types of pollutants in wastewater. Table 2 offers an overview of some of these studies, emphasizing the adaptability and efficacy of phytostabilization in dealing with contamination issues. These methods stand out as a valuable tool in the arsenal of phytoremediation strategies, providing sustainable solutions for environmental restoration in the face of diverse pollution challenges.

Table 2

Research studies on phytostabilization and rhizofiltration techniques

Type of wastewater .	Plant species used .	Pollutant .	Outcomes .	References .
Phytostabilization Technique
Mining wastewater	Wetland plants (Phragmites mauritianus and Typha spp.)	Co, Cu, Pb	P. mauritianus and Typha spp. provide the potential for phytostabilization.	Nabuyanda et al. (2022)
Land-derived wastewater	Avicennia marina	Pb, Cu, and Zn	A. marina has shown the ability compartmentalization of HMs.	Nath et al. (2014)
Canal wastewater	Vossia cuspidate (Roxb.) and Griff.	Cr, Pb, Cu, Al, Zn, and Cd,	Spring plants accumulated the highest concentrations in: root (Cr, Cu, Pb); and lowest in: shoot (Al, Cd, Cr, Zn).	Galal et al. (2017)
Lake water	Ranunculus sceleratus	Mn, Ni, Zn, Cd, Cu, Pb	Bioaccumulation factor (BF): 27.1 (Ni) > 20.0 (Zn) > 16.4 (Cd) > 7.7 (Cu) > 3.9 (Mn) > 3.6 (Pb).	Farahat & Galal (2018)
Industrial wastewater	Petunia hydrida L. and Nicotiana alata L.	Ni, Cd, Pb, Cu, Cr, Mn, and Zn	Both are suitable for treatment of HMs in wastewater.	Khan et al. (2019)
Mining wastewater	S. grossus	Fe and Al	Boosts the phytostabilization of Al and Fe.	Ismail et al. (2020)
Wastewater	Salix species (Salix myrsinifolia and Salix schwerinii)	Lanthanum (La)	Salix could be a suitable candidate to accumulate rare earth elements.	Mohsin et al. (2022)
Swine wastewater	Eucalyptus grandis	Cu	It can be used for phytostabilization.	Negrini et al. (2022)
Sewage wastewater	Wetland plants (Typha latifolia and Phragmites australis)	Cu, Cd, Pb, Cr, Zn, and As	Both are suitable for phytostabilization.	Xiong et al. (2024)
Stormwater	Phragmites australis and Iris pseudacorus	Cd	Both have accumulated the highest Cd in roots than shoots. Appropriate for removing Cd polluted sites.	Mohsin et al. (2023)
Rhizofiltration Technique
Industrial wastewater	Water hyacinth (Eichhornia crassipes (Mart.) Solms)	Fe	Water hyacinth grown under poor-nutrient conditions is ideal to remove Fe.	Jayaweera et al. (2008)
Groundwater	Bean (Phaseolus vulgaris L.) and Sunflower (Helianthus annuus L.)	U	Removal efficiency for: sunflower (80%); bean (60–80%). U removal via rhizofiltration exceeded 90%.	Lee & Yang (2010)
Contaminated nutrient solution	Lettuce (Pistia stratiotes L.)	Cd and Pb	Pb treatment: transpiration rate decreases. Cd treatment: transpiration rate increases.	Veselý et al. (2011)
Aqueous environment	Azolla pinnata	Pb (II)	Efficiency of Pb removal depends on exposure duration. Max. uptake of Pb : 1,383 mg Kg−1 Reduction in Pb conc.: 83%.	Thayaparan & Iqbal (2013)
Eutrophic water	Pistia stratiotes	Pb, Cr, and Ni	Uptake of Ni is higher than others.	Abubakar et al. (2014)
Wastewater	Phragmites australis	As	Effective way to enhance rhizofiltration.	Pardo et al. (2016)
Domestic wastewater	Pistia stratiotes	Chemical oxygen demand (COD)	Max. absolute growth rate: 13.51–16.54 gdw/day. Avg. biomass productivity: 5.808 gdw/m 2 days.	(Olguín et al. (2017)
Industrial wastewater	Pea (Pisum Sativum L.)	Tetracycline	Cost-effective strategy Wastewater can be reused for irrigation.	Yagoubi et al. (2023)
Dairy wastewater	Coleus scutellarioides and Portulaca oleracea	Total suspended solids (TSS), total dissolved solids (TDS), biochemical oxygen demand (BOD), COD, total phosphorus (TP), phosphate (⁠⁠), and total nitrogen (TN)	Reduction: 79.43% (TSS); 64.36% (TDS); 82.36% (BOD); 81.86% (COD); 75.55% (TP) (Das & Paul 2023) 74.67% (TN).	Das & Paul (2023)
Domestic wastewater	Scirpus grossus	Ibuprofen and paracetamol	Removal efficiency: 45% (Ibuprofen); 31% (Paracetamol).	Falahi et al. (2022)

Type of wastewater .	Plant species used .	Pollutant .	Outcomes .	References .
Phytostabilization Technique
Mining wastewater	Wetland plants (Phragmites mauritianus and Typha spp.)	Co, Cu, Pb	P. mauritianus and Typha spp. provide the potential for phytostabilization.	Nabuyanda et al. (2022)
Land-derived wastewater	Avicennia marina	Pb, Cu, and Zn	A. marina has shown the ability compartmentalization of HMs.	Nath et al. (2014)
Canal wastewater	Vossia cuspidate (Roxb.) and Griff.	Cr, Pb, Cu, Al, Zn, and Cd,	Spring plants accumulated the highest concentrations in: root (Cr, Cu, Pb); and lowest in: shoot (Al, Cd, Cr, Zn).	Galal et al. (2017)
Lake water	Ranunculus sceleratus	Mn, Ni, Zn, Cd, Cu, Pb	Bioaccumulation factor (BF): 27.1 (Ni) > 20.0 (Zn) > 16.4 (Cd) > 7.7 (Cu) > 3.9 (Mn) > 3.6 (Pb).	Farahat & Galal (2018)
Industrial wastewater	Petunia hydrida L. and Nicotiana alata L.	Ni, Cd, Pb, Cu, Cr, Mn, and Zn	Both are suitable for treatment of HMs in wastewater.	Khan et al. (2019)
Mining wastewater	S. grossus	Fe and Al	Boosts the phytostabilization of Al and Fe.	Ismail et al. (2020)
Wastewater	Salix species (Salix myrsinifolia and Salix schwerinii)	Lanthanum (La)	Salix could be a suitable candidate to accumulate rare earth elements.	Mohsin et al. (2022)
Swine wastewater	Eucalyptus grandis	Cu	It can be used for phytostabilization.	Negrini et al. (2022)
Sewage wastewater	Wetland plants (Typha latifolia and Phragmites australis)	Cu, Cd, Pb, Cr, Zn, and As	Both are suitable for phytostabilization.	Xiong et al. (2024)
Stormwater	Phragmites australis and Iris pseudacorus	Cd	Both have accumulated the highest Cd in roots than shoots. Appropriate for removing Cd polluted sites.	Mohsin et al. (2023)
Rhizofiltration Technique
Industrial wastewater	Water hyacinth (Eichhornia crassipes (Mart.) Solms)	Fe	Water hyacinth grown under poor-nutrient conditions is ideal to remove Fe.	Jayaweera et al. (2008)
Groundwater	Bean (Phaseolus vulgaris L.) and Sunflower (Helianthus annuus L.)	U	Removal efficiency for: sunflower (80%); bean (60–80%). U removal via rhizofiltration exceeded 90%.	Lee & Yang (2010)
Contaminated nutrient solution	Lettuce (Pistia stratiotes L.)	Cd and Pb	Pb treatment: transpiration rate decreases. Cd treatment: transpiration rate increases.	Veselý et al. (2011)
Aqueous environment	Azolla pinnata	Pb (II)	Efficiency of Pb removal depends on exposure duration. Max. uptake of Pb : 1,383 mg Kg−1 Reduction in Pb conc.: 83%.	Thayaparan & Iqbal (2013)
Eutrophic water	Pistia stratiotes	Pb, Cr, and Ni	Uptake of Ni is higher than others.	Abubakar et al. (2014)
Wastewater	Phragmites australis	As	Effective way to enhance rhizofiltration.	Pardo et al. (2016)
Domestic wastewater	Pistia stratiotes	Chemical oxygen demand (COD)	Max. absolute growth rate: 13.51–16.54 gdw/day. Avg. biomass productivity: 5.808 gdw/m 2 days.	(Olguín et al. (2017)
Industrial wastewater	Pea (Pisum Sativum L.)	Tetracycline	Cost-effective strategy Wastewater can be reused for irrigation.	Yagoubi et al. (2023)
Dairy wastewater	Coleus scutellarioides and Portulaca oleracea	Total suspended solids (TSS), total dissolved solids (TDS), biochemical oxygen demand (BOD), COD, total phosphorus (TP), phosphate (⁠⁠), and total nitrogen (TN)	Reduction: 79.43% (TSS); 64.36% (TDS); 82.36% (BOD); 81.86% (COD); 75.55% (TP) (Das & Paul 2023) 74.67% (TN).	Das & Paul (2023)
Domestic wastewater	Scirpus grossus	Ibuprofen and paracetamol	Removal efficiency: 45% (Ibuprofen); 31% (Paracetamol).	Falahi et al. (2022)

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Plants with extensive root systems, such as legumes and grasses, are frequently utilized because they aid in immobilizing contaminants. By using this technique, HM bioavailability can be decreased by up to 80% (Ogundola et al. 2022). Plants with large root biomass, like vetiver grass, are very productive and may produce ten to fifteen tons of root mass per hectare. Large-scale land reclamation operations are most suited for phytostabilization, particularly in mining and waste sites where controlling the spread of pollutants is essential (Gnansounou et al. 2017; Bakshe & Jugade 2023). Although a promising method for treating wastewater, phytostabilization has a number of important drawbacks. It works less well in places where quick contamination removal is necessary. Choosing suitable plant species that can tolerate elevated pollution levels and diverse environmental circumstances is crucial to the effectiveness of this technique (Shen et al. 2022). The effectiveness of phytostabilization can be significantly impacted by soil parameters like pH, moisture content, and nutrient availability. There is also an environmental concern regarding the possibility of contaminant leakage or transport to non-target locations (Lacalle et al. 2023). The practical use of phytostabilization for wastewater treatment is made more difficult by the gradual stability of pollutants and the possibility of bioaccumulation in plant tissues.

In order to improve the immobilization of pollutants in soil and sediments, recent developments in phytostabilization approaches for wastewater treatment have concentrated on the employment of specific plants and biotechnological interventions. Scientists have discovered and employed hyperaccumulator plants, which are exceptionally effective in ensnaring HMs and other contaminants in their root zones. This prevents the pollutants from migrating into groundwater and lowers their bioavailability. It has also been demonstrated that the combination of rhizosphere engineering and mycorrhizal fungus enhances plant growth and pollutant stabilization capacities (Singh et al. 2022; Khan et al. 2023). Plants with improved resistance to hazardous conditions and higher phytostabilization effectiveness have also been developed via the use of genetic engineering techniques. These developments increase the efficiency of phytostabilization in the long term for treating polluted wastewater.

Rhizofiltration proves to be a valuable technique for tackling surface wastewater resulting from industrial and agricultural activities, with plants playing a critical role in the remediation process. In this method, plants are either exposed to wastewater soaked in their roots or submerged in purified water. The success of rhizofiltration hinges on selecting plants resistant to low oxygen concentrations, processing a large and rapidly developing root system, yielding substantial biomass, and demonstrating high tolerance to toxic compounds (Srivastava et al. 2014; Materac et al. 2015).

Supported by a study led by Raskin & Ensley (2000), the effectiveness of rhizofiltration is substantiated, demonstrating that plant roots actively absorb contaminants and HMs from their surroundings. Furthermore, this technique can reduce the ability of sediment to carry metals, particularly in cases of excessive metal deposition (Radziemska et al. 2017; DalCorso et al. 2019; Bakshe & Jugade 2023). Rhizofiltration has proven successful in handling HMs such as Pb, Cu, Co, Cd, uranium (U), and As, which are often challenging to remove using conventional techniques. This economically viable and ecologically benign approach deploys plant roots to collect and eliminate these HMs from polluted water streams (Srivastava et al. 2021; Elehinafe et al. 2022).

Over the past decade, researchers worldwide have delved into rhizofiltration using various plant species, establishing its efficiency in eliminating HMs from wastewater. Table 2 provides a summary of researchers contributing to rhizofiltration technology, showcasing the diverse plant species employed for contaminant removal. This method underscores the adaptability and utility of rhizofiltration in long-term water remediation projects, emphasizing its role as an effective and sustainable solution for addressing water pollution.

Aquatic plants, such as water hyacinth (Eichhornia crassipes) and duckweed (Lemna minor), are widely used because of their great resistance to water contaminants. These are useful for up to 95% reduct (Kristanti & Hadibarata 2023; Zhou et al. 2023). For every tonne of dry biomass, plants can acquire 1–2 kg of HMs. Ponds and other little bodies of water can be treated by rhizofiltration. Biomass management and disposal requirements prevent it from being scaled to bigger aquatic bodies (Newete & Byrne 2016). Rhizofiltration is an efficient method for treating wastewater, although it has several drawbacks. The effectiveness of the technique could be jeopardized due to varying pollutant concentrations, which can be higher than the tolerance limit of plants (Kafle et al. 2022). It is important yet difficult to maintain ideal conditions, especially for large-scale applications, such as pH, temperature, and nutrient availability. The possibility of pollutants being released again into the environment through the roots of plants calls for cautious management and control methods (Bakshe & Jugade 2023).

The effectiveness and scalability of rhizofiltration as wastewater treatment technology have been the focus of recent improvements. The creation of specific plant species and hybrid systems that enhance the absorption and removal of pollutants from wastewater are examples of innovations (DalCorso et al. 2019). Plants with improved metal accumulation and tolerance have been created through genetic engineering. The efficacy of rhizofiltration has been boosted by its combination with other treatment techniques, including built wetlands and bioreactors. The microbial communities connected to plant roots have been optimized by developments in our knowledge of plant–microbe interactions, which have further enhanced the removal of contaminants (Thijs et al. 2016; Agrahari & Kumar 2024).

Phytovolatilization represents a method in which pollutants are converted into hazardous compounds by green plants, utilizing the plant's stomata to release volatile substances into the surrounding environment (Pivetz 2001; Ghosh & Singh 2005; Leguizamo et al. 2017). Throughout this process, plants absorb pollutants from water or soil, converting them into less dangerous forms, and releasing them into the atmosphere. Plants naturally manage and transport numerous gases, including water vapor (H₂O), carbon dioxide (CO₂), oxygen (O₂), ethylene (C₂H₄), and signaling chemicals (Materac et al. 2015). The activation of systems that carry volatile organic compounds (VOCs) throughout the plant occurs based on the physiology of both the plant and the properties of the contaminant (Collins et al. 2006; Dettenmaier et al. 2009; Limmer & Burken 2014, 2016). Phytovolatilization finds frequent application in removing organic contaminants such as trichloroethylene (C₂HCl₃), benzene (C₆H₆), nitrobenzene (C₆H₅NO₂), phenol (C₆H₅OH), and atrazine (C₈H₁₄ClN₅) from soil and water, as well as HMs like Hg, selenium (Se), or As (Komives & Gullner 2005; Gonçalves et al. 2007; Wang et al. 2009).

Pollutants like Se and Hg are volatilized by plants like mustard and poplar. Under ideal circumstances, this process can volatilize up to 70–80% of certain pollutants. Depending on the kind of plant and surrounding conditions, the rate varies greatly; certain plants can release up to 50 g of Hg per hectare per year (Awgchew & Nigussie 2022). Areas with particular pollutants that may be safely volatilized can benefit from phytovolatilization (Qadir et al. 2020). The widely utilized wastewater treatment method known as phytovolatilization is restricted in its applicability due to a number of limitations. Potential volatile chemical releases into the atmosphere, which can lead to air pollution and endanger the health of those around, are a significant problem. Sites with a combination of contaminants or areas subject to stringent air quality laws are less appropriate for it. A number of variable environmental factors, including soil type, temperature, and humidity, as well as plant species, have a substantial impact on the effectiveness of this method (Limmer & Burken 2016).

The efficiency and efficacy of phytovolatilization as a wastewater treatment method have been the subject of recent improvements. By adding or overexpressing genes linked to the detoxification and emission processes, genetic engineering has been used to improve plants' capacity to volatilize toxins, such as HMs and organic pollutants (Kafle et al. 2022; Mamun et al. 2024). Plant species with stronger volatilization capacity and quicker growth rates have emerged as a result of improvements in plant breeding and selection. The more accurate manipulation of plant physiology has been made possible by advances in our knowledge of the molecular processes behind contaminant absorption, transport, and volatilization (Anas et al. 2020; Mahboob et al. 2023). To improve overall treatment efficiency, novel ways to combine phytovolatilization with other green technologies such as phytoremediation and artificial wetlands have also been investigated. As a result of all these developments, phytovolatilization is becoming a more viable and efficient wastewater treatment option.

As we navigate through the complexities of phytoremediation techniques, each method uncovers the unique role plants play in mitigating environmental contaminants. From phytoextraction's metal accumulation to phytodegradation's enzymatic breakdown of organics and the immobilization in phytostabilization, the upcoming section will delve into the critical aspect of selecting suitable plants for wastewater treatment. Understanding the diverse strategies employed by plants in phytoremediation mechanisms sets the stage for exploring how specific plant species, with their hyperaccumulation abilities, tolerance, and growth characteristics, become pivotal in constructing effective and sustainable solutions for wastewater treatment.

The remarkable capacity of plants to naturally accumulate HMs has gained increasing attention from the environmental science community and remediation approaches (Lajayer et al. 2019). This special ability arises from the intricate relationships between plants and the surrounding soil, where roots serve as the primary point of contact for metal absorption. HMs, including Zn, Pb, and Cd, are specifically absorbed by plants through a combination of metabolic and transport routes (Jabeen et al. 2009). These metals can be absorbed and stored in various plant parts, such as roots, leaves, and stems, creating a natural filtration system for pollutants in the soil. Effective wastewater treatment through phytoremediation hinges on the careful selection of plant species that exhibit specific traits conducive to the remediation process.

This section explores three pivotal aspects in the selection of suitable plants: hyperaccumulators, tolerance and adaption, and growth characteristics. Notably, certain plant species are termed hyperaccumulators, signifying their extraordinary ability to accumulate large quantities of HMs without experiencing harm (Muszyńska & Hanus-Fajerska 2015). The potential of leveraging this inherent ability to mitigate HM contamination in wastewater treatment through phytoremediation projects is considerable. Such projects offer a sustainable and environmentally friendly method for addressing the challenges associated with HM pollution.

By delving into the characteristics of hyperaccumulators and understanding their role in the phytoremediation process, researchers can strategically choose plant species that maximize metal accumulation in wastewater treatment scenarios. Table 3 presents the methods of phytoremediation, the mechanisms of pollutant removal, and the selection criteria for plant species. Additionally, considering the tolerance and adaptation mechanisms of plants in polluted environments, along with assessing growth characteristics, contributes to the development of robust and effective phytoremediation strategies. As we explore these critical aspects of plant selection, the subsequent sections will delve into the precise details of how these traits influence the success of wastewater treatment projects through phytoremediation.

Table 3

Phytoremediation includes processes/mechanisms for contaminant removal and selection criteria of plant species (Yadav et al. 2018)

Approach .	Pollutants .	Mechanism .	Selection criteria of plant species .
Phytoextraction	Ni, Pb, Zn, Cd, Cu with EDTA addition for radionuclides, Pb, short chained aliphatic compounds, and pentachlorophenol	Hyperaccumulation	Tolerance to high metal-accumulation capability, high metal concentrations, accumulation of trace elements in above-ground parts, rapid growth rate, extended root system for exploring large soil volumes, easy to harvest, easy agricultural management, high translocation factor, resistance to pathogens and pests, good adaptation to prevailing environmental and climate conditions, repulse herbivores to avoid food chain contamination.
Phytodegradation	Herbicides – alachlor, atrazine, chlorinated aliphatic compounds – trichloroethylene (TCE), mixtures benzene toluene ethylbenzene and xylene (BTEX), nutrients – ⁠, ⁠, ⁠, 2,4,6-trinitrotoluene (TNT), ammunition wastes, rapid detonating explosive (RDX)	Plant degradation	Vegetation should be easy to maintain, hardy and easy growing, tolerance to water logging and drought conditions, deep rooting plants such as willow, poplar, aspen, cottonwood etc., transform the toxic substances into less toxic or non-toxic products, and high transpiration rate.
Phytostabilization	Cd, Pb, As, Zn, Cr, Cu, U, Se, hydrophobic organics – polychlorinated biphenyl (PCBs), polycyclic aromatic hydrocarbons (PAHs), furans, dioxins, DDT, pentachlorophenol, dieldrin	Complexation	Ability to keep translocation of metals from roots to shoots as flat as possible, ability to develop extended and abundant root systems, capacity to retain contaminants in roots or rhizosphere (excluder mechanism).
Rhizofiltration	Heavy metals such as Cd, Pb, Ni, Zn, Cu, Radionuclides – Sr, Cs, hydrophobic organics, U, and radionuclides	Rhizosphere accumulation	High adsorption surface, metal-resistant plants, terrestrial plants preferred because of fibrous and much longer root system, tolerance of hypoxia,
Phytovolatilization	Chlorinated solvents like trichloroethylene, carbon tetrachloride, tetrachloroethylene, methylene chloride, 1,1,1-trichloroethane, carbon tetrachloride, Se, Hg ion	Volatilization by leaves	Contaminants could be transformed to less-toxic substances, Hg ion may be transformed into less-toxic substance, ability to use terrestrial/aquatic plants for, ex-situ or in-situ application, species other than hyperaccumulators may be used, metabolites or contaminants released to atmosphere subject to more effective or rapid natural degradation processes (such as photodegradation).

Approach .	Pollutants .	Mechanism .	Selection criteria of plant species .
Phytoextraction	Ni, Pb, Zn, Cd, Cu with EDTA addition for radionuclides, Pb, short chained aliphatic compounds, and pentachlorophenol	Hyperaccumulation	Tolerance to high metal-accumulation capability, high metal concentrations, accumulation of trace elements in above-ground parts, rapid growth rate, extended root system for exploring large soil volumes, easy to harvest, easy agricultural management, high translocation factor, resistance to pathogens and pests, good adaptation to prevailing environmental and climate conditions, repulse herbivores to avoid food chain contamination.
Phytodegradation	Herbicides – alachlor, atrazine, chlorinated aliphatic compounds – trichloroethylene (TCE), mixtures benzene toluene ethylbenzene and xylene (BTEX), nutrients – ⁠, ⁠, ⁠, 2,4,6-trinitrotoluene (TNT), ammunition wastes, rapid detonating explosive (RDX)	Plant degradation	Vegetation should be easy to maintain, hardy and easy growing, tolerance to water logging and drought conditions, deep rooting plants such as willow, poplar, aspen, cottonwood etc., transform the toxic substances into less toxic or non-toxic products, and high transpiration rate.
Phytostabilization	Cd, Pb, As, Zn, Cr, Cu, U, Se, hydrophobic organics – polychlorinated biphenyl (PCBs), polycyclic aromatic hydrocarbons (PAHs), furans, dioxins, DDT, pentachlorophenol, dieldrin	Complexation	Ability to keep translocation of metals from roots to shoots as flat as possible, ability to develop extended and abundant root systems, capacity to retain contaminants in roots or rhizosphere (excluder mechanism).
Rhizofiltration	Heavy metals such as Cd, Pb, Ni, Zn, Cu, Radionuclides – Sr, Cs, hydrophobic organics, U, and radionuclides	Rhizosphere accumulation	High adsorption surface, metal-resistant plants, terrestrial plants preferred because of fibrous and much longer root system, tolerance of hypoxia,
Phytovolatilization	Chlorinated solvents like trichloroethylene, carbon tetrachloride, tetrachloroethylene, methylene chloride, 1,1,1-trichloroethane, carbon tetrachloride, Se, Hg ion	Volatilization by leaves	Contaminants could be transformed to less-toxic substances, Hg ion may be transformed into less-toxic substance, ability to use terrestrial/aquatic plants for, ex-situ or in-situ application, species other than hyperaccumulators may be used, metabolites or contaminants released to atmosphere subject to more effective or rapid natural degradation processes (such as photodegradation).

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Hyperaccumulators, a specific subclass of accumulator plants, are commonly found in naturally mineralized soils, showcasing a unique ability to collect elevated concentrations of metals in their leaves (Bhargava et al. 2012). Unlike other plants, hyperaccumulators can accumulate metals in their above-ground tissues without displaying any poisoning symptoms (Baker et al. 2020). These extraordinary plants are distributed across various regions, including Europe, North America, New Caledonia, and South Africa, thriving in soils abundant in metal content (Baker 1989).

The classification of a plant as a hyperaccumulator hinges on its capacity to accumulate metals beyond the Ni-toxicity threshold of 10–15 μg g⁻¹, with concentrations exceeding 1 mg g⁻¹ Ni in the shoot. Threshold values have been established for each HM based on its unique phytotoxicity, providing a systematic approach to characterizing hyperaccumulation (Rascio & Navari-Izzo 2011). The efficiency of hyperaccumulators in eradicating HMs from polluted soils is influenced by the rate of biomass generation and the bioconcentration factor (BCF), representing the ratio of metal content in soil to shoot tissue. The roots play a vital role in absorbing and cleansing metals while sustaining growth, absorption, and biomass generation (Guerinot & Salt 2001; Clemens et al. 2002; McGrath & Zhao 2003). Hyperaccumulators typically exhibit BCF values higher than 1, occasionally surpassing 50–100, sparking ongoing discussions about the relationship between metal hyperaccumulation and tolerance (Bhargava et al. 2012).

More than 0.2% of angiosperms, representing a significant proportion, display the remarkable phenomenon of hyperaccumulation of HM ions (Rascio & Navari-Izzo 2011). This phenomenon extends across a diverse range of more than 450 vascular plant species representing 45 angiosperm groups, including those within the Cyperaceae, Asteraceae, Brassicaceae, Caryophyllaceae, Fabaceae, Cunoniaceae, Lamiaceae, Flacourtiaceae, Poaceae, Euphorbiaceae, and Violetaceae families (Padmavathiamma & Li 2007). Beyond their ecological and physiological significance, the interest in hyperaccumulator plants has surged due to the potential utility of their accumulation features. This interest opens avenues for practical applications, like the development of phytoremediation techniques for wastewater treatment or HM-contaminated soils (Rascio & Navari-Izzo 2011).

Within the realm of phytoremediation, the success of plants in remediating formidable environmental conditions hinges on their resilience, illustrated by a delicate interplay of tolerance and adaptation. With an increase in contamination, plants demonstrate their capacity to withstand heightened pollutant levels and adjust to the distinctive conditions prevalent in wastewater environments (Mahar et al. 2016). As HM ions permeate the cellular domain, plants deploy sophisticated tolerance strategies to counteract the associated toxicity (Dalvi & Bhalerao 2013). Detoxification becomes crucial when surplus HM ions accumulate within the cytosol, compelling plants to mitigate their toxic effects. This intricate process involves chelation, where HM ions form complexes with ligands, diminishing the concentrations of free metal ions to benign levels (Manara 2012).

Various inorganic and organic ligands within the cytoplasm play pivotal roles in mediating HM chelation, encompassing metallothioneins, organic acids, phytochelatins, amino acids, and cell wall polyphenols/pectins/proteins (Gupta et al. 2013). For example, by complexing and decreasing the bioavailability of HM, organic acids stop them from remaining free ions in the cytoplasm. This intricate interplay of tolerance mechanisms and adaptive responses unveils plants' remarkable ability to navigate and mitigate the challenges posed by diverse contaminants, offering profound insights into the selection of robust species for effective phytoremediation (Yan et al. 2020).

In the realm of phytoremediation, the growth characteristics of chosen plants emerge as pivotal determinants of wastewater treatment efficacy. Factors like rapid growth (Abdelkrim et al. 2019), extensive root systems (Abdelhameed & Metwally 2019), and significant biomass yield are instrumental contributors to the efficient removal of pollutants (Aken 2008). These desirable growth attributes not only enhance the overall phytoremediation process but also facilitate cost-effective and sustainable approaches to wastewater treatment. A profound understanding and effective utilization of the growth characteristics specific to each plant species become imperative for optimizing their potential in environmental cleanup endeavors.

The ability of hyperaccumulator plants to flourish under elevated levels of HM can be attributed to multiple biochemical pathways that help maintain lower metal concentrations in the cytoplasm as compared to the soil, safeguarding cytoplasmic organelles from the toxic effects of HMs (Nedjimi 2009). Hyperaccumulator plants efficiently accumulate substantial quantities of HMs in their above-ground parts during normal growth and reproduction, with some exhibiting the capacity to accumulate non-essential HMs, such as Pb, Ag, Cd, and Hg, which lack functions (Nedjimi & Daoud 2009). The efficacy of phytoextraction is further heightened by plants with a high growth rate, resulting in a huge quantity of plant biomass coupled with a deeper root system (Nedjimi 2021).

Phytoremediation is an environmentally friendly and sustainable method to clean up contaminated environments. It has been successfully used in various case studies. Remediating HM-contaminated soils with hyperaccumulator plants, such as Alyssum species, is one prominent example (Li et al. 2003). By accumulating and concentrating metals like Zn and Ni in their tissues, these plants have demonstrated the potential to lower soil metal concentrations. Wetland plants, for instance, Phragmites australis, have also been successfully used to cleanse water tainted with contaminants like petroleum hydrocarbons (Williams 2002). A thorough model for wastewater stabilization pond optimization is provided by Ali & Üçüncü (2023), which provides insightful information on enhancing the effectiveness of wastewater treatment methods, such as phytoremediation. Tahiri et al. (2023) assesses the presence of pharmaceutical compounds in wastewaters and aquatic environments, highlighting the need for effective treatment solutions such as phytoremediation to address emerging contaminants. In order to assess the efficacy of phytoremediation in enhancing groundwater safety and lowering health risks, Nguyen & Huynh (2023) provide a thorough description of groundwater quality and relate it to human health. These case studies demonstrate how phytoremediation may be used to remediate polluted land and water in a sustainable manner, highlighting its adaptability in tackling a variety of environmental issues. A comprehensive understanding of phytoremediation through a detailed bibliographical table featuring additional case studies is displayed in Table 4.

As a potential technique for cleaning up the environment, phytoremediation has a number of advantages and implementation-related challenges. One significant advantage is that it is environmentally friendly since plants use their own natural mechanisms to remove pollutants, which reduces the need for large-scale infrastructure (Futughe et al. 2020; Lata & Siddharth 2021). Furthermore, phytoremediation is economical, particularly in contrast to more conventional remediation techniques. The technique also improves esthetics, as well-chosen plants enhance the esthetic appeal of green places and aid in ecological restoration (Farraji et al. 2016).

There are obstacles in the way of widely using phytoremediation, though. In order to see significant effects, the approach might be lengthy and patient (Babu et al. 2021). Based on site-specific factors including soil composition and climate, phytoremediation's efficacy may differ (Jaskulak et al. 2020). It is important to select the right plant species for the area and toxins present, and the possibility of contaminants being released back into the ecosystem after plants are harvested is one of the challenges. Despite these challenges, further study and technical developments hope to increase phytoremediation's effectiveness and adaptability, making it a practical and long-term solution for dealing with environmental pollution. To optimize phytoremediation's potential in various remediation circumstances, it is essential to comprehend both the potential advantages and challenges.

There are several wastewater techniques available through phytoremediation, each having advantages and disadvantages of their own. The most important factor to compare when contrasting various strategies is their efficacy. Heavy metals like Ni and As are effectively removed from wastewater by hyperaccumulators such as Alyssum and Pteris vittate (Sytar et al. 2020). Wetland plants that use phytoextraction and biosorption, such as Junicus (rush) and Typha (cattail), are also good at eliminating heavy metals (Ali et al. 2020). While certain species, like Vetiveria zizanoides (vetiver) and Salix (willow), can breakdown pesticides and solvents by phytodegradation (Khan et al. 2020; Kafle et al. 2022).

The growth conditions of various plants are important factors in determining their efficiencies. Eichhornia crassipes (water hyacinth) and Lemna (duckweed) are examples of hydrophytes that do well in wet environments and are excellent at removing nutrients (Lu et al. 2018). They do, however, need steady water levels and may grow invasive. Because they are suited to land-based systems, terrestrial plants like Sorghum and Rudbeckia are helpful in the treatment of industrial wastewater. For these plants to flourish, more watering and soil amendments might be needed (Gawronski et al. 2011).

The viability of phytoremediation is also affected by maintenance and management issues. Perennials need less frequent replanting but can be more difficult to manage than annuals due to their slower growth rates, which make them simpler to harvest yet necessitate replanting every season. Different plants have different nutritional requirements. Others require high nutrient levels for optimal development, which might be difficult to achieve in nutrient-poor wastewater. On the other hand, other plants can survive with low nutrient levels but may be less efficient in removing contaminants (Ajayi & Ogunbayio 2012; Slocombe et al. 2020).

A key consideration in the decision-making process is cost and economic viability. The selection of plants, preparation of the site, and installation might result in significant upfront expenses when putting up a phytoremediation system. This initial cost can be minimized, though, by selecting inexpensive or native plants (Fernandez 2014). Phytoremediation sometimes uses less energy than certain mechanical or chemical treatment techniques, but operational expenses still include possible replanting, harvesting, and continuous upkeep.

Sustainable wastewater management needs innovation and improvements in the field of phytoremediation. Plants that have undergone genetic modification may be better able to absorb and break down pollutants. Hybrid systems provide comprehensive purification solutions by integrating phytoremediation with other techniques. The global reach of phytoremediation is increased by robust plant species that flourish in a variety of temperatures. Economic analysis shed light on large-scale, cost-effective solutions. A climate that is ready for adoption is nurtured by regulatory frameworks. The modern monitoring systems guarantee real-time effectiveness evaluation. The initiatives for public education spread the seeds of knowledge about the ecological effects of phytoremediation. The green solutions are incorporated into urban areas for sustainable development through integration with urban planning. Phytoremediation helps in purifying water sources by addressing HMs and newly discovered pollutants. Phytoremediation is expected to be a key component of sustainable wastewater treatment in the future.

Phytoremediation is more practically feasible in locations with appropriate soil and climate since plants need certain conditions to grow and eliminate pollutants. Sites that face severe environmental conditions or high pollution levels may provide difficulties that reduce the viability of phytoremediation. A disadvantage for circumstances needing quick cleanup is that phytoremediation often works over a longer period of time than more instantaneous chemical or mechanical treatments. Therefore, even if the technique seems promising, its use will rely on technological considerations as well as a thorough site evaluation and timeline consideration.

Several policy recommendations might be taken into consideration to facilitate the application of phytoremediation techniques:

• (1) Governments ought to offer grants and financial incentives for the advancement of phytoremediation technology research and development. Through this investment, biotechnology, plant breeding, and hybrid treatment technologies may all be advanced and made more widely available and efficient.

• (2) Adoption of phytoremediation in the management of polluted sites might aided by the establishment of precise rules and regulations. Policies should guarantee that pollutants are adequately handled and disposed of, as well as the safe management of plant biomass.

• (3) Encouraging cooperation between government, business, and academic institutions can result in the creation of creative ideas and the effective execution of phytoremediation initiatives. Collaborations can facilitate the exchange of best practices, resources, and information.

• (4) By raising understanding of the advantages and drawback of phytoremediation, public education campaigns can help these technologies gain traction and acceptability. Adoption can also be accelerated by educating industry executives and legislators about successful case studies.

• (5) Promoting pilot initiatives and testing grounds can yield important information on how well phytoremediation works under different circumstances. These initiatives can direct larger-scale deployments and contribute to the development of technological confidence.

Policymakers may handle environmental pollution more effectively and sustainably by addressing these factors and fostering an atmosphere that encourages the development and use of phytoremediation.

Phytoremediation, which includes important technologies including phytoextraction, rhizofiltration, phytostabilization, phytodegradation, and phytovolatilization, is a very flexible and sustainable wastewater treatment method. Phytoextraction is a promising approach that can successfully treat HM contamination through the use of hyperaccumulator plants. The case studies that are being presented highlight the practical success of phytoremediation in a variety of wastewater, demonstrating both its cost-effectiveness and environmental friendliness in addressing the problems associated with water pollution worldwide. The use of plants in remediation strategies – especially when it comes to techniques like phytoextraction – offers hope for a cleaner and greener future as we navigate the terrain of environmental stewardship and makes a significant contribution to the discussion about sustainable wastewater treatment methods.

The authors extend their appreciation to the Department of University of Petroleum & Energy Studies (UPES), Dehradun, and UPES for granting access to library facilities for conducting this research.

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

The authors declare there is no conflict.