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Article

Algae and Hydrophytes as Potential Plants for Bioremediation of Heavy Metals from Industrial Wastewater

by
Naila Farid
1,
Amin Ullah
1,*,
Sara Khan
1,
Sadia Butt
2,
Amir Zeb Khan
3,
Zobia Afsheen
1,
Hamed A. El-Serehy
4,
Humaira Yasmin
5,6,
Tehreem Ayaz
7 and
Qurban Ali
8,*
1
Department of Health and Biological Sciences, Abasyn University Peshawar, Peshawar 25000, Pakistan
2
Department of Microbiology, Shaheed Benazirbhutoo Women University Peshawar, Peshawar 25000, Pakistan
3
Pak-Austria Fachhochschule: Institute of Applied Sciences and Technology (IAST), Haripur 22721, Pakistan
4
Department of Zoology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia
5
Department of Infectious Disease, Faculty of Medicine, South Kensington Campus, Imperial College, London SW7 2BX, UK
6
Department of Biosciences, COMSATS University, Islamabad 45550, Pakistan
7
School of Resources and Environmental Engineering, East China University of Science and Technology, Shanghai 200237, China
8
Department of Plant Breeding and Genetics, University of the Punjab, Lahore 54599, Pakistan
*
Authors to whom correspondence should be addressed.
Water 2023, 15(12), 2142; https://doi.org/10.3390/w15122142
Submission received: 7 April 2023 / Revised: 29 May 2023 / Accepted: 29 May 2023 / Published: 6 June 2023
(This article belongs to the Special Issue Adsorption Technology for Water and Wastewater Treatments)
Browse Figures
Versions Notes

Abstract

:
Aquatic bodies contaminated by heavy metals (HMs) are one of the leading issues due to rapidly growing industries. The remediation of using algae and hydrophytes acts as an environmentally friendly and cost effective. This study was performed to investigate the pollution load, especially HMs, in the wastewater of the Gadoon Industrial Estate and to utilize the hydrophytes (Typha latifolia (TL) and Eicchornia crassipes (EI)) and algae (Zygnema pectiantum (ZP) and Spyrogyra species (SS)) as bioremediators. The wastewater was obtained and assessed for physiochemical parameters before treating with the selected species. The pot experiment was performed for 40 days. Then the wastewater samples and selected species were obtained from each pot to analyze the metal removal efficiency and assess for metal concentrations using atomic absorption spectrophotometry. The dissolved oxygen (DO; 114 mg/L), total suspended solids (TSS; 89.30 mg/L), electrical conductivity (EC; 6.35 mS/cm), chemical oxygen demand (COD) (236 mg/L), biological oxygen demand (BOD; 143 mg/L), and total dissolved solids (TDS; 559.67 mg/L), pH (6.85) were analyzed. The HMs were noted as Zn (5.73 mg/L) and Cu (7.13 mg/L). The wastewater was then treated with the species, and significant reductions were detected in physicochemical characteristics of the wastewater such as DO (13.15–62.20%), TSS (9.18–67.99%), EC (74.01–91.18%), COD (25.84–73.30%), BOD (21.67–73.42%), and TDS (14.02–95.93%). The hydrophytes and algae removed up to 82.19% of the Zn and 85.13% of the Cu from the wastewater. The study revealed that the hydrophytes and algae significantly decreased the HM levels in the wastewater (p ≤ 0.05). The study found TL, EI, ZP, and SS as the best hyper accumulative species for Zn and Cu removal from wastewater. The HMs were removed in the order of Cu > Zn. The most efficient removal for Cu was found by Typha latifolia and Zn by Zygnema pectiantum. It was concluded that bioremediation is an environmentally friendly and cost-effective technique that can be used for the treatment of wastewater due to the efficiency of algae and hydrophytes species in terms of HM removal.

Graphical Abstract

1. Introduction

Industrial wastewater (IWW) is considered one of the significant sources of aquatic contamination [1]. Due to the important use of heavy metals (HMs) in industrial processes, different poisonous HMs are widely used in many industrial activities such as mining, smelting, plating, fertilizer manufacturing, the textile, chemical, plastics, and pigments industries, etc. [2,3]. Heavy-metal-contaminated water is a serious issue due to the non-degradable nature of HMs and their tendency to accumulate in natural water bodies [4,5,6]. When the metals are discharged in the water bodies, they settle down and enter the aquatic bodies, leading to severe health problems and even causing the death of aquatic organisms [7].
The conventional methods used for metal removal from wastewater include electrochemical methods (electrocoagulation, electroflotation, and electrodeposition), coagulation–flocculation, floatation, membrane filtration, ion exchange, and chemical precipitation [8]. However, these methods have the drawbacks of maintenance costs, expensive operation, and secondary contamination due to the formation of toxic sludge. For landfill leachate treatment, constructed wetlands may be regarded as more environmentally friendly and sustainable solutions. Constructed wetlands have been used to remove pollution from various wastewater streams. In constructed wetlands, wastewater is remediated by physical (e.g., filtration and sedimentation) and chemical processes (e.g., adsorption and precipitation), as well as biological processes (e.g., uptake from the water column and root zone and microbial degradation) [9]. Constructed wetlands have been used to treat a wide range of storm water runoff, waste streams, landfill leachate, agricultural drainage including mine drainage, domestic wastewater, as well as industrial effluents [9,10]. Plants induce physicochemical and biological processes to remediate metals from wastewater effluents [11], which help in its treatment [12]. Hydrophytes such as Pistia stratiotes [13], Lemna gibba [14], and Eichhornia crassipes [12] are free-floating and known for pollution absorption particularly for HMs in polluted water. Similarly, other classes of emergent species such as Typha latifolia [15] have the capability of metal accumulation in higher concentration in shoots and roots [16]. According to the study of Khan et al. [17] regional species of hydrophytes are adapted to local climatic conditions and appropriate to use in constructed wetlands for the treatment of wastewater. So, one of the most effective and best substitutes for the conventional methods is bioremediation, which uses biological materials to convert toxic metals into less harmful substances [18,19]. Bioremediation is a cost-effective and environmentally friendly method in the revitalization of the environment [20,21]. There are two main approaches to bioremediation. Phytoremediation (plant-centered) is a technique that uses either genetically modified or raw plants to restore polluted water and land sources [22]. Some hydrophytes such as water cabbage (Pistia stratiotes), duckweed (Lemna gibba) [14], and water hyacinth (Eichhornia crassipes) [12] are floating hydrophytes famous for pollution absorption capability mostly for metals in IWW.
Phycoremediation is a valuable technique used to remediate metal-polluted water. The algae efficiently remove metals from wastewater [23,24]. In living algal cells, metal absorption occurs through binding with the intracellular ligands and the cell surface. The metal-bonded ligands accumulate further by active biological transport [25]. The metal removal mechanisms rely on various functional groups such as hydroxyls, amines, and carboxylates forming complexes with metal [26] and decreasing metal concentrations in the treated water. Earlier, studies have verified that algal species improve the wastewater quality and IWW by metal absorption [24,27,28]. Moreover, the microalgal biomass after bioremediation can be processed further to produce biochar, biodiesel, value-added products, and metal extraction, representing the process as environmentally sustainable and cost effective. Algae gained the attention of researchers as a potential applicant for biodiesel production among different feedstock. Microalgae cultivation can use non-agricultural land, suggesting that the land requirement for algae biodiesel production is low [29]. Algae can utilize CO2 as a carbon source for oil (i.e., biodiesel) and biomass production. Algae have rapid growth potential and have oil contents up to 50% dry weight of biomass [30]. The waste biomass can be converted into biochar, which plays a crucial role in protecting and repairing the environment [31].
In Pakistan, it is alarming that most industries and cities lack facilities for wastewater treatment. Huge industrial effluents are being directly released to surface water, resulting in severe pollution. Due to organic loads and toxic materials such as HMs, the IWW forms a main source of aquatic pollution in Pakistan. It causes water to be unsuitable for drinking, irrigation, or any other use. HM pollution has become a severe risk to living organisms in the environment. It can cause different health issues such as lung insufficiency, nervous disorders, bone injury, cancer, teratogenic and embryotoxic effects, and hypertension in humans. To deal with this issue, a variety of methods can be utilized, but these methods are expensive and badly affect the environment. In developing countries such as Pakistan, these methods cannot be used to remove HMs. Therefore, it is expected that hydrophytes and algal species may contribute in reclaiming the wastewater discharged from the Gadoon Industrial Estate, Pakistan. This study aims to assess the physiochemical parameters of the wastewater collected from the Gadoon Industrial Estate and the removal efficiency of the HMs and to compare the HM removal efficiency of algae and hydrophytes.

2. Materials and Methods

2.1. Algae and Hydrophyte Collection and Transplantation

In the study, the algal species spirogyra spp. and Zygnema pectinatum were collected from the Khiyali River, Peshawar. The new buds of Typha latifolia (cattail) and Eichhornia crassipes (water hyacinth) were collected from the ponds in Sabi village, District Peshawar. The species were first washed with tap and distilled water. The algae were then observed and identified by the procedure adopted by [32]. To remove dust and sand, the selected species were washed thoroughly and acclimatized and transplanted into IWW for 40 days at room temperature (18–20 °C). Figure 1 shows the collection of hydrophytes and algae.

2.2. Collection and Analysis of IWW

The IWW was obtained from the Gadoon Industrial Estate (34°7′8″ N 72°38′45″ E) using the procedure mentioned by Ayaz et al. [15]. The wastewater sample was obtained during the month of May with average temperatures ranging from 78 to 103 F° and an average rainfall of 3.3 inches. The Gadoon Industrial Estate has many different industrial units such as the steel, chemical, soap and oil, textile, marble, and ghee industries. The study area consists topographically of flood deposits and uneven natural and ground drains and contains widespread gravel deposits with shingle beds and clay and silt stratifications, generally flat in the west and south of the industrial estate. The solid waste substances were removed [32]. Then the IWW was analyzed for physiochemical characteristics such as temperature, TDS, electrical conductivity (EC), pH, TSS, DO, BOD, COD, and metals (Cu and Zn). The metals were then analyzed by atomic absorption spectrophotometry in the Central Resource Laboratory, University of Peshawar.

2.3. Experimental Design

The pot experiment was performed to observe the efficiency of metal (Cu and Zn) removal by individual hydrophytes and algal species (Figure 2). For this experiment, four clean pots were first rinsed using double-deionized distilled water and 10% HNO3 (diluted nitric acid). The treatment pots for hydrophytes were then marked as TL (containing 50 g Typha latifolia) and EI (containing 50 g Eichhornia crassipes) and were provided with 20 L of IWW. Similarly, the algal pots were named as ZP (containing 15 g Zygnema pectinatum) and SS (containing 15 g Spirogyra spp.) provided with 5 L of wastewater sample for transplantation. The hydrophytes were transplanted in sediments containing IWW. All four pots were placed at room temperature (27 °C) under natural light/dark 14:10 conditions for 40 days. After experimentation, species and water samples were obtained from all containers and were analyzed for different physiochemical characteristics and metals (Cu and Zn).

2.4. Sampling and Analysis of Sediment

For the transplantation of the hydrophytes, clean sediment was utilized in each pot (5 kg). Before experimentation, triplicate samples of the sediment were obtained and analyzed from TL and EI containers. The samples were observed for HMs (Zn and Cu) and various physiochemical characteristics. Temperature, EC, and pH were determined in the sediment samples (10 g) using an EC meter (InoLab level-1) and a pH Meter (Model: pH-208). Using the Australian standard procedure adopted by Ayaz et al. [15], the soil moisture content (MC) was determined, whereas the TOM (total organic matter) was observed using the method adopted by Walkley and Black [33]. On the ignition method, through weight loss, the TOC (total organic carbon) was calculated [34]. For the MC, TOM, and TOC, 50 g of sediment sample was used. In sediment, (0.5 g) metals were extracted using a wet digestion procedure [35] and quantified by atomic absorption spectrophotometry (AAS-700 PerkinElmer: Norwalk, CT, USA) in the Central Resource Laboratory, University of Peshawar.
Water samples were collected from the TL, EI, ZP, and SS containers at the end of the experiment. The samples were examined for physicochemical parameters and HMs (Zn and Cu). A quantity of 50 mL of water samples were taken, and the physicochemical characteristics such as EC, pH, and temperature were observed using the EC meter (InoLab-WTB GmbH; Weilheim, Germany) and the pH Meter (Model: pH-208), respectively. The TDS and TSS were determined for the water sample (10 mL) using the gravimetric method. The DO, BOD5, and COD were observed for the water sample (200 mL titrametrically by standard procedure adopted by the American Public Health Association [36]). The samples were also examined using atomic absorption spectrophotometry for HMs (Zn and Cu).

2.5. Sampling, Preparation, and Analysis of Hydrophyte

After experimentation, samples of TL, EI, ZP, and SS were collected in triplicate and adequately labeled to observe the metal removal efficiency of selected species. The root and aerial parts of the TL and EI were processed separately for further analysis using standard methods [17]. The harvested species samples were washed adequately to remove dust, clay, sand, and particles. The samples were then dried at 70 °C in an oven and then ground and stored in polythene bags for wet digestion [35]. After wet digestion, the extracted samples were quantified for heavy metals using atomic absorption spectrophotometry.

2.6. Formula

2.6.1. Bioconcentration Factor

The bioconcentration factor (BCF) of algal and hydrophyte efficiency for metal accumulation from the wastewater samples was determined using Equation (1) [37,38].
B C F   % = C a l g a e C w a t e r × 100
where Calgae refers to the metal concentration in the algae and Cwater is the metal concentration in the water.

2.6.2. Translocation Factor

The translocation factor (TF) was used to measure the metals translocated from wastewater and accumulated in the hydrophyte’s tissues using Equation (2) as below:
T C F % = C a e r i a l C   r o o t × 100
Caerial refers to the metals accumulated in the aerial parts, and Croot refers to the metal concentrations in the root part.

2.6.3. Bioaccumulation Measurement

The bioaccumulation capacity (q) was determined using Equation (3) as given below [39].
q = C i − C f M × V
Ci is the initial metal concentration, Cf is the final metal concentration, M is the amount of algal or hydrophyte dry biomass (g), and V is the water volume in (L).

2.6.4. Bioremoval Efficiency

The bioremoval efficiency (%) was measured using Equation (4) [24].
R = C i − C f C i × 100
R refers to the removal percentage, Ci is the initial metal concentration in wastewater, and Cf is the final metal concentration in wastewater.

2.7. Statistical Analysis

The statistical analysis was carried out as follows: Microsoft Excel and the statistical package for social sciences (SPSS) was used. ANOVA and t-test were applied for the significance between the variables of the parameters.

3. Results and Discussion

3.1. Physicochemical Characteristics of Sediment Sample

Table 1 summarizes the physicochemical analysis of sediments. The results showed lower concentrations of Zn and Cu (5.30 and 19.20 mg/kg) below the maximum permissible limit set by Pak-EPA (Pakistan Environmental Protection Agency, 2008) before starting the experiment. However, the levels of Zn and Cu raised to 7.47 and 20.82 mg/kg in the pots, respectively, ensuring the sedimentation and presence of metals from the water samples. Mass balancing suggested that the HMs were primarily deposited in sediments and hydrophytes. This character was also observed in the research studies reported by Hadad et al. [40] and Mays and Edwards [41].

3.2. Characteristics and Pollution Load of IWW

The physiochemical parameters’ values of IWW are given in Supplementary Materials Table S1. The IWW collected from all four containers, including TL (treatment container for Typha latifolia), EI (treatment container for Eicchornia crassipes), ZP (treatment container for Zygnema pectinatum), and SS (treatment container for Spyrogyra spp.), was observed before and after the treatment or experimentation for parameters such as EC, pH, TSS, BOD, temperature, TDS, DO, and COD.
The pH (6.85) observed for IWW was within the maximum permissible limit set by Pak-EPA. The EC, DO, BOD, COD, TSS, and TDS values determined for IWW were 6.35 mS/cm, 114 mg/L, 143 mg/L, 236 mg/L, 89.30 mg/L, and 559.67 mg/L. The TSS and TDS values were analyzed below the Pak-EPA limit (150 mg/L and 3500 mg/L, respectively). However, the COD and BOD values exceeded the limits (150 mg/L and 80 mg/L, respectively) as set by Pak-EPA. The concentrations of Zn (5.73 mg/L) and Cu (7.13 mg/L) in the IWW exceeded the maximum permissible limit of Pak-EPA.
Previously, similar findings (pH 7.6) were reported by Fito et al. [42], who carried out a study on the wastewater of the sugar industry. The EC results agreed with the results (320 S/cm) of Asia and Akporhonor [43], who analyzed the physicochemical characteristics of IWW from the rubber industry. The present TSS value was primarily similar to the findings (43 mg/L) reported by Shamshad et al. [24]. Hossain et al. [44] investigated the physical and chemical parameters of the IWW discharged from various industries (Bangladesh) and observed similar findings (EC: 2.64 mS/cm). Similarly, the present values conformed with the EC (0.24–5.04 mS/cm), DO (341 mg/L), BOD (143 mg/L), and COD values of the IWW in a research study reported by Ayaz et al. [15], a phytoremediation study performed on the Hayatabad Industrial Estate. However, the results were different from the EC (149.1–881.3 mS/cm), TSS (2470 mg/L), and COD (1231 mg/L) values observed by Aniyikaiye et al. [45] in a study conducted on the IWW released from the Nigerian paint industries. The present results were much different from the DO (1.83 mg/L) and BOD (25 mg/L) values reported on the phycoremediation of the wastewater of the Hayatabad Industrial Estate performed by Khan et al. [46]. Similarly, Singh et al. [47] carried out a similar study on the textile industry of Ludhiana, India, using wastewater collected from different dyeing mills, and higher COD (3050 mg/L) and BOD values (790 mg/L) were reported. Similarly, the TSS finding (397.5 mg/L) of the research study of Abrha et al. [48] on the IWW obtained from Ethiopian beverage industries was much different from this study’s findings. In another study performed on treatments for removing pharmaceutical wastes from wastewater, Badawy et al. [49] reported high TDS values. Higher values of TDS (7072 mg/L) in the textile industry wastewater have been reported by Paul et al. [50]. The differences in the findings can be accredited to the differences in sampling sites and study areas.

3.3. Effect of Hydrophytes and Algal Species on Physicochemical Parameters

The effects of hydrophytes and algae on various characteristics of the water samples are shown in the Supplementary Materials Table S1. The results revealed that Typha latifolia had significantly (p < 0.05) reduced EC (91.18%), TSS (50.94%), TDS (14.02%), DO (13.15%), BOD (21.67%), and COD (25.84%) during 40 days. In a recent study, the effect of Eicchornia crassipes was found lower on EC (77.48%) and TSS (9.18%) and higher on TDS (95.93%), DO (60.52%), BOD (73.42%), and COD (73.30%) than Typha latifolia. Similarly, the algal species Zygnema pectinatum had also significantly (p < 0.05) decreased the pollution of IWW such as EC (74.01%), TSS (63.04%), TDS (75.84%), DO (18.42%), BOD (38.46%), and COD (38.55%) during 40 days. In a recent study, the effect of Spyrogyra spp. was found to be lower on TDS (73.51%), BOD (29.37%), and COD (26.27%) and higher on EC (80.31%), TSS (67.99%), and DO (62.20%) than Zygnema pectinatum (Supplementary Materials Table S1). The results are consistent with the results reported by Khan et al. [46], the research conducted for the remediation of the IWW of the Hayatabad Industrial Estate by algae (Oedogonium westi, Cladophora glomerata, Zygnema insigne, and Vaucheria debaryana) who recorded a significant decrease in the COD (30.7%), EC (85.9%), TDS (79%), and BOD (52.4%). However, these findings were different from the findings reported by Sharma et al. [51] in their study on Chlorella minutissima, and significant reductions in the COD (80.5%), TDS (94.4%), and BOD (93%) of the IWW were detected. Similarly, the results of this study were inconsistent with the findings of Okpozu et al. [52], whose study reported on the bioremediation of cassava IWW by Desmodes musarmatus and detected a reduction in the COD by 92% and the BOD by 87%. The differences in the results could be linked to the wastewater characteristics, species of algae, and nutrients. Okpozu et al. [52] transplanted the algae in Bold’s basal medium and hydrolyzed cassava wastewater.

3.4. Effects of Selected Species on Heavy Metals

3.4.1. Zinc (Zn)

The average or mean of the Zinc concentration at the initial stage of the IWW was recorded as 5.73 mg/L. The mean Zn concentrations observed in the water samples collected after 40 days of the experiment from TL, EI, ZP, and SS were 1.63, 2.17, 1.02, and 2.24 mg/L, respectively (Figure 3). The efficiency of the Zn removal was noted as ranging from 60.90 to 82.19%, where 71.55, 62.12, 82.19, and 60.90% was removed by TL, EI, ZP, and SS, respectively, as shown in Table S1. The t-test results showed that TL, EI, ZP, and SS significantly (p ≤ 0.05) decreased the Zn level in the final stage water samples.
The Zn accumulation in the hydrophyte species differs in selected species, and the Zn level was observed to be the maximum in the underground parts of the hydrophyte species compared with the upper or aerial parts. The aerial parts of the TL and EI uptake were 71.23 and 33.61 mg/kg, respectively. The maximum uptake by the aerial tissues of the hydrophyte species was determined (71.23 mg/kg) in TL, and the minimum uptake (33.61 mg/kg) was determined in EI. The Zn uptakes by the root tissue of TL and EI were discovered to be 105.41 and 59.05 mg/kg, respectively (Figure 4). The Zn concentration recorded in the algal biomass after 40 days of experimentation is shown in Figure 5.
The translocation factors or bioconcentrations factor determined for TL, EI, ZP, and SS for Zn were 67.57, 56.91, 76.26, and 52.70%, respectively (Figure 6). The ZP was recorded for the highest and the SS was recorded for the lowest bioconcentration factor, as shown in Figure 5. The bioaccumulation capacities (q) of TL, EI, ZP, and SS for Zn were 1.64, 1.42, 1.57, and 1.16 mg/g. TL was observed as having the highest and SS was observed as having the lowest bioaccumulation capacity (Figure 7). The bioremoval efficiencies recorded for TL, EI, ZP, and SS were 71.55, 62.12, 82.19, and 60.90%, respectively. The highest Zn bioremoval efficiency was determined for ZP, and lowest was determined for SS (Supplementary Materials Table S1).
However, the algal bioaccumulation values did not support the results (0.745–1.286 mg/kg) of Khan et al. [46]. The bioaccumulation capacity variation may have been due to the different algal species used for bioremediation or the differences in metal concentrations in the IWW collected. The results obtained from the hydrophytes agreed with the results (98.8–99.3%) of the research study presented by Kanagy et al. [53]. Moreover, the findings were much higher than those obtained from the constructed wetland remediating IWW in the central Mediterranean [54]. The present results were much high than those in the literature (48.3%) reported by Khan et al. [17]. The t-test showed that the Zn level in the IWW samples was more reduced (p ≤ 0.05) than the initial samples of TL, EI, ZP, and SS, suggesting the efficient removal of Zn by selected hydrophytes from the IWW.
The comparative study of the bioremoval efficiency, bioaccumulation capacity, and bioconcentration factor observed for hydrophyte treatments (TL and EC) revealed that Typha latifolia was the most effective species for the remediation of Zn as compared with Eicchornia crassipes. Our study’s findings aligned with the literature presented by Ayaz et al. [15], revealing that Typha latifolia was more effective in metal removal from IWW than Eicchornia crassipes. Similarly, the comparative study of removal efficiency, bioaccumulation capacity, and bioconcentration factor observed for algal treatments by ZP and SS revealed that Zygnema pectinatum was the most effective species for Zn remediation as compared with Spyrogyra species.

3.4.2. Copper (Cu)

The mean of copper concentration in the initial stage IWW was 7.13 mg/L. The mean Cu concentrations observed in the water samples collected from TL, EI, ZP, and SS were 1.06, 1.37, 1.34, and 1.29 mg/L, respectively, as shown in Figure 8. The maximum Cu level was observed in EI samples, and the lowest value was observed in TL for the final point samples. Efficiencies of Cu removal were noted that ranged from 80.78 to 85.13%, where 85.13, 80.78, 81.20, and 81.90% were removed by TL, EI, ZP, and SS, respectively (Table S1). In a previous study conducted by Mane and Bhosle [55], higher percentages of bioremoval for Cu (89.6%) and Zn (81.53%) were observed by living Spirogyra sp. In other phycoremediation studies executed on wastewater, Uddin et al. [56] concluded that 92% of the Cu removal efficiency was observed for Spirogyra on ninety minutes of treatments. The t-test results showed that TL, EI, ZP, and SS significantly (p ≤ 0.05) decreased the Cu level in the final stage water samples compared with the initial stage.
The Cu bioaccumulation in selected hydrophytes species differed in various species, and the Cu level was observed to be maximum in the roots of the hydrophyte as compared with the aerial tissue. The upper or aerial parts of the TL and EI took up 63.09 and 59.91 mg/kg of Cu, respectively (Figure 3). The maximum uptake by the aerial parts (63.09 mg/kg) was determined in TL, and the minimum uptake (59.91 mg/kg) was determined in EI. The Cu absorption by the roots of TL and EI was determined to be 83.02 and 98.75 mg/kg, respectively. The lowest uptake by the root (83.02 mg/kg) was recorded in TL, and the highest absorption (98.75 mg/kg) was recorded in EI. The Cu uptakes detected in ZP and SS were 5.19 and 5.23 mg/g, respectively (Figure 5). The highest Cu uptake (5.23 mg/g) was observed in SS, and the lowest uptake (5.19 mg/g) was observed in ZP.
The study results indicated the highest uptake of Cu by EI, followed by TL. The analysis showed that Cu concentrations differed in various species. The Cu concentrations were observed to be higher in the roots as compared with the aerial parts of the hydrophytes. The findings of the study agreed with the literature on hydrophytes reported by Kumari and Tripathi [57], Victor et al. [58], and Galal et al. [59].
The translocation factor or bioconcentration factors determined for TL, EI, ZP, and SS for Cu were 75.99, 60.66, 72.79, and 73.35%, respectively. TL was recorded as having the highest and EI was recorded as having the lowest bioconcentration factor (Figure 6). Figure 7 shows the bioaccumulation capacities (q) of TL, EI, ZP, and SS for Cu, which were 2.42, 2.30, 1.93, and 1.94 mg/g. TL was observed as having the highest and ZP was observed as having the lowest bioaccumulation capacity (Figure 7). The bioremoval efficiencies recorded for TL, EI, ZP, and SS were 85.13, 80.78, 81.20, and 81.90%, respectively. The highest Cu bioremoval efficiency was determined for TL, and lowest was determined for EI (Supplementary Materials Table S1).
The comparative study of copper bioremoval efficiency, bioaccumulation capacity, and bioconcentration factors observed for hydrophyte treatment using TL and EI revealed that Typha latifolia was the most effective species for the remediation of Cu as compared with Eicchornia crassipes. Our study’s findings agreed with the study presented by Ayaz et al. [15], showing that Typha latifolia more effectively removed Cu from IWW compared with Eicchornia crassipes. Similarly, comparing the copper bioremoval efficiency, bioaccumulation capacity, and bioconcentration factors observed for algal treatments revealed that Spyrogyra species were the most effective species for Cu remediation as compared with Zygnema pectinatum.

4. Conclusions

The pot experiments concluded that hydrophytes and algae have a key role in the bioremediation of IWW and efficiently reduce metal level in industrial wastewater (IWW). Zygnema pectinatum (ZP) had the best Zn removal efficiency, and Typha Latifolia was the best bioremediator for Cu. The species removed 85.13% of Cu and 82.19% of Zn. The results recommend that Typha latifolia, Eicchornia crassipes, Zygnema pectinatum, and Spyrogyra spp. are the best hyper accumulative species for Zn and Cu from IWW. The heavy metal (Zn and Cu) concentrations of IWW were significantly reduced (p ≤ 0.05) after the treatments, which clearly showed the significance of hydrophytes and algae in the removal of metals. Moreover, the selected species survived in the conditions of stress triggered by the metal concentrations. Therefore, this property can be encouraging evidence for hydrophytes and algae to be utilized for remediation. So, the phytoremediation and phycoremediation are inexpensive, environmentally friendly treatment processes that can be utilized for the remediation of IWW contaminated with metals.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/w15122142/s1: Table S1: Physiochemical parameters of wastewater samples.

Author Contributions

Conceptualization, N.F., A.U. and H.Y.; Methodology, A.U. and S.K.; Software, T.A., S.K., A.Z.K. and S.B.; Validation, N.F. and H.A.E.-S.; Formal analysis, A.U., Q.A. and S.B.; Investigation, A.U., A.Z.K., Z.A. and H.Y.; Resources, A.U., Z.A. and S.K.; Data curation, N.F. and A.U.; Writing—original draft, N.F. and S.K.; Writing—review & editing, Q.A.; Supervision, A.U.; Project administration, H.A.E.-S.; Funding acquisition, H.A.E.-S. All authors have read and agreed to the published version of the manuscript.

Funding

Researchers Supporting Project Number (RSP2023R19) of King Saud University, Riyadh, Saudi Arabia.

Data Availability Statement

The datasets generated during the current study are available from the corresponding author on reasonable request.

Acknowledgments

The authors would also like to extend their sincere appreciation to the Researchers Supporting Project Number (RSP2023R19), King Saud University, Riyadh, Saudi Arabia.

Conflicts of Interest

The authors declare no conflict of interest.

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Water 15 02142 g001 550
Figure 1. Collection sites of selected hydrophytes and algae.
Figure 1. Collection sites of selected hydrophytes and algae.
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Figure 2. Experimental pots at initial and final stage.
Figure 2. Experimental pots at initial and final stage.
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Figure 3. Concentration of zinc in water samples.
Figure 3. Concentration of zinc in water samples.
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Figure 4. Heavy metal concentrations in hydrophytes.
Figure 4. Heavy metal concentrations in hydrophytes.
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Figure 5. Heavy metal concentrations in algal biomass.
Figure 5. Heavy metal concentrations in algal biomass.
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Figure 6. Bioconcentration factor (BCF) (%) or translocation factor of heavy metals in species.
Figure 6. Bioconcentration factor (BCF) (%) or translocation factor of heavy metals in species.
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Figure 7. Bioaccumulation of heavy metals in hydrophytes and algae.
Figure 7. Bioaccumulation of heavy metals in hydrophytes and algae.
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Figure 8. The Cu concentration in water.
Figure 8. The Cu concentration in water.
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Table
Table 1. Physiochemical parameters of sediment sample.
Table 1. Physiochemical parameters of sediment sample.
Parameters
(n = 3)		Samples *Mean ± SD
pHInitial8.09 ± 0.03
Final8.02 ± 0.03
EC (mS/cm)Initial341.5 ± 2.14
Final94.0 ± 2.85
MC (mg/m3)Initial0.62 ± 0.03
Final0.85 ± 0.013
TOM (mg/kg)Initial3.24 ± 0.03
Final3.81 ± 0.03
TOC (mg/kg)Initial1.78 ± 0.013
Final2.39 ± 2.011
Zn (mg/kg)Initial5.30 ± 3.17
Final7.47 ± 2.70
Cu (mg/kg)Initial19.07 ± 4.01
Final20.82 ± 4.96
* Initial: samples at the initial stage of the experiment. Final: samples at the final stage of the experiment.
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Farid, N.; Ullah, A.; Khan, S.; Butt, S.; Khan, A.Z.; Afsheen, Z.; El-Serehy, H.A.; Yasmin, H.; Ayaz, T.; Ali, Q. Algae and Hydrophytes as Potential Plants for Bioremediation of Heavy Metals from Industrial Wastewater. Water 2023, 15, 2142. https://doi.org/10.3390/w15122142

AMA Style

Farid N, Ullah A, Khan S, Butt S, Khan AZ, Afsheen Z, El-Serehy HA, Yasmin H, Ayaz T, Ali Q. Algae and Hydrophytes as Potential Plants for Bioremediation of Heavy Metals from Industrial Wastewater. Water. 2023; 15(12):2142. https://doi.org/10.3390/w15122142

Chicago/Turabian Style

Farid, Naila, Amin Ullah, Sara Khan, Sadia Butt, Amir Zeb Khan, Zobia Afsheen, Hamed A. El-Serehy, Humaira Yasmin, Tehreem Ayaz, and Qurban Ali. 2023. "Algae and Hydrophytes as Potential Plants for Bioremediation of Heavy Metals from Industrial Wastewater" Water 15, no. 12: 2142. https://doi.org/10.3390/w15122142

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