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Article

Novel Vertical Flow Wetland Filtration Combined with Co-Zeotype Material Based Catalytic Ozonation Process for the Treatment of Municipal Wastewater

1
Department of Chemistry, College of Science, University of Hafr Al Batin, P.O. Box 1803, Hafr Al Batin 39524, Saudi Arabia
2
Institute of Environmental Engineering and Research, University of Engineering and Technology, GT Road, Lahore 54890, Pakistan
3
School of Science, Department of Chemistry, University of Management and Technology, Lahore 54770, Pakistan
4
Department of Chemical Engineering, University of Engineering and Technology, Lahore 54890, Pakistan
5
Department of Physics, College of Science, University of Hafr Al Batin, P.O. Box 1803, Hafr Al Batin 39524, Saudi Arabia
6
Department of Chemistry, University Colleges at Nairiyah, University of Hafr Al Batin, P.O. Box 1803, Hafr Al Batin 39524, Saudi Arabia
7
Department of Mechanical Engineering, College of Engineering, University of Hafr Al Batin, P.O. Box 1803, Hafr Al Batin 31991, Saudi Arabia
8
Renewable Energy Research Center, Fukushima Renewable Energy Institute, National Institute of Advanced Industrial Science and Technology, AIST, 2-2-9 Machiikedai, Koriyama 963-0298, Japan
*
Authors to whom correspondence should be addressed.
Water 2022, 14(21), 3361; https://doi.org/10.3390/w14213361
Received: 14 September 2022 / Revised: 15 October 2022 / Accepted: 17 October 2022 / Published: 23 October 2022

Abstract

:
Municipal wastewater treatment to recycling level is an important means to conserve water resources. Untreated wastewater leads to a reduction in per capita availability of water and an increase in environmental pollution. Therefore, in the current study, a filtration process based on Typha Angustifolia planted vertical flow wetland and Rice husk (VFCW) in combination with catalytic ozonation based on Cobalt loaded zeotype catalyst was used for the first time to treat municipal wastewater. The results at optimized conditions show that about 89%, 93%, and 97% of BOD5, COD, and TKN respectively were removed based on combined VFCW/Co-zeotype/O3 processes. More than 90% elimination of heavy metals including Cr, Cu, Cd, Fe, Ni, and Zn was also observed. Hence, it is concluded that the VFCW/Co-zeotype/O3 process has potential as an alternative to conventional treatment for municipal wastewater treatment.

1. Introduction

Applying appropriate treatment methods for the abatement of various pollutants helps in the recycling and reuse of wastewater. It may help to protect both the surface and groundwater from pollution and depletion [1]. Groundwater in different cities is extracted, consumed and discharged to surface water bodies causing severe pollution, along with depletion of groundwater for future generations [2,3]. The industrial and domestic wastewater released directly into rivers and other water bodies also leads to the contamination of surface and groundwater resources [4].
The conventional treatment technologies for municipal wastewater treatment may not be highly effective in treating wastewater to recycling levels. The introduction of more challenging (biological resistant) pollutants and heavy metals make conventional treatments less effective [5,6]. These processes include aerated lagoons, activated sludge process, trickling filter, rotating biological contractors, etc. A major problem in treating wastewater is the associated cost and complexity of conventional wastewater treatment technologies [6]. Hence, the presence of persistent organic pollutants such as pharmaceuticals, illicit drugs, endocrine-disrupting and personal care products reduced the effectiveness of biological treatment methods [6,7]. Conventional technologies are also not highly efficient for the abatement of both nutrients and heavy metals [8]. To overcome these challenges, low-cost treatment processes that are effective against a variety of pollutants are highly needed [7,9]. Recent studies suggest that a combination of conventional technologies with advanced treatment methods are considered to be the most cost effective best performing process for the treatment of wastewater [10,11,12].
Filtration based on constructed wetlands (CWs) utilizes natural processes i.e., wetland plants and associated microbial clusters, to assist in treating wastewaters [13]. Natural wetland systems, being the habitat of wildlife, eliminate contaminants from water flowing towards receiving lakes, streams and oceans [14]. CWs have an advantage over conventional techniques of low operational and capital costs [15].
It was found that heterogeneous catalytic ozonation includes metal oxides, such as Al2O3 and TiO2, and metals on supports acting as catalysts [16,17,18]. Such catalysts act as both adsorptive substances and help ozone oxidize the attached substances with (OH·) to give oxidation by-products [19,20,21]. The results show that metals on supports have higher efficiency than metal oxides. Support medium, active components and method of preparation affect the performance of the catalyst. A support medium having a large surface area and potent pore structure makes the catalyst a thermally and mechanically stable active center. This mechanism is proposed for metal oxide catalysts reacting with both ozone and organic compounds. This increases the solubility of O3 and also initiates its decomposition [19,20]. Moreover, metal oxides, zeolites and zeotypes are widely used as catalysts in catalytic ozonation due to their essential characteristics [22,23]. Therefore, in the current investigation, zeolite was selected as support and Co was loaded as an active site on zeolite. Previous findings indicate that cobalt-based materials were found to be effective catalysts in various catalytic processes. The adsorption ability and unique redox behavior of cobalt-based salts make them interesting materials to be applied as catalyst in various processes [24,25,26,27,28].
Nowadays, municipal wastewater has become more challenging due to the presence of persistent organic pollutants, therefore sewage treatment using CWs alone sometimes cannot meet agricultural reuse standards [10,11]. Therefore, a combination of both biological and advanced oxidation treatment is required [29]. In the current study, the authors investigated the Typha Angustifolia planted vertical flow wetland and rice husk bed filtration for the treatment of municipal wastewater, along with Co-zeotype 3A catalytic ozonation, implied as post-treatment after the filtration process. In the author’s previous studies, horizontal flow constructed wetlands with catalytic ozonation processes were used to treat landfill leachate [30]. Since vertical flow constructed wetlands (VFCW) require less area compared with horizontal CWs, VFCWs provide a combination of biological, chemical and physical treatment of wastewater, removing organics, heavy metals and pathogens using AOPs [31]. Elimination of BOD5, COD, TKN and heavy metals was investigated using the VFCW/Co-zeotype/O3 combined process. This technique may help to re-utilize the treated municipal wastewater for agricultural purposes. Especially, it may be utilized in the future at household levels by treating the municipal wastewater generated from the source (Figure 1) and its reuse for gardening. To the author’s knowledge, this study is the first example using a combination of vertical flow wetlands filtration in combination with cobalt loaded catalytic ozonation process. This study may be useful for achieving socio-economic and environmental goals leading to sustainable development.

2. Experimental

2.1. Materials and Methods

Wastewater sample was collected from Sagan Drain Lahore in polythene bottles as per the standard method. Characterization of this wastewater sample was carried out to calculate pollution load. Parameters i.e., turbidity, pH, BOD5, COD and TSS by filtration method, fecal coliform and total Kjeldhal nitrogen (TKN) were measured by standard methods [32]. Chemicals including cobalt nitrate Co(NO3)2.6H2O, zeolite, potassium iodide (KI), nitric acid (HNO3), sodium thiosulphate (Na2S2O3), and starch solution were purchased from Sigma Aldrich UK. The rice husk and Typha Angustifolia plants were obtained from the local market. Typha Angustifolia plant was procured and used in the constructed wetland. Potentially toxic metals such as iron (Fe), zinc (Zn), cadmium (Cd), chromium (Cr), nickel (Ni), and copper (Cu) were quantified from municipal wastewater samples by implying atomic absorption spectroscopy (AAS) fixed with graphite furnace following the standard method [33]. The limits of detection and quantifications for nickel were 0.08 mg/L & 0.1 mg/L and for zinc 0.09 mg/L & 0.05 mg/L, respectively. Each experiment was performed three times and the average values were reported.

2.2. Synthesis of Catalyst

Catalyst Co-Zeotype was prepared using an ion exchange process from Co(NO3)2·6H2O solution. 0.1 M solution of Co(NO3)2.6H2O was prepared and 2 g of zeolite were added to it and stirred for 3 h at room temperature on a magnetic stirrer hot plate (Model: RTH-340). The given solution was heated at 80 °C to evaporate water and then catalyst was further dried at 110 °C overnight in the oven. After complete evaporation of water, the dried catalyst was further calcined at a temperature of 600 °C, for 04 h at 10 °C/min heating rate. The final product was denoted as Co-zeotype [30].

2.3. Experimental Setup

The experimental setup consisted of three main units, the primary sedimentation tank, vertical flow constructed wetland unit (VFCW) and catalytic ozonation reactor (Figure 1). The sub-surface vertical flow constructed wetland unit was made using acrylic material with the dimensions of 0.5 m × 0.5 m × 1 m for length, width, and height, respectively, for an effective volume of 0.2225 m3. The VFCW was composed of a soil layer of 35 cm at the top for the growth of the plant. A rice husk bed was also provided between two gravel layers for filtration. A cylindrical batch reactor containing Co-zeotype catalyst pellets loaded in a rotary bucket was used for the catalytic ozonation process.

2.4. Experimental Procedure

The wastewater was first settled in a sedimentation tank for 45 min to remove settleable solids. The supernatant sewage from the settling tank was distributed vertically from the top of the VFCW unit and treated effluent was collected from the bottom. The constructed wetland was designed with a hydraulic retention time of 0.16 days and a hydraulic loading rate of 0.15 m/day. Experimentation was carried out for eight months under the continuous application of sewage. Timely removal of BOD5, COD, TKN and metals including Fe, Zn, Cr, Cd, Cu, and Ni were investigated from the VFCW. Treated effluent from the VFCW was further oxidized using catalytic ozonation. All the experimentation was carried out in a batch system having a reactor capacity of 2000 mL. The reaction was executed at the natural pH of the wastewater. The experiments were conducted by varying catalyst dosage and reaction time.

2.5. Characterization of Co-Zeotype Catalyst

Characterization of catalyst was done using scanning electron microscopy (SEM-EDX) (Hitachi H-7600 model) and Fourier Transform Infrared Spectroscopy using Bruker Vertex 70 model. The surface area and the pore size of Co-zeotype were determined through the BET method using nitrogen adsorption and desorption isotherms at 77 K (Micrometrics ASAP 2020) [30]. The study of the point of zero charges of Co-zeotype was conducted by applying the mass transfer method for both base material and catalyst [34].

2.6. Ozone Dose Analysis

Ozone dose was calculated using the iodometric method in the gaseous phase using 2% KI and 0.1 N HNO3, 0.25 N Na2S2O3, and starch solution [35].
Ozone   ( O 3 ) mg min = ( A + B ) × N × 24 T
A = Volume of titrant (Na2S2O3) used for trap (I)
B = Volume of titrant (Na2S2O3) used for trap (II)
N = Normality of titrant (Na2S2O3)
T = Total time of ozonation

3. Results and Discussion

3.1. Wastewater Characterization

Table 1 shows the results of wastewater characterization for BOD5, COD, TKN, TSS, and Cd exceeded the guideline values of the WHO. Initial characterization indicates that studied wastewater exceeds the National Environmental quality standards (NEQS) for BOD5, TKN and COD (80 mg/L, 40 mg/L, and 150 mg/L respectively). Moreover, the presence of heavy metals (Fe and Cd) in significant amount may also indicate that the wastewater requires appropriate treatment.

3.2. Characterization of Catalyst

The Co-zeotype was found to have a surface area of 37.1 m2/g and the pore size was 3.2 nm (Table 2). The isoelectric point of the studied catalyst was found to be slightly acidic (6.3 ± 0.2). The point of zero charge is an important property of materials to understand the charge on the catalyst at specific pH values and indicates the availability of Lewis and Bronsted acid sites, as they may alter pH [16,17,18]. The SEM images presented in Figure 2 suggest that the addition of a minute quantity of cobalt may not have a significant impact on the surface morphology of Co-zeotype 3A. Moreover, the studied catalyst has a porous surface that may be good for adsorbing pollutants, leading to their decomposition on the catalyst surface.
It is pertinent to mention here that in the current investigation we did not synthesize the zeolite, and the obtained zeolite was deposited with Co and confirmed with EDS. Moreover, this study is the continuation of the authors’ previous findings where the authors confirmed in detail the characteristics of zeolite and zeotype materials, involving XRD and BET analysis [21,23,30,36].
The Fourier transform infrared spectroscopy FTIR plot, as presented in Figure 3. The broad peak at 3398.35 cm−1 and a small peak at 1639.59 cm−1 were attributed to the O-H bond and absorbed water molecules present in the synthesized catalyst sample, respectively. Silicon bonds Si-O-Si are confirmed from the presence of a sharp and deep peak at 992.74 cm−1 [37]. Si-O and O-Si-O bonds and Co were confirmed due to the emergence of peaks below 800 cm−1. The range of peaks that occur due to the presence of the O-Si-O group is from 400–800 cm−1 [37]. All these peaks show that the required catalyst Co-zeotype was successfully synthesized.

3.3. Wastewater Treatment by VFCW

Results obtained from the VFCW system are shown in Figure 4 and Figure 5, respectively. The present study investigates the retention time of VFCW for 4 consecutive days. An optimum retention time of 3.5 h was obtained after four runs on different days (Figure 4).
Results (Figure 5) show that the significant removal of BOD, COD and TKN from their initial values (BOD5 = 229 mg/L, COD = 460 mg/L, TKN = 34 mg/L) was achieved, and was found to be 110 mg/L, 282.5 mg/L and 25.6 mg/L for BOD5, COD and TKN, respectively. The possible mechanism of removal of BOD5 and COD was due to uptake by microorganisms and filtration for suspended solids removal, while for nitrogen it was due to uptake by plants [38]. At the start, growth of microbes was low, therefore the removal of both BOD5 and COD remained low. When microbes’ concentration became sufficient, removal increased significantly. The presence of microbes is possible both at the surface and in soil and gravel [39]. At the start, all the possible removal of BOD5 and COD was due to the removal of all suspended organic matter due to filtration of wastewater through VFCW. Moreover, the presence of rice husk in filtration media may also help to remove COD, BOD5, and TKN via adsorption.

3.4. Contact Time Optimization for Simple Ozonation

Figure 6 shows the contact time optimization results of simple ozonation. It was found that with an increase in contact time removal all three parameters increased, i.e., BOD5, COD and TKN. After 100 min, removal became constant. Therefore, 100 min was selected as the optimum contact time for ozonation experiments.

3.5. Catalyst Dose Optimization for Catalytic Ozonation

Figure 6 exhibits the optimization of contact time for catalytic ozonation. The optimum time for the catalytic ozonation was found to be 60 min. It was found that after 60 min of contact time removal, all three parameters become constant and catalytic ozonation gave more removal efficiency at less time; the results are presented in Figure 7 for respective parameters (COD, BOD5, and TKN). Considering the economic factors, the optimum dose for catalyst was selected as 0.25 g (Figure 6).
Removal of COD and TKN showed a linear response to catalyst dose as shown in Figure 7. Optimum removal was achieved at 0.25 g/L dose. Maximum removal of COD was 85%, while this was 80% for TKN. All experiments were conducted at an ozonation flow rate of 1.8 mg/min. Faster removal was achieved for higher doses while low doses took more time to reach the required removal. The main reason for this phenomenon could be the increase in the number of active sites at the start for higher doses, while sites were less for lower doses at the start, which reduces the removal rate [40].

3.6. Comparison of Treatment Processes

Figure 8 shows the comparison of BOD5, COD and TKN from VFCW, catalytic ozonation and combined VFCW/Co-zeotype/O3 process. It was found that concentrations remaining after combined treatment meet WHO guidelines for agricultural reuse. Overall removal of BOD5, COD, and TKN was found to be 87.5, 92.85, and 93.75%, respectively, in the case of the combined process, which was the highest as compared to single VFCW and catalytic ozonation treatments (Figure 8).

3.7. Removal of Heavy Metals

Table 3 shows the results using the combined VFCW/Co-Zeotype/O3 process. Significant removal of heavy metals was achieved by the combined treatment. Maximum 90% of removal was achieved for Fe, while only 47% removal was achieved for Cu. The concentration of metals in treated wastewater was below the NEQS values. A possible mechanism for heavy metals removal was adsorption in soil, plants, rice husk and precipitation after oxidation [41]. Heavy metals are mostly present in dissolved form. They had percolated to the underdrain system. Most of the removal was achieved by oxidation.
It is important to mention here that the municipal wastewater sample was obtained from the Saggiyan main drain that may contain pollution from various municipalities including small industry, hospitals, schools, restaurants, workshops and domestic wastewater. The current treatment was to recycle domestic wastewater (household) that may have an extremely low pollution load as compared with the studied wastewater sample. However, to test the proposed technology under more challenging conditions, the wastewater samples from the Saggiyan main drain were included. The proposed process was found to be highly efficient for the removal of the BOD5, COD, TKN and potentially toxic metals. However, the Cd value was found to be slightly higher than NEQS. Therefore, it is recommended that effluent is recycled again in the proposed system when required in order to achieve NEQS.

3.8. Proposed Process Mechanism

The current investigation is based on a combination of various processes (Figure 1) for the removal of pollutants such as COD, BOD5, and TKN. The COD, BOD5 and TKN first removed by the microbial activity occurred on the roots of Typha Angustifolia plant and soil [38]. Moreover, the filtration process may further lead to the significant removal in COD and BOD5 values. The given results presented in Figure 5 clearly suggested the significant removal of COD and BOD5 in vertical flow wetland process. In addition to the above, as the water passed through different layers of the filtration unit (Figure 1), it may filter and adsorb heavy metals on its surface, and this it may be hypothesized that rice husk layer may significantly adsorb heavy metals. Table 3 clearly specifies that the studied heavy metals in municipal wastewater were found to be less than standard limits after passing through the filtration unit. Finally, the wastewater was subject to an advanced oxidation processes involving ozone and zeotype 3A catalyst in order to further remove COD, BOD5 and TKN. The Co-zeotype/O3 may involve the hydroxyl radical’s production [20] leading to the removal of BOD5, COD and TKN.
It is well known that the metal-loaded zeolites and zeotypes with aqueous ozone led directly to the generation of hydroxyl radicals that may remove the pollutants in the bulk, as well as on the surface, of the catalyst. Therefore, in the current investigation, it is proposed that the significant removal of COD/BOD5/TKN in wastewater in the case of the Co-Zeotype/O3 process may be due to the generation of hydroxyl radicals as compared with the single ozonation process [42,43,44].
The current investigation suggests that the removal of organic pollutants may be via a two-stage process (Figure 1). In the first stage, part of the organic pollutant may be adsorbed in the soil of a wetland where the bacteria present at the roots of Typha Angustifolia degrade the organic pollutants [30], while the rest of the organic substances pass through the different layers of filtration unit leading to the adsorption of the organic pollutants. Finally, the filtrated wastewater was placed into the oxidation unit where catalytic ozonation leads to the further reduction of COD/BOD5/TKN values [12,35,45].
Interestingly, in the current proposed treatment, a significant amount of potentially toxic metals was also found to be removed from wastewater. This may be due to the adsorption of heavy metals on rice husk, as well as their precipitation as a result of oxidation [23,42,45,46,47,48,49].

4. Conclusions

Typha Angustifolia planted VFCW showed significantly good results for municipal wastewater treatment. Removal of COD, BOD5 and TKN was 50%, 35%, and 13.5%, respectively, at the end of 3.5 hrs. in the VFCW and rice husk bed filtration process. VFCW combining catalytic ozonation using Co-Zeotype catalyst for municipal wastewater showed BOD5, COD, and TKN removal of 87.5%, 92.85, 93.75%, respectively. The removal of heavy metals such as Zn, Cu, Cr, Cd, Ni and Fe was found to be significant and remained within standard limits for effluent standards when the combined process was studied. Hence, it was concluded that VFCW/Co-Zeotype/O3 process may be applied to treat municipal wastewater.

Author Contributions

Conceptualization, A.I., U.Y.Q. and R.J.; Data curation, A.I., U.Y.Q., R.J., F.J. and A.A. (Amira Alazmi); Formal analysis, O.S.R. and U.Y.Q.; Funding acquisition, U.Y.Q.; Methodology, A.A. (Asia Akram), F.J. and I.U.-H.; Project administration, U.Y.Q.; Resources, A.I. and S.M.I.S.; Software, O.S.R. and S.M.I.S.; Supervision, A.I., U.Y.Q. and R.J.; Visualization, U.Y.Q. and O.S.R.; Writing—review & editing, A.I., O.S.R. and U.Y.Q. All authors have read and agreed to the published version of the manuscript.

Funding

This research work was funded by institutional fund projects under no IFP-A-2022-2-4-14. Therefore, author gratefully acknowledge technical and financial support from the ministry of education and University of Hafr Al Batin, Saudi Arabia.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

All relevant data are included in the paper.

Acknowledgments

The authors extend their appreciation to the Deanship of Scientific Research, University of Hafr Al Batin, for the continuous research support.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Experimental Setup.
Figure 1. Experimental Setup.
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Figure 2. SEM images of (a) Co-Zeotype 3A and (b) Zeotype 3A.
Figure 2. SEM images of (a) Co-Zeotype 3A and (b) Zeotype 3A.
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Figure 3. FTIR of the synthesized catalyst.
Figure 3. FTIR of the synthesized catalyst.
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Figure 4. Retention time of filter on different days.
Figure 4. Retention time of filter on different days.
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Figure 5. Municipal wastewater treatment using VFCW indicates the COD, TKN and BOD values.
Figure 5. Municipal wastewater treatment using VFCW indicates the COD, TKN and BOD values.
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Figure 6. Effect of ozone contact time on the removal of BOD5, COD and TKN.
Figure 6. Effect of ozone contact time on the removal of BOD5, COD and TKN.
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Figure 7. Simultaneous dose and contact time optimization for catalytic ozonation (a) 0.25 g, (b) 0.5 g, and (c) 1.0 g of catalyst dose, respectively.
Figure 7. Simultaneous dose and contact time optimization for catalytic ozonation (a) 0.25 g, (b) 0.5 g, and (c) 1.0 g of catalyst dose, respectively.
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Figure 8. % Removal of COD, TKN and BOD5 from VF and catalytic ozonation (Catalyst dose = 0.25 g; O3 = 1.8 mg/min; tO3 = 60 min; tRT = 3.5 h; T = 18 °C).
Figure 8. % Removal of COD, TKN and BOD5 from VF and catalytic ozonation (Catalyst dose = 0.25 g; O3 = 1.8 mg/min; tO3 = 60 min; tRT = 3.5 h; T = 18 °C).
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Table 1. Characterization results of Saggiyan drain wastewater.
Table 1. Characterization results of Saggiyan drain wastewater.
ParametersUnitsSaggiyan DrainNEQS
Temperature (°C)18 ± 240
EC (dS/m)90 ± 150
pH-7 ± 0.26–9
BOD5 (mg/L)177 ± 1880
COD 450 ± 25150
TKN 95.6 ± 1940
TDS 517 ± 283500
TSS 175 ± 13150
Fe 3.1 ± 0.022.0
Cd 2 ± 0.030.1
Zn 0.3 ± 0.015.0
Cr 0.45 ± 0.031.0
Ni 0.69 ± 0.021.0
Cu 0.17 ± 0.021.0
Table 2. Some physio-chemical properties of catalyst.
Table 2. Some physio-chemical properties of catalyst.
MaterialSurface Area BET (m2/g)Pore Size (nm)Pore Volume (cc/g)Cobalt Content [%] EDXPoint of Zero Charge (pHpzc)
Co-Zeotype 3A37.13.2112.457.036.3 ± 0.2
Table 3. Heavy Metals Removal by Wetland Filtration and catalytic ozonation.
Table 3. Heavy Metals Removal by Wetland Filtration and catalytic ozonation.
Metals (mg/L)NEQSAfter Treatment% Removal
Fe 2.00.0190
Zn 5.0BDL *-
Cd 0.1150
Cr 1.00.0588
Ni 1.0BDL-
Cu 1.00.0947
* BDL = Below Detection Limit.
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Qazi, U.Y.; Ikhlaq, A.; Akram, A.; Rizvi, O.S.; Javed, F.; Ul-Hasan, I.; Alazmi, A.; Ibn Shamsah, S.M.; Javaid, R. Novel Vertical Flow Wetland Filtration Combined with Co-Zeotype Material Based Catalytic Ozonation Process for the Treatment of Municipal Wastewater. Water 2022, 14, 3361. https://doi.org/10.3390/w14213361

AMA Style

Qazi UY, Ikhlaq A, Akram A, Rizvi OS, Javed F, Ul-Hasan I, Alazmi A, Ibn Shamsah SM, Javaid R. Novel Vertical Flow Wetland Filtration Combined with Co-Zeotype Material Based Catalytic Ozonation Process for the Treatment of Municipal Wastewater. Water. 2022; 14(21):3361. https://doi.org/10.3390/w14213361

Chicago/Turabian Style

Qazi, Umair Yaqub, Amir Ikhlaq, Asia Akram, Osama Shaheen Rizvi, Farhan Javed, Iftikhar Ul-Hasan, Amira Alazmi, Sami M. Ibn Shamsah, and Rahat Javaid. 2022. "Novel Vertical Flow Wetland Filtration Combined with Co-Zeotype Material Based Catalytic Ozonation Process for the Treatment of Municipal Wastewater" Water 14, no. 21: 3361. https://doi.org/10.3390/w14213361

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