Current World Environment

Introduction

Water pollution generated from various sources poses a significant threat globally, indicating the urgent need for effective wastewater treatment. Turbidity, indicating suspended particles in water, demands attention due to its impact on water quality for various purposes. Wastewater treatment typically offer coagulation to remove suspended solids consciously improve water quality. The traditional method involves chemical coagulants like alum, which have several drawbacks like high cost, sludge disposal issues and raising concerns for environmental & human health. This issue has led to the exploration of alternative, eco-friendly solutions.Natural waste derived from plant materials such as papaya seed powder and tamarind seed powder provide a sustainable and eco-friendly alternative. These materials, along with orange peels and neem leaves, serve as effective bio-coagulants for wastewater treatment due to their inherent natural properties.

Papaya seeds function as a natural coagulant due to the presence of positively charged proteins. These proteins bind negatively charged particles such as silt, clay, bacteria, and toxins found in wastewater. This interaction enhances the formation and settling of flocs, leading to clearer water through processes of adsorption and charge neutralization. Additionally, papaya seed powder has the ability to combine with solids in water, facilitating their sedimentation at the bottom. This property further aids in the clarification of water by removing suspended particles.¹

Tamarind seeds serve as natural coagulants (bio coagulants) due to their protein content, which functions as polyelectrolytes. The dissolved protein possesses the -NH3+ group, allowing it to bind to negatively charged particles. This interaction destabilises the particles, leading to the formation of larger aggregates that can ultimately be precipitated.²

Neem leaves, rich in tannins, flavonoids, and fatty acids, have been traditionally used for their medicinal properties, including potential effects on coagulation. Tannins in neem leaves can modulate the coagulation system.³

Orange peel pectin is a natural coagulant and adsorbent that successfully lowers turbidity and eliminates contaminants from water. Orange peels are a rich source of this polysaccharide, which has several uses, most notably in wastewater treatment. Pectin present in orange peels acts as a flocculant, facilitating the aggregation of suspended particles in water, which aids in turbidity reduction⁴ Orange peels contain bioactive compounds such as ascorbic acid and phenolics, which contribute to their ability to reduce turbidity and adsorb pollutants⁵ The functional groups present in orange peels, such as –OH and –COOH, enable effective adsorption of various pollutants, including heavy metals and dyes.⁶ Studies have shown that orange peels can remove contaminants like methyl orange from water, demonstrating their potential as low-cost adsorbents.⁷

Papaya seeds, tamarind seeds, orange peels, and neem leaves are widely available as agricultural byproducts. Orange peels come from fruit markets and juice industries, while papaya and tamarind seeds are sourced from food processing waste. Neem leaves are abundant in tropical regions, making all these materials easily accessible and sustainable for wastewater treatment.

This paper investigates the effectiveness of papaya seed, Tamarind seed powder, orange peels and neem leaves powder as a coagulant for turbidity removal in wastewater treatment. Through systematic experimentation, we assess its performance under different dosages. We aim to provide insights into a sustainable approach to addressing turbidity issues in wastewater. By harnessing the natural properties of papaya seeds, tamarind seeds, orange peels, and neem leaves, we aim to contribute to greener and more efficient water treatment solutions. This research highlights the significance of exploring natural alternatives in the pursuit of cleaner and safer water resources, ultimately achieving Sustainable Development Goal 6 i.e. Clean Water and Sanitation.

A significant number of academic studies have assessed the performance of different natural coagulants in relation to water treatment. Natural coagulants are classified into two distinct categories: those derived from plant sources and those that are not derived from plant sources. Plant-derived coagulants can be derived from various sources such as leaves, seeds, fruit waste, tree bark and more. These plant-derived coagulants have been studied more extensively than non-plant-derived ones, mainly due to their cost-effectiveness.⁸  Various natural coagulants, including moringa seeds, banana peel, cassava peel, starch, beans, nirmali seeds, jatropha curcas, watermelon, and okra, have been explored in previous studies.⁹ For instance, Kishor and Singh highlighted that natural coagulants like Moringa oleifera, Cicer arietinum, tamarind seed, papaya seeds and neem leaves can effectively remove turbidity and total dissolved solids (TDS) from water.¹⁰ These organic coagulants offer a viable and sustainable alternative to their chemical counterparts, as they are considered safe, environmentally friendly, cost-effective. In contrast to chemical coagulants, they do not augment the metal load or generate large volumes of sludge during water treatment. Furthermore, natural coagulants can be used alone or in combination with chemicals like aluminium sulfate to enhance water treatment.¹¹

In another study, Dollah found that the optimum pH for using orange peels as a natural coagulant is 5.0, with an optimal dosage of 60 mg/L, achieving up to 88.40% turbidity removal from synthetic water samples.¹² Similarly, Al-Aubadi and Hashim reported that orange peel coagulants could achieve 94% turbidity removal at a pH of 5.2. They also noted that plant coagulants could be used as coagulant aids with alum to increase coagulation efficiency and reduce the amount of alum needed.¹³

Several researchers have explored the use of citrus fruit peels for water treatment.¹⁴ shown that a mix of citrus microcarpa peels and citrus aurantiifolia peels with an 80:20 ratio had the highest turbidity removal efficiency of 77.6%, with optimal mixing conditions being 120 rpm rapid mixing for 3 min, 50 rpm slow mixing for 20 min, and 60 min of sedimentation time. Additionally, Hamzah  found that lemon peels could remove up to 89% of turbidity in water at an optimal dosage of 60 mg/L and pH of 4.0, making lemon peels a feasible and environmentally friendly alternative to synthetic chemical coagulants.¹⁵

Jamila El Gaayda et al. experimented on moringa seeds, and the results demonstrated removal efficiencies of 98.5% for turbidity and 92.2% for dye from synthetic wastewater.¹⁶

Moreover, Khan et al proposed that powdered neem seeds can be used as an effective coagulant to remove up to 86% of turbidity from water when used at an optimal dose of 3 g/L, pH of 13.2 and mixing conditions of 60 minutes at 80 rpm. This indicates that powdered neem seeds may serve as a viable alternative to traditional chemical coagulants in the treatment of drinking water.¹⁷

Additionally, tamarind seed extract has been shown to act as a bio coagulant in reducing wastewater pollutants, with effective concentrations at 80 mg/L and 120 mg/L. Pujiastuti  reported that tamarind seed powder achieved an 85% reduction in turbidity at a dosage of 30 mg/L, resulting in a final turbidity of 15 NTU. Furthermore, winged bean powder was found to achieve an 80% reduction in turbidity, emphasising the efficacy of these natural coagulants in water treatment.¹⁸

Yimer found that Papaya seed extract proved to be an effective coagulant for water treatment.

achieving 96.32% total coliform removal and reducing turbidity to 4.25 NTU, meeting WHO drinking water standards.¹⁹

Another research compares the efficiency of neem leaves and orange peels with textile waste and found neem leaf powered as a coagulant is more effective. The turbidity was reduced to approximately 4 NTU using neem, while orange peel powder reduced the turbidity to about 8 NTU. The pH remained alkaline with the use of neem, but it slightly decreased with the application of orange peel powder.²⁰

Farah Amira Binti Mohammad Lanan utilised fenugreek (Trigonella foenum-graecum) as a coagulant and okra (Abelmoschus esculentus) as a flocculant in the treatment of palm oil mill effluent (POME). The treatment accomplished removal efficiencies of 94.97% for turbidity, 92.70% for total suspended solids, and 63.11% for chemical oxygen demand.²¹

Many other natural coagulant like Petai belalang (Leucaena leucocephala),²² Prickly Pear Peel Waste ²³ Almond Hull, ²⁴ some of the researchers explored combined effects blend of plant based natural and synthetic coagulants like Moringa Oleifera-Cactus Opuntia-alum blend,²⁵ alum and neem leaves.²⁶

While various studies have explored the effectiveness of natural coagulants, there is a lack of comprehensive comparative analyses that evaluate the performance of multiple natural coagulants against each other under identical experimental conditions. This gap hinders the ability to identify the most effective coagulant for specific wastewater treatment scenarios.

Most studies on natural coagulants have been conducted at a laboratory scale, leaving a significant gap regarding their scalability for industrial applications. Research is needed to assess the practical challenges of implementing these coagulants in wastewater.

Table 1: Comparison of natural coagulant and traditional coagulant

Materials and Methods

Raw Water Quality

Wastewater samples were collected from a sewer manhole in Chandkheda, Ahmedabad, during September 2024. The pH of the water was measured at 6.9. Turbidity was recorded at 364 NTU. The Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) were 307 mg/L and 496 mg/L, respectively. These parameters represent the initial characteristics of the water used in the study.

Coagulant Preparation

Papaya seeds: The preparation of papaya seed coagulant for wastewater treatment involves several methodical steps to harness the natural coagulating properties of the seeds. First, fresh papaya seeds are extracted from the fruit and thoroughly washed to remove any residual pulp. These seeds are then dried by spreading them out under the sun for several days until fully dehydrated. Once dried, the seeds are reduced to a fine powder utilizing a high-performance blender. or grinder. To prepare the coagulant solution, 10gm of the papaya seed powder is dissolved in 500 ml distilled water, although this ratio can be adjusted based on the wastewater's characteristics. The solution is stirred thoroughly to ensure even dispersion of the powder. Lastly filter the solution to remove any remaining seed solids & collect the clear supernatant (liquid extract) and store it in a clean, airtight bottle.²⁷

Tamarind seeds: The tamarind seeds were gathered from kitchen refuse within the municipal jurisdiction. They were thoroughly cleansed and subsequently desiccated under sunlight for an extended duration until completely dehydrated. The desiccated seeds were thereafter processed into a fine powder utilizing a commercial mixer. Following the grinding process, the resultant material was subjected to sieving through a 750 um mesh, with the fraction exhibiting particle sizes smaller than 750 um designated for the experimental procedures. Fifty grams of the resultant powder was amalgamated with 1 L of distilled water and 1.0 M NaCl. The resultant mixture was agitated using a magnetic stirrer for a duration of 10 minutes to facilitate the extraction of the coagulation-active constituents. These constituents were subsequently filtered through filter paper, yielding a solution designated as crude extracts, which were prepared and preserved in a sterile container.

Neem Leaves: Neem leaves were collected and washed with distilled water, then dried naturally in sunlight for several days until fully dried. The dried leaves were crushed using a mixer and powdered, passing through a 75-micron sieve. To prepare a stock solution of the coagulant, 10 grams of the prepared powder was mixed with 1 litre of distilled water. The mixture was filtered through a muslin cloth. The resulting filtered solution, crude extract, was stored in a clean bottle for future use.

Orange Peel: Fresh orange peels were collected from a local market and thoroughly washed to remove dirt to prepare orange peel coagulant. Peels were dried naturally in sunlight until fully dried. After drying, the peels were manually cut into small pieces and finely crushed into a powder. Once dried, the powder was sieved through a mesh size of 600 µm to achieve uniform particle size. The resulting powdered orange peel was stored in an airtight container. To create the stock solution, 10 grams of the powdered peel were mixed with 1000 ml of distilled water, ensuring thorough dissolution by stirring. The solution was then left to stand to allow extraction of active compounds from the orange peel. The stock solution is filtered to remove any residual particles before storage in a clean, labelled container.²⁸²⁸

Jar test procedure

To determine the optimal dosages of the four coagulants mentioned, a systematic approach known as the jar test is employed. This process begins by filling six 1-liter beakers with raw wastewater samples, which are then labelled from 1 to 6 for easy identification.

Next, varying amounts of prepared stock solutions of each coagulant are added to the corresponding beakers. The mixtures are initially stirred vigorously at a rate of 100-150 revolutions per minute (rpm) for a duration of one minute. This rapid mixing phase is crucial as it ensures that the coagulants are evenly distributed throughout the wastewater, promoting effective interaction between the coagulants and the suspended particles.

Following the rapid mixing, the beakers are stirred at a slower rate of 20 rpm for a period  20 minutes. This slower stirring facilitates the formation of flocs, which are aggregates of particles that settle out of the water column. After the flocculation phase, the mixtures are allowed to settle undisturbed for 20 minutes. This settling period is essential for the flocs to grow larger and to separate from the treated water effectively.²⁹

Once the settling time has elapsed, the turbidity of the supernatant in each beaker is measured using a turbidity meter. Turbidity is an important indicator of water quality, as it reflects the concentration of suspended particles remaining in the water after treatment. The objective is to identify the optimum dosage of each coagulant, which is defined as the dosage that results in the lowest turbidity level. A lower turbidity indicates a more efficient coagulation process, leading to cleaner water.

To ensure accuracy and reliability of the results, multiple experiments are conducted with each coagulant. This comprehensive testing approach allows for the identification of the most effective dosage for coagulation, ultimately aiding in the treatment of wastewater and improving overall water quality.

Table 2: Raw Water Quality

Fourier transformed infrared analysis (FTIR)

The Bruker Alpha FTIR equipped with ZnSe optics was utilised for Fourier Transform Infrared Analysis (FTIR) to identify the organic functional groups. The FTIR spectrum was recorded in the mid-IR range of 400–4000 cm^-¹ utilising the attenuated total reflectance (ATR) method in ATR scanning mode.

For FTIR analysis, a small amount of the fine powdered sample is placed directly on the ZnSe ATR crystal. The powder was lightly pressed onto the crystal to ensure good contact and optimal penetration of infrared radiation. The sample was then analyzed using the ATR technique to obtain the FTIR spectrum.

Results and Discussion

The research project evaluated the performance of naturally obtained coagulants, including orange peels, papaya seeds, tamarind seeds, and neem leaves, for turbidity reduction. The findings revealed that neem leaves, when applied at an optimal concentration of 400 mg/L, accomplished a maximum removal of turbidity with an efficiency of 99.86%. Conversely, papaya seeds and orange peels exhibited comparable efficiencies, approximately 91% at significantly lower concentrations of 200 mg/L, final turbidity of 30 NTU and 30.9 NTU, respectively. Although tamarind seeds proved to be effective with an efficiency of 89.14%, they necessitated a considerably higher dosage of 1250 mg/L, leading to a final turbidity value of 39.5 NTU. These results represent the differential efficiency of natural coagulants. Table 3 and Figure 1 refers to the optimum dosage and corresponding turbidity removal and efficiency for each coagulant.

Table 3: Optimum dose of different coagulant

Figure 1: Graph showing Efficiency of different coagulants Click here to view Figure

Neem leaves performed the best among the natural coagulants tested, likely due at neem leaves are rich in secondary metabolites, also having  flavonoids and tannins, which are responsible for bioactive properties³⁰. Tannins are known for their ability to bind and destabilize suspended particles in wastewater, which helps in the formation of flocs that settle effectively.³¹ The FTIR analysis (Figure 2) and Table 4 revealed key The significant wavelengths for neem leaves encompass 3340, 2915, 1724, 1600, and 1441 cm^-¹, which are associated with functional groups such as O-H stretching, C-H stretching, C=O, C=C, and C-H bending. The presence of these groups suggests that neem leaves can effectively interact with organic contaminants in the wastewater,³² contributing to their superior coagulation performance. However, neem leaves impart a slight color to the treated water, which suggests that additional treatment, such as adsorption or filtration, may be necessary to achieve colour removal.

Table 4: FTIR Spectral Profile of Natural Coagulants for Turbidity Removal

Figure 2: FTIR Spectrum for Neem leaves Click here to view Figure

Similarly, the use of papaya seeds aligns with findings by Yimer,³³ who determined that papaya seed extract could effectively eliminate up to 96.32% of turbidity in aqueous solutions. Our investigation revealed a marginally reduced turbidity removal efficacy (91.75%); however, this was achieved at a significantly lower concentration (200 mg/L), which may imply a more economically viable methodology. The lower dosage requirements in our study can be linked to the preparation method, where fine grinding and proper dispersion likely led to better coagulation efficiency. The FTIR analysis (Figure 3) showed peaks at 1744 cm^-¹, 1709 cm^-¹, and 1649 cm^-¹, which correspond to carbonyl (C=O), aromatic (C=C), and C-N stretches, respectively. These identified functional groups from proteins imply that papaya seed powder possesses a considerable propensity for adsorption with organic pollutants,³³ thereby reducing the turbidity. Papaya seeds showed a significant reduction in BOD (52%) and COD (68%), but the performance is slightly lower than neem leaves in these metrics. Table 5 shows the final water quality, including BOD and COD reduction, for each coagulant.

Table 5: Final water Quality with different coagulant

Figure 3: FTIR Spectrum for Papaya Seeds Click here to view Figure

Orange peels, which are often overlooked in studies on wastewater treatment, have been shown to be an affordable substitute. They are a very viable choice for communities because to their low cost and free procurement from waste streams, especially in regions with a lot of citrus output. According to similar studies, orange peels and biochar can remove up to 91.92% of the turbidity³⁴ and orange peel alone can remove up to 79.4% in wastewater.³⁵ Our results (91.51%) are in line with similar findings. Orange peels coagulating qualities are probably caused by important functional groups including O-H, C-H, C=O, and C-H bending, which were identified by the FTIR study (Figure 4). These functional groups, together with pectin and phenolic chemicals, help to remove turbidity by promoting the adsorption of suspended particles.³⁶ But compared to neem leaves, the overall efficiency is lower. The noteworthy decrease in BOD (79%) and COD (80%) is consistent with previous research,³⁵ underscoring their capacity to remove organic compounds.

Figure 4: FTIR Spectrum for Orange peels Click here to view Figure

In contrast, tamarind seeds need larger dosages to effectively remove turbidity, which is consistent with research that showed tamarind seed extract reduced turbidity by up to 85% at a dosage of 30 mg/L.³⁷ However, our research used tamarind seeds instead tamarind seed extract of needed a much greater dosage of 1250 mg/L to remove 89.14% of the turbidity. This suggests that tamarind seeds would not be as effective as orange peels or neem leaves for large-scale applications. Peaks at 3267, 2920, 1742, and 990 cm^-¹ were found in the FTIR study (Figure 5), which corresponded to C-H bending, carbonyl (C=O), and alcohol/ether (C-O) stretches. When compared to other coagulants, tamarind seeds may not be as cost-effective due to the large dosage that is necessary. In spite of this, tamarind seeds showed significant drops in BOD (67%) and COD (78%), which makes them appropriate for use in wastewater in areas where their waste byproduct is easily accessible, like in food processing facilities.

Figure 5: FTIR Spectrum for Tamarind Seeds Click here to view Figure

Although orange peels are readily available and offer a cost-effective alternative, their turbidity reduction efficacy (66.89%) was marginally lower than that of papaya seeds and neem leaves. Nonetheless, orange peels' effectiveness in removing BOD and COD (79% and 80%, respectively) shows that they can be a good choice for wastewater organic matter removal. When it comes to practical application, orange peels are the most economical choice because they don't require any processing fees.

On the other hand, although they work well, papaya and tamarind seeds might need to be specifically sourced from nearby food processing businesses, which could affect how cost-effective they are overall. While tamarind seeds may be neglected in regions that do not process tamarind in big amounts, papaya seeds, despite their effectiveness, are frequently limited in availability, particularly in countries without a substantial papaya manufacturing industry. Both seeds, however, performed rather well in terms of reducing BOD and COD.

Regarding the FTIR study, spectral analysis indicated the the availability of functional groups like hydroxyl (-OH) and carboxylic acid (-COOH),³⁸ and amines (-NH2) in these natural coagulants, confirming their potential to interact with suspended particles and organic pollutants in wastewater. These functional groups facilitate adsorption, bridging, and charge neutralization mechanisms, essential for the coagulation-flocculation process, thus validating their effectiveness.

According to this study, neem leaves are the best natural coagulant, removing 99.86% of turbidity; nevertheless, color removal requires an extra step. Because they are readily available and inexpensive to treat, orange peels are the most economical coagulant. They remove 91.51% of turbidity and significantly lower BOD and COD. Though their cost-effectiveness is dependent on local availability and processing needs, papaya and tamarind seeds also exhibit promise. Given the cost, accessibility, and viability of these materials in actual wastewater treatment systems, this study offers a thorough comparison of natural coagulants and emphasizes the need for additional research to maximize their industrial-scale utilization.

To better understand the efficiency differences among the coagulants tested and enhance their use in wastewater treatment, more research into the mechanisms underlying coagulation is required. This includes examining the role of particular functional groups found in the FTIR analysis.

Conclusion

The study demonstrated that neem leaves emerged as the most effective natural coagulant, achieving an impressive 99.86% turbidity removal. However, it is important to note that neem leaves impart a slight color to the treated water, necessitating additional treatment for complete acceptability in water usage. In terms of cost-effectiveness, neem leaves remain a viable option due to their natural abundance and minimal processing costs. They also showed significant effectiveness in BOD and COD reduction, with reductions of 75% in BOD and 89% in COD, further enhancing their appeal as an affordable and efficient coagulant.

When considering alternatives, orange peels exhibited a comparable efficiency of around 91% turbidity removal, making them a highly cost-effective choice due to their zero-cost availability as a waste material. This coagulant also achieved substantial reductions in BOD (79%) and COD (80%), reinforcing its potential as an economical and sustainable solution.

Papaya seeds, while demonstrating a turbidity removal efficiency of 91.75%, required a lower dosage (200 mg/L) compared to tamarind seeds. However, their availability may depend on food processing waste sources, impacting their overall cost efficiency. Despite this, their significant reduction of BOD (52%) and COD (68%) makes them a promising option where availability is not a constraint.On the other hand, tamarind seeds required a higher dosage (1250 mg/L) to achieve 89.14% turbidity removal, which may affect their cost-effectiveness when compared to other natural coagulants. Nevertheless, they demonstrated strong reductions in BOD (67%) and COD (78%), making them suitable for applications where their waste byproduct is readily available, such as in food processing industries.

Regarding the FTIR study, spectral analysis indicated the presence of functional groups such as hydroxyl (-OH), carboxylic acid (-COOH), and amines (-NH2) in these natural coagulants, confirming their potential to interact with suspended particles and organic pollutants in wastewater. These functional groups facilitate adsorption, bridging, and charge neutralization mechanisms, essential for the coagulation-flocculation process, thus validating their effectiveness.

This research was conducted only at laboratory scale, without considering long-term stability, toxicity, or industrial-scale variability, potentially limiting real-world applicability.

In conclusion, while neem leaves offer the highest efficiency, their cost-effectiveness must be weighed against the need for additional color removal treatment. Orange peels stand out as the most practical and economical coagulant, given their wide availability, zero procurement cost, and strong turbidity and organic matter removal efficiency. Papaya seeds and tamarind seeds remain viable options, but their cost-effectiveness depends on sourcing feasibility and processing requirements.

This study emphasizes the importance of balancing removal efficiency, availability, and overall cost-effectiveness when selecting natural coagulants. Future research should focus on optimizing the industrial-scale application of these coagulants, including exploring cost-efficient methods for mitigating secondary drawbacks such as coloration and enhancing overall feasibility.

Acknowledgement

The authors would like to express their sincere gratitude to the Department of Civil Engineering, Vishwakarma Government Engineering College, Gujarat Technological University, Ahmedabad, for providing the necessary support and resources for this research.

The authors also appreciate the Student Startup and Innovation Policy (SSIP 2.0) for their financial and technical support, which was crucial in facilitating this study.

Special thanks are also extended to Dr. K. R. Gurjar from the Chemistry Department at Vishwakarma Government Engineering College for providing valuable assistance and support during the FTIR analysis.

Funding Sources

This project was financially supported by the Student Startup Innovation Policy (SSIP 2.0) and Vishwakarma Government Engineering College (VGEC).

Conflict of Interest

The authors do not have any conflict of interest.

Data Availability Statement

This statement does not apply to this article.

Ethics Statement

This research did not involve human participants, animal subjects, or any material that requires ethical approval.

Informed Consent Statement

This study did not involve human participants, and therefore, informed consent was not required.

Permission to reproduce material from other sources:

Not Applicable

Author Contributions

Dhriti Ramdas Rawat: Conceptualization of the study, methodology development, and supervision of research work. Contributed to the analysis and interpretation of results and manuscript review.

Khushboo Mahendra Parmar: Conducted data collection, assisted in data analysis, and contributed to the literature review. Assisted in manuscript writing and formatting.

Shraddha Shriram Thorat: Performed the experimental work, contributed to data analysis and interpretation, and drafted the initial manuscript. Assisted in manuscript editing and final proofreading

References

1. Yimer A, Dame B. Papaya seed extract as coagulant for potable water treatment in the case of Tulte River for the community of Yekuset district, Ethiopia. Environmental Challenges. 2021;4:100198. doi:10.1016/j.envc.2021.100198
   CrossRef
2. Zainol N, Nasuha Mohd Fadli N. Surface Water Treatment Using Tamarind Seed as Coagulants via Coagulation Process. IOP Conf Ser Mater Sci Eng. 2020;864(1):012172. doi:10.1088/1757-899X/864/1/012172
   CrossRef
3. Marcinczyk N, Gromotowicz-Poptawska A, Tomczyk M, Chabielska E. Tannins as Hemostasis Modulators. Front Pharmacol. 2022;12. doi:10.3389/fphar.2021.806891
   CrossRef
4. Mahdy S, Amin A, Abouzeid R, M. I. Moustafa I, Youssef A, ELhabasha ES. Development and Evaluation of Pectin extracted from Citrus sinensis peel and micro/nanocellulose from the solid fraction of citrus wastes. Egypt J Chem. 2023;0(0):0-0. doi:10.21608/ejchem.2023.232794.8532
   CrossRef
5. Rodriguez FJR, Lourdes CVZ. USE OF ORANGE PEELS (Citrus sinensis Whashington Navel) FOR OBTAINING PECTIN AS AN ADSORBENT IN THE BIOREMEDIATION OF EFFLUENTS CONTAMINATED WITH LEAD. Journal of Agricultural Sciences Research (2764-0973). 2024;4(2):2-10. doi:10.22533/at.ed.973422408027
   CrossRef
6. Nyika J, Dinka MO. The potential of reusing fruit bio-adsorbents for water purification: A minireview. Mater Today Proc. Published online July 2023. doi:10.1016/j.matpr.2023.07.285
   CrossRef
7. LAWAL A, ABDULSALAM A. Removal of Methyl Orange from Aqueous Solution Using Orange Peel as a Low Cost Adsorbent. Journal of the Turkish Chemical Society Section A: Chemistry. 2024;11(1):39-46. doi:10.18596/jotcsa.1313059
   CrossRef
8. Yusoff MS, Aziz HA, Alazaiza MYD, Rui LM. Potential use of oil palm trunk starch as coagulant and coagulant aid in semi-aerobic landfill leachate treatment. Water Quality Research Journal. 2019;54(3):203-219. doi:10.2166/wqrj.2019.041
   CrossRef
9. Shewa WA, Dagnew M. Revisiting Chemically Enhanced Primary Treatment of Wastewater: A Review. Sustainability. 2020;12(15):5928. doi:10.3390/su12155928
   CrossRef
10. Kishor B, Singh M. A Review on Removal of Turbidity and TDS from Water by Using Natural Coagulants. Vol 521.; 2020. www.irjmets.com
11. Koul B, Bhat N, Abubakar M, Mishra M, Arukha AP, Yadav D. Application of Natural Coagulants in Water Treatment: A Sustainable Alternative to Chemicals. Water (Basel). 2022;14(22):3751. doi:10.3390/w14223751
    CrossRef
12. Dollah Z, Habibah U, Rahman A, Hamzah N, Hasan D, Rosseli SR. Potential of Orange Peels as Natural Coagulant in Water Treatment.
13. Al-Aubadi IMK, Hashim LQ. Purification of Turbid Water Using Orange Peel Extract and Luffa Mucilage. Basrah Journal of Agricultural Sciences. 2022;35(2):259-270. doi:10.37077/25200860.2022.35.2.19
    CrossRef
14. Dollah Z, Abdullah ARC, Hashim NM, Albar A, Badrealam S, Mohd Zaki ZZ. Citrus fruit peel waste as a source of natural coagulant for water turbidity removal. In: Journal of Physics: Conference Series. Vol 1349. Institute of Physics Publishing; 2019. doi:10.1088/1742-6596/1349/1/012011
    CrossRef
15. Hamzah N. LEMON PEELS AS FRUIT WASTE NATURAL COAGULANT FOR FUTURE ALTERNATIVES IN WATER TREATMENT.; 2015. https://www.researchgate.net/publication/283318924
16. El Gaayda J, Titchou FE, Barra I, et al. Optimization of turbidity and dye removal from synthetic wastewater using response surface methodology: Effectiveness of Moringa oleifera seed powder as a green coagulant. J Environ Chem Eng. 2022;10(1):106988. doi:10.1016/j.jece.2021.106988
    CrossRef
17. Khan Q, Imran U, Ullman JL, Khokhar WA. Turbidity removal through the application of powdered azadirachta indica (neem) seeds. Mehran University Research Journal of Engineering and Technology. 2023;42(1):1. doi:10.22581/muet1982.2301.01
    CrossRef
18. Pujiastuti P, Wibowo YM, Narimo. The biocoagulation test of tamarind seed (Tamarindus indica) and winged bean (Psophocarpus tetragonolobus L.) powder in chemical laboratory wastewater. In: ; 2022:100002. doi:10.1063/5.0104367
    CrossRef
19. Yimer A, Dame B. Papaya seed extract as coagulant for potable water treatment in the case of Tulte River for the community of Yekuset district, Ethiopia. Environmental Challenges. 2021;4. doi:10.1016/j.envc.2021.100198
    CrossRef
20. Anju S, Mophin-Kani K. EXPLORING THE USE OF ORANGE PEEL AND NEEM LEAF POWDER AS ALTERNATIVE COAGULANT IN TREATMENT OF DAIRY WASTEWATER. Int J Sci Eng Res. 2016;7(4). http://www.ijser.org
21. Lanan FABM, Selvarajoo A, Sethu V, Arumugasamy SK. Utilisation of natural plant-based fenugreek (Trigonella foenum-graecum) coagulant and okra (Abelmoschus escluentus) flocculant for palm oil mill effluent (POME) treatment. J Environ Chem Eng. 2021;9(1):104667. doi:10.1016/j.jece.2020.104667
    CrossRef
22. Alnawajha MM, Abdullah SRS, Hasan HA, Othman AR, Kurniawan SB. Effectiveness of using water-extracted Leucaena leucocephala seeds as a coagulant for turbid water treatment: effects of dosage, pH, mixing speed, mixing time, and settling time. Biomass Convers Biorefin. 2024;14(10):11203-11216. doi:10.1007/s13399-022-03233-2
    CrossRef
23. Aguilera Flores MM, Robles Miranda OE, Medellín Castillo NA, et al. Evaluation of the Potential of a Biocoagulant Produced from Prickly Pear Peel Waste Valorization for Wastewater Treatment. Water (Switzerland). 2024;16(10). doi:10.3390/w16101444
    CrossRef
24. Gomes A, Jorge N, Teixeira A, Peres JA, Lucas MS. Cattle Wastewater Treatment Using Almond Hull and Cherry Pit as Coagulants–Flocculants. In: The 4th International Electronic Conference on Applied Sciences. MDPI; 2023:222. doi:10.3390/ASEC2023-15494
    CrossRef
25. Gandiwa BI, Moyo LB, Ncube S, Mamvura TA, Mguni LL, Hlabangana N. Optimisation of using a blend of plant based natural and synthetic coagulants for water treatment: (Moringa Oleifera-Cactus Opuntia-alum blend). S Afr J Chem Eng. 2020;34:158-164. doi:10.1016/j.sajce.2020.07.005
    CrossRef
26. Kurniawan S, Ahmad A, Imron M, et al. Performance of Chemical-Based vs Bio-Based Coagulants in Treating Aquaculture Wastewater and Cost-benefit Analysis. Pol J Environ Stud. 2023;32(2):1177-1187. doi:10.15244/pjoes/156419
    CrossRef
27. Bain NF, Dolhan MM, Arbaan NS. Removal Of Turbidity Using Papaya Seed As A Natural Coagulant. ICEETE Conference Series. 2024;2(1):50-56. doi:10.36728/iceete.v2i1.160
    CrossRef
28. Shamira Shaharom M, Siti Quraisyah Abg Adenan D. POTENTIAL OF ORANGE PEEL AS A COAGULANT FOR WATER TREATMENT. Vol 7.; 2019.
29. of Indian Standards B. IS 3025-50 (2001): Methods of Sampling and Tests (Physical and Chemical) for Water and Waste Water, Part 50: Jar Test (Coagulation Test).
30. Widiyana AP, Illian DN. PHYTOCHEMICAL ANALYSIS AND TOTAL FLAVONOID CONTENT ON ETHANOL AND ETHYL ACETATE EXTRACT FROM NEEM (AZADIRACHTA INDICA JUSS.) LEAVES UTILIZING UV–VIS SPECTROPHOTOMETRIC. Jurnal Farmasi Sains dan Praktis. Published online April 29, 2022:71-77. doi:10.31603/pharmacy.v8i1.6582
    CrossRef
31. Anjos BF dos, Azevêdo TKB de, Silva ECA da, et al. Assessment of chemically modified vegetable tannins as coagulants for water treatment. Ambiente e Agua - An Interdisciplinary Journal of Applied Science. 2024;19:1-12. doi:10.4136/ambi-agua.2985
    CrossRef
32. Devi RS, Dhurai B, Sivakumar P. Adsorption of acid dyes from wastewater using Azadirachta Indica neem (leaf) biochar. In: ; 2022:030002. doi:10.1063/5.0108146
    CrossRef
33. Yimer A, Dame B. Papaya seed extract as coagulant for potable water treatment in the case of Tulte River for the community of Yekuset district, Ethiopia. Environmental Challenges. 2021;4:100198. doi:10.1016/j.envc.2021.100198
    CrossRef
34. Kalengyo RB, Ibrahim MG, Fujii M, Nasr M. Utilizing orange peel waste biomass in textile wastewater treatment and its recyclability for dual biogas and biochar production: a techno-economic sustainable approach. Biomass Convers Biorefin. 2024;14(16):19875-19888. doi:10.1007/s13399-023-04111-1
    CrossRef
35. Yadav SK, Sharma A. Study of Orange and Banana Peels as Natural Coagulants. In: ; 2023:249-257. doi:10.1007/978-981-19-5077-3_20
    CrossRef
36. LAWAL A, ABDULSALAM A. Removal of Methyl Orange from Aqueous Solution Using Orange Peel as a Low Cost Adsorbent. Journal of the Turkish Chemical Society Section A: Chemistry. 2024;11(1):39-46. doi:10.18596/jotcsa.1313059
    CrossRef
37. Vargas Ruiz AI, Rosas Aguirre AA, Luna García DI, et al. Extracto de semillas de tamarindo (Tamarindus indica) como coagulante natural en la potabilización de aguas. JÓVENES EN LA CIENCIA. 2024;28. doi:10.15174/jc.2024.4429
    CrossRef
38. Subramonian W, Wu TY, Chai SP. A comprehensive study on coagulant performance and floc characterization of natural Cassia obtusifolia seed gum in treatment of raw pulp and paper mill effluent. Ind Crops Prod. 2014;61:317-324. doi:10.1016/j.indcrop.2014.06.055
    CrossRef