Next Article in Journal
Daily Rhythms and Oxygen Balance in the Hypersaline Lake Moynaki (Crimea)
Next Article in Special Issue
Parametrical Study for the Effective Removal of Mordant Black 11 from Synthetic Solutions: Moringa oleifera Seeds’ Extracts Versus Alum
Previous Article in Journal
Framing Water Policies: A Transdisciplinary Study of Collaborative Governance; the Katari River Basin (Bolivia)
 
 
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Review

Application of Natural Coagulants in Water Treatment: A Sustainable Alternative to Chemicals

1
Department of Biotechnology, Lovely Professional University, Phagwara 144411, Punjab, India
2
Department of Plant Science and Biotechnology, Kebbi State University of Science and Technology (KSUSTA), Aliero 863104, Kebbi, Nigeria
3
Department of Infectious Diseases and Immunology, University of Florida, Gainesville, FL 32608, USA
4
Department of Nephrology and Hypertension, Mayo Medical Science Building, Rochester, MN 55902, USA
5
Department of Life Sciences, Yeungnam University, Gyeongsan 38541, Republic of Korea
*
Authors to whom correspondence should be addressed.
These authors contributed equally to this work.
Water 2022, 14(22), 3751; https://doi.org/10.3390/w14223751
Submission received: 2 November 2022 / Revised: 14 November 2022 / Accepted: 15 November 2022 / Published: 18 November 2022

Abstract

:
Water treatment (WT) is currently among the major areas of research due to the depletion of water resources and fearmongering regarding environmental pollution, which has compelled the upgrading of conventional WT technology towards recycling and reuse. This review aims to provide the current state of natural coagulants and their application in the purification of surface water as sufficient clean water is required for household needs, health security, and environmental safety. A thorough and systematic review of the existing literature was performed, and the information related to water treatment using natural coagulants was compiled from 237 articles under various sections using a computerized bibliographic search via PubMed, Scopus, Web of Science, Google Scholar, CAB Abstracts, and several websites. The work provides explicit information related to natural coagulants and their merits and limitations, outlines methods to increase their coagulation performance, and highlights their coagulation mechanism, efficacy, valorization potential, and sustainability. From the information obtained, it can be concluded that although chemical coagulants are efficient in WT, they are usually expensive, toxic, associated with health issues, and thus non-sustainable. A sustainable alternative is the use of natural coagulants, which are readily available, economical, easy to use, biodegradable, non-toxic, eco-friendly, effective, and generate lower sludge volumes. They work via an adsorption process that involves polymeric bridging or neutralization of the charge. The WT efficiency of natural coagulants ranges from 50–500 nephelometric turbidity units (NTUs), which is similar to chemicals. Thus, they can be deployed in WT regimes and can contribute to the health security of rural populations in developing countries. It is unfortunate that, despite the known benefits of natural coagulants, their acceptance, commercialization, and widespread industrial application across the globe are still low. Therefore, there is a need for more exhaustive investigations regarding the mode of action, adoption, and commercialization of natural coagulants as a sustainable alternative to chemicals for a circular economy.

1. Introduction

Water is an indispensable and precious substance for living beings on earth, as it is required for various domestic, agricultural, and industrial activities [1,2]. Approximately 1400 million cubic kilometers of water are available on earth, with 97.5% and 2.5% in marine and freshwater bodies, respectively [1]. Thousands of pollutants that are hazardous to man and ecosystems were identified in water bodies worldwide [3]. Water pollution is caused by several non-anthropogenic mechanisms such as hydrogeologic processes, changes in the climate, natural disasters like floods, droughts, earthquakes etc., as well as atmospheric deposition, which may be slow or fast. Such natural forces frequently result in high amounts of dissolved organic material and unsustainable quantities of specific minerals or metals [4]. Fluoride is found in a variety of rocks and minerals in the Earth’s crust, including fluorospar, cyyolite, and fluorapatite [5,6,7], which seep out through weathering processes and precipitation, contaminating surface water and groundwater, and consequently public water systems [8,9]. Anthropogenic influences include industrialization (nitrates, nitrites, lead, sulfur, mercury), R & D activities, urbanization, mining (metal wastes and sulphides), tourism, agricultural practices (the use of fertilizers, manures, herbicides, insecticides, fungicides, and crop residue), animal waste (from slaughterhouses, excreta), emerging contaminants (industrial chemicals, pesticides, pharmaceuticals, personal care products), radioactive wastes (uranium), marine dumping, accidental oil spills, microplastics, and the improper disposal of sewage from various sources such as restaurants, hospitals, households, and leakage from landfills and sewer lines. Additionally, various heavy metals such as zinc, lead, copper, etc., have also been reported to pollute the water, thereby making it unfit for human use [10,11,12]. The release of heavy metals into the atmosphere via fossil-fuel burning and other industrial activities of humans, which eventually enter streams through rainfall, as well as the release of industrial effluents and sewage water into streams and surface water bodies, constitute the anthropogenic origin of water pollutants. The most prominent heavy-metal pollutants of human sources include chemical element such as arsenic, cadmium, chromium, copper, nickel, lead, as well as mercury. Contaminant sources are described as either point (localized pollution) or nonpoint (pollution from different origins). Nonpoint pollutants represent the second category of pollution source, in which contaminants originate through widely scattered (and often difficult to detect) origins. Spontaneous weathering of ores and tiny metal particles in the air, water, and soils near coal-burning power plants via smokestacks is one example of localized metal contamination. The mining industry is the most common cause of metal pollution in waterways. Due to solubility, in acid solutions, they commonly utilize acid mine drainage systems to extract heavy metals from ores. They disseminate the acid solution, which contains high quantities of metals, into the groundwater after the drainage process [4,13,14]. In addition to heavy metals, water may be polluted by a range of contaminants due to the use of land for agriculture [15]. Of these pollutants, dissolved organic carbon [16], nutrients (nitrogen and phosphorus) [17], and pesticides [18,19] are the most important issues for certain land-owning UK water utilities due to the need to remove them from raw water to meet regulatory standards. Similarly, nutrient (nitrogen and phosphorus) loading in waterways from point and nonpoint origins is an environmental issue that influences surface water quality [20], as poorly managed agricultural activities can cause nutrient and insecticide pollution of surface and groundwater. Although nutrients are required for survival, excessive nutrient loading into water bodies can have an influence on the specified uses of water [21,22]. Nitrates in runoff can be leached or transferred [23]. Nitrates are tightly linked to agricultural land and grasslands [24], with concentrations peaking in the spring and during significant run-off occurrences. Water flow and pesticide dissemination are influenced by antecedent factors such as geography, soil type, agricultural method, and crop type [4].
These pollutants are associated with several water-borne diseases such as cholera, giardiasis, diarrhea, jaundice, typhoid, amoebic dysentery, Alzheimer’s disease, and dementia [25,26]. Researchers have revealed that approximately 1.2 billion people are unable to obtain clean usable water and more than 6 million people die annually due to polluted-water-related issues [27,28,29], with 4 million people being affected by diarrhea-related issues, of which 2 million were reported to be children. Furthermore, fluoride, which is widely present in groundwater, leads to crippling skeletal fluorosis [26].
Currently, there is a scarcity of potable water in different parts of the globe due to several reasons including deficiency in resources and financial constraints associated with water treatment industries [30,31]. Moreover, the increasing human population and lack of water-harvesting technologies have caused vulnerability in the situation and have hiked the cost of WT [32,33]. Therefore, it is crucial to provide clean and safe water for human use in an effort to mitigate the spread of water-related diseases and also promote health security.
Due to complication of the waste water-treatment process and the enormous number of parameters that must be established, it is important to establish the characteristic variables relevant to quality of water as auxiliary variables. The four types of data listed below can be used to evaluate the quality or effect of water quality in water treatment plants.
  • Physical data: Thes are water that need to be monitored during the treatment process, which include total suspended particles, temperature, conductivity, clarity, total dissolved solids, etc.
  • Chemical data: Chemical water-quality metrics of the national comprehensive discharge standard for contaminants in water, such as pH, biochemical oxygen demand, biochemical oxygen consumption, heavy metals, nitrates, etc.
  • Biological data: Waterborne microorganisms such as E. coli, mayflies, and other microbes are examples of biomarkers.
  • Environmental data: Environmental data encompass the entire water supply process, including weather, hydrology, soil, and ecological indices [34,35].
The aforementioned chemical, physical, or biological pollutants (from soil erosion, runoff, or due to high microbial count) discharged in water may be deposited on the waterbed or may remain suspended in water, causing turbidity, which is among the most common characteristics of polluted water [36,37,38,39,40]. One NTU has been recommended by the WHO as the highest point of water turbidity for human use [41].
Many scientific researches have been carried out on the treatment of polluted water using various strategies such as chemical precipitation, lime coagulation, ion exchange, reverse osmosis, and solvent extraction [42]. Although the chemical method is the most effective and commonly used technique, a transition from chemical to natural coagulants has been observed due to various limitations posed by chemical-based coagulants [40,43].
The natural coagulants deployed in WT are of plant, animal, or microbial origin [44,45]. These include starch, cellulose derivatives, gelatin, galactomannans, chitosan, alginate, glues, and microbial polysaccharides, which are all non-toxic. Molecule bridging, adsorption, and charge neutralization constitute the stages of the treatment process using natural coagulants. The major benefits of natural coagulants in waste water purification are that they are renewable, non-toxic, biodegradable, and cost-effective, and can efficiently remove turbidity [46,47]. The benefits of natural coagulants are presented in Figure 1. Therefore, natural coagulants (especially of plant origin) have drawn the attention of scientists in recent years [48].
This review encompasses reports on the use of natural coagulants as a sustainable alternative to chemical coagulants, in which the potential/success rate of plant-based and non-plant-based products have been discussed in relation to WT. The benefits, limitations, future prospects, and economic aspects of natural coagulants have also been included in this review.

1.1. The Concept of Water Treatment

Water treatment (WT) is the act of removing contaminants from polluted water. Such pollutants may include colloidal/dust particles, pathogens, suspended molecules, and various other toxic materials that are noxious and harmful to human health. Water purification/treatment can be achieved using primary and secondary stages. In the primary stage, sedimentation and filtration processes are deployed to remove solid particles from the water using a mechanical method, whereas, in the secondary stage, biological agents (anaerobic or aerobic microorganisms) are used for the breakdown and removal of the remaining waste, as well as other minute particles from the water. Presently, there are no suitable low-cost sustainable water treatment procedures available, especially for the rural population. Water treatment is achieved using chemical, physical, and biological techniques.
Chemical techniques include coagulation, ion exchange, disinfection, catalytic reduction, oxidation, and softening processes [49,50]. Adsorption, UV processes, settling, and media and membrane filtration are some of the processes that constitute physical methods of WT [51,52]. Biological methods include phytoremediation, bioreactor processes, microbial biodegradation, and the use of wetlands [53]. In some cases, two or more processes are used in a hybrid manner to improve efficiency [48,54,55].
Synthetic coagulants are highly effective in small concentrations and are capable of removing 99% of turbidity, heavy metals, and organic and inorganic substances [56,57]. Despite their effectiveness, their use is associated with several drawbacks as they are costly and are associated with a number of environmental effects [57,58]. To overcome the problem associated with the use of chemical coagulants, it is necessary to promote the utilization of natural coagulants for the treatment of turbid water and wastewater. To treat polluted waters, several parameters are taken into consideration for an efficient purification process. Such parameters include the pH, initial turbidity, temperature of the water, rapid mixing and coagulant dosage, biological oxygen demand, total dissolved solids, total suspended solids, total hardness, conductivity, acidity, alkalinity, etc., of the polluted water. Table 1 summarizes these parameters and their significance in the water purification process.

1.2. Factors Affecting WT

Understanding the most suitable conditions in the process of coagulation (the interaction between the coagulant and the pollutant) is vital because it facilitates understanding the highest efficiency of the coagulant in addition to a reduction in the operational cost and sludge volume. The factors associated with coagulation procedures in WT are the form/type of coagulant, dosage, mixing procedure of the coagulant, and the nature of the water to be purified [59]. The three vital conditions used to assess the impact of coagulant dosage in eliminating the water contaminants are under dosage, optimum dosage, and over dosage. Under dosage is the situation in which the coagulant dosage is insufficient to remove the dirt in contaminated water. Thus, an additional quantity will be needed to achieve the required level of purity [50]. However, using more coagulant, beyond the required quantity, will increase the impurity of the water and the excess will lead to saturation of the colloid surface. This will cause destabilization of the particles, which ultimately forms a repulsion force between the contaminants and, as a result, hinders the floc formation.

2. Strategies of Water Treatments

The most popular and conventional method for WT is the use of chemical-based coagulants including ferric chloride (FeCl3), alum (AlCl3), synthetic polymers (polyacrylamide), and poly aluminum [47,60]. However, the use of this approach is not sustainable as it leads to the production of a large volume of non-biodegradable sludge [61]. Natural coagulants, on the other hand, serve as an alternative sustainable strategy for the removal of turbidity and WT, as they are cheap, safe, and biodegradable. Natural coagulants are derived from three major sources, which include plants, animals, and microorganisms. A brief discussion on chemical coagulants and explicit information on natural coagulants are presented below.

2.1. Water Treatment Using Chemical Coagulants

The application of chemicals in removing colloidal impurities in water is referred to as chemical coagulation, whereas flocculation is the formation of flocs as a result of neutralizing the charge [62]. The most popular and generally used chemical coagulant in WT is ‘alum’, of which the chemical formula is KAl (SO4)2·12H2O and the chemical name is potassium aluminum sulphate. At a pH of 8.0 and a concentration of 450 mgL−1, alum eliminates 99% of the color from the turbid and water [63]. When combined with other coagulants, alum’s potency increases. For instance, when aluminum sulphate was combined with poly ferric sulphate (PFS) and polyacrylamide (PAA), the chemical oxygen demand (COD) removal efficiency increased from 68% to 82% [64,65]. In a previous study, ferric chloride/iron (III) chloride at a pH of 6.0 was used as a coagulant to reduce the COD levels of water from the cosmetic industry by 63.9% [66]. Ferric chloride was also used to treat water from molasses and was reported to reduce the color and COD by 96% and 86%, respectively [67]. Chemical coagulants are effective at minimizing the chemical and biochemical oxygen demand, as well as oil and grease [68,69]. In another study, for the treatment of black liquor water, several chemical coagulants including aluminum chloride, poly-aluminum chloride, and anionic PAA (polyacrylamide) were used. The composite could eliminate 95% of total dissolved solids (TDS), 88% of the color, and 80% of COD [70]. These methods utilize additives (chemicals) to segregate small-sized particles in large flocs prior to their removal via sedimentation [71,72]. Poly-aluminum chloride and poly-titanium chloride can reduce the water turbidity from 7.0 NTU to 1.2 NTU [36,38,73,74]. Poly-aluminum ferric chloride at a 5mg/L concentration and pH of 7.5 can eliminate the color and turbidity from water by 86 and 100%, respectively, at pH of 7.5. Similarly, water turbidity can be reduced from 9 NTU to less than 1.0 NTU in a short span of 15 min using polymeric zinc-iron-phosphate [75,76].
Thus, chemical coagulants have a number of benefits as they are easily obtainable and can operate over a broad pH spectrum. They can be used alongside additives for long-term storage and increased efficiency. Other benefits include higher efficiency at low concentrations, easy water dissolvability, and the removal of turbidity and microorganisms such as E. coli by 99%. However, it is also true that the use of chemical coagulants jeopardizes the environment and human health. They are known to persist in water until the coagulation process is over, are not biodegradable, and, as a result, treated water contains traces of these chemicals [77,78], which leads to various neurological disorders including Alzheimer’s disease [79,80,81], dementia, encephalopathy, and Hippocampal neuron staining. Aluminum traces may cause diseases such as Down’s syndrome and Parkinson’s disease, convulsions, and even death [82,83]. Moreover, high operational costs, the large quantity of sludge, and the cost of disposal are some of the limitations of chemical coagulants [84].

2.2. Emerging Use of Natural Coagulants

Considering the global issues related to chemical WT (being expensive, toxicity to humans and the environment, corrosive and carcinogenic nature, altering the pH of treated water, producing hazardous and non-biodegradable sludge, high disposal costs, etc.) [57,58,85], there is a need to explore other possible measures so as to reduce the ill effects of such coagulants on the ecosystem [86,87,88]. Thus, there has been a recent paradigm shift in water and WT, which encouraged industries to improve the culture of water operators in adopting and implementing sustainable development in their activities. Among functional practices is the replacement of chemicals with natural substances in WT processes, which has led to decreased environmental effects in terms of production, consumption, and secondary waste management. Natural coagulants are polyelectrolytes, which can be anionic, cationic, or neutral polymers [46]. They are safe and cost-effective with a great capacity to maintain the pH of the water being treated. Unlike chemical coagulants, natural coagulants do not increase the metal load during treatment and are characterized by the generation of a low volume of sludge, thereby making the cost of disposal very low [89,90], due to which they are a sustainable alternative to chemicals. Earlier research proved the effectiveness of natural coagulants in WT applications [46,91,92,93,94].

2.2.1. Sustainability of Natural Coagulants

Sustainability is the mode of development that fulfills the needs of current and future generations [95]. Although the crucial factor in the treatment of water is performance efficiency, the reliability of technology is also essential as per the concept of sustainability asserted by the United Nations. Thus, the concept of sustainability involves a combination of social, environmental, and financial aspects [96].
The social aspect of the sustainability of natural coagulants involves industrial acceptance and public health improvement. Industrial acceptance encompasses the ability of natural coagulants to provide results similar to chemical coagulants and be used as an alternative. However, due to the lack of real or pilot-scale use of plant-based coagulants and the lack of approval and regulatory guidelines in the treatment of potable water, industries hesitate to adopt natural coagulants. WT using natural coagulants, especially in rural areas, may facilitate health and hygiene and improve the living standards of all individuals (Figure 2). The technical aspect of sustainability involves treatment efficiency, product stability, availability of materials, and compatibility with other techniques. Several natural coagulants have been time-tested and proven to be very efficient in the treatment of water and wastewater. Due to their natural origin, natural coagulants are considered safe and non-toxic. However, the toxicity of organic coagulants in humans and the environment still remains unclear, and there is a need to confirm their environmental safety. Thus, meticulous selection and dose optimization of efficient natural coagulants could provide promising results in WT and may act as a substitute for chemical coagulants. As discussed previously, natural coagulants offer reliability and robustness, are easily available, and can be obtained from a wide range of sources such as plants, microorganisms, or animals [93,97,98]. However, their susceptibility to biodegradation by microbial or other environmental factors adversely affects their long-term storage (shelf-life) and commercialization [99,100]. Environmental sustainability criteria involve the utilization of biodegradable and plant-based coagulants that are eco-friendly and capable of generating biodegradable sludge [101], which can be used for several other purposes such as agricultural practices, landfills, and in civil engineering industries [102,103].
The economic aspect of sustainability involves the use of cost-effective coagulants for WT. However, this claim is dissatisfactory as it does not address several other factors such as the cost of processing and maintenance or the variation due to geographical regions. Hence, the cost advantage of natural coagulants over chemical coagulants has not been well addressed. Therefore, one efficient strategy to increase the economic sustainability of natural coagulants is to use a combination of coagulants in order to compensate for the procurement cost and consumption demand along with the synergistic increase in clean-up efficiency [53]. Hybridizing natural coagulants with other coagulants to lower their utilization cost is an additional method to enhance the economics of WT. In contrast, the use of versatile natural coagulants may also result in a reduction in overall costs because many treatment functions can be carried out with a single substance in a single treatment unit. Moreover, as the majority of stated claims were based on lab-scale experimentation, it is challenging to translate the advantages of employing natural coagulants, such as the ‘creation of fewer sludge’ and ‘no need for pH adjustment’ into economic benefits. The ‘cost-effectiveness’ that is tangentially related to the advantages of employing natural coagulants must be more thoroughly evaluated in pilot studies. Because there has not been a thorough analysis of the total expenses of the coagulation process from extraction to the effects on other treatment units, we cannot draw conclusions on the economic aspect of natural coagulants [53].

2.2.2. Plant-Based Coagulants

Coagulants derived from plants are more readily available than those from either animals or microorganisms [92]. There are sufficient reports on the deployment of various plant-based products such as bagasse [104], banana peels [105,106], Jatropha curcas L. [107], and Moringa oleifera [105] for the treatment of polluted water. Macromolecules including proteins, polysaccharides, and some functional groups are known to promote the process of adsorption, polymer bridging, and charge neutralization [108]. They are usually effective in the treatment of water, with medium turbidity in the range of 50–500 NTU. However, the efficacy of natural coagulants can be enhanced through the optimization of the extraction and purification processes of coagulants [109]. Therefore, the proper extraction process using plant-based materials can exhibit better performance in the coagulation process, leading to greater/higher waste removal efficiency.
Some of the most widely used plant-based coagulants include Moringa oleifera Lam. (seeds), Cicer arietinum L. (seeds), Azadiracta indica A. Juss. (leaves), Cactus latifolia L.(leaves), Pisum sativum L. (seeds), Vigna mungo L. (Hepper) (seeds), Arachis hypogea L.(seeds), Zea mays L. (seeds), Dolichos lablab Linn. (fruits), Phaseolus vulgaris L. (seeds), etc. [110,111,112]. In addition to these, seeds of nirmali are also the source of anionic polyelectrolytes, and their carboxylic acid (–COOH) and hydroxyl (–OH) groups boost the effectiveness of coagulation. Galactomannan and galactan, polysaccharides from the seeds of Strychno spotatorum L.fil., are potent enough to decrease water turbidity by 80%. Moreover, plants such as Acacia, Catenae, and Schinopsis can also be used to remove contaminants from water as they possess naturally occurring tannins [113]. Species of cactus such as Opuntia latifaria L. are also used as natural coagulants as they contain certain compounds, such as d-galactose, d-rhamanosei, d-xylose, l-arabinose, and galacturonic acid, which are responsible for the bridging action with contaminants in water during the coagulation process [114]. The fruit of Prunus armeniaca L. has also been reported for its use as a purifying agent in ancient periods in countries such as Egypt and China, historically dating back to the 1100s [115]. The form of natural coagulants used in the coagulation process can also influence turbidity removal efficiency. For example, when the seeds of Tamarindus indica L. were blended in water [116], it was more effective than the water extract derived from ground seeds [117]. In addition to turbidity removal, the common bacteria present in surface water (e.g., Escherichia coli) can also be eliminated [47]. The wastes of many fruits possess coagulation properties, whereas some exhibit antimicrobial activity due to the presence of saponins, phenols, and flavonoids [47,118,119]. It was reported by [120] and [121] that the colloids present in the leaves of H. undatus Haw. resemble those present in the seeds of M. oleifera Lam. and are cationic in nature. The processes of colloid adsorption and neutralization of the charge are considered feasible means of coagulation, which results in the formation of flocs. Table 2 summarizes the reports on the use of natural coagulants in WT and their relative pollutant removal efficiency.
The most commonly utilized natural coagulants derived from plants are explained below.

2.2.3. Tannins

Tannin is a polyphenol compound used in the leather industry and is obtained from the wood and bark of trees such as Castanea, Acacia, and Schinopsis [151,152]. The use of tannin extracted from valonia/Asia minor oak has been investigated by several researchers as an effective coagulant in WT [95,96,153,154,155]. They concluded that tannin is a superior alternative to chemical coagulants. Tannin can be used in the removal of dyes such as indigo, azo, triphenylmethanones, and anthraquinonic [156]. The chemical structure of tannins derived from plants and the degree of tannin modification affect their efficiency in water treatment. Tannin contains phenolic groups and is a strong anionic hydrogen donor. The phenolic groups form phenoxide due to rapid deprotonation and are balanced by resonance. It is also considered an amphoteric compound, which not only reduces the turbidity and heavy metals but also the color of water and thus functions as an alternative to chemical coagulants. Thus, it can be concluded that the higher the number of phenolics, the greater the capacity to coagulate will be.

2.2.4. Nirmali Seeds

Nirmali is a medium-sized tree mainly used as a traditional medicinal plant native to Sri Lanka, southern and central India, and Burma [157]. The seeds of this plant have been reported to have been used over 4000 years ago as a natural coagulant in the treatment of water [158,159]. The majority of research on its usage as a natural coagulant is confined to the Indian sub-continent [117,158,160,161]. Extracts of nirmali seeds are anionic polyelectrolytes that use coagulation (charge neutralization and bridging) for the removal of contaminants in water [162]. It has been observed that the coagulation efficiency can be increased due to the presence of alkaloids, lipids, and carbohydrates containing–COOH and free –OH groups present on the surface. In a previous study, galactomannan and galactan obtained from nirmali seeds reduced the turbidity of a kaolin solution by approximately 80% [163]. The presence of –OH groups, along with galactan and galactomannan chains, is mainly responsible for the water-cleaning property.

2.2.5. Moringa Seeds

Moringa oleifera Lam. (horseradish or drumstick tree) is a versatile, medium-sized tree that usually grows in semi-arid, tropical, or sub-tropical areas and in various parts of Africa, Asia, Northwest India, and South America [164] belonging to the Moringaceae family. M. oleifera Lam. is non-toxic and is the most frequently identified natural coagulant utilized for WT [165]. In addition to its use as a source of food, fodder, and medicine, each part of the Moringa plant, including the leaves, seeds, flowers, roots, and bark, can be used as a coagulant for WT [166,167,168]. The seeds of Moringa, in addition to containing edible oil, also contain substances that are soluble in water [169]. Muller et al. [170] and Jahn et al. [171] were among the pioneer researchers who reported the use of M. oleifera Lam. seeds for the coagulation process in WT. Muyibi et al. [172] also reported it to be a minimal or low-cost natural coagulant that can be feasibly deployed in WT, at least in rural or semi-urban areas. The work of Ndabigengesere et al. [169], which reported the coagulation property of Moringa seeds in the treatment of water, ignited interest among environmental scientists. The active coagulating agents present in Moringa seeds are reported to be cationic proteins, which are dimeric in nature, possess an isoelectric point between 10 and 11 and a molecular weight of 12–14 kDa, and function via charge neutralization and adsorption mechanisms.
Gassenschmidt et al. [173] also reported that protein is the active ingredient of coagulation in Moringa seeds, possessing a mass of 6.5 kDa and an isoelectric point higher than 10. In a similar report, other researchers [174] stated that the protein has an isoelectric point greater than 9.6 and a mass of 6.5 kDa. In contrast to the aforementioned reports, [175] reported that the coagulating agent is an organic polyelectrolyte rather than a polysaccharide, protein, or lipid, with a molecular mass of 3.0 kDa.
As per the aforementioned reports, the most active coagulating agent is cationic proteins; however, Moringa may contain several other coagulating agents, which need to be studied further. Cationic proteins in the seeds of Moringa work via various electrostatic mechanisms such as neutralization, charge reversal, and adsorption [176]. These bind with impurity particles, which are usually negatively charged. Okuda et al. reported that the coagulation performance of Moringa extracts can be improved by using bivalent cations (Mg2+ and Ca2+) [175]. Sulaiman et al. [177] used the seeds of Moringa in WT and observed excellent results. Dotto et al. [178] used the same method in the treatment of textile mill water and a significant COD reduction was reported. For the treatment of water from the dairy industry, seed powder was able to remove ~100% of the turbidity and 99.50–100% of the fecal coliform count. In a similar report, the seed powder could remove ~ 83.63% of the turbidity from laundry water [179]. Hence, M. oleifera is among the most versatile and reliable natural coagulants and has been proven to be a promising sustainable alternative to chemical coagulants.

2.2.6. Chickpea Seeds

Cicer arietinum L. (Fabaceae), commonly known as chickpea, is an important pulse crop that is grown in arid and semi-arid zones with good soil moisture and adequate rainfall. Hiremath et al. [180] and Jaseela et al. [181] used chickpea seeds to treat water released from the dairy industry and reported the removal of turbidity of 86.29%. Another group reported a more than 95% reduction of preliminary turbidity, which was similar to that of alum [182]. Choy et al. (2015) reported that the presence of high sugar and protein contents in chickpea were mainly responsible for the removal/coagulation of particles [92].

2.2.7. Peanut Seeds

The seeds of Arachis hypogea L. (peanut) are an important source of protein and are well known for their high lipid content. Traditionally, the seeds have been used against inflammation while the seed oil has been used as an ointment [183]. The lipid part of the peanut constitutes approximately half of its dry weight, but the lipid does not contribute to its purification properties. As a result, the relative percentage of the active agent is markedly decreased, leading to lower efficiency in the removal of raw surface-water turbidity. Mataka et al. [184] reported that peanut seeds exhibit a similar effect as that of moringa seeds, and delipidated cakes were found to be more effective (in the removal of heavy metals from wastewater) than the crude seed extract. Therefore, the effectiveness of peanut coagulation activity can be increased by removing the lipidic portion from the seeds.

2.2.8. Soybean Seeds

The seed extracts of Glycine max L. (soybean) can be used as the main coagulant or a coagulant aid to alum for cleaning contaminated raw surface water [185,186]. The coagulation efficiency of soybean seeds was excellent in the clarification of surface water beyond 450 NTU, whereas, as a coagulant aid to alum, ~96% turbidity removal was reported [186]. Although soybean seeds have a large lipid fraction that is considered second to groundnut, the lipid part does not contribute to coagulation activities. Therefore, seed delipidation (the removal of lipids) improves the coagulation potential. Moreover, deoiled seeds of soybeans have been reported to be less expensive bioadsorbents for the treatment of water contaminated by different dyes [93,187,188]. Soybean seeds possess palmitic acid, whereas stearic acid found in Hibiscus esculentus has been associated with bactericidal activities. Thus, their extracts have potential anti-bacterial properties and can treat raw surface water [183,189].

2.2.9. Cacti Mucilage

Opuntia ficus indica (OFI) (L.) P. Mill is the most common species of cactus, which has been used mainly for its medicinal properties and as a dietary source, as well as for treating water. Cactus latifaria has also been used as an organic coagulant [150]. Opuntia possesses a high coagulation capacity due to the presence of mucilage, which is a complex carbohydrate, and, hence, it is used as a potential coagulant for treating water [190,191]. Thus, it is eco-friendly and can be used as an alternative to aluminum and iron salts due to its abundance, renewability, adaptability, and biodegradability [66]. Rebah et al. also reported the potential of Opuntia in the treatment of wastewater [192]. Opuntia’s mucilage has different sugar molecules including d-galactose, d-xylose, l-rhamnose, l-arabinose, and galacturonic acid [190]. However, the most active coagulating agent is galacturonic acid [193], which contributes to the removal of 50% turbidity. Galacturonic acid may also exist in a polymeric form as polygalacturonic acid. It is anionic due to the presence of carboxylic functional groups, which undergo partial deprotonation in an aqueous solution [194]. The mucilage in Opuntia species functions mainly via adsorption and the bridging coagulation process in which dirt particles bind to the mucilage and facilitates the removal of turbidity.

2.2.10. Okra Seed Extract

The coagulation potential of okra (Abelmoschus esculentus (L.) Moench) seed extracts has been examined by [195] who asserted that seeds extracted using distilled water and a sodium chloride solution can be used as organic coagulants for the removal of turbidity from water with an efficiency of 54.5% and 92% for distilled water and a NaCl (1.0 N) solution, respectively. Raji et al. [196] discovered that okra seed extracts were very effective in the removal of turbidity from 580 to 5 NTU at a dose of 300 mg/L and pH 7.0, which is within the standard limit recommended by WHO. Similar work conducted by Thakur et al. [197] and Mishra et al. [198] revealed that okra seed extracts can effectively remove dirt from the water even at a dose of 200 mg/L. The work of [174] also shows the effectiveness of okra seed extracts in WT with more than 69% and 95% removal efficiencies for dissolved and suspended solids (from the effluents), respectively.

2.3. Animal-Based Coagulants

Animals may also act as a crucial source of coagulating agents. They are usually extracted from shellfish exoskeletons, the shells of lobsters, shrimps, insects, crabs, diatoms, and molluscs, and freshwater and marine sponges. Chitosan is a high-molecular-weight biopolymer developed via the deacetylation of chitin. It occurs naturally as a complex sugar (polysaccharide) and is water-loving (hydrophilic), biodegradable, environmentally safe, and capable of absorbing several metal ions efficiently as it contains amino groups in its polymeric chain [199]. The deployment of chitosan as a natural coagulant in the treatment of polluted water in different sectors, including agriculture, textile, detergent, and food industries, as well as paper mills, has been well reported [200,201]. The characteristic feature of chitosan regarding cleaning water is its ability to react and generate a positive charge that destabilizes the negative charge of the colloidal particles [202]. Actinobacteria are also effective in the treatment of contaminated water [203]. Efficient flocculating activity was observed when Cellulomonas and Stretptomyces spp. were deployed as flocculants in the treatment of kaolin-contaminated water. The substantial effects of these species were shown to be due to the presence of several molecules including proteins, natural sugar, polysaccharides, and uric acid, as indicated by chemical analysis [199]. Chitin is a naturally occurring and the second-most abundant polysaccharide (after cellulose). Every year, at least 10 gigatons of chitin are synthesized and destroyed throughout the biosphere. Chitin is a renewable resource found mainly in complexes with other polysaccharides and proteins. Chitin and its metabolites are utilized as chelating agents in the purification of water by segregating organic substances and heavy metals, as well as in the treatment of sewage via the precipitation of certain anionic wastes and the collection of contaminants such as PCBs (polychlorobenzene). The utilization of 10 mg per liter of chitosan in water has already received approval from the Environmental Protection Agency (EPA) [204].

3. Extraction of Natural Coagulants

The process of extraction of plant-based natural coagulants involves three steps: Primary, secondary, and tertiary extraction. In primary extraction, seeds are first collected and then dried conventionally. This is then followed by manual/mechanical pulverization and seed grinding (into a fine powder). During this process, settling tank is used to keep water temporarily where heavier solids sink to the bottom and lighter ones float to the surface. These materials are then held back once settled, while the rest of the liquid is discharged to the more rigorous secondary phase of water treatment process. The tanks are sometimes equipped with mechanical scrapers that drive the continually collected sludge at the base of the tank to a hopper, which pushes it to sludge-treatment facilities. This is most commonly used by local communities in rural areas. However, it is associated with a major disadvantage in that the coagulating agent constitutes a small portion of the seed powder, hence leading to an organic load in treated water. This drawback is overcome by secondary and tertiary stages. This is accomplished by removing their active components and purifying them to remove unwanted organic matter. In the secondary stage, active coagulants are extracted via the solvent method, which includes salt solution extraction, water extraction, or alcohol/organic solvent extraction methods. Out of these, the water extraction method is the most popular as it is abundant and cost effective [174,175]. The tertiary stage is a rather uncommon method because it involves high costs and is mostly limited to academic research [174,175]. The major objective of of tertiary water treatment is to improve the water quality to attain the standard domestically, industrially, and the specific needs regarding the safe discharge of water. Tertiary treatment of water also deals with the removal of microbes/pathogens, which ensures that water is safe for drinking purposes in the case of water treated by municipalities [174,175]. The natural coagulant extraction process is shown in Figure 3.

4. Mechanism of Action of Natural Coagulants

Coagulation is a method of destabilizing unsettled/slow-settling tiny particles with a size of 0.001 to 1.0 μm and above by adding a coagulating agent, which increases the floc size and the settling velocity [59]. This approach is crucial for water pretreatment as it removes dispersed/suspended contaminants and grants purified water the requisite quality for further processing. The global market for coagulants is expected to exceed USD 6.01 billion by the end of 2022, representing a 5.9% compound annual increase from 2017 to 2022 (4.35 billion in 2016) [59].
The mechanism of action of natural coagulants is similar to that of polyelectrolytes and contains a variety of functional groups such as –OH, –COOH, and –NH2. The schematic representation of coagulation mechanisms as revealed through FT-IR and SEM is shown in Figure 4. The green circles represent the positively charged coagulants and the red colored circles represent the negatively charged colloidal particles. The mode of action of natural coagulants can be grouped into sweep flocculation, charge neutralization, double-layer compression, and antiparticle bridging. Sweep flocculation/coagulation is seen as a technique that eliminates colloids via entrapment/enmeshment using a net-like structure containing amorphous metal hydroxide precipitates that are formed by the hydrolysis process [205]. Several analyses including initial floc-aggregation, the relative settling factor, and the flocculation index revealed that the flocs developed through this method are relatively smaller in size with good settling capacity but are characterized by a slow rate of floc formation [205]. The floc produced via sweep flocculation has a high fractal dimension, which shows that flocs are complex [206]. Stronger flocs that are tolerant of breakage are theoretical features of the high fractal dimension. However, the flocs of sweep flocculation are large with greater floc production but are easily broken. Charge neutralization occurs via the adsorption process between the coagulants and the colloid surface, which are oppositely charged [193]. Before reacting with the colloids, chemical coagulants undergo a hydrolysis process to form several cationic species. A patch-wise medium referred to as the electrostatic patch mechanism is deployed for the charge neutralization process. Various cationic species will patch on the surface of the colloids resulting in particle surfaces with positive and negative charges. Colloids’ surfaces with a mixed charge will reduce the repulsive forces and increase van der Waals forces between particles [207]. Flocs produced via the charge neutralization method are stronger than those developed by sweep flocculation but weaker than those formed through inter particle bridging, despite their globular-shaped smaller particles [205], and also have a greater fractal dimension [193]. Double-layer compression is an approach that employs ions with the opposite charge of the colloidal particles to infiltrate the double layer that surrounds the colloids. Counter ions will make the double layer thinner and smaller in volume [208]. Continuous electrolyte compression reduces the electrostatic repulsion and increases van der Waals forces, facilitating the joining of the two destabilized colloids [205]. The flocs produced via this mechanism are larger in size because the rate of aggregation of the particles is high. However, they have a low level of sedimentation due to certain friction forces unnecessarily forming between the larger flocs. Moreover, the floc strength of the coagulants depends on the ionic charge of the coagulant. Monovalent ions that are weakly charged will produce large but loose flocs that require a longer time to settle. Nevertheless, the double layer is significantly charged with a high repulsive force towards weakly charged ions, which lessens the likelihood of agglomeration. The inter particle bridging relies on polymers that exist as a long chain with a highly reactive group dangling in the water. A particular region of the polymeric chain will attach itself to colloids, while the unattached portions of the polymeric chain attach to other colloidal particles to form a complex colloid–polymer–colloid structure in which the polymer serves as a bridge. The flocs that form are flaky with irregular void space between the network structures. Furthermore, the fractal dimension of the formed floc is low, which indicates it is not as complex as flocs formed by other mechanisms [48]. Theoretically, a low fractal dimension leads to the formation of weak flocs that are prone to breakage, but they are very strong and not easily broken into smaller clusters due to polymers that serve as bridges [52]. A study shows that the use of natural coagulants with the inter-particle bridging mechanism enhances the growth of the floc by at least thrice compared to the use of synthetic chemicals due to the ability of polymeric chains to stretch and get attached to as several colloids as possible [59].
This mechanism has been observed in the case of cactus mucilage and Cassia obtusifolia seed gum via adsorption and bridging wherein the long chains of polymers destabilize the charged impurities, forming bridges between them and culminating in macro flocs, which tend to settle faster (sedimentation). The adsorption process involves hydrogen bonds or dipole interactions. Proteins, lipids, and carbohydrates are the most common components of natural/bio-coagulants. Contaminant particles are anionic, whereas coagulating particles are cationic, which results in an electrostatic attraction between them and causes adsorption, charge reversal, and the neutralization of contaminant particles. Later on, flocs are generated and start settling (sedimentation) and are easily removed from the water, thus treating the water [176]. Polyelectrolytes possessing a high charge density show maximum flocculation ability.

5. Natural Coagulants—Constraints in Commercialization

Several extracts from natural sources have proven their coagulation potential in removing total dissolved solids (TDSs), total suspended solids (TSSs), chemical oxygen demand (COD), biological oxygen demand (BOD), turbidity, hardness, algae, and total coliforms. However, many such coagulants are yet to be accepted and commercialized. The major barriers that hinder their commercialization include monetary requirements, market awareness, research and development, and regulatory approvals [47]. Furthermore, Saleem et al. [93] demonstrated the ionic nature (cationic, anionic, and non-ionic) of coagulants and explored the barriers to their application and commercialization. The outcomes of the current studies are mostly restricted to the laboratory scale, having less relevance in real industrial applications. For natural coagulants to be successfully commercialized, there is a need for economically feasible extraction procedures and in-depth knowledge regarding their mode of action. Moreover, for any new products to be commercialized, approval from the relevant authority and other regulatory authorities must be granted, which is somewhat difficult as it requires ensuring product compliance with the respective standards. Strong motivation for green chemistry and cleaner production are crucial for the development of natural coagulants and their applications. Figure 5 outlines the constraints hindering the successful industrialization of natural coagulants. Among the major issues, the raw materials required to generate natural coagulants must be available at a large scale for successful and realistic applications. Furthermore, the technical support of experts and new equipment are required to sustainably implement the deployment of natural coagulants [108].

6. Future Prospects of Natural Coagulants

Over the past few decades, the implementation of pollution-prevention strategies and environmental impact assessment (EIA) has become increasingly important and have resulted in changes in water, waste, and energy management systems through the reduction, reuse, and recycling approaches of the circular economy, with the aim of achieving sustainability [209,210]. Natural coagulants derived from plants have the ability to replace synthetic coagulants for the treatment of wastewater from the textile industry [92]. There is a plethora of reports that highlight the performance of natural coagulants based on their flocculation or coagulation potential in WT but all have their own limitations that need to be investigated, improved, or overcome for fine-tuning and process improvement.
As aforementioned, the use of crude extracts of natural agents has been associated with mixing certain organic matter (dissolved organic carbon (DOC) and total organic carbon (TOC)) into clean water [203]. The significant increase in the organic residues of treated water is unacceptable and can lead to an increase in microbial activity, which further results in changes in color appearance, bad odors, and bad tastes [203]. Moreover, crude plant-based products have several inorganic and organic molecules such as fats and oils that do not contribute to the process of active coagulation [174]. Therefore, the meticulous optimization of physico-chemical parameters prior to its implementation on a large scale is crucial. Unfortunately, this requires more time and effort because the physical-chemical characteristics of water change over time. The major obstacle in introducing plant-based natural coagulants in industries is their lack of year-round availability in order to meet industrial requirements. Moreover, the processing technology required and the cost of processing/production are also limitations. In addition to this, there are several other issues including the choice/possibility and source/availability of the plants to be used. For instance, the use of Jatropha curcas seeds in WT has been associated with safety issues [148]. Among the issues related to the use of plant products (e.g., cereal crops) is the escalation in market prices of unprocessed grain due to increases in the human population and decreases in agricultural production [211]. Direct comparisons of coagulant forms, production stages, and costs involved in different geographical regions are extremely difficult due to differences in exchange rates, inflation factors, and cost value accuracies [46]. The needs and responses of markets will also influence the demand for natural coagulants as an alternative to chemicals. Although natural coagulants will not be commercialized immediately, these small initiatives will help to bridge the gaps and overcome the limitations (Figure 4). An appraisal of the social, economic, and ecological aspects can be maintained as a sustainability metric with the use of a pilot plant analysis. The approval of local authorities should be simple for the effective marketing of any new product [212]. As a remedy to the problem, policy framers should implement tax rebates, subsidy programs, tax reductions, incentives, and environmental laws and regulations so as to encourage reliance on plant-based natural coagulants.
Understanding the essence of water is important for developing a suitable water treatment process, implementing a protocol, determining appropriate residue requirements, determining the level of assessment necessary to verify the procedure, and deciding which residues to evaluate on the basis of toxicity [213]. Research on the active chemicals discovered in plant-based natural coagulants is another factor to consider when employing natural coagulants to improve coagulation–flocculation (CF) performance. The processes for identifying and isolating active coagulating compounds are too challenging due to the probability of interdependent effects among the components present [47,203]. Moreover, the coagulant type and dosage, total dissolved solids in the contaminated water, the distribution and size of colloidal particles of the water, the temperature of the water, ionic strength of the coagulants, pH of the water, and the configuration and percentage of organic matter in water are some of the factors that influence the coagulation CF effectiveness of the polluted water [214,215].
Active ingredients must be extracted, purified, isolated, and characterized in order to identify the chemicals that cause CF. The extraction of these compounds may directly increase the gross CF efficiency due to an increase in the relative amount of the agents [47]. Plant-based coagulants must thus be chosen for large-scale application based on the availability of annual species. Thus, meticulous research, tests, and trials are needed to find the most efficient natural coagulant or a hybrid of natural and chemical coagulants or natural coagulants alone, for the treatment of water [216].
Another important recently recognized cleaning agent for contaminated water is ‘biochar’. It is a carbonaceous porous substance generated through the thermochemical decomposition of feedstock biomass with or without oxygen (pyrolysis). Any natural/organic waste material could be used as feedstock biomass for the production of biochar. Examples of such organic wastes are plant residues, litter, algae, manures, wood chips, municipal solid wastes, and sewage sludge [217,218,219]. Biochar technology is considered a novel, cost-effective, and environmentally friendly resource that can be used as reliable technology in water treatment [220,221,222]. Biochar has been widely utilized as an adsorptive agent to eliminate metal contaminants, biological pollutants, and nutrients from the water. Thus, it can play a key role in environmental cleaning and reflects the concept of “treating wastes with wastes”, for a sustainable, circular economy. There are two substantial benefits behind the application of biochar for WT viz; (i) its production prevents the release of greenhouse gasses into the atmosphere, thus decreasing the impact of global warming in our environment [223], and (ii) biochar has a large surface area with numerous surface functional groups. These features have made it an effective, cheap, and ecologically safer adsorbent for WT [224,225,226]. ‘Engineered biochar’ has also been developed, which possesses a larger surface area, higher adsorption ability, and more widely available surface functional groups (SFG) than the normal biochar/activated carbon, indicating that it is a new type of carbon-based material with promising potential in treating water contaminated with agro-chemicals, pharmaceuticals, and metalloids/metals generated from agro-industrial activities and municipal waste [219,222,227,228]. It may also be used for the improvement of soil fertility, crop growth, and production [218], and for the production of clean energy, so as to partially replace fossil fuels [229]. It is also applied as an adsorbent and catalyst to different contaminants and reduces the emissions of greenhouse gases [218,230,231]. Rajapaksha et al. [232] mentioned that sulfamethazine can be removed effectively from the contaminated water using steam-activated biochar but the rate of such contaminant removal is pH dependent. Heavy metals from agricultural wastewater such as As, Cu, and Pb constitute another pervasive issue. The potential of biochar to remove these pollutants was reported to be 69.4 mg/g and 34.1 mg/g for Cu2+ and As5+, respectively, while the quantities for Cd2+ and Pb2+ were found to be 0.4 mg/g to 12.3 mg/g and 36 mg/g to 35 mg/g, respectively [233,234,235]. Biochar is also important for the treatment of polluted stormwater. Thus, the use of organic coagulants from plants and animal sources, including the application of biochar technology, represents a new, cost-effective, and environmentally friendly solution for WT. A recent study by Liu et al. [236] demonstrates that biochar impregnated with aluminum can significantly eliminate contaminants such as Zn2+, Cu2+, As5+, and other runoff contaminants in urban runoff water. Removal rates greater than 85% and 95% were determined when a biochar-based filtration medium was deployed to remove copper and zinc in polluted runoff stormwater. However, there is a need for careful testing and designing of the filtration media to achieve success in stormwater treatment systems [237].

7. Conclusions

Due to the growing population, long-lasting periods of drought, soil and water pollution, and other factors, safe drinking water has now become a challenging resource in many regions across the globe. In the current age of scarcity of water, efficient water treatment is a basic requirement for survival, health development, and economic growth, and has been one of the most important sustainable development goals (SDG) proposed by the UN that is to be achieved by the year 2030. It is vital to establish and incorporate improved water treatment techniques with increased performance and reduced financial inputs. The present review has unraveled the potential of natural coagulants in the purification of waters and has proven effective, as evidenced by various research reports published in the past two decades. They are biodegradable and thus eco-friendly in nature and their performance is similar to that of chemicals. However, a number of factors need to be considered when utilizing natural coagulants. This is because the process of extraction and purification is complex, there is a limited supply of raw materials, and the water is variable in its composition (contaminants). Additionally, some of these products can work against surface water microbes such as Escherichia coli while some can serve to remove heavy metals too. In order to achieve commercialization, natural coagulants must have such qualities/attributes (biodegradability, eco-friendliness, low costs, easily available, reduce–reuse–recycle, etc.) so as to make space in the well-established markets where chemical coagulants occupy the stage. Even though organic coagulants are less effective compared to chemicals, a strategic blending of certain coagulants can synergistically enhance the efficacy of the water treatment regime. A high dosage, a lengthy contact period, and the maintenance of pH below 7 of plant-based coagulants can also reduce turbidity to a certain extent. Considering human health and environmental issues associated with the use of chemicals, there is an urgent need for meticulous and in-depth studies to analyze the mechanism of action of natural coagulants and develop strategies for the year-round availability of coagulants so as to deploy them for large-scale treatment of water and increase the sustainability of WT regimes.

Funding

This research received no external funding.

Acknowledgments

The authors are thankful to the management of Lovely Professional University, Punjab, India, Kebbi State University of Science and Technology, Aliero, Nigeria, for the infrastructural support.

Conflicts of Interest

The authors declare no conflict of interest.

Abbreviations

NTU, nephelometric turbidity units; WT, water treatment; kDa, kilo-dalton; WHO, World Health Organization; UNESCO, United Nations Educational, Scientific and Cultural Organization; PFS, poly ferric sulphate; PAA, polyacrylamide; COD, chemical oxygen demand.

References

  1. Gleick, P.H. Water in Crisis; Oxford University Press: Oxford, UK; New York, NY, USA, 1993; Volume 100. [Google Scholar]
  2. Liu, S.X. Food and Agricultural Wastewater Utilization and Treatment; John Wiley & Sons: Hoboken, NJ, USA, 2008. [Google Scholar]
  3. World Health Organization. Evaluating Household Water Treatment Options: Health-Based Targets and Microbiological Performance Specifications; World Health Organization: Geneva, Switzerland, 2011. [Google Scholar]
  4. Khatri, N.; Tyagi, S. Influences of natural and anthropogenic factors on surface and groundwater quality in rural and urban areas. Front. Life Sci. 2015, 8, 23–39. [Google Scholar] [CrossRef]
  5. Murray, J.J.; World Health Organization. Appropriate Use of Fluorides for Human Health; World Health Organization: Geneva, Switzerland, 1986. [Google Scholar]
  6. Loganathan, P.; Hedley, M.; Grace, N.; Lee, J.; Cronin, S.; Bolan, N.; Zanders, J. Fertiliser contaminants in new zealand grazed pasture with special reference to cadmium and fluorine—A review. Soil Res. 2003, 41, 501–532. [Google Scholar] [CrossRef]
  7. Jagtap, S.; Yenkie, M.K.; Labhsetwar, N.; Rayalu, S. Fluoride in drinking water and defluoridation of water. Chem. Rev. 2012, 112, 2454–2466. [Google Scholar] [CrossRef] [PubMed]
  8. Mandinic, Z.; Curcic, M.; Antonijevic, B.; Carevic, M.; Mandic, J.; Djukic-Cosic, D.; Lekic, C.P. Fluoride in drinking water and dental fluorosis. Sci. Total Environ. 2010, 408, 3507–3512. [Google Scholar] [CrossRef] [PubMed]
  9. Gandhi, N.; Sirisha, D.; Smita, A.; Manjusha, A. Adsorption studies of fluoride on multani matti and red soil. Res. J. Chem. Sci. 2012, 2, 32–37. [Google Scholar]
  10. Nand, V.; Maata, M.; Koshy, K.; Sotheeswaran, S. Water purification using Moringa oleifera and other locally available seeds in fiji for heavy metal removal. Int. J. Appl. 2012, 2, 125–129. [Google Scholar]
  11. Ravikumar, K.; Sheeja, A. Heavy metal removal from water using moringa oleifera seed coagulant and double filtration. In Proceedings of the International Conference on Innovations in Civil Engineering Icice-2013, Kochi, India, 9–10 May 2013; p. 9. [Google Scholar]
  12. Aziz, N.; Jayasuriya, N.; Fan, L. Effectiveness of plant-based indigenous materials for the removal of heavy metals and fluoride from drinking water. In Proceedings of the 5th International Conference on Sustainable Built Environment Proceedings, Kandy, Sri Lanka, 16–18 December 2014; pp. 34–41. [Google Scholar]
  13. Dubrovsky, N.M.; Burow, K.R.; Clark, G.M.; Gronberg, J.; Hamilton, P.A.; Hitt, K.J.; Mueller, D.K.; Munn, M.D.; Nolan, B.T.; Puckett, L.J. The quality of our nation’s waters—Nutrients in the nation’s streams and groundwater, 1992–2004. US Geol. Surv. Circ. 2010, 1350, 174. [Google Scholar]
  14. Welch, J.; Simmons, V.; Meléndez, E.; Sees, M.; Gold, Y.; Heider, E.C. Assessment of non-anthropogenic addition of uric acid to a water treatment wetlands. Environments 2020, 7, 60. [Google Scholar] [CrossRef]
  15. Lovell, S.T.; Sullivan, W.C. Environmental benefits of conservation buffers in the United States: Evidence, promise, and open questions. Agric. Ecosyst. Environ. 2006, 112, 249–260. [Google Scholar] [CrossRef]
  16. Wallage, Z.E.; Holden, J.; McDonald, A.T. Drain blocking: An effective treatment for reducing dissolved organic carbon loss and water discolouration in a drained peatland. Sci. Total Environ. 2006, 367, 811–821. [Google Scholar] [CrossRef]
  17. Dorioz, J.-M.; Wang, D.; Poulenard, J.; Trevisan, D. The effect of grass buffer strips on phosphorus dynamics—A critical review and synthesis as a basis for application in agricultural landscapes in France. Agric. Ecosyst. Environ. 2006, 117, 4–21. [Google Scholar] [CrossRef]
  18. Lloyd, M. Scottish environmental protection agency: Making sense of a fragmenting environment. Scott. Aff. 1999, 29, 28–42. [Google Scholar] [CrossRef]
  19. Garrod, G.D.; Garratt, J.A.; Kennedy, A.; Willis, K.G. A mixed methodology framework for the assessment of the voluntary initiative. Pest Manag. Sci. Former. Pestic. Sci. 2007, 63, 157–170. [Google Scholar] [CrossRef]
  20. Smith, V.H.; Tilman, G.D.; Nekola, J.C. Eutrophication: Impacts of excess nutrient inputs on freshwater, marine, and terrestrial ecosystems. Environ. Pollut. 1999, 100, 179–196. [Google Scholar] [CrossRef]
  21. Bricker, S.; Longstaff, B.; Dennison, W.; Jones, A.; Boicourt, K.; Wicks, C.; Woerner, J. Effects of nutrient enrichment in the nation’s estuaries: A decade of change (national estuarine eutrophication update). NOAA Coast. Ocean Program Decis. Anal. Ser. 2007, 8, 21–23. [Google Scholar]
  22. Freeman, A.M.; Lamon, E.C., III; Stow, C.A. Nutrient criteria for lakes, ponds, and reservoirs: A bayesian treed model approach. Ecol. Modell. 2009, 220, 630–639. [Google Scholar] [CrossRef]
  23. Blanchard, P.; Lerch, R. Watershed vulnerability to losses of agricultural chemicals: Interactions of chemistry, hydrology, and land-use. Environ. Sci. Technol. 2000, 34, 3315–3322. [Google Scholar] [CrossRef]
  24. Avid Hirst, D.; ob Morris, R. Water quality of scottish rivers: Spatial and temporal trends. Sci. Total Environ. 2001, 265, 327–342. [Google Scholar]
  25. Koul, B.; Taak, P. Biotechnological Strategies for Effective Remediation of Polluted Soils; Springer: Berlin/Heidelberg, Germany, 2018. [Google Scholar]
  26. Miller, T.H.; Bury, N.R.; Owen, S.F.; MacRae, J.I.; Barron, L.P. A review of the pharmaceutical exposome in aquatic fauna. Environ. Pollut. 2018, 239, 129–146. [Google Scholar] [CrossRef]
  27. Connor, R. The United Nations World Water Development Report 2015: Water for a Sustainable World; UNESCO Publishing: Paris, France, 2015; Volume 1. [Google Scholar]
  28. Eman, N.A.; Suleyman, A.M.; Hamzah, M.S.; Md Zahangir, A.; Mohd Ramlan, M.S. Production of natural coagulant from moringa oleifera seed for application in treatment of low turbidity water. J. Water Resour. Prot. 2010, 2010, 259–266. [Google Scholar]
  29. Abdulredha, M.; Rafid, A.L.; Jordan, D.; Hashim, K. The development of a waste management system in kerbala during major pilgrimage events: Determination of solid waste composition. Procedia Eng. 2017, 196, 779–784. [Google Scholar] [CrossRef]
  30. Hashim, K.S.; Al Khaddar, R.; Jasim, N.; Shaw, A.; Phipps, D.; Kot, P.; Pedrola, M.O.; Alattabi, A.W.; Abdulredha, M.; Alawsh, R. Electrocoagulation as a green technology for phosphate removal from river water. Sep. Purif. Technol. 2019, 210, 135–144. [Google Scholar] [CrossRef]
  31. Mohammed, A.-H.; Hussein, A.H.; Yeboah, D.; Al Khaddar, R.; Abdulhadi, B.; Shubbar, A.A.; Hashim, K.S. Electrochemical Removal of Nitrate from Wastewater. IOP Conf. Ser. Mater. Sci. Eng. 2020, 888, 12037. [Google Scholar]
  32. Idowu, I.A.; Atherton, W.; Hashim, K.; Kot, P.; Alkhaddar, R.; Alo, B.I.; Shaw, A. An analysis of the status of landfill classification systems in developing countries: Sub-saharan africa landfill experiences. Waste Manag. 2019, 87, 761–771. [Google Scholar] [CrossRef] [PubMed]
  33. Abdulredha, M.; Kot, P.; Al Khaddar, R.; Jordan, D.; Abdulridha, A. Investigating municipal solid waste management system performance during the arba’een event in the city of kerbala, iraq. Environ. Dev. Sustain. 2020, 22, 1431–1454. [Google Scholar] [CrossRef] [Green Version]
  34. Arora, P. Physical, chemical and biological characteristics of water (e content module). Cent. Univ. Punjab 2017, 2018, 1–16. [Google Scholar]
  35. Zhou, M.; Zhang, Y.; Wang, J.; Shi, Y.; Puig, V. Water quality indicator interval prediction in wastewater treatment process based on the improved bes-lssvm algorithm. Sensors 2022, 22, 422. [Google Scholar] [CrossRef]
  36. Alenazi, M.; Hashim, K.S.; Hassan, A.A.; Muradov, M.; Kot, P.; Abdulhadi, B. Turbidity removal using natural coagulants derived from the seeds of Strychnos potatorum: Statistical and experimental approach. IOP Conf. Ser. Mater. Sci. Eng. 2020, 888, 12064. [Google Scholar] [CrossRef]
  37. Shubbar, A.A.; Sadique, M.; Shanbara, H.K.; Hashim, K. The Development of a New Low Carbon Binder for Construction as an Alternative to Cement. In Advances in Sustainable Construction Materials and Geotechnical Engineering; Springer: Berlin/Heidelberg, Germany, 2020; pp. 205–213. [Google Scholar]
  38. Abdulraheem, F.S.; Al-Khafaji, Z.S.; Hashim, K.S.; Muradov, M.; Kot, P.; Shubbar, A.A. Natural filtration unit for removal of heavy metals from water. IOP Conf. Ser. Mater. Sci. Eng. 2020, 888, 12034. [Google Scholar] [CrossRef]
  39. Alhendal, M.; Nasir, M.J.; Hashim, K.S.; Amoako-Attah, J.; Al-Faluji, D.; Muradov, M.; Kot, P.; Abdulhadi, B. Cost-effective hybrid filter for remediation of water from fluoride. IOP Conf. Ser. Mater. Sci. Eng. 2020, 1058, 12012. [Google Scholar] [CrossRef]
  40. Abdulla, G.; Kareem, M.M.; Hashim, K.S.; Muradov, M.; Kot, P.; Mubarak, H.A.; Abdellatif, M.; Abdulhadi, B. Removal of iron from wastewater using a hybrid filter. IOP Conf. Ser. Mater. Sci. Eng. 2020, 888, 12035. [Google Scholar] [CrossRef]
  41. Shabaa, G.J.; Al-Jboory, W.S.; Sabre, H.M.; Alazmi, A.; Kareem, M.M.; AlKhayyat, A. Plant-based coagulants for water treatment. IOP Conf. Ser. Mater. Sci. Eng. 2021, 1058, 12001. [Google Scholar] [CrossRef]
  42. Azizul-Rahman, M.; Mohd-Suhaimi, A.; Othman, N. Biosorption of pb (ii) and zn (ii) in synthetic waste water by watermelon rind (Citrullus lanatus). Appl. Mech. Mater. 2014, 465, 906–910. [Google Scholar] [CrossRef]
  43. Choudhary, M.; Ray, M.B.; Neogi, S. Evaluation of the potential application of cactus (Opuntia ficus-indica) as a bio-coagulant for pre-treatment of oil sands process-affected water. Sep. Purif. Technol. 2019, 209, 714–724. [Google Scholar] [CrossRef]
  44. Esa, N.M.; Ling, T.B.; Peng, L.S. By-products of rice processing: An overview of health benefits and applications. Rice Res. Open Access 2013, 1, 107. [Google Scholar]
  45. Prabhakaran, N.; Jothieswari, M.; Swarnalatha, S.; Sekaran, G. Tannery wastewater treatment process to minimize residual organics and generation of primary chemical sludge. Int. J. Environ. Sci. Technol. 2022, 19, 8857–8870. [Google Scholar] [CrossRef]
  46. Yin, C.-Y. Emerging usage of plant-based coagulants for water and wastewater treatment. Process Biochem. 2010, 45, 1437–1444. [Google Scholar] [CrossRef] [Green Version]
  47. Choy, S.Y.; Prasad, K.M.N.; Wu, T.Y.; Raghunandan, M.E.; Ramanan, R.N. Utilization of plant-based natural coagulants as future alternatives towards sustainable water clarification. J. Environ. Sci. 2014, 26, 2178–2189. [Google Scholar] [CrossRef]
  48. Nimesha, S.; Hewawasam, C.; Jayasanka, D.; Murakami, Y.; Araki, N.; Maharjan, N. Effectiveness of natural coagulants in water and wastewater treatment. Glob. J. Environ. Sci. Manag. 2022, 8, 101–116. [Google Scholar]
  49. Guo, Y.; Zelekew, O.A.; Sun, H.; Kuo, D.-H.; Lin, J.; Chen, X. Catalytic reduction of organic and hexavalent chromium pollutants with highly active bimetal cubios oxysulfide catalyst under dark. Sep. Purif. Technol. 2020, 242, 116769. [Google Scholar] [CrossRef]
  50. Alibeigi-Beni, S.; Habibi Zare, M.; Pourafshari Chenar, M.; Sadeghi, M.; Shirazian, S. Design and optimization of a hybrid process based on hollow-fiber membrane/coagulation for wastewater treatment. Environ. Sci. Pollut. Res. 2021, 28, 8235–8245. [Google Scholar] [CrossRef] [PubMed]
  51. Ali, I.; Gupta, V. Advances in water treatment by adsorption technology. Nat. Protoc. 2006, 1, 2661–2667. [Google Scholar] [CrossRef] [PubMed]
  52. O’Malley, E.; O’Brien, J.W.; Verhagen, R.; Mueller, J.F. Annual release of selected uv filters via effluent from wastewater treatment plants in australia. Chemosphere 2020, 247, 125887. [Google Scholar] [CrossRef] [PubMed]
  53. Ang, W.L.; Mohammad, A.W. State of the art and sustainability of natural coagulants in water and wastewater treatment. J. Clean. Prod. 2020, 262, 121267. [Google Scholar] [CrossRef]
  54. Hamzah, A.; Manikan, V.; Abd Aziz, N.A.F. Biodegradation of tapis crude oil using consortium of bacteria and fungi: Optimization of crude oil concentration and duration of incubation by response surface methodology. Sains Malays. 2017, 46, 43–50. [Google Scholar] [CrossRef]
  55. Kumar, K.; Chowdhury, A. Use of Novel Nanostructured Photocatalysts for the Environmental Sustainability of Wastewater Treatments. In Reference Module in Materials Science and Materials Engineering; Elsevier: Dublin, Ireland, 2018. [Google Scholar]
  56. Haydar, S.; Aziz, J.A. Coagulation–flocculation studies of tannery wastewater using combination of alum with cationic and anionic polymers. J. Hazard. Mater. 2009, 168, 1035–1040. [Google Scholar] [CrossRef]
  57. Parmar, K.; Prajapati, S.N.; Patel, R.; Dabhi, Y.M. Effective use of ferrous sulfate and alum as a coagulant in treatment of dairy industry wastewater. ARPN J. Eng. Appl. Sci. 2011, 6, 42–45. [Google Scholar]
  58. Tolkou, A.K.; Meez, E.; Kyzas, G.Z.; Torretta, V.; Collivignarelli, M.C.; Caccamo, F.M.; Deliyanni, E.A.; Katsoyiannis, I.A. A mini review of recent findings in cellulose-, polymer- and graphene-based membranes for fluoride removal from drinking water. C 2021, 7, 74. [Google Scholar] [CrossRef]
  59. Muhammad Burhanuddin, B. Recent advances on coagulation-based treatment of wastewater: Transition from chemical to natural coagulant. Curr. Pollut. Rep. 2021, 7, 379–391. [Google Scholar] [CrossRef]
  60. Alwi, H.; Idris, J.; Musa, M.; Ku Hamid, K.H. A preliminary study of banana stem juice as a plant-based coagulant for treatment of spent coolant wastewater. J. Chem. 2013, 2013, 165057. [Google Scholar] [CrossRef] [Green Version]
  61. Carvalho, M.S.; Alves, B.R.R.; Silva, M.F.; Bergamasco, R.; Coral, L.A.; Bassetti, F.J. Cacl2 applied to the extraction of Moringa oleifera seeds and the use for Microcystis aeruginosa removal. Chem. Eng. J. 2016, 304, 469–475. [Google Scholar] [CrossRef]
  62. Hamawand, I. Anaerobic digestion process and bio-energy in meat industry: A review and a potential. Renew. Sustain. Energy Rev. 2015, 44, 37–51. [Google Scholar] [CrossRef]
  63. Madhavi, V.; Vijaya Bhaskar Reddy, A.; Madhavi, G. Synthesis, Characterization, and Properties of Carbon Nanocomposites and Their Application in Wastewater Treatment. In Environmental Remediation through Carbon Based Nano Composites; Springer: Berlin/Heidelberg, Germany, 2021; pp. 61–83. [Google Scholar]
  64. Jiang, J.-Q.; Lloyd, B. Progress in the development and use of ferrate (vi) salt as an oxidant and coagulant for water and wastewater treatment. Water Res. 2002, 36, 1397–1408. [Google Scholar] [CrossRef]
  65. Loloei, M.; Rezaee, A.; Roohaghdam, A.S.; Aliofkhazraei, M. Conductive microbial cellulose as a novel biocathode for cr (vi) bioreduction. Carbohydr. Polym. 2017, 162, 56–61. [Google Scholar] [CrossRef]
  66. Bogacki, J.; Naumczyk, J.; Marcinowski, P.; Kucharska, M. Treatment of cosmetic wastewater using physicochemical and chemical methods. Chemik 2011, 65, 94–97. [Google Scholar]
  67. Liang, Z.; Wang, Y.; Zhou, Y.; Liu, H. Coagulation removal of melanoidins from biologically treated molasses wastewater using ferric chloride. Chem. Eng. J. 2009, 152, 88–94. [Google Scholar] [CrossRef]
  68. Panhwar, A.; Bhutto, S. Improved reduction of cod, bod, tss and oil & grease from sugarcane industry effluent by ferric chloride and polyaluminum chloride coupled with polyvinyl alcohol. Ecol. Eng. Environ. Technol. 2021, 22, 8–14. [Google Scholar]
  69. Panhwar, A.A.; Almani, K.F.; Kandhro, A.A. Environmental degradation by textile industry; performance of chemical coagulants and activated carbon for removal of cod, bod. Tech. J. 2020, 25, 16–20. [Google Scholar]
  70. Irfan, M.; Butt, T.; Imtiaz, N.; Abbas, N.; Khan, R.A.; Shafique, A. The removal of COD, TSS and colour of black liquor by coagulation–flocculation process at optimized ph, settling and dosing rate. Arab. J. Chem. 2017, 10, S2307–S2318. [Google Scholar] [CrossRef] [Green Version]
  71. Al-Saati, N.; Hussein, T.; Abbas, M.; Hashim, K.; Al-Saati, Z.; Kot, P.; Sadique, M.; Aljefery, M.; Carnacina, I. Statistical modelling of turbidity removal applied to non-toxic natural coagulants in water treatment: A case study. Desalination Water Treat. 2019, 150, 406–412. [Google Scholar] [CrossRef]
  72. Zubaidi, S.L.; Al-Bugharbee, H.; Muhsin, Y.R.; Hashim, K.; Alkhaddar, R. Forecasting of monthly stochastic signal of urban water demand: Baghdad as a case study. IOP Conf. Ser. Mater. Sci. Eng. 2020, 888, 12018. [Google Scholar] [CrossRef]
  73. Liao, L.; Zhang, P. Preparation and characterization of polyaluminum titanium silicate and its performance in the treatment of low-turbidity water. Processes 2018, 6, 125. [Google Scholar] [CrossRef] [Green Version]
  74. Mustereț, C.P.; Morosanu, I.; Ciobanu, R.; Plavan, O.; Gherghel, A.; Al-Refai, M.; Roman, I.; Teodosiu, C. Assessment of coagulation–flocculation process efficiency for the natural organic matter removal in drinking water treatment. Water 2021, 13, 3073. [Google Scholar] [CrossRef]
  75. Hashim, K.S.; Ali, S.S.M.; AlRifaie, J.K.; Kot, P.; Shaw, A.; Al Khaddar, R.; Idowu, I.; Gkantou, M. Escherichia coli inactivation using a hybrid ultrasonic-electrocoagulation reactor. Chemosphere 2020, 247, 125868. [Google Scholar] [CrossRef] [PubMed]
  76. Al-Jumeily, D.; Hashim, K.; Alkaddar, R.; Al-Tufaily, M.; Lunn, J. Sustainable and environmental friendly ancient reed houses (inspired by the past to motivate the future). In Proceedings of the 2018 11th International Conference on Developments in eSystems Engineering (DeSE), Cambridge, UK, 2–5 September 2018; pp. 214–219. [Google Scholar]
  77. Zouboulis, A.I.; Tzoupanos, N. Alternative cost-effective preparation method of polyaluminium chloride (pac) coagulant agent: Characterization and comparative application for water/wastewater treatment. Desalination 2010, 250, 339–344. [Google Scholar] [CrossRef]
  78. Walton, M.E.; Samonte-Tan, G.P.; Primavera, J.H.; Edwards-Jones, G.; Le Vay, L. Are mangroves worth replanting? The direct economic benefits of a community-based reforestation project. Environ. Conserv. 2006, 33, 335–343. [Google Scholar] [CrossRef]
  79. Flaten, T.P. Aluminium as a risk factor in alzheimer’s disease, with emphasis on drinking water. Brain Res. Bull. 2001, 55, 187–196. [Google Scholar] [CrossRef]
  80. Kandimalla, R.; Vallamkondu, J.; Corgiat, E.B.; Gill, K.D. Understanding aspects of aluminum exposure in alzheimer’s disease development. Brain Pathol. 2016, 26, 139–154. [Google Scholar] [CrossRef]
  81. Krupińska, I. Aluminium drinking water treatment residuals and their toxic impact on human health. Molecules 2020, 25, 641. [Google Scholar] [CrossRef]
  82. Bondy, S.C. Low levels of aluminum can lead to behavioral and morphological changes associated with alzheimer’s disease and age-related neurodegeneration. Neurotoxicology 2016, 52, 222–229. [Google Scholar] [CrossRef] [Green Version]
  83. Lukiw, W.J.; Kruck, T.P.A.; Percy, M.E.; Pogue, A.I.; Alexandrov, P.N.; Walsh, W.J.; Sharfman, N.M.; Jaber, V.R.; Zhao, Y.; Li, W.; et al. Aluminum in neurological disease—A 36 year multicenter study. J. Alzheimers Dis. Park. 2019, 8, 6–10. [Google Scholar] [CrossRef]
  84. Iwuozor, K.O. Prospects and challenges of using coagulation-flocculation method in the treatment of effluents. Adv. J. Chem.-Sect. A 2019, 2, 105–127. [Google Scholar] [CrossRef] [Green Version]
  85. Lee, J.; Jeon, J.H.; Shin, J.; Jang, H.M.; Kim, S.; Song, M.S.; Kim, Y.M. Quantitative and qualitative changes in antibiotic resistance genes after passing through treatment processes in municipal wastewater treatment plants. Sci. Total Environ. 2017, 605, 906–914. [Google Scholar] [CrossRef]
  86. Abdulhadi, B.; Kot, P.; Hashim, K.; Shaw, A.; Al Khaddar, R. In Influence of current density and electrodes spacing on reactive red 120 dye removal from dyed water using electrocoagulation/electroflotation (ec/ef) process. IOP Conf. Ser. Mater. Sci. Eng. 2019, 584, 12035. [Google Scholar] [CrossRef]
  87. Zubaidi, S.L.; Ortega-Martorell, S.; Al-Bugharbee, H.; Olier, I.; Hashim, K.S.; Gharghan, S.K.; Kot, P.; Al-Khaddar, R. Urban water demand prediction for a city that suffers from climate change and population growth: Gauteng province case study. Water 2020, 12, 1885. [Google Scholar] [CrossRef]
  88. Grmasha, R.A.; Al-sareji, O.J.; Salman, J.M.; Hashim, K.S. Polycyclic aromatic hydrocarbons (pahs) in urban street dust within three land-uses of babylon governorate, iraq: Distribution, sources, and health risk assessment. J. King Saud Univ.—Eng. Sci. 2022, 34, 231–239. [Google Scholar] [CrossRef]
  89. Owodunni, A.A.; Ismail, S. Revolutionary technique for sustainable plant-based green coagulants in industrial wastewater treatment—A review. J. Water Process Eng. 2021, 42, 102096. [Google Scholar] [CrossRef]
  90. Alazaiza, M.Y.D.; Albahnasawi, A.; Ali, G.A.M.; Bashir, M.J.K.; Nassani, D.E.; Al Maskari, T.; Amr, S.S.A.; Abujazar, M.S.S. Application of natural coagulants for pharmaceutical removal from water and wastewater: A review. Water 2022, 14, 140. [Google Scholar] [CrossRef]
  91. Renault, F.; Sancey, B.; Badot, P.-M.; Crini, G. Chitosan for coagulation/flocculation processes–an eco-friendly approach. Eur. Polym. J. 2009, 45, 1337–1348. [Google Scholar] [CrossRef]
  92. Choy, S.; Prasad, K.; Wu, T.; Ramanan, R. A review on common vegetables and legumes as promising plant-based natural coagulants in water clarification. Int. J. Environ. Sci. Technol. 2015, 12, 367–390. [Google Scholar] [CrossRef] [Green Version]
  93. Saleem, M.; Bachmann, R.T. A contemporary review on plant-based coagulants for applications in water treatment. J. Ind. Eng. Chem. 2019, 72, 281–297. [Google Scholar] [CrossRef]
  94. Mohd-Salleh, S.N.A.; Mohd-Zin, N.S.; Othman, N. A review of wastewater treatment using natural material and its potential as aid and composite coagulant. Sains Malays. 2019, 48, 155–164. [Google Scholar] [CrossRef]
  95. Brundtland, G.H. Report of the World Commission on Environment and Development: Our Common Future; UN: New York, NY, USA, 1987. [Google Scholar]
  96. Kamali, M.; Suhas, D.; Costa, M.E.; Capela, I.; Aminabhavi, T.M. Sustainability considerations in membrane-based technologies for industrial effluents treatment. Chem. Eng. J. 2019, 368, 474–494. [Google Scholar] [CrossRef]
  97. Kanmani, P.; Aravind, J.; Kamaraj, M.; Sureshbabu, P.; Karthikeyan, S. Environmental applications of chitosan and cellulosic biopolymers: A comprehensive outlook. Bioresour. Technol. 2017, 242, 295–303. [Google Scholar] [CrossRef] [PubMed]
  98. Do, M.; Ngo, H.; Guo, W.; Liu, Y.; Chang, S.; Nguyen, D.; Nghiem, L.; Ni, B. Challenges in the application of microbial fuel cells to wastewater treatment and energy production: A mini review. Sci. Total Environ. 2018, 639, 910–920. [Google Scholar] [CrossRef]
  99. Ho, Y.; Norli, I.; FM, A.; Morad, N. New vegetal biopolymeric flocculant: A degradation and flocculation study. Iran. J. Energy Environ. 2014, 5, 1. [Google Scholar] [CrossRef] [Green Version]
  100. Abidin, Z.; Norhafizah, M.; Robiah, Y.; Aishah, D. Effect of storage conditions on jatropha curcas performance as biocoagulant for treating palm oil mill effluent. J. Environ. Sci. Technol. 2019, 12, 92–101. [Google Scholar] [CrossRef] [Green Version]
  101. Dos Santos, J.D.; Veit, M.T.; Juchen, P.T.; da Cunha Gonçalves, G.; Palacio, S.M.; Fagundes-Klen, M. Use of different coagulants for cassava processing wastewater treatment. J. Environ. Chem. Eng. 2018, 6, 1821–1827. [Google Scholar] [CrossRef]
  102. Dezfooli, S.M.; Uversky, V.N.; Saleem, M.; Baharudin, F.S.; Hitam, S.M.S.; Bachmann, R.T. A simplified method for the purification of an intrinsically disordered coagulant protein from defatted Moringa oleifera seeds. Process Biochem. 2016, 51, 1085–1091. [Google Scholar] [CrossRef]
  103. Barbosa, A.D.; da Silva, L.F.; de Paula, H.M.; Romualdo, L.L.; Sadoyama, G.; Andrade, L.S. Combined use of coagulation (m. Oleifera) and electrochemical techniques in the treatment of industrial paint wastewater for reuse and/or disposal. Water Res. 2018, 145, 153–161. [Google Scholar] [CrossRef]
  104. Chitra, D.; Muruganandam, L. Performance of natural coagulants on greywater treatment. Recent Innov. Chem. Eng. Former. Recent Pat. Chem. Eng. 2020, 13, 81–92. [Google Scholar] [CrossRef]
  105. Maurya, A.; Reddy, B.; Theerthagiri, J.; Narayana, P.; Park, C.; Hong, J.; Yeom, J.-T.; Cho, K.; Reddy, N. Modeling and optimization of process parameters of biofilm reactor for wastewater treatment. Sci. Total Environ. 2021, 787, 147624. [Google Scholar] [CrossRef]
  106. Zaidi, N.; Muda, K.; Rahman, M.A.; Sgawi, M.; Amran, A. Effectiveness of local waste materials as organic-based coagulant in treating water. IOP Conf. Ser. Mater. Sci. Eng. 2019, 636, 12007. [Google Scholar] [CrossRef]
  107. Sibartie, S.; Ismail, N. Potential of Hibiscus sabdariffa and jatropha curcas as natural coagulants in the treatment of pharmaceutical wastewater. MATEC Web Conf. 2018, 152, 1009. [Google Scholar] [CrossRef]
  108. Kurniawan, S.B.; Abdullah, S.R.S.; Imron, M.F.; Said, N.S.M.; Ismail, N.; Hasan, H.A.; Othman, A.R.; Purwanti, I.F. Challenges and opportunities of biocoagulant/bioflocculant application for drinking water and wastewater treatment and its potential for sludge recovery. Int. J. Environ. Res. Public Health 2020, 17, 9312. [Google Scholar] [CrossRef]
  109. Pattnaik, P.; Dangayach, G.S. Sustainability of wastewater management in textile sectors: A conceptual framework. Environ. Eng. Manag. J. 2019, 18, 9. [Google Scholar] [CrossRef]
  110. Zhang, J.; Zhang, F.; Luo, Y.; Yang, H. A preliminary study on cactus as coagulant in water treatment. Process Biochem. 2006, 41, 730–733. [Google Scholar] [CrossRef]
  111. Choubey, S.; Rajput, S.; Bapat, K. Comparison of efficiency of some natural coagulants-bioremediation. Int. J. Emerg. Technol. Adv. Eng. 2012, 2, 429–434. [Google Scholar]
  112. Shakir, L.; Ejaz, S.; Ashraf, M.; Qureshi, N.A.; Anjum, A.A.; Iltaf, I.; Javeed, A. Ecotoxicological risks associated with tannery effluent wastewater. Environ. Toxicol. Pharmacol. 2012, 34, 180–191. [Google Scholar] [CrossRef]
  113. Mahmud, H.N.M.E.; Huq, A.O.; binti Yahya, R. The removal of heavy metal ions from wastewater/aqueous solution using polypyrrole-based adsorbents: A review. RSC Adv. 2016, 6, 14778–14791. [Google Scholar] [CrossRef]
  114. Kiso, Y.; Jung, Y.-J.; Park, M.-S.; Wang, W.; Shimase, M.; Yamada, T.; Min, K.-S. Coupling of sequencing batch reactor and mesh filtration: Operational parameters and wastewater treatment performance. Water Res. 2005, 39, 4887–4898. [Google Scholar] [CrossRef]
  115. Jahn, S.A.A. Drinking water from chinese rivers: Challenges of clarification. J. Water Supply: Res. Technol.—AQUA 2001, 50, 15–27. [Google Scholar] [CrossRef]
  116. Thakre, V.; Bhole, A. Relative evaluation of a few natural coagulants. J. Inst. Eng. Environ. Eng. 1985, 504, 89–92. [Google Scholar]
  117. Govindan, V. Coagulation studies on natural seed extracts. J. Indian Waterworks Assoc. 2005, 37, 145. [Google Scholar]
  118. Arukwe, U.; Amadi, B.; Duru, M.; Agomuo, E.; Adindu, E.; Odika, P.; Lele, K.; Egejuru, L.; Anudike, J. Chemical composition of Persea americana leaf, fruit and seed. Int. J. Recent Res. Appl. Stud. 2012, 11, 346–349. [Google Scholar]
  119. Ramesa, S.; Sooad, A.-d. Antibacterial properties of different cultivars of Phoenix dactylifera l. And their corresponding protein content. Ann. Biol. Res. 2012, 3, 4751–4757. [Google Scholar]
  120. Som, A.; Idris, J.; Hamid, K. Dragon fruit foliage as a low cost plant-based coagulant in latex concentrate wastewater treatment. Malays. J. Chem. Eng. 2007, 1, 47–59. [Google Scholar]
  121. Idris, J.; Md Som, A.; Musa, M.; Ku Hamid, K.H.; Husen, R.; Muhd Rodhi, M.N. Dragon fruit foliage plant-based coagulant for treatment of concentrated latex effluent: Comparison of treatment with ferric sulfate. J. Chem. 2013, 2013, 230860. [Google Scholar] [CrossRef] [Green Version]
  122. Patil, C.; Hugar, M. Treatment of dairy wastewater by natural coagulants. Int. Res. J. Eng. Technol. 2015, 2, 1120–1124. [Google Scholar]
  123. Camacho, F.P.; Sousa, V.S.; Bergamasco, R.; Teixeira, M.R. The use of moringa oleifera as a natural coagulant in surface water treatment. Chem. Eng. J. 2017, 313, 226–237. [Google Scholar] [CrossRef]
  124. Pallavi, N.; Mahesh, S. Feasibility study of Moringa oleifera as a natural coagulant for the treatment of dairy wastewater. Int. J. Eng. Res. 2013, 2, 201–203. [Google Scholar]
  125. Shan, T.C.; Matar, M.A.; Makky, E.A.; Ali, E.N. The use of Moringa oleifera seed as a natural coagulant for wastewater treatment and heavy metals removal. Appl. Water Sci. 2017, 7, 1369–1376. [Google Scholar] [CrossRef]
  126. Dehghani, M.; Alizadeh, M.H. The effects of the natural coagulant Moringa oleifera and alum in wastewater treatment at the bandar abbas oil refinery. Environ. Health Eng. Manag. J. 2016, 3, 225–230. [Google Scholar] [CrossRef]
  127. Muralimohan, N.; Palanisamy, T. Treatment of textile effluent by natural coagulants in erode district. Asian J. Chem. 2014, 26, 911. [Google Scholar] [CrossRef]
  128. Kazi, T.; Virupakshi, A.; Scholar, M. Treatment of tannery wastewater using natural coagulants. Development 2013, 2, 4061–4068. [Google Scholar]
  129. Anastasakis, K.; Kalderis, D.; Diamadopoulos, E. Flocculation behavior of mallow and okra mucilage in treating wastewater. Desalination 2009, 249, 786–791. [Google Scholar] [CrossRef]
  130. Carpinteyro-Urban, S.; Vaca, M.; Torres, L. Can vegetal biopolymers work as coagulant–flocculant aids in the treatment of high-load cosmetic industrial wastewaters? Water Air Soil Pollut. 2012, 223, 4925–4936. [Google Scholar] [CrossRef]
  131. Al-Hamadani, Y.A.; Yusoff, M.S.; Umar, M.; Bashir, M.J.; Adlan, M.N. Application of psyllium husk as coagulant and coagulant aid in semi-aerobic landfill leachate treatment. J. Hazard. Mater. 2011, 190, 582–587. [Google Scholar] [CrossRef]
  132. Shamsnejati, S.; Chaibakhsh, N.; Pendashteh, A.R.; Hayeripour, S. Mucilaginous seed of Ocimum basilicum as a natural coagulant for textile wastewater treatment. Ind. Crops Prod. 2015, 69, 40–47. [Google Scholar] [CrossRef]
  133. Chaibakhsh, N.; Ahmadi, N.; Zanjanchi, M.A. Use of Plantago major l. As a natural coagulant for optimized decolorization of dye-containing wastewater. Ind. Crops Prod. 2014, 61, 169–175. [Google Scholar] [CrossRef]
  134. Awang, N.A.; Aziz, H.A. Hibiscus rosa-sinensis leaf extract as coagulant aid in leachate treatment. Appl. Water Sci. 2012, 2, 293–298. [Google Scholar] [CrossRef] [Green Version]
  135. Wang, J.-P.; Chen, Y.-Z.; Wang, Y.; Yuan, S.-J.; Yu, H.-Q. Optimization of the coagulation-flocculation process for pulp mill wastewater treatment using a combination of uniform design and response surface methodology. Water Res. 2011, 45, 5633–5640. [Google Scholar] [CrossRef] [PubMed]
  136. Ismail, N.I.; Sheikh Abdullah, S.R.; Idris, M.; Abu Hasan, H.; Halmi, M.I.E.; Hussin AL Sbani, N.; Hamed Jehawi, O.; Sanusi, S.N.A.; Hashim, M.H. Accumulation of fecal by Scirpus grossus grown in synthetic bauxite mining wastewater and identification of resistant rhizobacteria. Environ. Eng. Sci. 2017, 34, 367–375. [Google Scholar] [CrossRef]
  137. Ronke, R.A.; Saidat, O.G.; Abdulwahab, G. Coagulation-flocculation treatment of industrial wastewater using tamarind seed powder. Int. J. ChemTech Res. 2016, 9, 771–780. [Google Scholar]
  138. Saharudin, N.; Nithyanandam, R. Wastewater treatment by using natural coagulant. 2nd Eureca. Engineering 2014, 2–3, 202720485. [Google Scholar]
  139. Thawari, D.; Verma, S. Coal washery wastewater treatment using natural coagulants and chemical precipitation. Int. J. Sci. Res. 2015, 4, 1877–1881. [Google Scholar]
  140. Awasthi, M.K.; Li, J.; Kumar, S.; Awasthi, S.K.; Wang, Q.; Chen, H.; Wang, M.; Ren, X.; Zhang, Z. Effects of biochar amendment on bacterial and fungal diversity for co-composting of gelatin industry sludge mixed with organic fraction of municipal solid waste. Bioresour. Technol. 2017, 246, 214–223. [Google Scholar] [CrossRef]
  141. Patel, H.; Vashi, R. Comparison of naturally prepared coagulants for removal of cod and color from textile wastewater. Glob. NEST J. 2013, 15, 522–528. [Google Scholar]
  142. Ramavandi, B.; Farjadfard, S. Removal of chemical oxygen demand from textile wastewater using a natural coagulant. Korean J. Chem. Eng. 2014, 31, 81–87. [Google Scholar] [CrossRef]
  143. Lekshmi, B.; Joseph, R.S.; Jose, A.; Abinandan, S.; Shanthakumar, S. Studies on reduction of inorganic pollutants from wastewater by Chlorella pyrenoidosa and Scenedesmus abundans. Alex. Eng. J. 2015, 54, 1291–1296. [Google Scholar] [CrossRef] [Green Version]
  144. Hanif, M.A.; Nadeem, R.; Zafar, M.N.; Bhatti, H.N.; Nawaz, R. Physico-chemical treatment of textile wastewater using natural coagulant cassia. J. Chem. Soc. Pak. 2008, 30, 385–393. [Google Scholar]
  145. Jeon, E.-C.; Son, H.-K.; Sa, J.-H. Emission characteristics and factors of selected odorous compounds at a wastewater treatment plant. Sensors 2009, 9, 311–326. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  146. 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, 238–244. [Google Scholar]
  147. Choy, S.Y.; Prasad, K.M.N.; Wu, T.Y.; Raghunandan, M.E.; Yang, B.; Phang, S.-M.; Ramanan, R.N. Isolation, characterization and the potential use of starch from jackfruit seed wastes as a coagulant aid for treatment of turbid water. Environ. Sci. Pollut. Res. 2017, 24, 2876–2889. [Google Scholar] [CrossRef] [PubMed]
  148. Pritchard, M.; Mkandawire, T.; Edmondson, A.; O’neill, J.; Kululanga, G. Potential of using plant extracts for purification of shallow well water in malawi. Phys. Chem. Earth Parts A/B/C 2009, 34, 799–805. [Google Scholar] [CrossRef]
  149. Babu, R.; Chaudhuri, M. Home water treatment by direct filtration with natural coagulant. J. Water Health 2005, 3, 27–30. [Google Scholar] [CrossRef] [Green Version]
  150. Diaz, A.; Rincon, N.; Escorihuela, A.; Fernandez, N.; Chacin, E.; Forster, C. A preliminary evaluation of turbidity removal by natural coagulants indigenous to venezuela. Process Biochem. 1999, 35, 391–395. [Google Scholar] [CrossRef]
  151. Bunce, J.T.; Ndam, E.; Ofiteru, I.D.; Moore, A.; Graham, D.W. A review of phosphorus removal technologies and their applicability to small-scale domestic wastewater treatment systems. Front. Environ. Sci. 2018, 6, 8. [Google Scholar] [CrossRef] [Green Version]
  152. Beltrán-Heredia, J.; Sánchez-Martín, J. Municipal wastewater treatment by modified tannin flocculant agent. Desalination 2009, 249, 353–358. [Google Scholar] [CrossRef]
  153. Bongiovani, M.C.; Camacho, F.P.; Coldebella, P.F.; Valverde, K.C.; Nishi, L.; Bergamasco, R. Removal of natural organic matter and trihalomethane minimization by coagulation/flocculation/filtration using a natural tannin. Desalination Water Treat. 2016, 57, 5406–5415. [Google Scholar] [CrossRef]
  154. Özacar, M.; Şengil, İ.A. The use of tannins from turkish acorns (valonia) in water treatment as a coagulant and coagulant aid. Turk. J. Eng. Environ. Sci. 2002, 26, 255–264. [Google Scholar]
  155. Bacelo, H.A.M. Tannin Resins from Maritime Pine Bark as Adsorbents for Water Treatment and Recovery of Substances. Ph.D. Thesis, University of Porto, Porto, Portugal, 2021. [Google Scholar]
  156. Beltrán-Heredia, J.; Sánchez-Martín, J.; Solera-Hernández, C. Anionic surfactants removal by natural coagulant/flocculant products. Ind. Eng. Chem. Res. 2009, 48, 5085–5092. [Google Scholar] [CrossRef]
  157. Jayaram, K.; Murthy, I.; Lalhruaitluanga, H.; Prasad, M. Biosorption of lead from aqueous solution by seed powder of Strychnos potatorum L. Colloids Surf. B Biointerfaces 2009, 71, 248–254. [Google Scholar] [CrossRef]
  158. Raghuwanshi, P.K.; Mandloi, M.; Sharma, A.J.; Malviya, H.S.; Chaudhari, S. Improving filtrate quality using agrobased materials as coagulant aid. Water Qual. Res. J. 2002, 37, 745–756. [Google Scholar] [CrossRef]
  159. Schulz, C.R.; Okun, D.A.; Donaldson, D.; Austin, J. Surface Water Treatment for Communities in Developing Countries; U.S. Agency for International Development: Washington, DC, USA, 1992. [Google Scholar]
  160. Selvaraj, K.; Sevugaperumal, R.; Ramasubramanian, V. Impact of match industry effluent on growth and biochemical characteristics of Cyamopsis tetragonoloba taub and amelioration of the stress by seaweed treatment. Indian J. Fund. Appl. Life Sci 2013, 3, 192–197. [Google Scholar]
  161. Sarawgi, G.; Kamra, A.; Suri, N.; Kaur, A.; Sarethy, I.P. Effect of Strychnos potatorum linn. Seed extracts on water samples from different sources and with diverse properties. Asian J. Water Environ. Pollut. 2009, 6, 13–17. [Google Scholar]
  162. Tripathi, P.; Chaudhuri, M.; Bokil, S. Nirmali seed—A naturally occurring coagulant. Indian J. Environ. Health 1976, 18, 72–81. [Google Scholar]
  163. Adinolfi, M.; Corsaro, M.M.; Lanzetta, R.; Parrilli, M.; Folkard, G.; Grant, W.; Sutherland, J. Composition of the coagulant polysaccharide fraction from Strychnos potatorum seeds. Carbohydr. Res. 1994, 263, 103–110. [Google Scholar] [CrossRef]
  164. Muthuraman, G.; Sasikala, S. Removal of turbidity from drinking water using natural coagulants. J. Ind. Eng. Chem. 2014, 20, 1727–1731. [Google Scholar] [CrossRef]
  165. Bhuptawat, H.; Folkard, G.; Chaudhari, S. Innovative physico-chemical treatment of wastewater incorporating Moringa oleifera seed coagulant. J. Hazard. Mater. 2007, 142, 477–482. [Google Scholar] [CrossRef]
  166. Anwar, F.; Bhanger, M. Analytical characterization of Moringa oleifera seed oil grown in temperate regions of pakistan. J. Agric. Food Chem. 2003, 51, 6558–6563. [Google Scholar] [CrossRef] [PubMed]
  167. Koul, B.; Chase, N. Moringa oleifera lam.: Panacea to several maladies. J. Chem. Pharm. Res. 2015, 7, 687–707. [Google Scholar]
  168. Farooq, B.; Koul, B. Comparative analysis of the antioxidant, antibacterial and plant growth promoting potential of five indian varieties of Moringa oleifera L. South Afr. J. Bot. 2020, 129, 47–55. [Google Scholar] [CrossRef]
  169. Ndabigengesere, A.; Narasiah, K.S.; Talbot, B.G. Active agents and mechanism of coagulation of turbid waters using Moringa oleifera. Water Res. 1995, 29, 703–710. [Google Scholar] [CrossRef]
  170. Muller, S. Wirkstoffe zur Trinkwasseraufbereitung aus Samen von Moringa Oleifera. Master’s Thesis, Universitat Heidelberg, Heidelberg, Germany, 1980. [Google Scholar]
  171. Jahn, S.A.A. Using moringa seeds as coagulants in developing countries. J. Am. Water Work. Assoc. 1988, 80, 43–50. [Google Scholar] [CrossRef]
  172. Muyibi, S.A.; Evison, L.M. Optimizing physical parameters affecting coagulation of turbid water with Morninga oleifera seeds. Water Res. 1995, 29, 2689–2695. [Google Scholar] [CrossRef]
  173. Gassenschmidt, U.; Jany, K.D.; Bernhard, T.; Niebergall, H. Isolation and characterization of a flocculating protein from Moringa oleifera lam. Biochim. Et Biophys. Acta Gen. Subj. 1995, 1243, 477–481. [Google Scholar] [CrossRef]
  174. Ghebremichael, K.A.; Gunaratna, K.; Henriksson, H.; Brumer, H.; Dalhammar, G. A simple purification and activity assay of the coagulant protein from Moringa oleifera seed. Water Res. 2005, 39, 2338–2344. [Google Scholar] [CrossRef]
  175. Okuda, T.; Baes, A.U.; Nishijima, W.; Okada, M. Isolation and characterization of coagulant extracted from Moringa oleifera seed by salt solution. Water Res. 2001, 35, 405–410. [Google Scholar] [CrossRef] [Green Version]
  176. Bolto, B.; Gregory, J. Organic polyelectrolytes in water treatment. Water Res. 2007, 41, 2301–2324. [Google Scholar] [CrossRef]
  177. Sulaiman, M.; Zhigila, D.A.; Mohammed, K.; Umar, D.M.; Aliyu, B.; Abd Manan, F. Moringa oleifera seed as alternative natural coagulant for potential application in water treatment: A review. J. Adv. Rev. Sci. Res 2017, 30, 1–11. [Google Scholar]
  178. Dotto, J.; Fagundes-Klen, M.R.; Veit, M.T.; Palacio, S.M.; Bergamasco, R. Performance of different coagulants in the coagulation/flocculation process of textile wastewater. J. Clean. Prod. 2019, 208, 656–665. [Google Scholar] [CrossRef]
  179. Ashmawy, M.; Moussa, M.; Ghoneim, A.; Tammam, A. Enhancingthe efficiency of primary sedimentation in wastewater treatment plants with the application of Moringa oliefera seeds and quicklime. J. Am. Sci. 2012, 8, 494–502. [Google Scholar]
  180. Hiremath, P.J.; Farmer, A.; Cannon, S.B.; Woodward, J.; Kudapa, H.; Tuteja, R.; Kumar, A.; BhanuPrakash, A.; Mulaosmanovic, B.; Gujaria, N. Large-scale transcriptome analysis in chickpea (Cicer arietinum L.), an orphan legume crop of the semi-arid tropics of asia and africa. Plant Biotechnol. J. 2011, 9, 922–931. [Google Scholar] [CrossRef] [Green Version]
  181. Jaseela, L.; Chadaga, M. Treatment of dairy effluent using Cicer arietinum. Int. J. Innov. Res. Sci. Engg. Technol 2015, 4, 4881–4885. [Google Scholar]
  182. Asrafuzzaman, M.; Fakhruddin, A.; Hossain, M. Reduction of turbidity of water using locally available natural coagulants. Int. Sch. Res. Not. 2011, 2011, 1–6. [Google Scholar] [CrossRef] [Green Version]
  183. Lim, T.K. Edible Medicinal and Non-Medicinal Plants; Springer: Berlin/Heidelberg, Germany, 2012; Volume 1. [Google Scholar]
  184. Mataka, L.; Henry, E.; Masamba, W.; Sajidu, S. Lead remediation of contaminated water using Moringa stenopetala and Moringa oleifera seed powder. Int. J. Environ. Sci. Technol. 2006, 3, 131–139. [Google Scholar] [CrossRef]
  185. Bhole, A. Relative evaluation of a few natural coagulants. Aqua J. Water Supply: Res. Technol. 1995, 44, 284–290. [Google Scholar]
  186. Mbogo, S.A. A novel technology to improve drinking water quality using natural treatment methods in rural tanzania. J. Environ. Health 2008, 70, 46–50. [Google Scholar]
  187. Gupta, V.K.; Mittal, A.; Malviya, A.; Mittal, J. Adsorption of carmoisine a from wastewater using waste materials—Bottom ash and deoiled soya. J. Colloid Interface Sci. 2009, 335, 24–33. [Google Scholar] [CrossRef] [Green Version]
  188. Mittal, A.; Mittal, J.; Malviya, A.; Kaur, D.; Gupta, V. Adsorption of hazardous dye crystal violet from wastewater by waste materials. J. Colloid Interface Sci. 2010, 343, 463–473. [Google Scholar] [CrossRef] [PubMed]
  189. De Carvalho, C.C.; Cruz, P.A.; da Fonseca, M.M.R.; Xavier-Filho, L. Antibacterial properties of the extract of Abelmoschus esculentus. Biotechnol. Bioprocess Eng. 2011, 16, 971–977. [Google Scholar] [CrossRef]
  190. Sáenz, C.; Sepúlveda, E.; Matsuhiro, B. Opuntia spp mucilage’s: A functional component with industrial perspectives. J. Arid Environ. 2004, 57, 275–290. [Google Scholar] [CrossRef]
  191. Nharingo, T.; Moyo, M. Application of opuntia Ficus-indica in bioremediation of wastewaters. A critical review. J. Environ. Manage. 2016, 166, 55–72. [Google Scholar] [CrossRef] [PubMed]
  192. Rebah, F.B.; Siddeeg, S. Cactus an eco-friendly material for wastewater treatment: A review. J. Mater. Environ. Sci. 2017, 8, 1770–1782. [Google Scholar]
  193. Miller, S.M.; Fugate, E.J.; Craver, V.O.; Smith, J.A.; Zimmerman, J.B. Toward understanding the efficacy and mechanism of Opuntia spp. As a natural coagulant for potential application in water treatment. Environ. Sci. Technol. 2008, 42, 4274–4279. [Google Scholar] [CrossRef]
  194. Manunza, B.; Deiana, S.; Pintore, M.; Gessa, C. Molecular dynamics study of polygalacturonic acid chains in aqueous solution. Carbohydr. Res. 1997, 300, 85–88. [Google Scholar] [CrossRef]
  195. Fahmi, M.R.; Hamidin, N.; Abidin, C.Z.A.; Fazara, U.; Ali, M.; Hatim, M. Performance evaluation of okra (Abelmoschus esculentus) as coagulant for turbidity removal in water treatment. Trans. Tech. Publ. 2014, 594, 226–230. [Google Scholar] [CrossRef]
  196. Raji, Y.O.; Abubakar, L.; Giwa, S.O.; Giwa, A. Assessment of coagulation efficiency of okra seed extract for surface water treatment. Int. J. Sci. Eng. Res. 2016, 6, 1–7. [Google Scholar]
  197. Thakur, S.S.; Choubey, S. Assessment of coagulation efficiency of Moringa oleifera and okra for treatment of turbid water. Arch. Appl. Sci. Res. 2014, 6, 24–30. [Google Scholar]
  198. Mishra, S.; Singh, S.; Srivastava, R. Okra seeds: An efficient coagulant. Int. J. Res. Appl. Sci. Eng. 2017, 5, 1–5. [Google Scholar]
  199. Nath, A.; Mishra, A.; Pande, P.P. A review natural polymeric coagulants in wastewater treatment. Mater. Today: Proc. 2021, 46, 6113–6117. [Google Scholar] [CrossRef]
  200. Wang, J.; Chen, X. Removal of antibiotic resistance genes (args) in various wastewater treatment processes: An overview. Crit. Rev. Environ. Sci. Technol. 2022, 52, 571–630. [Google Scholar] [CrossRef]
  201. Shewa, W.A.; Dagnew, M. Revisiting chemically enhanced primary treatment of wastewater: A review. Sustainability 2020, 12, 5928. [Google Scholar] [CrossRef]
  202. Zainal, S.F.F.S.; Abdul Aziz, H.; Mohd Omar, F.; Alazaiza, M.Y. Sludge performance in coagulation-flocculation treatment for suspended solids removal from landfill leachate using tin (iv) chloride and Jatropha curcas. Int. J. Environ. Anal. Chem. 2021, 1–15. [Google Scholar] [CrossRef]
  203. Oladoja, N.A. Headway on natural polymeric coagulants in water and wastewater treatment operations. J. Water Process Eng. 2015, 6, 174–192. [Google Scholar] [CrossRef]
  204. Dwarapureddi, B.K.; Saritha, V. Evaluation of factors affecting coagulation of water with natural polymers. Int. J. Adv. Res. Biol. Sci. 2015, 2, 98–113. [Google Scholar]
  205. Jiao, Y.-N.; Chen, H.; Gao, R.-X.; Zhu, Y.-G.; Rensing, C. Organic compounds stimulate horizontal transfer of antibiotic resistance genes in mixed wastewater treatment systems. Chemosphere 2017, 184, 53–61. [Google Scholar] [CrossRef]
  206. Li, Y.S.; Yan, L.; Xiang, C.B.; Hong, L.J. Treatment of oily wastewater by organic–inorganic composite tubular ultrafiltration (uf) membranes. Desalination 2006, 196, 76–83. [Google Scholar] [CrossRef]
  207. Chong, J.W.R.; Khoo, K.S.; Yew, G.Y.; Leong, W.H.; Lim, J.W.; Lam, M.K.; Ho, Y.-C.; Ng, H.S.; Munawaroh, H.S.H.; Show, P.L. Advances in production of bioplastics by microalgae using food waste hydrolysate and wastewater: A review. Bioresour. Technol. 2021, 342, 125947. [Google Scholar] [CrossRef]
  208. Ghernaout, D.; Elboughdiri, N.; Ghareba, S. Fenton technology for wastewater treatment: Dares and trends. Open Access Libr. J. 2020, 7, e6045. [Google Scholar] [CrossRef]
  209. Wu, T.Y.; Mohammad, A.W.; Jahim, J.M.; Anuar, N. Pollution control technologies for the treatment of palm oil mill effluent (pome) through end-of-pipe processes. J. Environ. Manag. 2010, 91, 1467–1490. [Google Scholar] [CrossRef] [PubMed]
  210. Nouri, J.; Nouri, N.; Moeeni, M. Development of industrial waste disposal scenarios using life-cycle assessment approach. Int. J. Environ. Sci. Technol. 2012, 9, 417–424. [Google Scholar] [CrossRef] [Green Version]
  211. FAO. Food Outlook: Global Market Analysis; FAO: Rome, Italy, 2012. [Google Scholar]
  212. Sutherland, J.; Folkard, G.; Poirier, Y. Moringa Oleifera. The Constraints to Commercialisation; CIRAD: Montpellier, France, 2002. [Google Scholar]
  213. Sahu, O.; Chaudhari, P. Review on chemical treatment of industrial waste water. J. Appl. Sci. Environ. Manag. 2013, 17, 241–257. [Google Scholar] [CrossRef]
  214. Rodrigues, A.C.; Boroski, M.; Shimada, N.S.; Garcia, J.C.; Nozaki, J.; Hioka, N. Treatment of paper pulp and paper mill wastewater by coagulation–flocculation followed by heterogeneous photocatalysis. J. Photochem. Photobiol. A Chem. 2008, 194, 1–10. [Google Scholar] [CrossRef]
  215. Santo, C.E.; Vilar, V.J.; Botelho, C.M.; Bhatnagar, A.; Kumar, E.; Boaventura, R.A. Optimization of coagulation–flocculation and flotation parameters for the treatment of a petroleum refinery effluent from a portuguese plant. Chem. Eng. J. 2012, 183, 117–123. [Google Scholar] [CrossRef]
  216. Verma, A.K.; Dash, R.R.; Bhunia, P. A review on chemical coagulation/flocculation technologies for removal of colour from textile wastewaters. J. Environ. Manage. 2012, 93, 154–168. [Google Scholar] [CrossRef]
  217. Colantoni, A.; Evic, N.; Lord, R.; Retschitzegger, S.; Proto, A.; Gallucci, F.; Monarca, D. Characterization of biochars produced from pyrolysis of pelletized agricultural residues. Renew. Sustain. Energy Rev. 2016, 64, 187–194. [Google Scholar] [CrossRef] [Green Version]
  218. Xiong, X.; Iris, K.; Tsang, D.C.; Bolan, N.S.; Ok, Y.S.; Igalavithana, A.D.; Kirkham, M.; Kim, K.-H.; Vikrant, K. Value-added chemicals from food supply chain wastes: State-of-the-art review and future prospects. Chem. Eng. J. 2019, 375, 121983. [Google Scholar] [CrossRef]
  219. Xiang, W.; Zhang, X.; Chen, J.; Zou, W.; He, F.; Hu, X.; Tsang, D.C.; Ok, Y.S.; Gao, B. Biochar technology in wastewater treatment: A critical review. Chemosphere 2020, 252, 126539. [Google Scholar] [CrossRef]
  220. Creamer, A.E.; Gao, B. Carbon-based adsorbents for postcombustion CO2 capture: A critical review. Environ. Sci. Technol. 2016, 50, 7276–7289. [Google Scholar] [CrossRef]
  221. Wang, S.; Zhang, H.; Wang, J.; Hou, H.; Du, C.; Ma, P.-C.; Kadier, A. Application of Biochar for Wastewater Treatment. In Biochar and Its Application in Bioremediation; Springer: Berlin/Heidelberg, Germany, 2021; pp. 67–90. [Google Scholar]
  222. Omran, B.A.; Baek, K.-H. Valorization of agro-industrial biowaste to green nanomaterials for wastewater treatment: Approaching green chemistry and circular economy principles. J. Environ. Manag. 2022, 311, 114806. [Google Scholar] [CrossRef]
  223. Yang, F.; Xu, Z.; Yu, L.; Gao, B.; Xu, X.; Zhao, L.; Cao, X. Kaolinite enhances the stability of the dissolvable and undissolvable fractions of biochar via different mechanisms. Environ. Sci. Technol. 2018, 52, 8321–8329. [Google Scholar] [CrossRef]
  224. Inyang, M.I.; Gao, B.; Yao, Y.; Xue, Y.; Zimmerman, A.; Mosa, A.; Pullammanappallil, P.; Ok, Y.S.; Cao, X. A review of biochar as a low-cost adsorbent for aqueous heavy metal removal. Crit. Rev. Environ. Sci. Technol. 2016, 46, 406–433. [Google Scholar] [CrossRef]
  225. Wang, B.; Gao, B.; Fang, J. Recent advances in engineered biochar productions and applications. Crit. Rev. Environ. Sci. Technol. 2017, 47, 2158–2207. [Google Scholar] [CrossRef]
  226. Zhang, Y.; Chen, P.; Liu, S.; Peng, P.; Min, M.; Cheng, Y.; Anderson, E.; Zhou, N.; Fan, L.; Liu, C. Effects of feedstock characteristics on microwave-assisted pyrolysis–a review. Bioresour. Technol. 2017, 230, 143–151. [Google Scholar] [CrossRef]
  227. Van Vinh, N.; Zafar, M.; Behera, S.; Park, H.-S. Arsenic (iii) removal from aqueous solution by raw and zinc-loaded pine cone biochar: Equilibrium, kinetics, and thermodynamics studies. Int. J. Environ. Sci. Technol. 2015, 12, 1283–1294. [Google Scholar] [CrossRef] [Green Version]
  228. Palansooriya, K.N.; Yang, Y.; Tsang, Y.F.; Sarkar, B.; Hou, D.; Cao, X.; Meers, E.; Rinklebe, J.; Kim, K.-H.; Ok, Y.S. Occurrence of contaminants in drinking water sources and the potential of biochar for water quality improvement: A review. Crit. Rev. Environ. Sci. Technol. 2020, 50, 549–611. [Google Scholar] [CrossRef]
  229. Cao, L.; Iris, K.; Cho, D.-W.; Wang, D.; Tsang, D.C.; Zhang, S.; Ding, S.; Wang, L.; Ok, Y.S. Microwave-assisted low-temperature hydrothermal treatment of red seaweed (Gracilaria lemaneiformis) for production of levulinic acid and algae hydrochar. Bioresour. Technol. 2019, 273, 251–258. [Google Scholar] [CrossRef]
  230. Ahmad, M.; Lee, S.S.; Dou, X.; Mohan, D.; Sung, J.-K.; Yang, J.E.; Ok, Y.S. Effects of pyrolysis temperature on soybean stover-and peanut shell-derived biochar properties and tce adsorption in water. Bioresour. Technol. 2012, 118, 536–544. [Google Scholar] [CrossRef]
  231. Shimabuku, K.K.; Kearns, J.P.; Martinez, J.E.; Mahoney, R.B.; Moreno-Vasquez, L.; Summers, R.S. Biochar sorbents for sulfamethoxazole removal from surface water, stormwater, and wastewater effluent. Water Res. 2016, 96, 236–245. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  232. Rajapaksha, A.U.; Vithanage, M.; Ahmad, M.; Seo, D.C.; Cho, J.S.; Lee, S.E.; Lee, S.S.; Ok, Y.S. Enhanced sulfamethazine removal by steam-activated invasive plant-derived biochar. J. Hazard. Mater. 2015, 290, 43–50. [Google Scholar] [CrossRef] [PubMed]
  233. Choy, S.Y.; Prasad, K.N.; Wu, T.Y.; Raghunandan, M.E.; Ramanan, R.N. Performance of conventional starches as natural coagulants for turbidity removal. Ecol. Eng. 2016, 94, 352–364. [Google Scholar] [CrossRef]
  234. Zhou, N.; Chen, H.; Xi, J.; Yao, D.; Zhou, Z.; Tian, Y.; Lu, X. Biochars with excellent pb (ii) adsorption property produced from fresh and dehydrated banana peels via hydrothermal carbonization. Bioresour. Technol. 2017, 232, 204–210. [Google Scholar] [CrossRef] [PubMed]
  235. Son, E.-B.; Poo, K.-M.; Chang, J.-S.; Chae, K.-J. Heavy metal removal from aqueous solutions using engineered magnetic biochars derived from waste marine macro-algal biomass. Sci. Total Environ. 2018, 615, 161–168. [Google Scholar] [CrossRef]
  236. Liu, Q.; Wu, L.; Gorring, M.; Deng, Y. Aluminum-impregnated biochar for adsorption of arsenic (v) in urban stormwater runoff. J. Environ. Eng. 2019, 145, 4019008. [Google Scholar] [CrossRef]
  237. Gray, M. Black is green: Biochar for stormwater management. In Proceedings of the WEFTEC 2016, New Orleans, LO, USA, 24–28 September 2016. [Google Scholar]
Figure 1. Advantages of natural coagulants over chemical-based coagulants.
Figure 1. Advantages of natural coagulants over chemical-based coagulants.
Water 14 03751 g001
Figure 2. Sustainability criteria of natural coagulants.
Figure 2. Sustainability criteria of natural coagulants.
Water 14 03751 g002
Figure 3. Schematic representation of natural coagulants’ extraction process.
Figure 3. Schematic representation of natural coagulants’ extraction process.
Water 14 03751 g003
Figure 4. Schematic representation of the mechanisms involved in natural coagulation process.
Figure 4. Schematic representation of the mechanisms involved in natural coagulation process.
Water 14 03751 g004
Figure 5. Various constraints in commercialization of natural coagulants.
Figure 5. Various constraints in commercialization of natural coagulants.
Water 14 03751 g005
Table 1. Parameters to be considered while treating water.
Table 1. Parameters to be considered while treating water.
ParameterInstrument UsedUnits of MeasurementImportance
TurbidityTurbidimeterNTUMeasure of relative clarity of water.
pHpH meterH+ conc.Indicator of water quality& measure of acidity/basicity.
TemperatureThermometer°CImpacts both biological & chemical characteristics of water.
ConductivityConductivity meterSm−1Measure of water capability to pass electrical flow.
AlkalinityPotentiometerV m−1Measure of capacity of water to neutralize acids.
AciditypH meterH+ conc.Indicator of industrial pollution.
Total dissolved solidsConductivity meterSm−1Measure of combined organic & inorganic substances dissolved in water.
Total suspended solidsSuspended solids density metermgL−1Includes all particles suspended in water which won’t pass through a filter.
Total hardnessPotentiometermgL−1Measure of amount of dissolved Ca & Mg.
Ca hardnessPotentiometermgL−1Measure of amount of dissolved Ca.
Mg hardnessPotentiometermgL−1Measure of amount of dissolved Mg.
ChloridesPotentiometermgL−1Indicator of pollution in water.
SulphateSpectrophotometermgL−1Indicator of algal growth in water.
AmmoniaSpectrophotometermgL−1Indicator of fecal pollution.
NitrateSpectrophotometermgL−1Indicator of sewage pollution.
NitriteSpectrophotometermgL−1Indicator of contamination from fertilizer run off.
CalciumSpectrophotometermgL−1Measure of water hardness.
MagnesiumSpectrophotometermgL−1Measure of water hardness.
IronSpectrophotometermgL−1Excess level indicates presence of contaminants.
ManganeseSpectrophotometermgL−1Excess level results in undesirable taste.
FluorideSpectrophotometermgL−1Reduces tooth decay.
SodiumSpectrophotometermgL−1Maintains blood pressure & osmotic pressure.
PotassiumSpectrophotometermgL−1Maintains osmotic pressure.
Dissolved oxygenColorimetermgL−1Indicator of water quality.
Biological oxygen demand (BOD)BOD metermgL−1Measure of water quality. Higher BOD signifies lower water quality.
Chemical oxygen demand (COD)COD metermgL−1Measure of water & waste water quality.
PesticidesSpectrophotometermgL−1Indicator of water toxicity.
E. coliPaper strip methodper 100 mLIndicator of fecal contamination.
Fecal coliformPaper strip methodper 100 mLIndicator of fecal contamination.
VelocityCurrent meterms−1The speed at which water flows.
DetergentpH meterH+ conc.Results in algal blooms &depletes oxygen in water leading to water pollution.
Table 2. Plant-based natural coagulants used in the treatment of polluted water.
Table 2. Plant-based natural coagulants used in the treatment of polluted water.
CoagulantPart UsedState of CoagulantOpt. DosageRemoval Efficiency (%)References
M.oleifera Lam. (Drumstick)SeedsPowder0.2 gL−1Turbidity removal (61.60%); COD removal (65.00%)[122]
M.oleifera Lam. (Drumstick)SeedsDeoiled powder6000 mgL−1TSS removal (95%)[123]
M.oleifera Lam. (Drumstick)SeedsPowder500 mgL−1Turbidity removal (96.80%)[124]
M.oleifera Lam. (Drumstick)SeedsPowder0.6 gL−1Turbidity removal (82%), COD removal (83%)[125]
M. oleifera Lam. (Drumstick)SeedsStock solution0.3 mgL−1Cu and Cd removal (98%); Pb removal (78%)[126]
M.oleifera Lam.
(Drumstick) and alum
SeedsSolution70 and 80 mgL−1COD removal (50.41%); Turbidity removal (86.14%); TSS removal (81.52%)[127]
M.oleifera Lam.
(Drumstick) and alum
SeedsStock solution50 mgL−1
each
BOD removal (80.67%); COD removal (66.73%)[128]
M.oleifera Lam.
(Drumstick)
Cicer arietinum L. (Chickpea)
SeedsPowder50 mgL−1Turbidity removal M. oleifera (82.2%);
Chickpea (81.2%);
Cactus (78.54%)
[129]
M. oleifera Lam. (Drumstick)
and Musa acuminate L. (Banana
peel)
SeedsPowder200 and 400
mgL−1
Pb removal (81%); Ni removal (74%); Cd removal (97%)[12]
Malus sylvestris L.
(European crab apple) and aluminum sulphate
SeedsStock solution62.5 mgL−1Turbidity removal (66%)[130]
Cyamopsis tetragonoloba L. (Taub.) (Guar)GumPowder300 mgL−1Turbidity removal (67.82%)[130]
P.ovata (Psyllium) and
PAC
HuskPowder0.4 and 7.2 gL−1Color removal (90%); COD removal (96%)[131]
Parkia biglobosa Jacq. (Locust bean)GumPowder300 mgL−1Turbidity removal (67.82%)[130]
Ocimum basilicum L. (Basil plant)SeedsStock solution1.6 mgL−1Color removal (68.50%); COD removal (61.60%)[132]
Opuntia ficus Linn. (Miller) (Cactus)MucilagePowder150 mgL−1Turbidity removal (49.56%)[130]
Plantago major Linn. (Carls) (Broadleaf plantain)MucilagePowder297.6 mgL−1Color removal (92.4%); COD removal (81.60%)[133]
Hibiscus rosasinensis Linn.(Carls) (China rose) and alumSeedsPowder500 and 400 mgL−1Turbidity removal;
Hibiscus (60%);
Alum (100%)
[134]
Trigonella foenum L. (Fenugreek)SeedsPowder0.1 gL−1Turbidity removal (58%); COD removal (63%)[122]
Abelmoschus esculentus L. (Okra)MucilagePowder3.2 mgL−1Turbidity removal (97.24%); COD removal (85.69%)[135]
Abelmoschus esculentus L. (Okra) and Iron (III) chloride hexa hydrateMucilageStock solution2.5 mgL−1Turbidity removal (74%)[130]
Cicer arietinum L. (Chickpea)SeedsPowder2 gL−1TDS removal (82%); COD removal (84%); BOD removal (83%)[136]
Cicer arietinum L. (Chickpea)SeedsPowder0.1 gL−1Turbidity removal (78.33%); COD removal (83%)[122]
Dolichos lablab Linn (Hyacinth bean)FruitsPowder0.2 gL−1Turbidity removal (71.74%); COD removal (75%)[122]
Tamarindus indica L. (Tamarind)SeedPowder400 mgL−1Turbidity removal (97,72%)[137]
Hibiscus sabdariffa L. (Roselle)SeedPowder60 mgL−1Turbidity removal (87.18%)[138]
Opuntia indica L. (Mill.) (Cactus)MucilagePowder0.4 gL−1Turbidity removal (78.54%); COD removal (75%)[128]
Momordica charantia L. (Bitter gourd)SeedSolution400 ppmTurbidity removal (61.03%)[139]
Gossypium barbadense L. (Cotton)SeedOil30 mLL−1TSS removal (66.27%)[140]
Ricinus communis L. (Castor)SeedOil40 mLL−1TSS removal (66.67%)[136]
S.potatorum L. f.(Nirmali)SeedStock solution60 mLL−1BOD removal (65.23%), COD removal
(72.71%), Turbidity removal (75.20%)
[140]
Musa acuminate L. (Banana)PeelJuice90 mLL−1Turbidity removal (98.50%)[60]
Zea mays L. (Maize)SeedPowder30 gL−1COD removal (68.82%);
Color removal (47.03%)
[141]
Plantago ovata Forssk(Isabgol)SeedPowder1.5 mgL−1COD removal (89.30%)[142]
P.vulgaris Gustav Hauser (French bean)SeedPowder1.5 mgL−1Color removal (73%)[143]
Cassia fistula L. (Golden shower)SeedPowder0.5 gL−1Color removal (71.3%)[144]
Vitis vinifera L. (Grape vine)SeedPowder1.5 mgL−1Color removal (80%)[145]
Citrus sinensis L. (Osbeck) (Orange)PeelPowder0.2 gL−1Turbidity removal (97%)[146]
Artocarpus heterophyllus Lam. (Jackfruit)SeedPowder60 mgL−1Turbidity removal (43%)[147]
Jatropha curcas L. Britton and Mills.(Barbados nut) SeedPowder14 mgL−1Turbidity removal (93%)[148]
Strychnos potatorum L. f. (Nirmali)SeedPowder1.5 mgL−1Turbidity removal (90%)[149]
Carica papaya Linn. (Papaw)SeedPowder0.4 g per 200 mLTurbidity removal (90%)[150]
Julifora Prosopis var. juliflora (Sw.) DC (Mesquite bean)SeedPowder1.5 mgL−1Turbidity removal (96%)[151]
Acacia mearnsii De Wild. (Black wattle)BarkPowder14 mgL−1Turbidity removal (75%)[151]
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Koul, B.; Bhat, N.; Abubakar, M.; Mishra, M.; Arukha, A.P.; Yadav, D. Application of Natural Coagulants in Water Treatment: A Sustainable Alternative to Chemicals. Water 2022, 14, 3751. https://doi.org/10.3390/w14223751

AMA Style

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. 2022; 14(22):3751. https://doi.org/10.3390/w14223751

Chicago/Turabian Style

Koul, Bhupendra, Nargis Bhat, Mustapha Abubakar, Meerambika Mishra, Ananta Prasad Arukha, and Dhananjay Yadav. 2022. "Application of Natural Coagulants in Water Treatment: A Sustainable Alternative to Chemicals" Water 14, no. 22: 3751. https://doi.org/10.3390/w14223751

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop