We live on planet Earth, where more than 70% of its surface is covered with water, and the oceans occupy 97% of the Earth’s water (by volume). This leaves only 3% of the planet’s total freshwater. Regarding this fresh water, 65% is trapped in glaciers and in the ice caps of mountains, and 30.2% is groundwater, which is too costly to extract. As a result, only 1.3% of surface water of the volume available for human use of the total proportion of water on this planet remains [1,2]. Water is important in all domains of life (human, industrial, and agricultural), which are driven by socio-economic development and increasing population growth [3].

For this reason, there is a global concern about the possibility of obtaining clean and safe water [4], especially in arid and semi-arid developing countries where the provision of potable water is an enormous undertaking [5]. The quality of water and its treatment becomes a source of increasing concern, particularly where water quality is poor, as well as where proper treatment is lacking [6]. Furthermore, it has been estimated that the inefficiency of sanitation, polluted water, or lack of water is causing 80% of all diseases and sicknesses in the world [7]. These detrimental effects are more prominent especially in underdeveloped countries [8]. Nearly 90% of all diseases humans have are caused by microorganisms, which should motivate us to stop their activity [9]. Hence, the result of disease spread and increasing health problems of people leads to a high rate of early deaths correlated with the consumption of polluted water, which is considered an important issue worldwide [10]. In this century, achieving water recycling processes will be one of the main challenges to ensure a worldwide water supply [11]. This context allows for the development of scientific knowledge in the use of alternative coagulants. Three million people globally lack water and sanitation services, which has a negative impact on their quality of life and undermines their basic human rights. Consequently, the emergence of many diseases and the threat to health security place a heavy strain on economies [12]. Water is widely used in different sectors and especially in productive sectors such as urban supply, industry, livestock, and agricultural production, which has led to water overuse [13].

The protection of the environment from wastewater contaminants is very important [14]. Water and wastewater are contaminated with numerous colloidal solid particles that are difficult to settle, resulting in water turbidity and color change [15], which must be addressed using coagulants [16]. One of the biggest challenges in water treatment is removing hydrophobic colloids because they are typically present in high concentrations compared to other pollutants [17]. In this context, coagulation has been practiced since the earliest times in human history to reduce turbidity by removing these impurities [18] through sedimentation in both drinking water and wastewater treatment [19]. Thus lowering turbidity improves water quality [20,21]. The coagulants used in water treatment processes are classified as natural, inorganic, and synthetic organic polymers [16,22]. The use of natural coagulants has quite a long history [23]. Natural coagulants are plant-based and used to remove turbidity, and have been used by various civilizations and communities for at least 4000 years [24]. Recently, there has been increased interest in using natural coagulants [25], which are gaining interest in developing countries [26], for the treatment of water and wastewater [27]. This interest emerged due to the many problems created by using synthetic coagulants [28], such as their highcost and health-related issues [29]. Furthermore, environmental impacts are associated with inorganic/synthetic organic coagulants [30]. For example, aluminum sulfate, aluminum polychloride [31], and aluminum chloride [32] are among the most frequent inorganic coagulants used in the coagulation or flocculation processes. However, these have negative impacts on human health and the environment, as reported by Megersa et al. [21]. Moreover, it has been reported that alum produces a large volume of sludge [33]. In addition, its use reduces the pH of the treated water [34,35,36], it is not biodegradable [37], and it has a link to Alzheimer’s disease, as reported by Campbell et al. [38], Ribes et al. [39], Rondeau et al. [40], and Wang et al. [41]. Moreover, it possesses strong carcinogenic properties and is expensive [42].

The natural coagulation activity of seeds can be similar to or even better than alum [43]. Moreover, most people in rural communities tend to easily find available water sources, despite their low quality due to the high cost of treated water, and this exposes them to many waterborne diseases [29]. In the response to this problem, people have conducted this research on a natural coagulant that has the best properties, such as being low cost, effective, non-toxic, and having no significant effect on the pH of the water treated. Natural coagulants that are plant-based represent one renewable source in wastewater treatment because they have many positive properties such as being biodegradable, non-hazardous, widely available, and environmentally friendly [10].Their cost is low, a lesser quantity of sludge is produced after using them in water treatment [14], they have a wider effective dosage range in the flocculation process [10], and they are becoming increasingly more important in replacing chemical coagulants [24], as seen in most parts of India and some parts of Africa and China.They have been used in the treatment of water over the past 2000 years, and have been certified eco-friendly organic polymers of natural coagulants [23,44]. Moreover, these natural coagulants can be locally grown in developing countries because they are cost-effective [45]. Additionally, their production increases opportunities for employment by creating a new cash crop for farmers, especially in rural areas [46]. Basic coagulation mechanisms have been elucidated for Moringa Oleifera seeds by applying them in treating turbid water in 1995 [47]. Since then, there has been widespread interest in them [48], and arguably that the Moringa Oleifera tree is the most studied in the environmental scientific community as a natural coagulant [37]. Because the seeds of Moringa Oleifera contain a water-soluble cationic coagulant protein, they are used as a primary coagulant in drinking water clarification and wastewater treatment through their ability to reduce the turbidity of treated water [49]. These proteins are considered the most widely investigated plant-based coagulant [24,50,51,52], having been researched by several scholars [5].The seeds of Moringa Oleifera possess good coagulating properties comparable to commercial alum used in turbidity removal [53]. Their antimicrobial activity has also been studied in previous studies [6,53,54,55,56,57,58], as have their antifungal [59,60,61,62,63] and antiviral effects [53,54,55,56,57]. They also play a role as an antiparasitic, such as in Haemanthus contorts eggs [64,65]. To avoid defects associated with chemical and physical processes, such as high costs, the generation of toxic waste, and the use of toxic reagents in removing mineral contaminants of liquid waste, new methods have emerged [66] for removing heavy metals from wastewater [67], which has become a global concern for both the environment and human health [68]. The use of the seeds of Moringa Oleifera plays a role in the removal of pollution resulting from toxic metals (e.g., arsenic [69,70,71],copper, lead, cadmium, chromium [72], etc.).

3. Properties of Moringa Oleifera Seeds