The potential and constraints of replacing conventional chemical coagulants with natural plant extracts in water and wastewater treatment

• Published in: Environmental Advances
• Main Authors: Denzil Diver, Innocent Nhapi, Walter Rutendo Ruziwa
• Format: Article
• Language: English
• Published: Elsevier 2023-10-01
• Subjects: Chemical coagulant; Coagulation; Natural coagulant; Turbidity; Water quality; Water treatment
• Online Access: http://www.sciencedirect.com/science/article/pii/S2666765723000790

Coagulation is a vital stage in treating contaminated water using coagulants that can be either synthetic or natural. Currently, water is being treated by water treatment plants that use aluminum- or iron-based salts and synthetic polymers for coagulation. However, these synthetic coagulants have flaws, including the production of large amounts of chemical sludge, considerable effects on the pH of the purified water, relatively expensive to use, and potentially toxic effects on the environment. The potential and constraints of replacing chemical coagulants with natural plant extracts for water treatment are reviewed in this paper. Various natural coagulants previously investigated for the removal of heavy metals, turbidity, pathogens, and other contaminants from surface and synthetic water were analyzed based on dosage rates, active ingredients responsible for coagulation, and extraction methods among other criteria. A comparative analysis was performed in studies in which both conventional chemical coagulants and natural plant extracts were used for water treatment. Various studies have shown that it is possible to replace chemical coagulants with plant-based extracts. It has been demonstrated that it is possible to replace chemical coagulants with natural plant-based extracts because seed extracts such as those of fenugreek can achieve turbidity removal efficiencies as high as 98% as compared to 85% for alum. The use of natural coagulants may be beneficial for water treatment plants because they may produce less sludge than chemical coagulants; this increases environmental sustainability while decreasing the cost of handling sludge. They are less toxic than chemical coagulants and do not pose any adverse threats to the environment; therefore, they are a safer alternative. However, studies are needed on how these plant-based coagulants can be commercialized in the same way that chemical coagulants are readily available.