A review on common vegetables and legumes as promising plant-based natural coagulants in water clarification

Coagulation and flocculation provide a rather straightforward method towards water clarification. However, ongoing debates over worrying health issues linked to chemical coagulants have paved the way to develop plant-based natural coagulants. Natural coagulants are not only water clarifying agents, but they also have antimicrobial and heavy metal removal properties in some instances. These are highly attractive in the transformation of raw surface water into potable drinking water. A total of 14 plant-based natural coagulants categorized as common vegetables and legumes are identified and presented collectively in this comprehensive review. The two main coagulation mechanisms leading to the observed coagulation activities are postulated to be charge neutralization and bridging. Turbidity removal efficiencies were proven to be greatly affected by pH variations and the dosage of natural coagulants used. The existing research gaps are acknowledged in this work to provide a platform towards the necessity of further research in the water treatment processes.