Advances in the quest for substitute for synthetic organic polyelectrolytes as coagulant aid in water and wastewater treatment operations

•The use of synthetic polyelectrolytes are synonymous with retinue of challenges.•Natural materials are studied as substitutes CA for synthetic polyelectrolytes.•Inadequate systematic scientific probe has limited the use of CA.•Improved scientific probe would promote the use non-conventional CA in CF process.

In order to optimize the performance efficiency and reduce the process economy of coagulation-flocculation (CF) based water treatment operations, coagulant aids (CA) are used as an auxiliary to the primary coagulant. Synthetic polyelectrolytes are widely used as CA but the use are synonymous with negative human and environmental challenges. As an antidote to the challenges associated with the use of synthetic polyelectrolytes, natural and eco-friendly materials have been studied as substitutes for the synthetic polyelectrolytes. At present, a comprehensive review on the efforts that have been made in the quest for substitutes for synthetic polyelectrolytes has been conducted. The justifications for the choice of the materials, the operational performance efficiency, the operational shortcomings and the underlying reaction mechanism of the process were expounded. The prospects and the limitations of the advances made in the quest for substitutes for the synthetic polyelectrolytes were also highlighted