Coagulation and flocculation are important phenomena that find widespread applications in water treatment. Polyelectrolytes are charged macromolecules that have found relevance in this domain due to their proven efficiency and effectiveness. The objective of the thesis would be to review and emphasize the fundamental mechanisms on which both natural and synthetic polyelectrolyte coagulants and flocculants operate. Advances in understanding phase characteristics and structure of aggregated polyelectrolyte complexes post interaction with charged impurities are discussed. These would help elucidate the correlation between salient polyelectrolyte properties such as molecular weight, persistence length, charge density, and aggregated complex properties such as turbidity and size. This review aims to provide relevant insights that enable better coagulants and flocculants for water treatment systems through examples to ultimately correlate several concepts and develop a collective understanding,