PolyDADMAC (polydiallyldimethylammonium chloride) can function both as a coagulant and flocculant in water treatment processes.

Coagulation:

 In this stage of water treatment, PolyDADMAC acts by neutralizing the negative charges on suspended particles, such as clay, silt, organic matter, and colloids. The positive charge on PolyDADMAC molecules allows them to destabilize these particles, causing them to aggregate together, which is an essential step towards forming larger flocs.

Flocculation:

After coagulation, PolyDADMAC continues to play a role in the flocculation process where it bridges between the aggregated particles to form large, dense, and easily removable flocs. These flocs settle out of suspension or are removed through filtration, thereby clarifying the water.

In essence, while the terms "coagulant" and "flocculant" describe different stages of the process, PolyDADMAC is often used to perform both functions due to its cationic nature and high molecular weight, making it effective at both particle destabilization and aggregation into larger structures.