Coagulants

Coagulants in Industrial Wastewater Treatment

Coagulants neutralize the electrical charge that keeps fine particles suspended in water, allowing them to come together. Most suspended solids in industrial wastewater carry a negative surface charge and repel each other. A coagulant eliminates that repulsion, producing small clumps called microflocs. Coagulation is almost always the first step in a two-step clarification process, followed by a flocculant to build those microflocs into larger, settleable masses.

The two main categories are inorganic salts — including alum, polyaluminum chloride (PAC), ferric chloride, and ferric sulfate — and organic (polymeric) coagulants. Inorganic options are lower cost and effective for phosphorus removal; organic coagulants generate significantly less sludge and are less pH-sensitive. The right choice depends on your wastewater chemistry, target effluent quality, and what you’re doing with the sludge.

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