Polymers are water-soluble chemicals used in water and wastewater treatment. They clump suspended solids, colloids, organic matter and impurities into larger particles that are easier to remove.

How It Works

Polymers are long chains of repeating monomers. Often used with inorganic coagulants (aluminium or iron salts), they work in two ways:

Charge neutralisation – cationic polymers offset the negative charge on particles so they can approach each other.
Bridging – high molecular weight chains attach to several particles at once, forming dense flocs that settle, float or filter easily.

Uses include clarification, sludge thickening and dewatering in drinking water plants, industrial effluent (mining, paper, textile, food) and sewage treatment.

Types of Polymers Used in Water Treatment

Type	Charge	Common examples	Typical uses
Cationic	Positive	Cationic polyacrylamide, polyDADMAC, polyamines	Sludge dewatering, biological effluent
Anionic	Negative	Anionic polyacrylamide	Mining, paper mills, municipal wastewater
Non-ionic	Neutral	Non-ionic PAM, polyethylene oxide	Specific suspended solids, retention aids
Natural / biopolymer	Varies	Starch, chitosan, alginate, guar gum	Eco-friendlier options
Amphoteric	Both	Mixed-charge polymers	Variable-charge waters

Benefits

Lower chemical doses and less sludge than inorganic coagulants alone
Stronger flocs, faster settling, clearer water
Less residual metal (e.g. aluminium) and lower ionic load
Better performance in cold, coloured or soft water
Can be tailored to specific contaminants

Limitations

Overdosing can re-stabilise particles instead of clearing water.
Synthetic polymers are generally not biodegradable and residual monomer is regulated.
Good results need proper dosing, mixing and jar testing.

Polymers are also used in membranes, adsorbent hydrogels and as scale inhibitors, but their core purpose is better solid–liquid separation.

Anionic polymersCationic polymersNon-ionic polymerswater treatment polymer