APPLICATIONS
Water treatment applications
Coagulation and flocculation behave differently in each industry, because the particles, the pH and the operating pattern are different. These notes describe what usually works and where it usually goes wrong.
Municipal water & sewage
Coagulation and flocculation for raw water clarification and for tertiary treatment of municipal sewage.
Typical starting point: PAC 10–30 mg/L for raw water, with 0.2–0.5 mg/L anionic PAM as a settling aid where flocs are small. Confirm both with a jar test, because alkalinity and temperature move the optimum more than turbidity does.
Industrial wastewater
Colour, turbidity and suspended solids removal in mixed industrial effluent, including parks with multiple discharge sources.
Mixed effluent is the hardest case: the stream changes during the day, so dosing has to follow the load. PAC at 30–50 mg/L with a cationic PAM is a common starting point for colour and turbidity, but only if the pH is held steady first.
Mining & tailings
Anionic PAM for tailings thickening and supernatant clarity; PAC ahead of it to destabilise fine clay.
Tailings thickeners usually run anionic PAM at 20–80 g per tonne of feed solids, dosed into the feed well with dilution water. Overdosing blinds the filter and raises the cost without improving underflow density.
Paper & pulp
Retention and drainage aids, plus white water clarification and sludge conditioning.
Retention aids and white water clarification use lower molecular weight cationic grades; sludge conditioning uses higher charge density. Test both, because the same mill can need two different products.
Textile & dyeing
Decolourisation of dyeing effluent, where cationic PAM is often used together with PAC.
Dyeing effluent responds to a combination: PAC or ferric coagulant first at pH 6–8, then cationic PAM. Reactive dyes need more coagulant than disperse dyes, so batch type matters more than colour intensity.
Oil & gas
Produced water treatment and drilling wastewater clarification.
Produced water carries oil, solids and salinity. Demulsification comes first, then PAC and a cationic polymer for the remaining suspended solids.
Food & beverage
Clarification of process water and wash water, and dewatering of organic sludge.
Organic sludge dewaters best with cationic PAM at 1–5 kg per tonne of dry solids. Food plant sludge varies by season, so the dose should be re-tested when the product mix changes.
Lithium & photovoltaic
Two-stage fluoride removal for battery, PV and semiconductor wastewater.
Fluoride is removed in two stages: pH adjusted to 5.5–6.5, defluoridation reagent under rapid mixing, then PAC to capture the fine crystals and anionic PAM to settle them. See the defluoridation page for the sequence.