pH and polymer performance
How pH affects your coagulant and your flocculant, and what the Sunfloc specification sheets say about pH.
A tenfold scale
Each whole pH unit is a tenfold change in acidity. Small pH moves are bigger chemical changes than they look, so correct pH in steps.
Coagulants have windows
Alum works best around pH 6.5 to 7.5; PAC tolerates roughly 5 to 9. Outside its window a coagulant leaves fines behind, and no polymer dose can fully make up for it.
What the Sunfloc sheets say
A 5 g/L solution of Anionic HQ reads pH 5.0–8.0; Cationic HQ reads 2.5–4.5. Cationic MQ lists a working range of pH 4–9.
Check pH first
When flocs suddenly go small, check pH at the coagulant dosing point before changing polymer grade or dose.
Correction chemicals
Lime or caustic soda raise pH; acids lower it. Dose them ahead of the coagulant, not after the polymer.
Related
Polyelectrolyte dosing guide
Starting doses, solution strength and how to work out kilograms per day.
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