Polyaluminium Chloride – DESCRIPTION
Polyaluminium Chloride (PAC) is used as a flocculent in water treatment applications including drinking water and wastewater treatment. PAC can perform over a wide pH range (5.0 – 8.0) but is most effective when the pH is close to 7.0, this can be achieved with the use of Soda Ash (Sodium Carbonate) or Sodium Bicarbonate. The flocculant produced from the PAC gradually settles (2-12 hr) to the bottom (depending on amount of PAC used and water volume), after which it can be removed by filtration.
Advantages compared to other coagulants like Alum
- Effective over a broader pH range compared to alum
- Reduced chemical costs – can perform just as effectively, even when at a lower dose compared to alum (at a higher dose)
- Low levels of residual aluminium in the treated water can be achieved, typically around 0.01 to 0.05 ppm.
- PAC works well at low water temperatures – flocs formed from PAC tend to settle equally well at low and normal water temperatures compared to Alum (aluminium sulphate) flocs that settle slowly at lower temperatures.
- Lower sludge production – low amount of sludge is produced compared to alum at an equivalent dose
- Improved treated water quality – increase in chloride from PAC in is lower than the increase in sulphate from Alum in the treated water i.e. lower overall water TDS.