Jar test seasonally
Source water changes through the year. A dose optimised in winter is rarely optimal in summer.
Application — potable water
PAC for drinking water treatment
Polyaluminium chloride is the coagulant of choice for potable water clarification across the region — wider effective pH range, lower alkalinity consumption, and lower residual aluminium than alum when it is dosed correctly.
What PAC does in a potable water plant
Raw surface and brackish water carries colloidal clay, silt, natural organic matter and colour-causing compounds. These particles carry a negative surface charge that keeps them dispersed indefinitely — they will not settle out in a clarifier on their own.
PAC introduces pre-hydrolysed, positively charged aluminium species that neutralise that charge almost instantly. The destabilised particles collide and aggregate into floc, which the clarifier settles and the filters polish. Because the aluminium species are already partly hydrolysed before they enter the water, PAC works faster and across a wider pH band than alum, which has to hydrolyse in situ.
The practical result at plant level is fewer pH excursions, less lime or soda ash needed to hold alkalinity, denser floc that settles faster, and better filter run times.
Typical dose guidance by raw water condition
| Raw water condition | Typical PAC dose (as product) | Notes |
|---|---|---|
| Low turbidity (< 10 NTU) | 3–10 mg/L | Higher basicity grades perform better; watch for pin floc |
| Moderate turbidity (10–50 NTU) | 10–25 mg/L | The most common operating band for regional surface water |
| High turbidity (50–500 NTU) | 25–60 mg/L | Lower basicity often more effective; consider polymer aid |
| High colour / high organics | 20–50 mg/L | Organic removal usually needs a higher dose than turbidity alone |
| Cold or low-alkalinity water | 10–30 mg/L | PAC's main advantage over alum shows here |
These are indicative ranges to frame a jar test programme — they are not a dosing recommendation. Optimum dose must be determined on your actual raw water by your plant team or consultant, and re-checked when source water quality changes seasonally.
Operating notes
Getting potable dosing right
Watch residual aluminium
Over-dosing raises residual Al in treated water. Most standards set a limit around 0.2 mg/L — check your local requirement.
Rapid mix matters
PAC acts in seconds. If your flash mix energy or contact time is inadequate, you will over-dose to compensate.
Monitor pH
PAC depresses pH less than alum, but it still does. Higher basicity grades depress it less.
Certification first
Confirm the drinking-water certification your authority requires — NSF/ANSI 60 or equivalent — before ordering.
Keep the CoA on file
Regulators and auditors ask for batch documentation on potable supply. Keep every CoA.
FAQ
Common questions
PAC is used in potable water treatment worldwide, provided the grade meets the drinking-water standard required in your jurisdiction — commonly NSF/ANSI 60 certification or a recognised national equivalent. Confirm the requirement with your authority or consultant before ordering.
Typically 3 to 60 mg/L as product, depending entirely on raw water turbidity, organic load and temperature. The only reliable way to set your dose is a jar test on your actual water.
Correctly dosed, residual aluminium stays well within typical limits. Over-dosing, poor pH control or inadequate rapid mixing are the usual causes of elevated residual aluminium.
In most regional conditions, yes — wider effective pH range, far lower alkalinity consumption, denser floc and lower sludge volume. Alum can still be competitive on cost for some high-turbidity waters.
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