DRINKING WATER
PAC for Drinking Water: Which Grade, Which Standard, Which Documents
Drinking-water PAC is not industrial PAC in a white bag. The active chemistry is the same; the limits on arsenic, lead, cadmium, mercury and hexavalent chromium are not, and neither is the paperwork. If the treated water goes into a distribution network, the specification and the documents have to match the rules of that market.
Same molecule, different impurity envelope
Both grades are polyaluminium chloride and both coagulate by charge neutralisation and bridging. What separates them is what else is allowed to be in the bag.
| Item | Industrial grade | Drinking-water grade |
|---|---|---|
| Standard in China | GB/T 22627-2022 | GB 15892-2020 |
| Al2O3, solid | 28% | 29% |
| Water-insoluble matter, solid | up to 1.5% | 0.6% or lower |
| Heavy metals | limited suite | individual limits for As, Pb, Cd, Hg, Cr(VI) |
| Colour | yellow to light yellow | white to near-white in most grades |
| Typical use | industrial effluent, mining, paper, sludge conditioning | municipal supply, food and beverage process water |
Why the grade costs more
The price gap is not a marketing margin. It comes from five places in the plant:
- Raw material route - refined aluminium sources with low iron instead of lower-grade ore, which raises cost per tonne of Al2O3
- Cleaner campaigns - reactors and lines are cleaned between drinking-water batches, and the first cuts are not saleable
- Testing - the full heavy-metal suite on every batch, not a periodic check
- Yield - a tighter specification means more out-of-spec material and more rework
- Documentation - batch traceability that has to survive an audit years later
The standards you will be asked about
Every market regulates drinking-water chemicals, and the schemes are not interchangeable.
- China - GB 15892-2020 for coagulants used in drinking water, within the product hygiene licence regime administered by the health authority
- United States and Canada - NSF/ANSI 60, which covers toxicological review, formulation control and plant inspection
- European Union - EN 883 for polyaluminium chloride products, alongside the Drinking Water Directive 2020/2184 and national approval schemes such as Regulation 31 in the UK
- Gulf, Southeast Asia and Africa - national registration in most markets, frequently built on NSF/ANSI 60 or EN 883 test data
What can be papered, and what cannot
We hold the Chinese hygiene licence for products in contact with drinking water, and our drinking-water grade is released against GB 15892-2020 with a per-batch certificate of analysis that includes the heavy-metal suite. For a Chinese municipal project, that is the document set an inspector will ask for.
For markets that require NSF/ANSI 60 or EN 883, the position is different and worth stating plainly: the product can meet the technical specification, but certification is a separate process run by the scheme owner and cannot be replaced by a supplier declaration. Tell us the destination market and the scheme at enquiry stage, so the answer arrives before the container sails rather than after.
Residual aluminium: the number the regulator looks at
Aluminium is controlled as an operational parameter in most regulations. The EU Drinking Water Directive sets a parametric value of 0.2 mg/L; China's GB 5749-2022 uses 0.2 mg/L; the US EPA secondary standard sits in the 0.05 - 0.2 mg/L range. Well-run plants aim well below the limit, because aluminium carry-over also fouls membranes and shows up as post-precipitation in the network.
Three things drive residual aluminium: the pH at the point of coagulation, the dose, and the quality of solid-liquid separation. The window pH 6.5 - 7.5 keeps aluminium in the hydroxide form that settles; above 8.5 aluminate re-forms and passes into the filtrate; below 6 the aluminium stays soluble. If residual aluminium is high, check the pH profile across the plant before changing the coagulant.
A jar test a waterworks can defend in an audit
The protocol below is unremarkable on purpose. What makes it defensible is that every step is recorded.
- Collect raw water in a clean container and use it the same day; measure pH, turbidity, alkalinity, temperature and, where relevant, UV254 or colour
- Prepare six beakers and dose a range that brackets the expected value, for example 5, 10, 15, 20, 30 and 40 mg/L
- Flash mix at 200 - 300 rpm for 60 seconds, flocculate at 40 - 60 rpm for 15 minutes, settle for 20 - 30 minutes
- Measure supernatant turbidity, pH and dissolved aluminium; keep the raw water pH record
- Repeat the best two doses in triplicate - the difference between them is usually smaller than the analytical noise
- Start the plant at the bench dose rather than above it, and hold it for two to three days before adjusting
Buyer mistakes worth avoiding
- Buying industrial grade and relying on downstream treatment to make it acceptable
- Comparing only Al2O3 and ignoring insolubles, which load the filters and the sludge handling
- Asking for heavy metals once, at qualification, instead of per batch
- Storing powder in a damp plant store where it cakes before it is used
- Buying a year of stock to capture a price - shelf life and warehouse conditions usually cost more than the discount
- Accepting a supplier declaration as a substitute for the certification the local authority actually requires
Frequently asked questions
Can industrial grade PAC be used in an emergency?
No. Emergency operation changes the treatment train, not the impurity limits on the chemical. If drinking-water grade is unavailable, the correct action is to reduce output or find an approved alternative coagulant, and to inform the regulator.
Is a higher Al2O3 content required for drinking water?
Not in itself. Drinking-water grade is defined by its impurity limits and its release standard, not by a higher Al2O3 figure. What matters is that the batch is released against the potable-water standard.
Which documents should arrive with each shipment?
A batch certificate of analysis with the heavy-metal suite, the safety data sheet, the technical data sheet and the packing list. Third-party inspection reports can be added when the contract or the letter of credit requires them.
Why does residual aluminium rise when the dose is correct?
Usually pH. Above 8.5 aluminate forms and passes the filters; below 6 the aluminium stays soluble. Check the pH after coagulation and before filtration before assuming the coagulant is at fault.