Polyaluminum chloride (PAC, also written polyaluminium chloride; CAS 1327-41-9) is a prehydrolyzed basic aluminum chloride coagulant, supplied for water treatment mainly as a liquid with at least 10 % Al2O3 and a basicity of about 50 %. Because part of the aluminum arrives already neutralized, PAC consumes less alkalinity than alum, which raises the question of where and at what dose plants use it.
Drinking-water plants dose 5 to 100 mg/L (ppm) as product (Australian Drinking Water Guidelines, NHMRC), and 250 mg/L as product is the most common NSF/ANSI/CAN 60 maximum use level (NSF listings, 2026-10-21). PAC is one of the coagulants in this reference of water treatment chemicals, each documented with the same identity, dose and compliance fields.
Three values decide most PAC programs: the dose basis (1 mg/L of a 10 % Al2O3 product is about 0.053 mg/L as Al), the coagulation pH (6.3 to 7.3 by water temperature) and the residual aluminum limit (0.05 to 2.9 mg/L by jurisdiction).
The identity card below summarizes the attributes that define PAC.
| Attribute | Value |
|---|---|
| Name | Polyaluminum chloride |
| Abbreviations | PAC, PACl |
| Synonyms | poly aluminum chloride, basic aluminum chloride, aluminum chloride hydroxide, aluminum hydroxychloride, PolyAC |
| CAS number | 1327-41-9 (shared in trade with aluminum chlorohydrate) |
| EC number | 215-477-2 |
| Formula | [Al(OH)aClb(SO4)c]n with a + b + 2c = 3 and a > 1.05 (Water New Zealand); example Al2(OH)3Cl3 (ADWG) |
| Class | Prehydrolyzed basic aluminum chloride |
| Function | Coagulant |
| Typical liquid | ≥ 10 % Al2O3, about 50 % basicity |
| NSF/ANSI/CAN 60 | Product-specific MUL; 250 mg/L as product on about 96 % of rows (NSF listings, 2026-10-21) |
| AWWA standard | ANSI/AWWA B408-25 |
| EN standard | EN 17034:2018 |
| GHS | Notified (ECHA C&L): H318, H290; no CLP Annex VI entry; product-specific, see supplier SDS |
Every value on this page is checked against primary sources (NSF listings, AWWA, CEN, EPA, Health Canada, WHO); see our methodology and fact-checking process.
What Is Polyaluminum Chloride (PAC)?#
PAC is a family of partly neutralized aluminum chlorides whose basicity (the molar ratio OH/(3 Al) x 100) sits between alum at 0 % and aluminum chlorohydrate at 83 %. The formula Al2(OH)3Cl3 is exactly 50 % basic, the value the Australian Drinking Water Guidelines give for medium-basicity liquid PAC.
Water New Zealand's supply standard (2nd edition, 2013) keeps water-treatment PAC generally at or below 60 % basicity. Sulfated PAC (PACS, CAS 39290-78-3) carries its own NSF/ANSI/CAN 60 listings.
The letters PAC also stand for powdered activated carbon, an adsorbent certified under NSF/ANSI/CAN 61 rather than 60 and covered on the powdered activated carbon (PAC) page.
The table below compares PAC forms, grades and physical properties.
| Form, grade or property | Strength or value | Basicity | Source |
|---|---|---|---|
| Liquid, medium basicity | ≥ 10 % Al2O3 | About 50 %; generally ≤ 60 % for water treatment | ADWG; Water New Zealand 2013 |
| Liquid PAC 10 / 14 / 18 (India) | 10.0 ± 0.5 % (MB) or 10.5 ± 0.3 % (HB); 13.5 ± 0.5 %; 17.5 ± 1.0 % Al2O3 | MB 40 ± 5 % (PAC 18: 45 ± 5 %); HB ≥ 64 % | IS 15573:2018, via GACL datasheet |
| Powder | ≥ 30 % Al2O3 (14 % Al); PAC 30: 29.0 ± 1.0 % Al2O3 | MB 40 ± 5 %; HB ≥ 64 % | Water New Zealand; GACL |
| Sulfated PAC (PACS) | Grade-specific | n/a | EN 17034:2018 scope; NSF MUL most common 200 mg/L, range 50 to 462 mg/L (NSF listings, 2026-10-21) |
| Appearance | Colorless to pale yellow liquid; white to pale yellow powder | n/a | ADWG |
| Specific gravity, liquid | 1.18 to 1.22 at 20 °C (68 °F) for 10 % Al2O3; 1.32 to 1.37 at 25 °C (77 °F) for 13.5 to 17.5 % Al2O3 | n/a | ADWG; GACL |
| pH as supplied | 2.2 to 2.8 | n/a | ADWG |
| Precipitated material | ≤ 0.2 % | n/a | Water New Zealand |
Liquid or powder: which PAC form is used where?#
Liquid PAC (about 10 to 18 % Al2O3) is dosed directly from bulk storage, while PAC powder carries about 30 % Al2O3, three times the aluminum per kilogram of a 10 % liquid (calculated), and ships in 25 or 50 kg bags. The powder (bulk density about 0.77 t/m³, Water New Zealand) is made down into a solution on site before dosing.
How Does Polyaluminum Chloride Work in Coagulation?#
PAC coagulates by delivering preformed polynuclear aluminum cations, such as the Al13 Keggin ion, that neutralize colloid charge and form electrostatic patches before hydrolyzing to aluminum hydroxide floc. PAC releases less acid on hydrolysis than alum, and Water New Zealand notes that it forms larger floc faster.
Coagulation by PAC precedes flocculation by the polymers fed after it, which bridge the destabilized particles. Rapid mix, floc growth and separation are explained under coagulation and flocculation in water treatment.
Why does PAC consume less alkalinity than alum?#
PAC consumes less alkalinity than alum because about half of its aluminum is already bound to hydroxide: a 50 % basicity PAC uses about 2.8 mg/L as CaCO3 per mg/L Al, against 5.56 for alum (first-order estimate). Per mg/L of a 10 % Al2O3 product, that is about 0.15 mg/L as CaCO3 (calculated).
Health Canada's 2021 aluminum guideline ranks 7 coagulants in 5 steps from least to most alkalinity consumed, as listed below.
- Aluminum chlorohydrate (ACH) and polyaluminum silica sulfate.
- Polyaluminum chloride (PACl).
- Polyaluminum sulfate.
- Alum and ferric sulfate.
- Ferric chloride.
The alkalinity of water at the intake decides whether this saving matters. P and M alkalinity are measured as set out under alkalinity of water.
Where Is PAC Used? Drinking Water, Municipal and Industrial Wastewater#
PAC is used in 3 water systems: drinking-water clarification, municipal wastewater treatment for phosphorus and solids, and industrial wastewater such as textile, paper and oily effluents.
The table below compares PAC use by system, with dose basis, feed point, control and target.
| System | Dose (basis) | Feed point | Control | Target or note | Source |
|---|---|---|---|---|---|
| Drinking water | 5 to 100 mg/L as product (10 % Al2O3) | Rapid mix; diaphragm pumps with dilution water | Jar test, coagulation pH, turbidity, residual Al | pH 6.8 to 7.3 cold water, 6.3 to 6.8 warm water | ADWG; Water New Zealand; Health Canada |
| Municipal wastewater | Jar test; stoichiometric 0.87 mg Al per mg P | Program-specific | Total phosphorus, turbidity | Permit phosphorus limit | WaterWorld (supplier-authored); Ten States wastewater, 2014 edition |
| Industrial wastewater | Jar test; one study 24 mg/L PAC + 1.5 mg/L anionic polymer | Program-specific | Color, oil and grease | Color coagulation at pH 4.5 to 5.5 | GACL; LAPSE 2019; Veolia |
Drinking water: clarification and enhanced coagulation#
Drinking-water plants dose PAC at 5 to 100 mg/L (ppm) as product (10 % Al2O3), about 0.5 to 10 mg/L as Al2O3 or 0.26 to 5.3 mg/L as Al (calculated), at the rapid mix, according to the Australian Drinking Water Guidelines. Health Canada places the PAC optimum at pH 6.8 to 7.3 in cold water and 6.3 to 6.8 in warm water.
40 CFR 141.2 defines enhanced coagulation as adding sufficient coagulant for improved removal of disinfection byproduct precursors, and 40 CFR 141.135 sets the TOC removal steps. Step 1 removal and Step 2 pH targets are tabulated under enhanced coagulation and TOC removal.
Is PAC better than alum in cold water?#
PAC often performs better than alum in cold water, which is why one utility switches to PAC below 12 °C (54 °F) and back to alum above it. Water at 0 °C (32 °F) is twice as viscous as at 25 °C (77 °F), and the optimum pH of aluminum coagulants falls about 0.4 units from 2 to 20 °C (35.6 to 68 °F) (Irish EPA, citing Pontius 1990). A jar test at the actual water temperature decides the switch point.
Municipal wastewater: chemical phosphorus removal and clarification#
PAC removes phosphorus from municipal wastewater by precipitating aluminum phosphate, with a stoichiometric need of 0.87 mg Al per mg P (1:1 molar, a supplier-authored WaterWorld figure), about 16 mg/L of 10 % Al2O3 product per mg/L P (calculated).
The Recommended Standards for Wastewater Facilities (Ten States Standards, 2014 edition) size the dose for stoichiometry plus competing reactions and mixing losses, avoid excess and set it by jar or pilot test. Aluminum, iron and lime programs are compared under chemical phosphorus removal from wastewater.
Industrial wastewater: color, paper and oily effluents#
Industrial plants use PAC to clarify textile, paper and oily effluents; color coagulation with aluminum salts normally runs at pH 4.5 to 5.5 (Veolia water handbook, a general figure for aluminum and iron salts).
In one study, 24 mg/L of PAC plus 1.5 mg/L of anionic polymer removed 99 % of oil and grease (LAPSE 2019); a single-study result can transfer to a plant only after a jar test on the actual effluent.
Industrial wastewater programs differ by effluent. Coagulants by industry are listed under industrial wastewater treatment chemicals.
How Is the PAC Dose Calculated and Fed?#
The daily PAC feed equals dose x flow: 30 mg/L as product at 10 MGD (37,854 m³/d) is 2,502 lb/day (1,136 kg/d), about 946 L/d (250 gal/d) of a 10 % Al2O3 liquid at specific gravity 1.20. The formulas are lb/day = mg/L x MGD x 8.34 / purity (Florida DEP) and kg/d = mg/L x m³/d / 1,000 (EOCP), with a purity of 1 for a dose as product.
The worked example below labels every input; all results are calculated.
| Worked example | Metric | US customary |
|---|---|---|
| Input: dose, as product (10 % Al2O3) | 30 mg/L | 30 ppm |
| Input: flow | 37,854 m³/d | 10 MGD |
| Input: purity in formula (dose as product) | 1 | 1 |
| Input: specific gravity of liquid | 1.20 | 1.20 |
| Result: product feed | 1,136 kg/d | 2,502 lb/day |
| Result: liquid volume | 946 L/d | 250 gal/d |
| Result: feed as Al2O3 | 114 kg/d | 250 lb/day |
| Result: feed as Al | 60 kg/d | 132 lb/day |
How do you convert a PAC dose between product, Al2O3 and Al?#
Multiply a PAC dose as product by the Al2O3 fraction for the dose as Al2O3, and by a further 0.529 (53.96 / 101.96) for the dose as Al: 1 mg/L of a 10 % product is 0.10 mg/L as Al2O3 and about 0.053 mg/L as Al.
An 18 % Al2O3 grade needs about 56 % of the product mass of a 10 % grade for the same Al2O3 dose (calculated), so jar results transfer between products only on an Al2O3 or Al basis, and the feed rate follows from the converted dosage. The dosage and feed rate calculator converts any dose and flow.
Which feed equipment and dilution does PAC dosing use?#
PAC is fed by diaphragm metering pumps into the rapid mix, usually with dilution water added after the pump (Water New Zealand).
Feeders operate down to 20 % of their maximum feed rate, or 10 % with two independent adjustments (Recommended Standards for Water Works, 2022 edition, 5.3 g).
The wetted parts of PAC dosing pumps use FRP, polyethylene, polypropylene or 316 stainless steel (ADWG). Pump types are compared under chemical dosing pumps.
How Is PAC Coagulation Controlled? pH, Turbidity and Residual Aluminum#
Plants control PAC coagulation with 5 measurements: jar tests, coagulation pH, settled and filtered turbidity, residual aluminum and streaming current or zeta potential. Coagulation pH is corrected with acid or alkali, never by overdosing coagulant, which raises dissolved residual metal (Irish EPA).
The 5 measurements and what each shows are listed below.
- Jar tests set the dose and the pH window.
- Coagulation pH sits at 6.3 to 7.3 for PAC, depending on temperature (Health Canada).
- Filtered turbidity stays at or below 0.3 NTU in at least 95 % of monthly combined filter effluent measurements, never above 1 NTU (40 CFR 141.173).
- Residual aluminum, total and dissolved, is monitored daily (Health Canada).
- Streaming current or zeta potential tracks charge: zeta slightly negative is normal, positive suggests overfeed, and a streaming current near zero means neutralized charge.
Turbidity in water leaving the filters is the end result. NTU and FNU are explained under turbidity in water.
How do plants keep residual aluminum low with PAC?#
Plants keep residual aluminum low by holding coagulation pH at 6.8 to 7.3 in cold water and 6.3 to 6.8 in warm water (Health Canada, 2021) and moving it with the seasons. In Health Canada's 10 case studies (2014 to 2017), residuals rose from below 0.05 mg/L to about 0.3 mg/L (acidic water at or below 5 °C (41 °F)) or 0.4 mg/L (alkaline water at or above 15 °C (59 °F)) without seasonal pH adjustment, and stayed below 0.06 mg/L with it.
Health Canada, citing Kimura et al. (2013), adds that basicity above 70 % keeps residual aluminum low in alkaline water, and recommends a filter-effluent turbidity goal of 0.1 NTU.
How is PAC dosed in a jar test?#
A jar test doses neat PAC with a micropipette: 10 mg/L as product in a 2 L jar needs 16.7 µL of a liquid at specific gravity 1.20 (worked example, calculated). The formula is µL = mg/L x jar liters / SG (USALCO). Mixing speeds and reading the jars follow the jar test procedure.
What Is PAC Compatible With? Polymers, Alkalis and Metals#
PAC is compatible with the flocculants (such as polyacrylamide) and pH chemicals fed beside it, but it reacts exothermically with concentrated bases and releases hydrogen with active metals.
The 3 interaction groups are listed below.
- Flocculant polymers: anionic polyacrylamide (PAM) fed after PAC builds the floc.
- Alkalis and acids: lime, caustic soda, soda ash and sulfuric acid adjust pH from separate feed points.
- Metals: PAC corrodes most metals, including ordinary stainless steel; 316 stainless steel is the exception (ADWG).
Which Standards Cover Polyaluminum Chloride? NSF/ANSI/CAN 60, AWWA B408 and EN 17034#
Three documents govern PAC for drinking water: NSF/ANSI/CAN 60 for health effects, ANSI/AWWA B408-25 for liquid product quality in North America and EN 17034:2018 in Europe.
The table below compares 6 documents by scope, edition and key requirement.
| Document | Scope | Edition or status | Key requirement for PAC |
|---|---|---|---|
| NSF/ANSI/CAN 60 | Direct drinking-water additives, health effects | Listings read 2026-10-21 | Product-specific MUL as product: 250 mg/L most common, range 22 to 625 mg/L; condition [AL]: aluminum in finished water ≤ 2 mg/L |
| ANSI/AWWA B408-25 | Liquid PAC for potable water, wastewater and reclaimed water | Current; replaces B408-18 | Minimum physical, chemical, sampling, testing, packaging and shipping requirements |
| EN 17034:2018 | Anhydrous aluminum chloride, basic aluminum chloride (PACl), ACH and PACS | Current; supersedes EN 881:2004 and EN 883:2004 (withdrawn) | European product standard; see EN standards for drinking water treatment chemicals |
| EN 1302:2024 | Aluminum-based coagulants | Current | Analytical methods |
| Water New Zealand PAC standard | Supply of PAC for water treatment | 2nd edition, 2013 | Specific impurity limit SIL (mg/kg) = MAV (mg/L) x 10^6 / (MD (mg/L) x SF), SF ≤ 10 |
| IS 15573:2018 | Polyaluminum chloride, India | BIS first revision, 2018-02-26 | Liquid PAC 10, 14 and 18 and powder PAC 30 grades |
What is the NSF/ANSI/CAN 60 maximum use level for PAC?#
No single NSF/ANSI/CAN 60 limit exists for PAC: maximum use levels are product-specific, and 250 mg/L as product appears on about 96 % of listing rows, within a range of 22 to 625 mg/L (NSF listings, 2026-10-21). Kemira PAX-18 is listed at 200 mg/L and Kemira PAX-XL1935 at 625 mg/L. MULs and the [AL] condition are covered under NSF/ANSI/CAN 60 certification.
The binding figure is the label MUL of the purchased product from its facility, summed over all feed points; certification ends when a product is repackaged, diluted or blended after leaving the certified facility.
The PAC listings cover 172 companies, 3,591 products (company plus trade designation), 10,942 product-function rows and 404 facility entries (NSF listings, 2026-10-21). 49 US states require NSF/ANSI/CAN 60 through legislation, regulations or policies (NSF survey of ASDWA members).
What do AWWA B408-25 and EN 17034:2018 specify?#
ANSI/AWWA B408-25 sets the minimum physical, chemical, sampling, testing, packaging and shipping requirements for liquid PAC in potable water, wastewater and reclaimed water, replacing B408-18.
AWWA has no separate ACH standard, so ACH is supplied against B408 (a 2023 City of Mansfield, Texas, bid cited B408-18). B408 sits with B403 and B407 in the coagulation group of the AWWA B-series standards.
EN 17034:2018 covers anhydrous and basic aluminum chloride, ACH and PACS, superseding the withdrawn EN 881:2004 and EN 883:2004; EN 1302:2024 gives the analytical methods.
What Is the Regulatory Status of PAC in Drinking Water Treatment?#
PAC is not a pesticide under FIFRA, not a biocide under the EU Biocidal Products Regulation and not listed in 21 CFR 173.310; what regulates it in drinking water is the aluminum it leaves behind and NSF/ANSI/CAN 60 certification (status 2026-10-20).
The aluminum values differ by type, and PAC is not listed under EPA RMP or OSHA PSM. Coagulation beside disinfection is shown under drinking water treatment chemicals.
The table below compares the aluminum values and listings that apply to PAC, with their type (status 2026-10-20).
| Instrument | Value | Type | Reference |
|---|---|---|---|
| NSF/ANSI/CAN 60 [AL] | Aluminum in finished water ≤ 2 mg/L | Certification condition | NSF listings |
| US secondary standard | Aluminum 0.05 to 0.2 mg/L | SMCL, non-enforceable | 40 CFR 143.3 under the Safe Drinking Water Act |
| European Union | Aluminum 200 µg/L; treatment chemicals under Article 12 | Indicator parameter | Annex I Part C of the EU Drinking Water Directive 2020/2184 |
| Health Canada (March 2021) | MAC 2.9 mg/L total aluminum; operational guidance value 0.100 mg/L (locational running annual average) | Guideline | Guidelines for Canadian Drinking Water Quality |
| WHO (2010) | No guideline value; health-based value 0.9 mg/L; practicable levels ≤ 0.1 mg/L (large plants) and ≤ 0.2 mg/L (small facilities) | Guidance | WHO/HSE/WSH/10.01/13, see WHO guidelines for drinking-water quality |
| FIFRA / EU BPR | Not a pesticide / not a biocide | n/a | Product status |
| 21 CFR 173.310 | Not listed in 21 CFR 173.310 | n/a | eCFR, current to 2026-10-16 |
| EPA RMP / OSHA PSM | Not listed | n/a | 40 CFR 68.130; 29 CFR 1910.119 App. A; see EPA RMP and OSHA PSM |
| OSHA / NIOSH | No PEL; REL TWA 2 mg/m³ as Al (soluble salts); IDLH not determined | Workplace | NIOSH Pocket Guide |
Is the 2 mg/L aluminum limit an EPA MCL?#
No: the 2 mg/L figure is a condition printed on NSF/ANSI/CAN 60 listings for aluminum coagulants, not an EPA maximum contaminant level; the only federal aluminum value is the non-enforceable secondary standard of 0.05 to 0.2 mg/L in 40 CFR 143.3. In Canada, the 0.100 mg/L operational guidance value is likewise not the MAC, which is 2.9 mg/L.
How Should PAC Be Handled and Stored Safely?#
PAC is an acidic liquid (pH 2.2 to 2.8 as supplied) that corrodes most metals, including ordinary stainless steel, so plants store it in fiberglass, polyethylene or polypropylene tanks, with 316 stainless steel as the metal exception (ADWG). GACL ships it in rubber-lined tankers and HDPE containers.
ECHA lists no harmonized (CLP Annex VI) entry for basic aluminum chloride (EC 215-477-2); the notified classification (ECHA C&L) is Eye Dam. 1 H318 and Met. Corr. 1 H290 and stays product-specific. NIOSH sets a REL of 2 mg/m³ TWA as Al (no OSHA PEL), and PPE and spill response follow the supplier SDS. Containment for chemical storage is covered under chemical storage tanks.
The table below summarizes PAC storage and handling data.
| Item | Value |
|---|---|
| pH as supplied | 2.2 to 2.8 (ADWG) |
| Specific gravity | 1.18 to 1.22 at 20 °C (68 °F) for 10 % Al2O3 (ADWG) |
| Tank materials | FRP, polyethylene, polypropylene; 316 stainless steel as the metal exception |
| Transport containers | Rubber-lined tankers, HDPE (GACL) |
| Incompatible | Bases (exothermic neutralization), active metals (hydrogen) |
| GHS | Notified (ECHA C&L): H318, H290; no CLP Annex VI entry; product-specific |
| Exposure limits | No OSHA PEL; NIOSH REL TWA 2 mg/m³ as Al; IDLH not determined |
| Process safety | Not listed under EPA RMP or OSHA PSM |
| Classification of the delivered grade | Supplier SDS |
What does a PAC safety data sheet (SDS) cover?#
A PAC safety data sheet (the older MSDS) gives the hazard classification, handling, storage, exposure-control and transport data for one specific product, and these differ by strength and supplier.
Check the 4 items below against the delivered grade.
- Confirm the product name, CAS 1327-41-9 and Al2O3 strength against the certificate of analysis.
- Compare the hazard section with the notified H318 and H290 classification.
- Check the exposure section against the NIOSH REL of 2 mg/m³ as Al.
- Confirm that bases and active metals are listed as incompatible.
What Are the Alternatives to Polyaluminum Chloride?#
The 4 main alternatives to PAC are alum, aluminum chlorohydrate (ACH), ferric chloride and sodium aluminate, and they differ most in how much alkalinity they consume or add.
The table below compares PAC with its 4 alternatives by identity, strength, alkalinity effect, MUL and standards.
| Coagulant | CAS | Typical liquid strength | Basicity or alkalinity effect | Most common NSF MUL (as product, NSF listings 2026-10-20) | AWWA | EN |
|---|---|---|---|---|---|---|
| Polyaluminum chloride (PAC) | 1327-41-9 | ≥ 10 % Al2O3 | About 50 %; less than alum | 250 mg/L | B408-25 | EN 17034:2018 |
| Aluminum sulfate (alum) | 10043-01-3 | 7.5 to 8.4 % Al2O3 | 0 %; 0.50 mg/L as CaCO3 per mg/L dry alum | 150 mg/L | B403-24 | EN 878:2016 |
| Aluminum chlorohydrate (ACH) | 12042-91-0 (1327-41-9 also used in trade) | 23 to 24 % Al2O3 | 83 to 84 %; least | 250 mg/L | Supplied against B408 | EN 17034:2018 |
| Ferric chloride | 7705-08-0 | 38 to 42 % FeCl3 | 0.92 mg/L as CaCO3 per mg/L FeCl3; most | 250 mg/L | B407-24 | EN 888:2023 |
| Sodium aluminate | 1302-42-7 (also 11138-49-1) | 24.6 to 25.4 % Al2O3 (45 % liquid) | Adds 0.54 mg/L alkalinity per mg/L Na2Al2O4 (88 %) | 89 and 105 mg/L | B405-24 | EN 882:2016 |
PAC vs alum (aluminum sulfate)#
PAC and alum both deliver aluminum, but alum (aluminum sulfate) is 0 % basic and consumes about twice the alkalinity per mg of aluminum (5.56 against about 2.8 mg/L as CaCO3, calculated), so PAC needs less lime or caustic soda in soft, low-alkalinity water. Alum works as a coagulant on its own, at 5 to 200 mg/L as the 14-hydrate (ADWG).
PAC vs aluminum chlorohydrate (ACH)#
ACH is the highest-basicity member of the PAC family (83 to 84 % against about 50 %), at 23 to 24 % Al2O3, so it consumes the least alkalinity and often needs about half the PAC dose (supplier figure, WaterWorld). The Australian Drinking Water Guidelines give ACH 3 to 100 mg/L as product, effective at pH 6 to 9. Grades and listings are covered on aluminum chlorohydrate (ACH).
PAC vs ferric chloride#
Ferric chloride works over a wider pH range than PAC (about 4 to 11) and suits hard water coagulated at pH 8.0 or more, but it consumes the most alkalinity of the common coagulants.
Ferric chloride leaves iron instead of aluminum, and iron carries a US secondary standard of 0.3 mg/L (40 CFR 143.3).
PAC Grades, Suppliers and Sourcing#
PAC is produced by aluminum-coagulant makers that include Chemtrade, GACL, Kemira and USALCO, in liquid grades from about 10 to 18 % Al2O3 and powder grades near 30 % Al2O3. EPA lists polyaluminum chloride among the 36 water-treatment chemicals in its supply chain profiles (counted 2026-10-20). Producers and distributors by region are listed under water treatment chemical suppliers.
The table below lists PAC makers named in listings and datasheets, alphabetically.
| Company | PAC products or grades named in sources | Note |
|---|---|---|
| Aquamark | Polyaluminum chloride | n/a |
| Chemtrade | PACl, PACS | Also PASS, ACH, alum, sodium aluminate |
| Ecolab (Nalco Water) | Nalco 8117 | Nalco part of Ecolab since 2011-12-01 |
| GACL | PAC 10, 14, 18 (liquid); PAC 30 (powder) | IS 15573:2018 grades |
| Holland Company | Polyaluminum chloride | n/a |
| Kemira | PAX-18 (NSF MUL 200 mg/L); PAX-XL series (PAX-XL1935 625 mg/L) | NSF listings, 2026-10-21 |
| USALCO | DelPAC 1525 | n/a |
| Veolia Water Technologies | Polyaluminum chloride | n/a |
Listed alphabetically; no company is a partner of this site and none pays for inclusion.
Buyers should check the NSF listing for the exact trade name and facility, because MULs differ by facility (VANPRESS PACl: 200 mg/L at Abbotsford, British Columbia).
IS 15573:2018 (BIS, first revision, 2018-02-26) defines the PAC 10, 14, 18 and 30 grades that GACL and other water treatment chemical manufacturers in India make.
How is PAC priced and quoted?#
PAC is quoted per wet ton of solution delivered (a short ton of 2,000 lb, or 907 kg, in US utility bids), so two offers compare only after converting each to cost per ton of Al2O3 at the quoted strength.
The quote factors are Al2O3 strength and basicity, form, package (drum, IBC, bulk or 25/50 kg bags), annual quantity, delivery point and documents; a 2023 City of Mansfield, Texas, bid held prices firm and delivered for 12 months and required a certificate of analysis, a notarized AWWA statement and an NSF certificate with the MUL.
Public procurement records show what buyers paid at a given date and place; they include delivery and local terms and are not a current price.
| PAC product | Bid range | Basis | Region | Date | Source |
|---|---|---|---|---|---|
| Delpac 1525 basic aluminum chloride, 2 bids | USD 0.3097 to 0.375 | per pound | Township of Livingston, New Jersey, US | bid opened 2025-03-12 | Township of Livingston Bid 6-2025 Chemicals, Bid Tabulation |
| Liquid polyaluminum chloride, 2 bids | USD 2.6351 to 2.73 | per gallon | Hanover Borough and Penn Township, Pennsylvania, US | bid opened 2025-02-05 | Hanover Borough Joint Municipal Bids for Chemical Products |
| Polyaluminum chloride, bulk, 1 bid | USD 618.00 | per wet ton | Washington County, Maryland, US | bid opened 2024-10-22 | Washington County PUR-1708 Water/Wastewater Treatment Chemicals, Bid Tabulation |
Each award holds for one specification and date, so send one specification and request quotes for water treatment chemicals on the same Al2O3 basis.
Where Does PAC Sit Among Coagulants for Water Treatment?#
PAC is the medium-basicity member of the prehydrolyzed aluminum coagulants, between monomeric salts such as alum and the high-basicity ACH, and one of 4 coagulant classes beside inorganic, organic and natural coagulants. All four classes are compared under coagulants for water treatment. Basicity, PACS and silicate variants are covered under prehydrolyzed aluminum coagulants.
Polyaluminum chloride FAQs#
How is polyaluminum chloride made?#
Liquid PAC is made by reacting aluminum hydroxide with hydrochloric and sulfuric acid at elevated temperature and adding calcium carbonate to raise basicity, with the gypsum removed by centrifuge (Water New Zealand).
Is PAC a coagulant or a flocculant?#
PAC is a coagulant: it destabilizes particles by charge neutralization, while the polymers fed after it act as the flocculants. Polymer types are compared under flocculants for water treatment.
Is polyaluminum chloride the same as aluminum chloride?#
No: aluminum chloride (AlCl3, CAS 7446-70-0) is a monomeric salt with 0 % basicity, while PAC is prehydrolyzed and partly neutralized. The monomeric salt is covered under aluminum chloride solution.
Does PAC need pH adjustment?#
PAC needs less alkali than alum, but plants still adjust coagulation pH into its optimum (about 6.3 to 7.3 by temperature, Health Canada) with lime, caustic soda or acid rather than by changing the PAC dose. These are compared under pH adjustment chemicals.