PAC here means polyaluminium chloride, and alum means aluminium sulfate. Metal coagulants and high-molecular-weight PAM usually have different jobs: coagulation destabilises or captures impurities, while PAM can bridge particles into larger flocs. Charged polymers may also contribute charge interactions, so the need for a separate coagulant depends on the feed, polymer and removal target [1].
Use the assay bands, dose/pH windows and price inputs below as illustrative comparison and trial-planning cases, not universal specifications, current quotations or ChinaPAM grade values. Confirm the actual product, assay, water chemistry and test protocol. PAM doses are on an active-polymer basis; metal-coagulant doses are supplied-product mass for the form stated. Al₂O₃, Al, FeCl₃ and Fe are different reporting bases.
| Property | Polyacrylamide (PAM) | Polyaluminium chloride (PAC) | Aluminium sulfate (alum) | Ferric chloride (FeCl₃) |
|---|---|---|---|---|
| Role | High-MW flocculant, commonly bridging; charged grades also have charge interactions | Pre-hydrolysed metal coagulant | Metal coagulant | Ferric metal coagulant |
| Form / assay examples | Dry-polymer example about 90% active; emulsion 25–50% active [1] | Powder planning case 28–30% as Al₂O₃; liquid case 10–18% as Al₂O₃ | Solid planning case 15–17% as Al₂O₃; liquid case about 8% as Al₂O₃ | Liquid planning case 38–42% as FeCl₃; solid case about 96% as FeCl₃ |
| Illustrative dose window | 0.3–5 mg active/L for clarification; 2–18 kg active/t DS for sludge | 10–50 mg product/L, powder planning case | 20–100 mg product/L, solid-alum planning case | 20–80 mg product/L, 40% liquid planning case |
| pH window to investigate — examples | 4–12 for anionic; 1–10 for cationic; grade and duty control | 5.0–9.0; verify basicity, feed and treatment target | 5.5–7.5; verify feed, dose and temperature | 4.0–11.0; verify feed, dose and treatment target |
| Alkalinity / pH effect | Check the formulation and operating pH; do not assume zero effect | High-basicity grades can consume less alkalinity than lower-basicity salts at a comparable target [1] | Hydrolysis consumes alkalinity and can lower pH [1] | Hydrolysis consumes alkalinity and can lower pH [1] |
| Sludge volume | Can condition and aggregate existing solids; does not supply an Al/Fe hydroxide precipitant | Depends on dose, basicity, counter ions and captured solids | Depends on dose, counter ions and captured solids | Depends on dose, counter ions and captured solids |
| Floc size and settling | Can enlarge or strengthen flocs when the grade and dose fit the feed [1] | Product, pH, mixing and feed dependent | Product, pH, mixing and feed dependent | Product, pH, mixing and feed dependent |
| Colloidal turbidity removal | May act as a flocculation aid; test whether pre-coagulation is needed | Metal-coagulation option; verify residual turbidity | Metal-coagulation option; verify residual turbidity | Metal-coagulation option; verify residual turbidity |
| Colour / organics (TOC) | Removal is target-dependent; do not assume polymer alone removes all dissolved organics | Can remove some organic matter through coagulation; verify pH and dose | Can remove some organic matter through coagulation; verify pH and dose | Can remove some organic matter through coagulation; no universal “best” ranking [1] |
| Phosphate removal | Can aid separation of P-bearing flocs; is not an Al/Fe phosphate precipitant | Al-based precipitation / co-removal option [1] | Al-based precipitation / co-removal option [1] | Fe(III)-based precipitation / co-removal option [1] |
| Cold-water check — e.g. below 10 °C | Recheck make-down and contact time for the selected grade | Selected high-basicity products can be useful in cold water [1] | May require adjusted pH and longer contact time [1] | Can be a cold-water option; check pH and residual iron [1] |
| Corrosion / handling | Use the exact grade/form SDS and compatible materials | Some liquid PAC products are corrosive to metals; check SDS and materials [2] | Liquid alum can be corrosive to metals; check SDS and materials [3] | Use corrosion-resistant compatible containment specified for the actual formulation [4] |
| Hypothetical price input — USD/t supplied product, not a quotation | 1,200–3,000; assumed PAM input | 250–500; assumed PAC-powder input | 150–300; assumed solid-alum input | 250–450; assumed 40% liquid FeCl₃ input |
For sludge, t DS means a tonne of dry solids; for mine tailings, the example uses a tonne of dry feed solids. Product assay is a mass fraction of the supplied product. An Al₂O₃-equivalent assay is not the same as elemental Al; a FeCl₃ percentage is not elemental Fe. A product’s neat pH is also different from the treated-water coagulation pH.
| Water / sludge | Coagulant planning case | PAM planning case | Conditions to verify |
|---|---|---|---|
| Drinking water, low turbidity | PAC powder: 10–30 mg product/L | Anionic or nonionic candidates; 0.3–0.8 mg active/L | Use only an exact product qualified for the intended use and permitted use level; verify residuals and water chemistry |
| River water, high turbidity / flood season | PAC powder or solid alum: 30–80 mg product/L | Anionic: 1–4 mg active/L | Compare the same clarity target, actual assay, alkalinity and total treatment cost |
| Municipal wastewater (CEPT) | 40% liquid FeCl₃: 20–40 mg product/L | Anionic: 0.3–1.5 mg active/L | Ferric salts can also remove orthophosphate under suitable conditions [1] |
| Textile dyeing effluent | Decolorant selected separately; PAC powder: 100–500 mg product/L | Anionic: 1–5 mg active/L | Define each product’s dose separately; verify colour and dissolved-organic removal rather than assuming PAM alone achieves them |
| Food DAF (fats, oil, grease) | PAC powder: 50–200 mg product/L; compare with a no-coagulant trial where appropriate | Cationic: 2–10 mg active/L | Test the treatment programme on the actual stream; do not assume a universal coagulant replacement |
| Metal plating | Metal-specific lime / NaOH programme; pH 9 is a trial-planning example, with FeCl₃ where qualified | Anionic: 1–5 mg active/L | Precipitation pH depends on the metals and chemistry; assess PAM after the defined precipitation step |
| Mine tailings | Test PAM alone; add coagulant if the application test supports it | Anionic: 20–60 g active/t dry solids | Particle size alone does not decide whether pre-coagulation is needed |
| Sludge dewatering | Optional FeCl₃ / PAC conditioning programme, selected by feed and test | Cationic: 4–18 kg active/t DS | A manufacturer example describes up to 30% less polymer with ferric pre-dosing; validate actual demand, cake and filtrate [1] |
Coagulant first, flocculant second
A common combined route is to disperse the coagulant, allow suitable initial reaction, then add PAM where it can contact the developing flocs without unnecessary shear [1]. For a bench-planning example, investigate 30–60 seconds of initial rapid mixing and PAM addition 30–120 seconds after the coagulant, provided adequate initial reaction has occurred. Optimize the actual mixing intensity, contact time and addition point; one fixed delay or sequence does not fit every process.
When PAM alone is enough
PAM alone may meet the target in some mineral slurries, sand-wash waters or sludge-conditioning duties. The feed’s size, chemistry and charge, together with the removal target, determine whether coagulation or another treatment step is needed. Do not infer the complete treatment programme from an industry name or a particle-size cutoff.
When to switch from alum to PAC or ferric
Consider testing an alternative when cold water, low alkalinity, residual metal, colour or phosphorus limits the current programme. Selected high-basicity PAC and ferric products can perform well in cold-water applications, but below 10 °C is not an automatic switching rule [1]. Compare the same water and outcome while checking dose basis, pH, alkalinity, residual Al/Fe, sludge handling, corrosion compatibility and cost.
Compare dose and cost on the same basis
Chemical-only cost (USD/m³) = supplied-product dose (mg/L) × product price (USD/t) ÷ 1,000,000. When PAM dose is stated as active polymer, divide it by the declared active fraction before using the formula. For an aluminium product, dose as Al₂O₃ = product dose × its Al₂O₃ mass fraction; for ferric chloride, dose as FeCl₃ = product dose × its FeCl₃ mass fraction. Convert to elemental Al or Fe separately if that is the comparison basis.
Hypothetical arithmetic examples — not current quotes or equal-performance claims:
- A PAC-powder case at 30% as Al₂O₃ and 30 mg product/L gives 9 mg/L as Al₂O₃. At an assumed USD 350/t product, chemical-only cost is USD 0.0105/m³.
- A 40% FeCl₃ liquid at 40 mg product/L gives 16 mg/L as FeCl₃, not 16 mg/L as elemental Fe.
- A 90%-active PAM at 1 mg active/L requires about 1.11 mg product/L. At an assumed USD 2,000/t product, chemical-only cost is about USD 0.00222/m³.
Use current grade/form quotations and trial doses at the same accepted treatment outcome before ranking total cost; include pH adjustment, sludge, equipment and handling costs where relevant.
Cationic Polymer Equivalents for Sludge Dewatering
For sludge-dewatering enquiries naming a cationic polymer, review the matching grade page and confirm suitability through your sludge tests. If your plant currently specifies one of the grades below, each page explains how we screen a same-type equivalent on your own sludge.
Zetag grades
- Zetag 7550 equivalent — cationic PAM screening
- Zetag 7557 equivalent — cationic PAM screening
- Zetag 8147 equivalent — high-charge cationic PAM powder
- Zetag 8167 equivalent — very high charge cationic PAM powder
Zetag FS / FS40 grades
- Zetag 7878 FS40 equivalent — cationic PAM screening
- Zetag 8846 FS equivalent — cationic PAM screening
- Zetag 8868 FS equivalent — cationic PAM screening
Other brands
- Magnafloc 455 alternative — cationic PAM screening
- Magnafloc 504 alternative — cationic PAM screening
- KemSep C-8402 equivalent — cationic PAM screening
Not sure which grade you need? Send us your current product name and application and we will suggest a screening route.
Frequently Asked Questions
Is polyacrylamide a coagulant or a flocculant?
High-molecular-weight PAM is commonly used as a flocculant, with bridging and, for charged grades, charge interactions. PAC, alum and ferric chloride are metal coagulants. The selected products and feed determine whether they are used separately or in a combined programme [1].
Can PAC replace polyacrylamide?
They are not one-for-one substitutes. Select coagulation and flocculation functions against the actual feed and target. Some programmes use both; others may not need both. Confirm the whole programme in bench and application trials.
Which is cheaper, PAC or alum?
There is no universal answer from price per tonne alone. Use the actual product assay, current quotation, trial dose and the same accepted treatment result. The numerical prices in Table 1 are assumptions for comparison, not a statement of current FOB China prices.
Request a PAM recommendation or quote
Send your water or sludge analysis, equipment, current products and dose bases, target result, trial quantity and destination. Request the grade-specific TDS, batch COA and SDS needed for your review.
Request a PAM quote or sample · Use the PAM selector
Related
- PolyDADMAC coagulant guide
- Flocculant and coagulant range
- PAM versus polyelectrolyte
- Jar-test procedure
- Raw-water clarification
- PAM pricing guide
- PAM specifications table
- Selection chart by process stream
- PAM physical and chemical properties