PAC Combined with Polymer — Optimizing Coagulation in Water Treatment
Table of contents
TL;DR: PAC (Poly Aluminium Chloride) combined with anionic Polymer (PAM) creates superior coagulation: PAC neutralizes colloid charge, anionic Polymer bridges flocs — resulting in flocs 3–5× larger, settling rate increased by 40–60%, and PAC dosage reduced by 10–20%. Loc Thien supplies PAC 30% and anionic Polymer A1110 for water plants, industrial parks, textile dyeing. Batch-tested COA/MSDS. Hotline: 0979 891 929.
1. What are PAC and Polymer? Mechanism of Action for Each
1.1 PAC — Inorganic Coagulant
PAC (Poly Aluminium Chloride) is an inorganic polymeric coagulant, general formula [Al₂(OH)ₙCl₆₋ₙ]ₘ, widely used in drinking water and industrial wastewater treatment. PAC works through charge neutralization: when dissolved in water, PAC hydrolyzes to form Al³⁺ ions and highly positively charged polynuclear complexes. These complexes adsorb onto the surface of negatively charged colloidal particles (typically with zeta potential of -15 to -30 mV), reducing electrostatic repulsion between particles, allowing them to approach and aggregate into flocs of 0.5–2 mm.
Loc Thien’s PAC 30% has a basicity of 40–85%, Al₂O₃ content ≥ 30%, solution pH 3.5–5.0. Packed in 25 kg HDPE bags, batch COA included.
1.2 Anionic Polymer — Organic Coagulant Aid
Anionic Polymer (Anionic Polyacrylamide — APAM) is a long-chain organic polymer, molecular weight 12–25 million Daltons, carrying negative charge from carboxyl groups (-COO⁻). Anionic Polymer does not alter colloid charge (that role belongs to PAC), but serves as a physical bridge between already-formed flocs. One polymer strand can simultaneously adsorb onto multiple flocs, gathering them into larger, denser masses that settle more readily.
Typical specifications of anionic Polymer A1110: white powder/granules, density 0.6–0.8 g/cm³, 0.1% solution pH 6.5–7.5, solubility ≥ 95% after 60 minutes of gentle stirring.
2. Synergistic Mechanism: PAC + Anionic Polymer = Large Flocs, Fast Settling
PAC and anionic Polymer complement each other through two sequential steps:
Step 1 — Coagulation with PAC: PAC is dosed into the water first, with rapid mixing (G = 200–400 s⁻¹) for 30–60 seconds. PAC hydrolyzes, neutralizes colloid charge, breaking the stable colloidal state. Particles aggregate into micro-flocs 50–200 µm in diameter.
Step 2 — Large floc formation with anionic Polymer: Dose anionic Polymer after step 1, 30 seconds after PAC addition. Slow mixing (G = 20–40 s⁻¹) for 3–5 minutes. The ultra-long molecular chains of anionic Polymer adsorb onto multiple micro-flocs simultaneously, pulling them together to form tightly bonded flocs 2–8 mm in diameter.
Results of this combination:
- Floc size: 0.5–2 mm (PAC alone) → 2–8 mm (PAC + Polymer) — 3–5× increase
- Settling rate: increased by 40–70% compared to PAC alone
- Effluent turbidity: reduced by 20–50%
- PAC dosage: reduced by 10–20% at same effluent quality
3. Optimal Mixing Ratio — Dosage Guide
Dosage depends on influent water quality, pH, turbidity and TSS levels. Reference dosage ranges from studies and practical applications:
| Water type | PAC (mg/L) | Anionic Polymer (mg/L) | Optimal pH |
|---|---|---|---|
| Surface water — low turbidity (< 50 NTU) | 100–150 | 0.5–1.0 | 6.5–7.5 |
| Surface water — high turbidity (50–500 NTU) | 150–200 | 1.0–2.0 | 6.5–7.5 |
| Industrial park wastewater — medium TSS (200–500 mg/L) | 200–300 | 1.0–1.5 | 7.0–8.0 |
| Industrial park wastewater — high TSS (> 500 mg/L) | 300–400 | 1.5–2.5 | 7.0–8.0 |
| Textile dyeing wastewater | 150–250 | 1.0–2.0 | 6.0–8.0 |
| Electroplating wastewater | 100–200 | 0.5–1.0 | 7.0–8.5 |
Sequential dosing procedure:
- Dose PAC, rapid mix at 200–400 rpm for 1 minute
- Stop rapid mixing, switch to slow mixing at 40–60 rpm
- Dose anionic Polymer (pre-dissolved to 0.1–0.3%), slow mix for 3–5 minutes
- Allow quiescent settling for 10–30 minutes
Note: Anionic Polymer must be pre-dissolved 30–60 minutes with clean water at stock concentration of 0.1–0.3%, gently stirred to avoid polymer chain breakage. Overly vigorous or prolonged mixing will break polymer chains, reducing floc formation efficiency.
4. Comparison: PAC Alone vs. PAC + Anionic Polymer
| Criterion | PAC alone | PAC + Anionic Polymer | Improvement |
|---|---|---|---|
| Floc size | 0.5–2 mm | 2–8 mm | 3–5× increase |
| Settling time (sedimentation tank) | 40–60 min | 15–25 min | 50–60% reduction |
| Effluent turbidity (NTU) | 5–15 NTU | 1–5 NTU | 40–70% reduction |
| PAC dose reduction (%) | — | 10–20% | Chemical savings |
| Treatment cost (VND/m³) | Higher due to increased PAC dose | 15–30% lower due to reduced PAC + higher efficiency | 15–30% reduction |
| Sludge generation | More inorganic sludge, difficult to dewater | Denser sludge, 10–30% volume reduction, easier dewatering | 10–30% reduction |
5. Case Study: Mekong Delta Surface Water Plant
Source water characteristics: Tien River at Sa Dec — Dong Thap, turbidity ranging 80–150 NTU, pH 6.8–7.2, TSS 60–120 mg/L, COD 30–50 mg/L. Plant capacity 20,000 m³/day.
Before optimization (PAC alone):
- PAC dose: 250 mg/L
- Flocs: 0.5–1 mm, light, slow settling
- Settling time: 45 minutes
- Post-settling turbidity: 8–12 NTU
- Effluent COD: 18–22 mg/L
After adding anionic Polymer (PAC + Polymer combination):
- PAC dose: 150 mg/L (40% reduction)
- Anionic Polymer A1110 dose: 1.0 mg/L
- Flocs: 3–5 mm, dense, fast settling
- Settling time: 20 minutes (55% reduction)
- Post-settling turbidity: 0.2–2.0 NTU
- Effluent COD: 10–15 mg/L
- Reduced filter loading, extended filter run cycle from 12h to 18h
Results: Plant saved 22% on total monthly chemical costs, sedimentation system capacity increased by 40% through reduced retention time, sludge volume reduced by 25%.
6. PAC + Polymer Applications by Industry
6.1 Drinking Water Treatment
Surface water from rivers and lakes typically contains silt, algae, microorganisms and dissolved organic matter. PAC 30% at 100–150 mg/L combined with anionic Polymer 0.5–1 mg/L reduces turbidity from 100–500 NTU to below 2 NTU, meeting QCVN 01-1:2018/BYT. This combination is especially effective when source water turbidity fluctuates during rainy/flood seasons.
6.2 Textile Dyeing Wastewater Treatment
Textile dyeing wastewater has high color (200–500 Pt-Co), COD 500–1500 mg/L, alkaline pH 9–11. PAC at 200–300 mg/L neutralizes charge and precipitates color, anionic Polymer 1–2 mg/L forms large flocs for rapid settling. Color removal efficiency reaches 70–90%, COD reduced by 50–80% at the primary coagulation stage.
6.3 Electroplating Wastewater Treatment
Electroplating wastewater contains heavy metals (Ni, Zn, Cu, Cr) at 20–100 mg/L, low pH 2–4. After raising pH to 8–9 with NaOH, PAC at 100–200 mg/L combined with anionic Polymer 0.5–1 mg/L forms metal hydroxide flocs, settling within 15–20 minutes. Heavy metal effluent meets QCVN 40:2025/BTNMT (replacing QCVN 40:2011, effective September 1, 2025) Column A.
7. Storage, Preparation and Safety Guide
Storage
- PAC 30%: store in dry place, avoid moisture. 25 kg HDPE bags, under shelter. Shelf life 24 months.
- Anionic Polymer A1110: avoid moisture absolutely (polymer is highly hygroscopic, clumps when exposed to moisture). Store in cool, dry place, temperature < 40°C. Use immediately after opening bag.
Anionic Polymer Preparation
- Fill mixing tank with clean water — water volume based on 0.1% concentration (1 kg polymer + 1000 L water)
- Start slow stirrer at 60–80 rpm
- Sprinkle polymer gradually into water (do not pour all at once)
- Stir continuously for 45–60 minutes until polymer is completely dissolved
- Stock solution used within 24h, do not exceed 48h
Safety
- PAC and anionic Polymer in solid form are not flammable or explosive
- When handling: wear gloves, safety goggles, dust mask
- Polymer powder can create slippery surfaces when spilled — clean immediately
8. Why Choose PAC + Polymer from Loc Thien?
Certified quality:
- PAC 30% with batch COA, Al₂O₃ ≥ 30%, basicity 40–85%
- Anionic Polymer A1110 officially imported, viscosity and solubility tested before delivery
- Quality control process per TCVN standards, tested by QC technicians Phan Cam Thuy, Vo Thi Nhu Hoa
Reliable supply:
- 6 warehouses nationwide (Ba Ria – Vung Tau, Dong Nai, Binh Duong, Da Nang, Can Tho and Bac Ninh)
- Delivery within 4h in HCMC city area, 24–48 hours to southern industrial parks and the Mekong Delta, 2–3 days to Northern and Central Vietnam
- 5–30 ton tankers for liquid PAC, trucks for powder PAC/Polymer
Technical support:
- Technical staff support jar-test to determine optimal dosage at customer’s system
- Mixing consultation tailored to each specific water source
Technical Support & B2B Procurement Hotline
Loc Thien Chemical specializes in direct manufacturing of FeCl₂ / FeCl₃ and direct industrial supply of basic chemicals (NaOH, HCl, H₂SO₄, PAC, NaOCl, H₂O₂, FeSO₄) with direct B2B pricing and dedicated 5–30-ton tanker delivery across Vietnam.
- Hotline / Zalo: +84 979 891 929
- Official Email: [email protected]
- Direct Manufacturer: Ferrous Chloride (FeCl₂ 30%) & Ferric Chloride (FeCl₃ 38–40%)
- Primary Supplier: NaOH 32%/45%/50%/99%, HCl 32%, H₂SO₄ 98%, PAC 30–31%, NaOCl 10–12%, H₂O₂ 35%/50%
- Compliance & Quality: FeCl₂ ZDHC MRSL v3.1 test report (Smart testing, 5 substance groups, TUV Rheinland Vietnam), ISO 9001:2015, Quatest 3, Full COA & GHS SDS
Frequently Asked Questions (FAQ)
1. Can PAC and Polymer be mixed in the same tank before dosing?
No. PAC and anionic Polymer must be dosed separately, PAC first then Polymer. Mixing them together will cause polymer hydrolysis in the acidic PAC environment, losing its bridging effect.
2. Does anionic Polymer dissolve completely in water?
Yes, if prepared correctly: concentration 0.1–0.3%, gentle stirring for 45–60 minutes. Polymer dissolves completely forming a clear viscous solution. If white suspended particles remain, increase stirring time.
3. Can anionic Polymer dosage vary by season?
Yes. In the rainy season, surface water has higher turbidity, requiring increased Polymer dose to 1.5–2 mg/L. In the dry season, turbidity is low, Polymer dose can be reduced to 0.5–1 mg/L.
4. Can anionic Polymer work with saline wastewater?
Yes. Anionic Polymer performs well in high-salinity environments (up to 35‰). Studies on seawater treatment systems show that splitting the Polymer dose into multiple additions produces denser flocs compared to a single dose.
5. Is excess anionic Polymer harmful?
Yes. Overdosing (above 5 mg/L) makes flocs too large and sticky, settling slowly or floating to the tank surface. Excess polymer may increase effluent COD. Always perform jar-test to determine the optimal dose.
6. Can PAC + Polymer treat oily wastewater?
PAC + anionic Polymer effectively treats suspended solids in oily wastewater, but mechanical oil separation (oil separation tank, DAF) is needed before the coagulation step.
🛒 Need PAC 30% or anionic Polymer A1110? Get a quote for PAC 30% and Polymer A1110 — Batch COA/MSDS, delivered to industrial parks nationwide. | Detailed anionic Polymer A1110 specifications. Hotline: 0979 891 929.
Article reviewed by QC Specialist Phan Cam Thuy, Vo Thi Nhu Hoa — Loc Thien Chemical Testing Department. PAC 30% data based on actual batch COA at warehouse. Case study data referenced from Mekong Delta surface water treatment research and industrial park system operational data.
QC: Phan Cam Thuy & Vo Thi Nhu Hoa. Batch COA. Hotline 0979 891 929.