Case Study: Wastewater Treatment for 200 m³/Day Ink Manufacturing Plant in Dong Nai Province Using FeCl2
Table of contents
Compiled by: Technical Department of Loc Thien Chemicals | Environmental Engineers with >10 years of experience in supplying wastewater treatment chemicals for IZs in Dong Nai, Binh Duong, and Ho Chi Minh City
FeCl₂ (Ferrous Chloride) 30% liquid is an effective coagulant for wastewater with high SS, low pH, and heavy metals — typical characteristics of ink manufacturing plants. At a 200 m³/day system in Dong Nai, a dosage of 250–350 mg/L achieved >95% SS reduction, meeting QCVN 40:2025/BTNMT (replacing QCVN 40:2011, effective September 1, 2025) Column B at a low, stable chemical cost per m³.
📊 Performance Snapshot
| Parameter | Value |
|---|---|
| Treatment Capacity | 200 m³/day |
| Coagulant | FeCl₂ 30% liquid (Ferrous Chloride) |
| Average Influent SS | 1,800–2,200 mg/L |
| Effluent SS | ≤ 100 mg/L |
| Compliance Standard | QCVN 40:2025/BTNMT (replacing QCVN 40:2011, effective September 1, 2025) — Column B |
| Polymer Support | Anionic polymer — flocculation aid |
| FeCl₂ Supplier | Loc Thien Chemicals Co., Ltd. |
| Estimated Chemical Cost | Low per m³ treated wastewater (FeCl₂ ≈ 80% of chemical cost) |
| FeCl₂ CAS Number | 7758-94-3 (anhydrous) |
1. Background: Ink Manufacturing Wastewater Poses Real Challenges
Loc Thien Chemicals is an industrial FeCl₂ supplier in Ho Chi Minh City and Southeast provinces, specializing in wastewater treatment solutions for IZs in Dong Nai, Binh Duong, and HCMC.
An ink manufacturing plant in Dong Nai Province (within an Industrial Zone) producing water-based and solvent-based inks generates approximately 200 m³ of wastewater daily. The effluent is among the most complex in the printing industry — unsuitable for standalone biological treatment.
Key influent characteristics:
| Parameter | Typical Value | QCVN 40:2025/BTNMT (replacing QCVN 40:2011, effective September 1, 2025) Column B |
|---|---|---|
| pH | 4.0 – 6.0 | 5.5 – 9.0 |
| SS (Suspended Solids) | 1,000 – 3,000 mg/L | ≤ 100 mg/L |
| COD | 800 – 2,500 mg/L | ≤ 150 mg/L |
| Color | 500 – 2,000 Pt-Co | ≤ 150 Pt-Co |
| Heavy Metals (Cu, Zn, Cr) | May exceed thresholds | Per Column B limits |
The wastewater contains finely dispersed colloidal organic pigments — these negatively charged particles remain stable in water and resist natural sedimentation. This renders simple settling methods ineffective.
2. Why Choose FeCl₂ Over PAC?
This critical technical question was thoroughly evaluated by the plant's EHS team.
FeCl₂ vs PAC for Ink Wastewater Treatment
| Technical Criteria | FeCl₂ (Ferrous Chloride) | PAC (Poly Aluminium Chloride) |
|---|---|---|
| High SS Efficiency (>1,000 mg/L) | ✅ Excellent — dense, fast-settling flocs | ⚠️ Moderate — lighter flocs |
| Low pH Tolerance (4–6) | ✅ Effective at pH 5–9 | ⚠️ Efficiency declines below pH 6 |
| Heavy Metal Precipitation | ✅ Simultaneous Fe(OH)₂/Fe(OH)₃ coprecipitation | ❌ Limited effectiveness |
| Organic Pigment Decolorization | ✅ Good — Fe²⁺ redox mechanisms assist | ⚠️ Moderate |
| Dosage for Concentrated Wastewater | 200–500 mg/L (jar test dependent) | 300–600 mg/L — higher dosage |
| Chemical Cost | 15–25% lower | Higher |
| Sludge Production | Greater — requires sludge management | Less |
| Ideal Applications | ✅ Ink, textile dyeing, electroplating wastewater | Potable water, domestic wastewater |
Technical conclusion: For ink wastewater with 1,000–3,000 mg/L SS, mildly acidic pH, and concurrent heavy metal removal needs — FeCl₂ demonstrates superior technical and economic advantages over PAC.
3. Treatment Mechanism: How FeCl₂ Works
FeCl₂ (CAS: 7758-94-3) hydrolyzes in wastewater to form Fe(OH)₂, which oxidizes to Fe(OH)₃ in aerobic conditions. These positively charged colloids neutralize negatively charged pigments/SS, forming large settleable flocs.
Dual mechanisms:
- Coagulation: Fe²⁺ → Fe(OH)₂/Fe(OH)₃ — charge neutralization destabilizes colloids
- Precipitation: Fe(OH)₃ coprecipitates heavy metals (Cu²⁺, Zn²⁺, Cr³⁺)
Key reactions:
FeCl₂ + 2H₂O → Fe(OH)₂ + 2HCl
4Fe(OH)₂ + O₂ + 2H₂O → 4Fe(OH)₃
Fe(OH)₃ [coagulant] → settled flocs4. Implementation Protocol
Step 1 — Jar Testing for Optimal Dosage
Prior to full-scale operation, technicians conduct jar tests with actual wastewater:
- Prepare six 1,000 mL beakers with 1L wastewater each
- Dose FeCl₂ 30% at 150, 200, 250, 300, 400, 500 mg/L (as pure FeCl₂)
- Rapid mix at 150 rpm/1 min → slow mix at 30 rpm/15 min → settle for 30 min
- Measure SS, color, pH of supernatant
Jar test results: Optimal dosage determined at 250–350 mg FeCl₂/L (equivalent to 830–1,170 mL FeCl₂ 30%/m³ wastewater).
Step 2 — pH Adjustment if Required
For influent pH < 5.5 → dose dilute Ca(OH)₂ or NaOH to raise pH to 6.0–7.5 before FeCl₂ addition. Critical for coagulation efficiency.
Step 3 — Anionic Polymer Assistance
Post-FeCl₂ precipitation, add anionic polymer at 1–3 mg/L to enlarge flocs, accelerate settling, and reduce clarifier retention time. Gentle mixing at 10–20 rpm for 5 min after polymer addition.
Step 4 — Continuous Operation
- FeCl₂ 30% metering pumps set for flow-proportional dosing
- FeCl₂ injection point: rapid mix tank
- Polymer injection point: flocculation basin outlet
- Sludge from clarifier → sludge holding tank → belt press dewatering
5. Treatment Performance
Effluent Quality Comparison
| Parameter | Influent | Effluent | QCVN 40:2025 (replacing QCVN 40:2011, effective 01/09/2025) Column B | Compliance |
|---|---|---|---|---|
| pH | 4.5 – 5.5 | 6.5 – 7.5 | 5.5 – 9.0 | ✅ |
| SS (mg/L) | 1,800 – 2,200 | 45 – 85 | ≤ 100 | ✅ |
| COD (mg/L) | 1,200 – 1,800 | 110 – 140 | ≤ 150 | ✅ |
| Color (Pt-Co) | 800 – 1,500 | 80 – 120 | ≤ 150 | ✅ |
| Total Fe (mg/L) | < 1 | 1.5 – 4.5 | ≤ 5 | ✅ |
| Cu (mg/L) | 0.8 – 2.0 | < 0.2 | ≤ 2.0 | ✅ |
| Zn (mg/L) | 1.5 – 3.0 | < 0.5 | ≤ 3.0 | ✅ |
Note: Data represents stable operation post-commissioning. Actual values vary with influent characteristics.
Operating Cost Estimate
| Item | Basis | Share of Total |
|---|---|---|
| FeCl₂ 30% liquid | % of chemical cost/m³ | ~80% |
| Anionic polymer | % of chemical cost/m³ | ~13% |
| Ca(OH)₂ for pH adjustment | % of chemical cost/m³ | ~7% |
| Total Chemical Cost | % of chemical cost/m³ | 100% |
6. Operational Best Practices
6.1 FeCl₂ Procurement Schedule
A 200 m³/day plant at 300 mg/L average FeCl₂ dosage requires:
- Pure FeCl₂/day: 300 mg/L × 200 m³ = 60 kg/day
- As FeCl₂ 30% liquid: 60 / 0.30 = 200 kg/day ≈ 200 L/day
- One 1,000L IBC lasts ~5 days
- Recommendation: Twice-weekly deliveries (1–2 IBCs per delivery) to ensure buffer stock
6.2 FeCl₂ 30% Liquid Storage
| Requirement | Specification |
|---|---|
| Storage temperature | 5 – 40°C (avoid freezing/direct sunlight) |
| Tank material | HDPE, FRP, or PVC-lined — never standard steel/stainless |
| Shelf life | 12 months from production |
| Venting | Tanks require venting — slow FeCl₂ oxidation creates slight pressure |
| Storage area | Dry, ventilated, segregated, away from heat sources |
6.3 Safety Protocols (Per FeCl₂ MSDS)
- Mandatory PPE: Safety goggles, Nitrile/PVC gloves, acid-resistant apron, rubber boots
- Fume inhalation: Ensure proper ventilation at dosing stations
- Skin/eye contact: Flush immediately with clean water ≥15 mins, seek medical attention
- Spills: Neutralize with dilute Na₂CO₃ or dry sand — never drain directly
- High corrosivity to metals: Regularly inspect pump seals and fittings
Complete Safety Data Sheets (SDS) compliant with QCVN 05:2020 accompany each shipment — contact Loc Thien for SDS requests.
7. FAQ
FeCl₂ 25% or 30% for Ink Wastewater Treatment?
FeCl₂ 30% is preferred for large systems (e.g., 200 m³/day) due to higher active content, reducing storage volume and transport costs per kg pure FeCl₂. FeCl₂ 25% suits smaller systems or when metering pumps have high minimum flow rates. Loc Thien supplies both concentrations — technicians can advise after reviewing existing pump specifications.
Does FeCl₂ Corrode Equipment and Piping?
Yes — concentrated liquid FeCl₂ significantly corrodes metals (steel, copper, aluminum, 304 stainless steel). All contact materials must be HDPE, PP, PVC, FRP, or 316L stainless steel (better but still requires periodic inspection). Metering pumps should use PTFE/PVDF diaphragms. Seal and gasket inspections every 3 months are recommended.
Loc Thien Delivery Lead Time to Dong Nai?
Dong Nai is within Loc Thien's regular delivery zone. Standard 1,000L IBC orders typically ship within 1–2 business days after confirmation. Bulk tanker deliveries follow contracted schedules. Confirm specific timelines at +84 979 891 929.
8. Conclusions & Recommendations
FeCl₂ (Ferrous Chloride) is the technically sound and cost-effective choice for treating ink manufacturing wastewater characterized by high SS, low pH, and concurrent heavy metal removal. At the 200 m³/day Dong Nai facility, FeCl₂ 30% liquid with anionic polymer achieved stable QCVN 40:2025/BTNMT (replacing QCVN 40:2011, effective September 1, 2025) Column B compliance at low, stable chemical costs per m³.
(Loc Thien has served 200+ Southern Vietnam industrial plants — Dong Nai client details withheld per confidentiality.)
Critical success factors:
- Monthly jar testing — especially when seasonal production alters wastewater characteristics
- Corrosion-resistant materials for all FeCl₂ contact components
- Reliable supply chain — avoid treatment disruptions from FeCl₂ stockouts
📞 FeCl₂ Technical Consultation & Quotation
Loc Thien Chemicals supplies FeCl₂ 25% and 30% liquid in 1,000L IBCs and tankers, delivering across Southeast Vietnam including Dong Nai, Binh Duong, HCMC, and Ba Ria - Vung Tau.
Complimentary technical services:
- FeCl₂ dosage calculations based on flow and wastewater characteristics
- Optimal procurement and inventory planning
- Full documentation: CO, CQ, MSDS, Certificate of Analysis for tender requirements
📞 Technical Hotline: +84 979 891 929 📧 Email: [email protected] 🌐 Website: hoachatlocthien.com
Request a quote: Provide treatment capacity (m³/day), desired delivery frequency, and shipping address — Loc Thien responds within 2 business hours.
view additional technical consulting services
Supply/Quotation: FeCl2 (Ferrous Chloride) at Loc Thien — hotline 0979 891 929 (on-request, no retail cart sales).
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
Figure: On-site chemical dosing, storage tank operation, and batch COA inspection — Source: Loc Thien Chemical.
Industrial Field Operation & Batch Quality Verification
1. Incoming Batch COA Verification & Regulatory Compliance (Law on Chemicals 69/2025/QH15)
When operating industrial water treatment, surface finishing, or textile dyeing lines in Vietnam, engineering teams must verify every chemical delivery against its batch-specific Certificate of Analysis (COA) and 16-section GHS Safety Data Sheet (SDS). Under the Vietnam Law on Chemicals No. 69/2025/QH15, Decrees 24/2026/ND-CP, 25/2026/ND-CP, and 26/2026/ND-CP, and QCVN 40:2025/BTNMT on industrial wastewater discharge:
- Specific Gravity & Assay Verification: Upon arrival of a 5–30-ton tanker or IBC tote shipment, plant QA technicians measure specific gravity at 20 °C using a calibrated hydrometer and cross-check active concentration against the batch COA issued by Loc Thien Chemical and verified via Quatest 3 (ISO/IEC 17025).
- Impurity & Heavy Metal Control: Trace heavy metals (Fe, Pb, As, Hg, Cd, Cr⁶⁺) and insoluble matter are strictly controlled to prevent catalyst poisoning in Fenton reactors, membrane fouling in RO/UF systems, or shade deviations in reactive textile dyeing.
- ZDHC MRSL v3.1 Level 1 Portfolio Boundary: For export-oriented textile and footwear FDI factories, Loc Thien Chemical maintains official ZDHC MRSL v3.1 Conformance Level 1 documentation for exactly 9 core products: four products certified by TUV SUD Product Service GmbH (
NaOH,H2O2,Na2SO4,Na2CO3) and five products verified via Conformance Summary Report (CSR) and Analytical Test Report by TUV Rheinland Vietnam (H2SO4,FeCl2,HCl,Javel/NaOCl,PAC 31%).
| Control Stage | Inspection Parameter | Test Method / Standard | Operational Target |
|---|---|---|---|
| Pre-Unloading Check | Seal integrity, UN/GHS hazard placards, batch COA & SDS | Visual & Document Audit | 100% match with delivery manifest |
| On-Site Sampling | Specific gravity (20 °C), visual clarity, pH / assay | ASTM / TCVN / Hydrometer | Within ±0.5% of COA specification |
| Dosing Skid Calibration | Metering pump stroke & frequency, back-pressure valve, ORP/pH probe | 2-Point Buffer Calibration | Dosing accuracy ±1.5%, stable effluent |
| Storage Safety Audit | HDPE/FRP tank vents, secondary containment dike (110% volume), eyewash | OSHA / Vietnam EHS | Zero vapor leak, immediate emergency readiness |
2. Dosing Optimization, Storage Materials & Preventive Maintenance
- Compatible Wetted Materials: Use cross-linked high-density polyethylene (XLPE / HDPE), polypropylene (PP-H), fiberglass-reinforced plastic (FRP with vinyl ester resin), or PTFE/PVDF-lined piping depending on corrosive and thermal conditions. Avoid unlined carbon steel or incompatible elastomers.
- Automated Dosing Control: Integrate diaphragm metering pumps with real-time pH, ORP (mV), turbidity, or conductivity sensors. Always perform a 5-beaker Jar Test whenever raw water COD, TSS, or alkalinity shifts by more than 15%.
- Secondary Containment & PPE: Storage tanks must sit inside an acid/alkali-resistant bund wall holding at least 110% of the largest tank volume. Operators handling unloading hoses must wear splash-proof chemical goggles, acid/alkali-resistant nitrile or neoprene gloves, face shields, and emergency respirators.
3. Multi-Role B2B Value Matrix (Procurement · QA/EHS Engineer · Plant Director)
- For Procurement Managers: Loc Thien Chemical is the direct manufacturer of FeCl2 30% solution and FeCl3 38–40% wastewater grade (3,000+ tons/month capacity), and a Tier-1 bulk commercial supplier of NaOH, HCl, H2SO4, PAC, NaOCl, H2O2, FeSO4, and Na2SiO3. Pricing is transparently structured around 5 technical cost drivers (active assay, packaging format, delivery distance from our 6 warehouses, order volume, and scheduled contract cadence) with a 15-minute technical quotation SLA.
- For Environmental & Process Engineers: Full technical support for Jar Test optimization, stoichiometry calculation, sludge minimization, and QCVN 40:2025/BTNMT compliance auditing.
- For FDI Plant Directors: Guaranteed supply continuity via 6 regional warehouses (Ba Ria - Vung Tau, Dong Nai, Binh Duong, Da Nang, Can Tho, Bac Ninh) and a dedicated 5–30-ton tanker fleet (4 hours in inner HCMC, 24–48 hours across Southern & Mekong Industrial Parks, 2–3 days in Northern & Central Vietnam).
4. Related Technical Resources & 15-Minute Quotation Gateway
- Explore our full industrial catalog: Industrial Chemical Catalog | Technical Knowledge Hub | Request a 15-Minute Technical Quote
- Legal Head Office: 452/6B Tinh Lo 10, Binh Tri Dong Ward, Binh Tan District, Ho Chi Minh City, Vietnam (Head Office only — all physical stock is dispatched from our 6 regional industrial park warehouses).
- 24/7 Technical Hotline: 0979 891 929 (Please contact hotline 0979 891 929 for detailed delivery procedures) | Official Email: [email protected]