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- 🌊 1. PROJECT OVERVIEW – EVAPORATION FOR TREATING HAZARDOUS WASTEWATER
- 📊 2. INFLUENT WASTEWATER CHARACTERISTICS
- 💧 3. REQUIRED EFFLUENT QUALITY
- 🔬 4. PROPOSED TECHNOLOGY – HEAT PUMP VACUUM EVAPORATOR (HPVE)
- 🔁 5. PROCESS FLOW – HAZARDOUS WASTEWATER EVAPORATION TREATMENT
- ⚙️ 6. TECHNICAL SPECIFICATIONS – HPVE SYSTEM
- 🌱 7. PERFORMANCE & ENVIRONMENTAL BENEFITS
- 🏁 8. RESULT
🌊 1. PROJECT OVERVIEW – EVAPORATION FOR TREATING HAZARDOUS WASTEWATER
Scope of Work: Evaporation For Treating Hazardous Wastewater
TVTS provided engineering consulting, detailed design, and installation of an evaporation system for hazardous wastewater treatment at a waste-to-energy plant and hazardous waste collection & treatment facility.
Capacity: 100 m³/day
This type of hazardous wastewater presents the following characteristics:
Extremely high TDS and chloride concentration, causing severe corrosion.
Very high COD, which makes conventional biological or physico-chemical treatment ineffective.
Presence of heavy metals and persistent compounds, requiring advanced water separation technology.
For this project, TVTS implemented a Heat Pump Vacuum Evaporator (HPVE) system — an advanced solution for hazardous wastewater evaporation treatment that concentrates contaminants, removes salts, and recovers clean water compliant with QCVN 40:2025 – Column B.
📊 2. INFLUENT WASTEWATER CHARACTERISTICS
| No. | Parameter | Unit | Analytical Result |
|---|---|---|---|
| 1 | pH | – | 9.2 |
| 2 | Ammonium (NH₄⁺) | mg/L | 0.16 – 1.35 |
| 3 | COD | mg/L | >30,000 |
| 4 | Chloride (Cl⁻) | mg/L | >117,000 |
| 5 | Hardness (as CaCO₃) | mg/L | <2,000 |
| 6 | Copper (Cu) | mg/L | 43 – 93 |
| 7 | Nickel (Ni) | mg/L | 40 |
The wastewater contains high salinity, heavy metals, and extremely elevated organic load — typical for hazardous waste treatment facilities.
💧 3. REQUIRED EFFLUENT QUALITY
According to QCVN 40:2025/BTNMT – Column B, the treated wastewater must meet the following limits:
| No. | Parameter | Unit | Permissible Limit |
|---|---|---|---|
| 1 | pH | – | 6.0 – 9.0 |
| 2 | Ammonium (NH₄⁺) | mg/L | ≤10 |
| 3 | COD | mg/L | ≤90 |
| 4 | Chloride (Cl⁻) | mg/L | ≤1,000 |
| 5 | Copper (Cu) | mg/L | ≤3 |
| 6 | Nickel (Ni) | mg/L | ≤3 |
| 7 | Total Nitrogen | mg/L | ≤40 |
🔬 4. PROPOSED TECHNOLOGY – HEAT PUMP VACUUM EVAPORATOR (HPVE)
Operating Principle
The evaporation process operates under deep vacuum conditions (-85 to -95 kPa), which reduces the boiling temperature to 35–60°C.
The compressor compresses refrigerant gas and recovers vapor heat for reuse in the next evaporation cycle. This closed-loop system reduces energy consumption by up to 70% compared to conventional thermal evaporation.
COP (Coefficient of Performance): 3.0 – 4.5
Key Advantages
🔹 Low energy consumption: 100–115 W per liter of condensate (~130–155 kWh/m³ evaporated water).
🔹 Operates fully on electricity — no steam boiler or cooling tower required.
🔹 Handles wastewater with Cl⁻ >120,000 mg/L and high COD.
🔹 Fully automated operation; supports batch mode.
🔹 Low evaporation temperature (30–40°C), suitable for heat-sensitive compounds.
🔹 Durable industrial compressor; easy maintenance and long service life.
📈 Water recovery efficiency: 95%, enabling discharge compliance or reuse.
🔁 5. PROCESS FLOW – HAZARDOUS WASTEWATER EVAPORATION TREATMENT
1️⃣ Collection & Equalization Tank
The system collects hazardous wastewater in an equalization tank equipped with a 2 mm bar screen to remove coarse solids. Submersible pumps transfer wastewater to the softening stage.
2️⃣ Softening – Coagulation – Physico-Chemical Sedimentation
Dosing NaOH removes Ca²⁺ and Mg²⁺ by forming CaCO₃ and Mg(OH)₂ precipitates.
PAC and polymer promote floc formation and solid-liquid separation.
Clarified water flows to the intermediate tank before evaporation.
3️⃣ Sludge Thickening & Dewatering
The system pumps chemical sludge to a thickening tank, then dewaters it using a filter press. The plant sends dewatered sludge to incineration or landfill.
4️⃣ Two-Stage HPVE Crystallization System
Stage 1:
Vacuum: -85 kPa
Boiling temperature: 55–60°C
Concentrates wastewater and initiates salt crystallization
Stage 2:
Vacuum: -95 kPa
Boiling temperature: 35–37°C
Utilizes secondary vapor heat for further evaporation
The system transfers condensate to the RO unit.
A centrifuge separates salt crystals from the concentrate, and the system recirculates mother liquor.
The plate heat exchanger condenses vapor into clean condensate. The cooling water absorbs heat and transfers it to the refrigerant evaporator, eliminating the need for a cooling tower.
The closed-loop heat recovery process achieves power consumption of only 100–115 W per liter of condensate.
The system sends condensate to the STRO membrane system for final polishing or discharge compliance.
5️⃣ RO Water Reuse System
The high-pressure pump increases pressure to 10 bar. The RO system recovers 95% permeate and returns 5% concentrate to the evaporation unit.
⚙️ 6. TECHNICAL SPECIFICATIONS – HPVE SYSTEM
| Item | Specification |
|---|---|
| System Type | HPVE (Heat Pump Vacuum Evaporator) |
| Treatment Capacity | 4,600 – 4,700 L/h |
| Operating Time | 22 – 23 hours/day |
| Evaporation Temperature | 35–40°C |
| Power Consumption | 100 – 115 W/L condensate |
| Water Recovery Rate | 95% |
| Clean Water Flowrate | 3,650 – 3,800 L/h |
| Condensate EC | < 1,000 µS/cm |
| Construction Material | Titanium Grade 2 – resistant to chloride corrosion |
🌱 7. PERFORMANCE & ENVIRONMENTAL BENEFITS
| Parameter | Before Treatment | After HPVE + RO |
|---|---|---|
| COD (mg/L) | >30,000 | <100 |
| Chloride (mg/L) | >117,000 | <1,000 |
| Heavy Metals (Cu, Ni) | 40–90 | <3 |
| Water Recovery | – | 95% |
| Sludge Volume | High | Reduced by 90% |
💧 The treated water meets QCVN 40:2025 – Column B and can support equipment washing or cooling systems.
🏁 8. RESULT
TVTS applies evaporation for hazardous wastewater treatment using HPVE technology to:
Treat wastewater with extremely high TDS and COD.
Reduce operating costs by 60–70% compared to conventional evaporation.
Achieve discharge compliance and move toward Zero Liquid Discharge (ZLD).
“TVTS does not just supply equipment — we deliver sustainable engineering solutions for hazardous wastewater treatment.”
