Seawater Desalination Boron Pollution Prevention Process
13 Jul 2025
Boron Removal Process Flow
graph TB 
A[Seawater Intake] --> B[Enhanced Pretreatment]
B --> C[pH Adjustment Unit]
C --> D[Primary SWRO]
D --> E[Boron-Specific Secondary RO]
E --> F[Ion Exchange Resin]
F --> G[Product Water Tank]
B --> H[Brine Discharge]
subgraph **Core Boron Removal**
C -->|NaOH dosing ↑pH to 9.5| D
D -->|Permeate Boron: 2~3ppm| E
E -->|Specialized high-boron-rejection membrane| F
F -->|Lewatit® S108 resin| G
end
Key Process Design Parameters
| Process Stage | Core Measures | Technical Parameters | Boron Removal Rate |
|---|---|---|---|
| pH Adjustment | NaOH dosing + mixing reactor | pH=9.5±0.2 (Boric acid→Borate ion) | +40% rejection↑ |
| Primary SWRO | Brackish water membrane (BWRO) + high pressure | Operating pressure ≥65 bar, Recovery 45% | 60~70% |
| Boron-Specific RO | Boron-trap membrane (e.g., Dupont FilmTec™ BW-4) | Cross-flow design, velocity ≥1.5m/s, pH 9.0 | 90~95% |
| Ion Exchange | Macroporous chelating resin (Benzimidazole groups) | Breakthrough control: 0.3mg/L, Regeneration with 4% H₂SO₄ | >99.9% |
Note: At pH>9.5, boron converts from neutral B(OH)₃ to charged B(OH)₄⁻, increasing RO rejection from <40% to >85%
Intelligent Control System
- pH Co-regulation
if [B]₁ > 1.5mg/L: # Primary RO permeate boron exceeded
PID_dosing(NaOH) → Target pH=9.5 ±0.1
else:
Maintain pH=7.8~8.2 # Standard anti-scaling mode -
Resin Regeneration Trigger
- Activated when online boron analyzer >0.4mg/L
- Thermal regeneration at 50°C (↑ desorption efficiency)
Cost Optimization Strategies
| Measure | Cost Impact (1000m³/d plant) | Boron Removal Improvement |
|---|---|---|
| Boron-Specific RO Membranes | +¥500K/year (membrane cost ↑30%) | 95%→99% |
| Thermal Energy Recovery | Steam savings ¥120K/year | Regeneration efficiency +40% |
| Concentrate Recycling | ↓15% wastewater discharge | System recovery ↑ to 60% |
Contingency Plans
| Failure Mode | Automated Response | Backup Solution |
|---|---|---|
| pH excursion (>10.0) | HCl neutralization + feed pause | Switch to cartridge filter bypass |
| Resin breakthrough | Switch to standby vessel + alarm | Secondary RO boost pressure |
| Scaling alert (LSI>2.0) | Auto-inject antiscalant (SHMP+AA) | Trigger CIP cycle |
Project Data (10,000m³/d SWRO Plant, Middle East)
| Process Stage | Feed Boron (mg/L) | Product Boron (mg/L) | Capital Cost Share |
|---|---|---|---|
| Conventional Single-stage SWRO | 4.8 | 1.9 | - |
| This Solution | 4.8 | 0.15 | +18% |
| OPEX | Standard: ¥2.8/m³ | This process: ¥3.1/m³ | Compliance guaranteed |
Verification: Online ICP-MS (LOD: 0.001mg/L) + ISO 17381 weekly validation
Full technical documentation including PID diagrams and resin specifications can be provided upon request. Validated for high-boron seawater (e.g., Red Sea, Mediterranean).
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