I. Process Selection Guidelines
The choice of water treatment process should be based on the customer's water quality requirements:
- When the required water quality is below 10 μS/cm and the pure water flow rate is less than 3 tons/hour, either reverse osmosis (RO) or ion exchange systems can be used.
- When the water quality requirement remains below 10 μS/cm but the pure water flow exceeds 3 tons/hour, RO is preferred due to its lower operational cost. Ion exchange becomes economically unfeasible at this scale.
- If water quality requirements are below 5 μS/cm, a double-pass RO system is recommended regardless of the flow rate.
- For applications requiring higher pH values, ion exchange is not advisable, as the pH tends to fluctuate over time. RO systems, in contrast, maintain stable pH levels.
II. Key Considerations After Selecting the Process
- For RO or double-pass RO systems, special attention should be paid to the pretreatment stage and membrane selection. Pretreatment capacity should be approximately twice the required pure water output. It is advisable to use imported membrane elements, such as DOW (DuPont) membranes, to ensure performance and longevity.
- For ion exchange systems, high-quality resin is essential. A resin capture system should be included to prevent resin leakage during regeneration.
III. Comparison of the Two Main Purification Technologies
- Reverse Osmosis (RO):
RO employs a physical filtration process. It uses a semi-permeable membrane that allows only water molecules to pass through, effectively removing dissolved salts and other contaminants. The concentrated reject water is discharged from the system. RO systems are known for their ease of operation and consistent water quality, making them a leading technology in modern water treatment.
- Ion Exchange:
This is a chemical process in which resin beads react with ions in the water to produce high-purity water. Once the resin becomes saturated, it must be regenerated with hydrochloric acid and caustic soda, a more complex and maintenance-heavy process.
IV. Typical Process Flows for Industrial Pure Water Equipment
Single-Pass RO System:
Tap Water Tank → Booster Pump → Multimedia Filter → Activated Carbon Filter → Softening Filter → RO System → Pure Water Tank
Double-Pass RO System:
Tap Water Tank → Booster Pump → Multimedia Filter → Activated Carbon Filter → Softening Filter → First-Stage RO → Intermediate Water Tank → High-Pressure Pump → Second-Stage RO → Pure Water Tank
Ion Exchange System:
Tap Water Tank → Booster Pump → Multimedia Filter → Activated Carbon Filter → Cation Exchange Bed → Anion Exchange Bed → Pure Water Tank
