Two-Stage Reverse Osmosis Water Treatment Equipment

Two-stage reverse osmosis (Double-Pass RO) is a high-purity water production process that connects two reverse osmosis units (or two sets of RO membrane modules) in series. The product water from the first-stage RO flows into an intermediate tank, and is then pumped by the second-stage high-pressure pump into the second-stage RO membrane module for secondary desalination, resulting in higher quality purified water.

Compared with single-stage RO, two-stage RO achieves a higher desalination rate (typically ≥99%), with product water conductivity controlled below ≤2 μS/cm. The effluent quality is stable and reliable, meeting the high requirements of high-end industries such as pharmaceuticals, electronics, and chemicals. For raw water with poor quality (such as high-salinity surface water or reclaimed water), two-stage RO can also stably produce qualified purified water.

Main Components:

1. Pre-treatment Unit

• Raw water tank, raw water pump

• Multi-media filter (removes suspended solids, sediment)

• Activated carbon filter (removes residual chlorine, organic matter, odor)

• Water softener or scale inhibitor dosing system (prevents membrane scaling)

• Cartridge filter (5μm, security filtration)

2. First-Stage RO Unit

• First-stage high-pressure pump

• First-stage RO membrane modules (anti-fouling membranes)

• First-stage RO cleaning system

3. Intermediate Unit

• Intermediate tank (stores first-stage RO product water)

• Intermediate booster pump (optional, may be omitted if second-stage HP pump has adequate suction capability)

4. Second-Stage RO Unit

• Second-stage high-pressure pump

• Second-stage RO membrane modules (low-pressure membranes can be used)

• Second-stage RO cleaning system

5. Post-Treatment Unit (Optional)

• UV sterilizer

• Ozone generator

• Cartridge filter

• pH adjustment system

6. Control System

• PLC fully automatic control

• Touch screen interface

• Online conductivity meter, flow meter, pressure gauge, pH meter

• Auto start/stop, automatic flushing, low pressure protection, overpressure protection, low water protection, auto-stop when tank is full

• Remote monitoring (optional)

Features:

• Product water flow: Customized (0.25-100 T/H)

• Desalination rate: ≥99% (cumulative for two stages), product conductivity ≤2 μS/cm

• Total recovery rate: 60%-75% (first stage 50%-60%, second stage 75%-85%)

• Stable effluent quality with strong resistance to feed water quality fluctuations

• High degree of automation: PLC fully automatic control for unattended operation

• Independent cleaning system for each stage for easy maintenance

• 304/316L stainless steel piping and frame, corrosion-resistant

• Modular design for easy expansion

• Optional energy recovery device to reduce operating costs

Applications:

• Pharmaceutical industry: Purified water, water for injection pre-treatment, oral liquid water

• Electronics industry: Electronic-grade ultrapure water pre-treatment (as pre-treatment for EDI)

• Food & beverage: High-end purified water, beverage ingredient water, dairy products, liquor blending water

• Chemical industry: Fine chemicals, cosmetics, process pure water

• Power industry: Boiler feed water (medium/high pressure boilers)

• Laboratories: Analytical testing, research water

• Biotechnology: Culture media preparation, biological reagent water