• 2025-07-22

Two-way reverse osmosis

The two-stage reverse osmosis system achieves dual goals through two-stage treatment:

Production water purification mode: send the primary RO product water to the secondary RO unit to obtain higher purity water quality

Concentrated water recovery mode: send the primary RO concentrated water to the secondary RO unit to improve water resource utilization

The single-stage reverse osmosis system can remove about 99% of dissolved solids and simultaneously produce purified water (product water) and concentrated wastewater (concentrated water).

System operation principle

The two-stage RO system consists of two-stage reverse osmosis units in series, and the first stage has a larger processing capacity than the second stage. A buffer water tank needs to be set between the two stages to store the product water or concentrated water of the first RO and provide a stable water source for the second RO. The pretreatment scheme is dynamically adjusted according to the application target:

Concentrated water recovery application: Because the primary concentrated water is close to the dissolved saturation state, the two-stage system needs to be pretreated

Water purification application: When the secondary inlet water is the primary produced water, only the primary system can be pretreated

Core application value

1. Meet high-end water quality requirements

When the terminal process requires ultra-low TDS water quality (such as medicine and electronics industry), the following combination can be used:

Brackish water RO + Brackish water RO

Seawater RO + Brackish water RO

2. Improve water resource utilization

To address the global water shortage problem:

The maximum recovery rate of a single-stage RO system is 80%

The recovery rate of a two-stage RO system can reach 90%-95%

In the zero liquid discharge (ZLD) solution, DPRO is used in conjunction with an evaporator/salt crystallizer to achieve ultimate salt separation

Technical solution comparison

RO+mixed bed deionization (MBDI)

Can produce 18.2MΩ·cm ultrapure water, but resin regeneration requires the use of acid and alkali chemicals, which poses environmental risks

DPRO+electrodeionization (EDI)

No chemical regeneration is required, especially suitable for semiconductor-grade ultrapure water preparation

Technical advantages

This system achieves:

≥99.9% dissolved solids removal rate

Production water conductivity ≤0.1μS/cm

System recovery rate up to 95%

The full range of brackish water RO equipment supports two-stage configuration