How many ways can you name the arrangement of membranes?

Grade: Refers to the number of times the raw water has penetrated, that is, the number of times the produced water has passed through the reverse osmosis membrane element. The desalination rate of first stage reverse osmosis can reach 98-99%, so multi-stage reverse osmosis can achieve a desalination rate of over 99.5%.

Duan: Refers to the number of times the original water flows through a pressure vessel, that is, the number of times the concentrated water flows through different pressure vessels. According to the needs, multiple membrane components can be arranged into one, two, or even multiple stages, and the membrane components in each stage can be arranged into one, two, or even multiple segments. The so-called first stage refers to the feed liquid undergoing a first pressurized reverse osmosis separation, the second stage refers to undergoing a second pressurized reverse osmosis separation, and so on; Arrange identical membrane components into a segment at the same level.

The basic arrangement and combination of reverse osmosis membranes can be divided into the following six ways:

1. Through continuous membrane treatment, water and concentrated solution are continuously drawn out of the system. The characteristic of this method is that the water recovery rate is not high.

2. The concentrated liquid is returned to the feed liquid storage tank and mixed with the raw material liquid in a step-by-step cycle, and then separated again through reverse osmosis membrane modules. The characteristic is that the water quality of the permeate has decreased.

3. In the first stage multi-stage continuous type, the concentrated solution from the previous stage is used as the raw material for the second stage, and the cut through water is continuously discharged. Features suitable for situations with large water treatment capacity, high recovery rate, reduced amount of concentrated solution, but high proportion of solute in concentrated solution.

4. One level multi-stage cyclic type

Use the permeate water from the next stage as the raw material liquid for the previous stage and separate it. This concentrated solution can achieve higher concentration and is suitable for separation with concentration as the main purpose.

5. Multi segment conical arrangement

Both parallel connection within the segment and series connection between segments can meet the water recovery requirements of the reverse osmosis system and ensure that there is approximately the same flow state in each component of the device. High pressure pumps are needed to prevent a decrease in production efficiency.

6. Multi stage and multi-stage configuration of reverse osmosis membrane components

The multi-stage configuration of reverse osmosis membrane modules also has a cyclic approach, where the permeate water from the first stage is used as the feed water for the next stage and separated again. This continuous process leads the permeate water from the last stage out of the system. The concentrated liquid is mixed with the feed liquid from the subsequent stage to the preceding stage, and then separated. This method improves the recovery rate and water quality, but the consumption of the pump increases and there is a distinction between continuous and continuous methods. The selection and arrangement of membrane components should follow the design guidelines of the membrane, as well as consider various factors such as system usage, raw water conditions, equipment space limitations, system water production scale, and system water recovery rate, in order to comprehensively select the number of membrane components to be installed in the reverse osmosis pressure vessel and the basic arrangement of membrane components.

Information source: New Perspectives on Water Treatment