Grade : refers to the permeation times of the raw water, that is, the number of times the product water permeates the reverse osmosis membrane element. The desalination rate of one-stage reverse osmosis can reach 98-99%, so multi-stage reverse osmosis can achieve a desalination rate of more than 99.5%.

Section : refers to the number of times the raw water flows through the pressure vessel, that is, the number of times the concentrated water flows through different pressure vessels.

According to needs, a plurality of membrane modules can be arranged into one-stage, two-stage or even multi-stage, and the membrane modules in each stage can be arranged into one-stage, two-stage or even multi-stage. The so-called first stage means that the feed liquid is separated by one pressurized reverse osmosis, the second stage refers to the second pressurized reverse osmosis separation, and so on; in the same stage, the same membrane modules are arranged into one section. 

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

1. One-stage, one-stage continuous type

After membrane treatment, the permeated water and concentrate are continuously drawn out of the system. The characteristic of this method is that the recovery rate of water is not high.

2. One-stage, one-stage cycle

Part of the concentrated liquid is returned to the feed liquid storage tank to be mixed with the raw material liquid, and then separated through the reverse osmosis membrane module again. Features The water quality of the permeate has decreased.

3. One-level multi-stage continuous type

The concentrated liquid of the previous stage is used as the raw material liquid of the next two stages, and the cut permeated water is continuously discharged. The characteristics are suitable for occasions with large water treatment capacity, the recovery rate is high, the amount of concentrated liquid is reduced, but the proportion of solute in the concentrated liquid is high.

4. One-stage multi-stage circulation type

The permeated water of the next stage is used as the raw material liquid of the previous stage, and the separation is carried out. In this way, the concentrate can obtain a higher degree of concentration and is suitable for separation where concentration is the main purpose.

5. Multi-segment cone arrangement

Both in parallel within the section and in series between the sections, this can not only meet the requirements of the water recovery rate of the reverse osmosis system, but also ensure that each component in the device has roughly the same flow state. A high-pressure pump is required to prevent a drop in productivity.

6. Multistage and multistage configuration of reverse osmosis membrane module

The multi-stage and multi-stage configuration of the reverse osmosis membrane module also has a circulating type to separate the permeated water of the first stage as the feed water of the next stage, so that the permeated water of the last stage is drawn out of the system continuously. The concentrated liquid is mixed with the feed liquid of the previous stage from the latter stage, and then separated. This method improves the recovery rate and water quality, but the consumption of the pump increases and the continuous type is divided.

The selection and arrangement of membrane modules should comply with the design guidelines for membranes, and also consider many factors such as system usage, raw water conditions, equipment space limitations, system water production scale and system water recovery rate to comprehensively select the built-in membrane of the reverse osmosis pressure vessel. Number of elements and basic arrangement of membrane modules.