What are some ways that membranes can be arranged?

Level Refers to the number of times the raw water permeates, that is, the number of times the produced water passes through the reverse osmosis membrane element. The desalination rate of the first-stage reverse osmosis can reach 98~99%, so multi-stage reverse osmosis can achieve a desalination rate of more than 99.5%.

Stage 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 the needs, multiple membrane modules can be arranged into one level, two levels or even multiple levels. The membrane modules in each level can also be arranged into one stage, two stages or even multiple stages. The so-called first level refers to the feed liquid being subjected to once pressurized reverse osmosis separation, the second level refers to being subjected to twice pressurized reverse osmosis separation, and so on; in the same level, the same membrane modules are arranged into one stage.

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

1. Single-stage continuous

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

　　 2. Single-stage circulating

　　Part of the concentrate is returned to the feed liquid storage tank and mixed with the raw material liquid, and then separated again through the reverse osmosis membrane module. The characteristic is that the quality of the permeate is reduced.

　 　3. Single-stage multi-stage continuous

　　The concentrate of the previous stage is used as the raw material liquid for the next stage, and the separated permeate is continuously discharged. It is suitable for occasions with large water treatment capacity, high recovery rate, and reduced amount of concentrate, but the proportion of solute in the concentrate is higher.

　　 4. Single-stage multi-stage circulating

　　The permeate of the next stage is used as the raw material liquid for the previous stage for separation. In this way, the concentrate can achieve a higher concentration, which is suitable for separation where concentration is the main purpose.

　 　5. Multi-stage conical arrangement

　　It is both parallel within the stage and series between stages, so it can meet the water recovery rate requirements of the reverse osmosis system and ensure that there is a roughly the same flow state in each component in the device. A high-pressure pump is needed to prevent a decrease in production efficiency.

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

　　The multi-stage and multi-stage configuration of reverse osmosis membrane modules also has a circulating type, in which the permeate of the first stage is used as the feed water for the next stage for further separation, and so on continuously, and the permeate of the last stage is drawn out of the system. The concentrate is mixed with the feed liquid from the previous stage to the next stage, and then separated. This method improves the recovery rate and water quality, but the pump consumption increases and is different from the continuous type.

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