There are several common processes in the design of reverse osmosis membrane separation process:
In this way, the concentrated solution and the water produced are continuously introduced. The recovery rate of water is not high, and the industrial application is less.
The other form is a first-stage recycling process, which is to return the concentrated water part to the feed tank, so that the concentration of concentrated solution increases continuously, so the water yield is large, but the water quality of the water is decreased.
(2) the level of multiple process when using reverse osmosis as enrichment process, an enrichment can not meet the requirements, you can use this multi-step way, this way concentrated liquid can reduce the size and concentration increased, water rate increased accordingly.
When the desalination rate of seawater was reduced from 35000 mg/L to 500mg/L, it was required to divide the NaCl from 35000 mg/L to 500mg/L, and it was divided into two steps if the salt rate was as high as 98.6%.
The first step is to remove the NaCl 90%, and the second step is to remove the NaCl 89% from the first step, which can meet the requirements.
If the removal rate of the membrane is low, and the permeability of water is high, two steps are used to compare the economy, while at low pressure and low concentration, the service life of the film can be improved.
(4) multistage reverse osmosis process in this process, will be the first level concentrate as a secondary feed liquid, liquid secondary again as the next level of feed liquid, at this time due to the in vitro through the water at all levels to discharge directly, so as the series increase water recovery rate rise, rise of concentrated liquid volume reduction.
The number of membrane components should be reduced gradually in order to ensure the flow rate of liquid and control the concentration polarization.