RO membrane technology common problems and solutions

1.How often should the reverse osmosis system be cleaned?

In general, when the standardized flux drops by 10-15%, or the system desalination rate drops by 10-15%, or the operating pressure and the pressure difference between sections increase by 10-15%, the RO system should be cleaned. The cleaning frequency is directly related to the pre-degree of the system. When SDI15 <3, the cleaning frequency may be 4 times a year; when SDI15 is about 5, the cleaning frequency may be doubled but the cleaning frequency depends on each project site The actual situation.

2.What is SDI?

(SDI, also known as fouling index) is a measure of the silt density index of the influent water, which is an important parameter that must be determined prior to RO design. The SDI15 value must be ≤5 for membrane system feed water. 

  

3.General feed water should be used RO process or ion exchange process?

In general, the higher the salt content, the more economical RO is, and the lower the salt content, the more economical ion exchange is. At present, the use of reverse osmosis + ion exchange process or multi-stage reverse osmosis or reverse osmosis + other depth desalination technology combination process has become a recognized technical and economic more reasonable water treatment program.

4.How many years do reverse osmosis membrane elements generally last?

The service life of the membrane depends on the chemical stability of the membrane, physical stability of the element, cleanability, water source, pretreatment, cleaning frequency and operation management level. According to economic analysis, it is usually more than 5 years.

5.What is the difference between reverse osmosis and nanofiltration?

Nanofiltration is a membrane liquid separation technology located between RO contract ultrafiltration. RO can remove solutes with molecular weight less than 0.0001 microns, while nanofiltration can remove solutes with molecular weight around 0.001 microns.

6.Who sells membrane cleaning agent or provides cleaning services?

Water treatment companies can provide special membrane cleaning agent and cleaning services, users can buy cleaning agent for membrane cleaning according to the recommendations of membrane companies or equipment suppliers.

7.What is the upper concentration of silica in the feed water of RO membrane?

The concentration of silica allowed depends on temperature, pH and scale inhibitor, usually the maximum concentration allowed at the concentrated water end is 100ppm without scale inhibitor, some scale inhibitors can allow the concentration of silica in concentrated water up to 240ppm.

8.Can reverse osmosis remove microorganisms such as viruses and bacteria?

Reverse osmosis (RO) is very dense and has a very high removal rate for viruses, phages and bacteria, at least 3log or more (removal rate >99.9%).

9.What is the effect of temperature on water production?

The higher the temperature, the higher the water production and vice versa. When operating at higher temperatures, the operating pressure should be lowered to keep the water production constant and vice versa.

10.How long is the downtime allowed without system flushing?

If the system uses scale inhibitor, when the water temperature is between 20~38℃, about 4 hours; when it is below 20℃, about 8 hours; if the system does not use scale inhibitor, about 1 day.