CNIn the desalination water treatment equipment, the use of reverse osmosis membrane desalination treatment is the most advanced and most economical technology. In the daily operation of reverse osmosis equipment, often found reverse osmosis water equipment desalination rate of excessive decline in the situation, then the desalination rate of pure water equipment, the reasons for the decline?
1、High pressure caused by desalination rate decreased
Increasing pressure is also accompanied by a rapid decline in desalination rate. At normal flow rates, the rise in pressure is usually due to the ingress of contaminants, contaminants and scale caused by the barrier of the membrane element water flow, resulting in a decrease in water production. When the set of water flow exceeds the set, there will be excessive pressure, when the start of the water pressure to raise too fast, the occurrence of water hammer pressure difference will be great, if the membrane has been contaminated, especially microbial contamination, pressure Will increase. The pressure difference between the feed water and the concentrate is the hydraulic resistance, which is related to the flow rate and temperature of the feed water. It should keep the water and concentrated water at a certain flow rate. The possibility of high pressure difference are: scale, microbial contamination, scale inhibitor precipitation, filter filter media leakage, water / concentrated water seal damage
2、 Online chemical cleaning unreasonable
Ultra-pure water equipment in operation is inevitable pollution. Pretreatment and addition of various kinds of pharmaceuticals can only minimize the possibility of reverse osmosis contamination, and can not be completely eliminated. Therefore, long-running reverse osmosis system after a certain period of time after the operation, must be fully demonstrated and confirmed which kind of pollutants. For the characteristics of polyamide film, according to the appropriate dirt to select the appropriate cleaning agent:
a, hydrochloric acid (36% -38%), prepared into 0.12% dilute solution to remove the metal oxide.
b, sodium hydroxide, formulated as 0.1% dilute solution, removal of silica, microbial film, organic, etc., the pH is about 12. The role of the organic microbial mucosa hydrolysis damage and stripping, for silica gel scale, the formation of sodium silicate is soluble, and thus descaling.
c, ethylenediaminetetraacetic acid four sodium, as a chelating agent is widely used in industrial cleaning, 1% aqueous solution pH10.5-11.5, adding the concentration of 0.5% -1%.
d, sodium dodecyl sulfonate, an anionic surfactant, the purpose of the organic compounds dispersed in the solution, can reduce the surface tension of the solution, causing positive adsorption, so that the solution surface solute molecules concentration is greater than the solution Concentration of internal solute molecules. Sodium dodecyl sulfonate is the most important surfactant for reverse osmosis cleaning, adding a concentration of 0.025%.
e, formaldehyde, formaldehyde on bacteria, fungi, viruses, spores and protozoa, etc. are very strong kill force, adding the concentration of 0.5% -35.
3、 Residual chlorine control poor
Sodium hypochlorite as a fungicide, widely used in pure water pretreatment. In the reverse osmosis system, in order to prevent reverse osmosis of microbial contamination, reverse osmosis water to be chlorinated. Determination of residual chlorine with a colorimeter, control the residual chlorine concentration in the sand filter inlet is generally 0.5mg / L, not less than 0.3mg / L, in the reverse osmosis safety filter should be less than 0.1mg / L. The polyamide film is a prominent problem to prevent it from being oxidized. The residual chlorine value and strong oxidation of the water are all adversely affected, and must be strictly controlled. It is therefore important to regularly check the residual chlorine value of reverse osmosis water.
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