Ineffective monitoring of residual chlorine in reverse osmosis equipment

Ineffective monitoring of residual chlorine in reverse osmosis equipment

If the pump for adding NaHSO3 fails or the liquid fails, or the membrane is damaged by residual chlorine when the activated carbon is saturated.

Improper cleaning and incorrect cleaning methods lead to damage of membrane performance

Equipment in the process of use, in addition to the normal decay of performance, due to pollution and caused by the decay of equipment performance is more serious.

EDI high-purity water equipment is usually contaminated with chemical scale, organic and colloidal contamination, microbial contamination, etc.. Different contaminants show different symptoms. The symptoms of membrane contamination are also different from one membrane company to another.

In the project we found that the symptoms of contamination are not the same as the duration of contamination.

For example, if the membrane is contaminated with calcium carbonate scale, when the contamination time is one week, the main symptoms are rapid decrease of desalination rate, slow increase of pressure difference, and no significant change of water production, and the performance can be fully restored by citric acid cleaning. Pollution time for a year (a pure water machine), salt flux from the initial 2mg / L rose to 37mg / L (the original water for 140mg / L ~ 160mg / L), water production from 230L / h down to 50L / h, after cleaning with citric acid, salt flux down to 7mg / L, water production rose to 210L / h.

In addition, pollution is often not a single, the symptoms of its performance also have some differences, making the identification of pollution more difficult.

Identify the type of pollution to be integrated raw water quality, design parameters, pollution index, operating records, equipment performance changes and microbiological indicators to determine.

(1) Colloidal contamination: Colloidal contamination occurs, usually accompanied by the following two characteristics: A, pre-treatment in the microfilter clogged very quickly, especially the differential pressure increases quickly, B, SDI value is usually above 2.5.

(2) Microbial contamination: When microbial contamination occurs, the total number of bacteria in the permeable water and concentrated water of the RO equipment is relatively high, and the maintenance and disinfection must not be carried out as required.

(3) calcium scale: can be based on the original water quality and design parameters to determine. For carbonate-type water, if the recovery rate is 75%, when the design is added scale inhibitor, the LSI of the concentrated solution should be less than 1; when no scale inhibitor is added, the LSI of the concentrated solution should be less than zero, and generally no calcium scale will be produced.

(4) A 1/4 inch PVC plastic pipe can be inserted into the component to test the performance change of different parts of the component to judge.