The new rejuvenation chemical treatment is introduced in this paper. This chemical treatment repairs the deteriorated RO membranes, and recovers the salt rejection ratio immediately. In the past, such kind of rejuvenation methods have been developed and reported only with table test basis and pilot plant test basis as seen in the IVREFERENCES [1][2][3]. This report describes the feature of the newly developed rejuvenation chemical treatment for the performance deteriorated RO membranes, the results of table tests, and the experience of the application to commercial RO plants in Japan and China. The new rejuvenation chemicals (hereafter RC) have totally different features compared to the ones previously referred.

The features of RC treatment are:

(1) On site treatment. It dose not required unloading the membranes from the pressure vessels.

(2) RC is applied only after cleaning. The continuous dose of RC is not necessary.

(3) RC is made form food additives. So it provides safe handling for the plant maintenance works.

At first the test was carried out to verify the effect to recover rejection rate of NaCl and SiO2 . The test results show that the RC treatment increased them from 74% to 95% for NaCl rejection, and from 28% to 83% for SiO2 rejection. The flux was kept more than 1.0m/day (25.26GFD) which corresponds approximately to new membrane. Next, the RC treatment was applied to an actual RO plant that had the problem of membrane performance deterioration. The RC treatment was applied under the off-line condition without unloading the RO membranes. We were successful to rejuvenate these deteriorated RO membranes at the commercial plant, and were able to prolong RO membrane’s life. The RC treatment increased the rejection from 90.8% to 96.2%. Practical application method and the effects of rejuvenation are introduced in this paper by showing experimental data on table tests and the experience on the commercial RO plant. The Big benefit is that the new Rejuvenation Chemical treatment provides a significant contribution to improve the quality of RO permeate water immediately at site when it is required.

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