Our SWRO plant is shutdown due to selectivity drop. We think the higher feed temperature (around 35oC) is the main cause of this problem. The effect seems permanent since its performance can not be recovered even after 2 weeks of shutdown. Does anybody have the same experience ? Is there any solution ?
i think that it is possible to try to find indigenous SWRO plants then try backcrosses
Either you have biofilm development, either you have scales.
You have to perform a chemical cleaning to restore membrane capabilities
Hi Mr. Wenden, I do not think the drop of rejection is related to relatively high temperature of the water. One simple reason why the SWRO membranes do not reject so well is the significant fouling occurring during the time the membranes have been shutdown, if the SWRO membranes have not been flushed (or CIP was performed) before the shutdown. Letting stagnant seawater stay in the SWRO membranes results in their permanent loss of productivity and rejection. Has the differential pressure of the SWRO system increased over the 2-week period when you have shut the system down?
If your productivity has not decreased after two weeks of shutdown - just the salt rejection, than it is likely that the raw feed water you have fed to the SWRO membranes before their shutdown contained an oxidant - chlorine (sodium or calcium hypochlorite), permanganate, chloramine, or other.
My suggestion is to perform both low-pH and high-pH CIP of the membranes with soaking time of 30 min and circulation of 30 min and see if the system rejection and/or productivity have improved/recovered. If rejection does not improve significantly, it is very likely that you have oxidized your membranes. There are different solutions to this challenge depending on what is the TDS of the permeate produced by your system.
It is due to membrane fouling, therefore you have to restore membrane capabilities by chemical cleaning ..