Irreversible RO Fouling

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Hi everyone, I just came on board with a team of engineers who are currently designing and will be constructing a Water Treatment Plant, and one of the treatment process that is currently been considered is the use of RO in place of some other conventional process, however, during the 1st pilot study, they found out that the fouling on RO was irreversible.

The Foulant analysis showed an heterogeneous mixture of organic and inorganic materials. On the organic side of things, mainly Carbohydrates were observed, amorphous organics, silica, fungi, algae and gram positive and negative bacteria were also observed. On the inorganic side of things, silicon was the primary contributor to the surgace foulant. however, salts (Mg, Na, K), aluminum and calcium were also observed. Additional, granular foulant coated the membrane which as a combination of clay (aluminum silicates), excess silica and Mn.

So a 2nd pilot study is on the way, and our goal is to determine what is causing this irreversible fouling and how we can effectively prevent it. If I may add we currently pulling from the Red river and Red Lake river and they are mixed at 15% to 85% due to Red lake river's hardness.

I was wondering if anyone one of you gentlemen and ladies can share with me the best way to approach to design this study and what parameters (i.e SDI) I should be measuring during this study. Our current plan is to setup 4 parallel RO skids and try different pretreatment processes on the feed water before it goes through the RO. Less I forget, a UF will be placed upstream. Thank you very much for your time. FYI we have recently observed an increase in Sulfate concentration in the raw water, at least in the past 3 months.