Hi Nadeem, My first piece ...

Hi Nadeem,

My first piece of advice would be that you don't purchase any equipment or change your process until you have a good idea of what the issue is.

SDI is a generic measurement, which will tell you that the water is likely to cause fouling of your RO membranes, but won't actually tell you what the foulant is. For example, high SDI can be associated with iron, manganese, calcium, silica, algae as well as many others.

The fact that the high SDI does not appear to be associated with discolouration of the filter might help to narrow down the list of suspects but ultimately you will probably need to do a detailed analysis of the water.

Let me know if you are able to provide system design details and water quality data.

Daniel