For membrane I don't know what kind of membrane you used, and pore size of it.
My opinion is to use an integrated system, a bag filter, then inorganic membrane, at last organic RO system, it depends on the content of your waste water and your final treated requirement. If necessary chemical...
You don't mention what kind of memrane you are using. Every manufacturer should have their manual also. If it's ceramic membrane pilot plant, I can give you one. some more information and pictures may be more helpful.
William Lee
cnwilliamlee@gmail.com