Turbidity has no direct correlation to required micron rating for pre-filters.
- i.e. your typical cotton wound or poly spun pre-filter will catch sediment and other solids, will also partially help with other particulate matter, but depending on the current FWA you will apply the correct pre-treatment (i.e. flocculent or chlorine injection) and upstream vessel filtration (3-5 vessel in service with 1 in staged B/W).
Depending on your application your design requirements will change.
Small on demand WTP often wrongly depend on staged filter cartridges before RO (i.e. 50mic followed by 10mic or 5mic).
A better setup will cost more, but saves money, increases output and reliability...
===> For Potable WTP Pre-injection, Contact Tank to Feed Tank, MMF, CMF, Interim Injection if required, Contact Tank (RO Feed Tank), SMBS if required, Anti-Scalant, DGD, Polisher Cartridges, RO, Calcite Filter and post chlorination... proven best and most adaptable to design changes.
Check the file I attached and let me know if you want to try. Better2earth aims to provide circular solutions to common problems with a technology that is environmentally sustainable.
I think the question should be what is causing the turbidity and in what are you getting turbidity through. E.g. are you flushing a main, is it after a burst repair or is it some other problem is this in a manufacturing environment. Otherwise it is as Eran and Jibok says there is no correlation between turbidity or filter size. If on a water main you can just flush until clear.
Turbidity is caused by particles suspended or dissolved in water that scatter light making the water appear cloudy or murky. Particulate matter can include sediment - especially clay and silt, fine organic and inorganic matter, soluble colored organic compounds, algae, and other microscopic organisms.
So, it is difficult to estabish a direct relation between turbidity and filter size. Particulates from 1 to 150 microns can cause turbidity. Typically turbidity can be reduced to 20 micron with standard backwashable filter, however flow rates of 200l/min/m2 is recommended. Turbidity can be reduced to 10 micron with a multimedia filter while providing flow rates of 600l/min/m2. Cartridge filters of various sizes are also available down into the submicron range.