Turbidity is caused by ...

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.