I started getting vertical dark lines in my ADF scans on the the highly great Canon MF4570dw Laser/Multifunction.
Use this to determine location of small bits of dust on your scans. Then clean the glass under the ADF guide, slide it out carefully.
Print the OpenOffice file Dirty Printer Test Sheet and then feed the ADF. Your white streaks can be located and the cleaning intensified at that location. Takes several tries in my experience.
See: Black vertical line on scans and inspired by the suggestion from Fixya Lines when scanned