First thing you should do is after you have connected the scanner to your computer, go to Finder, navigate to Applications and then double-click on the "Image Capture" icon. Press the "Scan" button on your scanner. The Image Capture application will recognize the connected scanner and will display a preview of the picture. Select any special options you want for the scanned picture and click "Scan" in the lower-right corner of the preview window. A scanned image of the picture will now be saved to the "Pictures" section of your user folder. I am advising you to try this as your MAC OS might recognize the scanner without the drivers.
If that doesn't work, try the drivers from Agfa website for SnapScan E20
. Website doesn't specify for which MAC OS version they are. In addition, here's a link to th manual