Those images want fixing up!
Hopefully calibre can do some good with them -- although calibre is really outsourcing the work to imagemagick, so if you know what you are doing you can probably do better than off-the-shelf settings in calibre.
imagemagick and a variety of other tools can do batch processing just like calibre, so it's not like your choices are "open each file in Photoshop/GIMP and fix it" or "use those calibre settings".
Perhaps you should hunt down the people in charge and ask them to rescan using a better-quality scanner and output to PNG. They could be doing a much better job digitizing.