Regarding additives to help the settling, perhaps contact your water treatment specialty chemcials and treatment programs vendor. You likely already use one at your water treatment or boiler plants, if you have one. (eg: Betz, Nalco).
You didn't supply details, but, of course, further analysis of fundamentals, such as pH (is it even precipitating?), existing process hydraulics (cone basin?.. clarifier?), etc, would be a good first step.
Good luck.