Antiice,
If I was projecting this system, I would carefully think about adopting an agitator, or mixing system to the tank. Instead of forcing the pump recycling the solution you can avoid the separation of the solids and it is possible to keep the solution in permanent homogeny through a mixer...
Fuady,
Agitation and fluid motion is a very complex subject. There is a lot of publication about it, and respected companys investing in research & development. NJIT (www.njti.edu) has some very good publications. There are also computer programs to do projects on agitators, including...
Codeware offers some kind of simulation for PVs at their web site www.codeware.com
also see www.cerebroinc.com, they also have some demos available on line. Those are not training program, but works nice and are free. Good lucky.