To provide technology for achieving more efficient water filtration systems for the mineral industry, the Bureau of Mines performed demonstration filtration tests at three iron ore mines and one steel mill. A comparison of equivalently sized magnesium oxide (mgo) and sand filters showed that mgo had a higher capacity and could operate at higher filtration rates than sand. In demonstration tests when alum (alk(so4)2) was the coagulant, suspended solids breakthrough occurred even though the pressure across the filter (head loss) was 7 psig or less. Under these circumstances, the mgo demonstrated 20 to 100 pct greater filtration capacity, defined in terms of the volume of water filter before breakthrough. When an organic flocculant was used at one location, head loss was the run-limiting factor; the filters essentially plugged without any solids breakthrough.