Process, apparatus and article for treating an aqueous solution containing biological contaminants. The process includes contacting an aqueous solution containing a biological contaminant with an aggregate composition comprising an insoluble rare earth-containing compound to form a solution depleted of active biological contaminants. The aggregate includes more than 10.01% by weight of the insoluble rare earth-containing compound. The insoluble rare earth-containing compound can include one or more of cerium, lanthanum, or praseodymium. A suitable insoluble cerium-containing compound can be derived from a cerium carbonate, a cerium oxalate or a cerium salt. The composition can consist essentially of cerium oxides, and optionally, a binder and/or flow aid. The aggregate includes no more than two elements selected from the group consisting of yttrium, scandium, and europium when the aggregate is to be sintered. Although intended for a variety of fluid treatment applications, such applications specifically include removing or deactivating biological contaminants in water.