Abstract: Modification of phosphoric acid manufacturing provides improved process waters: decontaminated water pH-adjusted to be only slightly acidic, scrubber process water, gypsum stack water, and a composite of the latter two waters. The composite water undergoes two-stage neutralization with clarification, eliminating precipitatable contaminants, in forming the pH-adjusted water, which in turn is useful in forming scrubber process water or gypsum stack water, as needed, Resulting gypsum stacks and rainfall surge ponds, having been made relatively fluoride-free through such processing modification, and preferably also having been lined, supersede previous gypsum stacks and acid gypsum ponds—whether lined or not.

Abstract: Generation, use, and treatment of new and unique process waters in or for wet-process phosphoric acid manufacturing to substantially eliminate discharge of contaminants to the environment. Acid pond water from conventional wet-process phosphoric acid manufacturing, contaminated with compositions containing fluorine, heavy metals, and radioactive elements such as radium-226, plus residual P.sub.2 O.sub.5, is superseded. Substantially all contaminants from the wet-process are insolubilized and removed, whereas P.sub.2 O.sub.5 normally lost is recovered. Decontaminated gypsum stack water with a mildly acidic pH results from stepwise raising of wastewater pH, with clarification, and subsequent re-acidification, to provide a decontaminated process water with slightly acidic pH adapted to match the pH of environmental ground water. The process is made more economical, while enhancing protection of surrounding air, soil, and water from contaminants.

Abstract: Phosphoric acid wastewater treatment to substantially eliminate discharge of contaminants to the environment. Acid pond water from conventional wet-phosphoric acid manufacturing is replaced by gypsum pond water having a pH closely matching that of the surroundings. Essentially all fluorides are insolubilized and substantially all phosphoric acid is recovered, minimizing loss to the environment.

Abstract: Method for neutralizing waste cooling pond waters of wet process phosphoric acid plants, and for neutralizing similar waste waters from phosphate complexes, wherein neutralization is performed in two stages and wherein the flocculent precipitate from the second neutralization stage is disposed of by dissolving it in incoming untreated waste water prior to the first neutralization stage. Neutralization in the first neutralization stage is accomplished by addition of limestone to the waste water, and neutralization in the second neutralization stage is accomplished by addition of limestone to the water phase from the first neutralization stage. The precipitate from the first neutralization stage is readily separable from the liquid phase, and is suitable for disposal in the gypsum stack of a wet process phosphoric acid plant. The fully neutralized water meets federal and state requirements for disposal in surface and underground water systems as to pH and as to fluoride and phosphate content.