Abstract: A method is provided for treating contaminated wastewater of pH ranging from about 1.5 to 3 containing phosphate ions and fluoride ions. The method comprises treating the said wastewater with an amount of alkaline agent selected from the group consisting of limestone (CaCO.sub.3) and lime [CaO or Ca(OH).sub.2 ] sufficient to raise and maintain the pH at a level of about 3.5 to 6.5 following uniform mixing thereof in a first stage precipitation step to effect substantial precipitation of the contaminants. The treated wastewater is passed to a first stage settler to effect solid/liquid separation and provide a sludge of the precipitated contaminants which is removed and separated to provide an effluent substantially impoverished in the aforementioned contaminants, following which the contaminant-impoverished effluent is treated in a second stage precipitation step with lime in an amount sufficient to raise and maintain the pH of the effluent at a level of at least about 10.

Abstract: A method is provided for removing ammonia from wastewater containing in excess of about 15 ppm NH.sub.3 (N)-T. The method comprises treating the wastewater with an alkaline reagent selected from the group consisting of lime and caustic sufficient to raise the pH to provide a free ammonia equivalence (FAE) to a value of at least about 12.4, the free ammonia equivalence being determined as follows:FAE=pH+(.theta./15).sup.0.5wherein pH is the pH value of the treated wastewater and .theta. is the temperature of the wastewater in degrees Fahrenheit. The treated wastewater is gas-stripped to lower the total ammonia content of the treated wastewater to a value of less than about 10 ppm NH.sub.3 (N)-T, the gas stripping being controlled to maintain the free ammonia equivalence of the wastewater phase being stripped to a value of at least about 12.4, following which the stripped wastewater is acidified to lower the un-ionized ammonia content to less than about 0.05 ppm NH.sub.3 (N).

Abstract: A method is provided for the treatment of wastewater of pH ranging from about 1.5 to 3 containing at least about 100 ppm phosphorus as phosphate ions, at least about 50 ppm fluorine as fluoride ions and ammonia in excess of about 15 ppm NH.sub.3 (N)--T, the method comprising removing the phosphate and fluoride ions from the wastewater in a two-stage precipitation step; the first stage precipitation being conducted at a pH ranging from about 3.5 to 6.5 using an alkaline material selected from the group consisting of limestone (CaCO.sub.3) and lime [CaO or Ca(OH).sub.2 ] sufficient to form a precipitate which is removed to provide a filtrate of the wastewater which is treated in a second stage precipitation at a pH of at least about 10.5 using lime as the alkaline material sufficient to form a precipitate which is removed to provide substantially a clear effluent containing ammonia.