Simultaneous ammonia and fluoride treatment for wastewater

A method for treating wastewater containing ammonia and fluoride to remove fluoride and ammonia therefrom, comprising the following steps:

• measuring the oxidation-reduction potential of said wastewater;
• adding an oxidizer to said wastewater in sufficient quantity to increase the oxidation-reduction potential of said wastewater to be more oxidizing than that of a chloramine solution;
• adding a soluble calcium salt to the wastewater at a concentration greater than stoichiometric, said soluble calcium salt lowering the solubility of fluoride in the wastewater and promoting precipitation of solid calcium fluoride;
• separating treated wastewater with a lower level of suspended solids from a concentrate with a higher level of suspended solids;
• destroying excess oxidizer and oxidation by-products in said wastewater.

A method for treating wastewater containing ammonia and fluoride to remove fluoride and ammonia therefrom, comprising the following steps:

• diluting said wastewater to achieve ammonia and fluoride concentrations that can be safely treated without excessive heating and generation of gaseous ammonia fumes;
• adjusting the pH of said wastewater prior to and during treatment to pH 7-8 to minimize formation of toxic by-products by addition of a solution containing an alkaline compound selected from the group consisting of potassium hydroxide, sodium hydroxide, lime, slaked lime, sodium carbonate, and calcium carbonate;
• measuring the oxidation-reduction potential of said wastewater using an oxidation-reduction potential measuring device;
• adding an oxidizer to said wastewater in sufficient quantity to increase the oxidation-reduction potential of said wastewater to be more oxidizing than that of a chloramine solution, said oxidizer being selected from the group consisting of sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, chlorine, chlorine dioxide, ozone, and hydrogen peroxide;
• adding a soluble calcium salt to the wastewater at a concentration greater than stoichiometric, said soluble calcium salt lowering the solubility of fluoride in the wastewater and promoting precipitation of solid calcium fluoride, said soluble calcium salt being selected from the group consisting of lime, slaked lime, calcium chloride, calcium bromide, calcium nitrate, calcium carbonate, and calcium sulfate;
• destroying excess oxidizer and oxidation by-products in said wastewater by adding one or more oxidation by-product and excess oxidant neutralizing reagents to said wastewater, said one or more oxidation by-product and excess oxidant neutralizing reagents being selected from the group consisting of hydrogen peroxide, sodium bisulfite, sodium sulfite, and sodium thiosulfate;
• adding one or more coagulating and flocculating reagents to said wastewater, said one or more coagulating and flocculating reagents being selected from the group consisting of EnChem™ 0696 coagulant, EnChem™ 9025 polymer, ferric alum, aluminum chloride, potassium aluminum sulfate, potassium aluminum chloride, polyaluminum chloride, ferric chloride, ferric sulfate, and polymeric organic flocculating agents;
• and
• separating treated wastewater with a lower level of suspended solids from a concentrate with a higher level of suspended solids by passing said wastewater through a solids separation device, said solids separation device being selected from the group consisting of a conventional settling tank, a filtration membrane system, and an EnChem™ membrane filtration system.

A method for treating wastewater containing ammonia and fluoride to remove fluoride and ammonia therefrom, comprising the following steps:

• diluting said wastewater to achieve ammonia and fluoride concentrations that can be safely treated without excessive heating and generation of gaseous ammonia fumes;
• adjusting the pH of said wastewater prior to and during treatment to pH 7-8 to minimize formation of toxic by-products by addition of a solution containing an alkaline compound selected from the group consisting of potassium hydroxide, sodium hydroxide, lime, slaked lime, sodium carbonate, and calcium carbonate;
• measuring the oxidation-reduction potential of said wastewater using an oxidation-reduction potential measuring device;
• adding an oxidizer to said wastewater in sufficient quantity to increase the oxidation-reduction potential of said wastewater to be more oxidizing than that of a chloramine solution, said oxidizer being selected from the group consisting of sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, chlorine, chlorine dioxide, ozone, and hydrogen peroxide;
• adding a soluble calcium salt to the wastewater at a concentration greater than stoichiometric, said soluble calcium salt lowering the solubility of fluoride in the wastewater and promoting precipitation of solid calcium fluoride, said soluble calcium salt being selected from the group consisting of lime, slaked lime, calcium chloride, calcium bromide, calcium nitrate, calcium carbonate, and calcium sulfate;
• adding one or more coagulating and flocculating reagents to said wastewater, said one or more coagulating and flocculating reagents being selected from the group consisting of EnChem™ 0696 coagulant, EnChem™ 9025 polymer, ferric alum, aluminum chloride, potassium aluminum sulfate, potassium aluminum chloride, polyaluminum chloride, ferric chloride, ferric sulfate, and polymeric organic flocculating agents;
• separating treated wastewater with a lower level of suspended solids from a concentrate with a higher level of suspended solids by passing said wastewater through a solids separation device, said solids separation device being selected from the group consisting of a conventional settling tank, a filtration membrane system, and an EnChem™ membrane filtration system;
• and
• destroying excess oxidizer and oxidation by-products in said wastewater by contacting said wastewater with a solid material that absorbs and adsorbs and catalyzes destruction of said excess oxidizer and oxidation by-products.