Methodology of Organization of Closed Water Circulation of Enterprises for the Production of Extraction of Phosphoric Acid and Mineral Fertilizers

Abstract— Wastewater from industrial enterprises of the phosphorus sub-industry creates environmental risks on a regional scale. Based on the results of industrial monitoring of the production of extraction of phosphoric acid and mineral fertilizers, the operating range of concentrations of fluorine ions (0.6–4.0 g/dm³) and phosphorus in terms of P₂O₅ (10–15 g/dm³) in industrial effluents was obtained. The change in the controlled components is due to seasonal phenomena, the technology used for processing raw materials, fluctuations in the total volume of wastewater. In laboratory conditions, an installation has been created that simulates the process of cleaning acidic wastewater by neutralization, as a result of which products are formed – poorly soluble compounds of hazard class 3–4. The difference between the laboratory and the industrial scheme is the recycling of part of the resulting sludge. The latter initiates the deposition process and reduces the sedimentation time. The recirculation coefficient of the precipitationd sludge, which is the mass ratio of the amount of solid phase introduced during the neutralization process to the mass of the solid phase formed as a result of the reaction, varied from 1 to 8. The recirculation coefficient was determined based on the ratio of the concentration of the solid phase formed as a result of the reaction (20 g/dm³) to the concentration of the solid phase after thickening of the suspension (100 g/dm³). It has been experimentally established that with a multiplicity of sludge circulation equal to three, higher indicators of the wastewater neutralization process are provided: a decrease in the consumption of alkaline reagent and pH from 10–11 to 7–8, an increase in the degree of extraction of phosphorus and fluorine compounds, a decrease in their concentration in purified water to regulated values (fluorine ions less than 0.05 mg/dm³ and phosphate-ions less than 0.2 mg/dm³) and a more advanced water circulation system at the enterprise.