Modeling and Optimization of Phosphate Recovery from Industrial Wastewater and Precipitation of Solid Fertilizer using Experimental Design Methodology

M. S. Shalaby, S. El-Rafie, A. H. Hamzaoui and A. M’nif

Abstract
In this work, the experimental design methodology is applied to optimize phosphate salts precipitation as struvite and others applied in soil fertilization from treated industrial wastewater stream. This is a process to maximize phosphate recovery percentage from inlet wastewater stream containing interfering foreign ions. Therefore, these optimized conditions could be used as input data for engineering design-software for successive equipment required in wastewater treatment plant. A four factors Box–Behnken experimental design was used to model and optimize the operating parameters. The optimum operating conditions were quite efficient in trapping 86.10 % recovered phosphates in industrial stream, and 92.6 % in synthetic solution at pH of 10.89, time of reaction of 34.76 min, temperature of 25.23 °C and R of 2.25 with an insignificance effect for molar ratio (R) between Mg and PO4 ions. If these optimal parameters were shifted, the reached recovery percentage would decrease with the precipitated struvite. The precipitated salts were subjected to characterization through different chemical techniques confirming the presence of struvite with schertelite as a mixed slow release fertilizer.

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Keywords
wastewater treatment, calcium interference, surface response, design methodology, phosphorous depletion