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Calcium phosphate precipitation in nitrified wastewater from the potato-processing industry

Monballiu, A., Ghyselbrecht, K., Crabeels, X., Meesschaert, B.
Environmental technology 2019 v.40 no.17 pp. 2250-2266
bicarbonates, buffering capacity, calcium, calcium carbonate, calcium phosphates, chemical precipitation, environmental technology, food industry, food processing wastes, magnesium ammonium phosphate, natural resources, nitrification, pH, wastewater
Increasing environmental concerns and the awareness of the finite nature of natural resources make the valorization of waste materials to become a real challenge. The objective of the current research is to investigate the possibility of phosphate recovery as calcium phosphate salts from the wastewater from the potato-processing industry. Batch tests demonstrated that at high pH, struvite and calcium carbonate precipitations are competitive processes and that bicarbonate inhibits the precipitation of calcium phosphate salts. A biological nitrification of the wastewater removed the buffering capacity, the competitive formation of struvite and paved the way for phosphate precipitation as calcium phosphate salts as it also led to the simultaneous removal of (bi)carbonates. It is demonstrated that 75% of the phosphate precipitated as calcium phosphate at a [Ca²⁺]/[P] ratio of 2.5 at pH 8.5 and as such it provides a convenient alternative for the currently applied struvite processes in the agro-industrial industry.