Efficient phosphate recovery as vivianite: synergistic effect of iron minerals and microorganisms

Abstract

Vivianite is a promising phosphorus recovery solution that has the potential to simultaneously relieve phosphorus shortage and phosphorus pollution. By producing vivianite, dissimilatory iron reducing bacteria may substantially enhance the phosphate collection efficiency. The transformation of phosphate and the formation of vivianite were investigated in ferrihydrite (Fe(OH)₃)–P and magnetite (Fe₃O₄)–P systems, respectively. Phosphate significantly promoted the process of dissimilatory iron reduction by drawing Fe(II) from the mineral surface. For the ferrihydrite system, the presence of phosphate significantly inhibited the dissimilatory iron reduction in the initial stage of the culture, but significantly improved reduction efficiency in a long time scale. The iron reduction efficiency increased by 18.3%, 22.8% and 41.3% for the Fe/P ratios of 4, 2 and 1 batches of ferrihydrite, respectively, compared to those of the control group after 336 h culture. However, for the magnetite system, phosphate enhanced the dissimilatory reduction during the whole culture process and the iron reduction efficiency improved by 4.65%, 7.25% and 15.80% for the Fe/P ratios of 4, 2 and 1 batches, respectively, compared to those in the control group. Under a high iron phosphorus ratio (Fe/P = 4), the recovery efficiency of phosphate was the highest, which was 98.8% and 57.4% in the ferrihydrite system and magnetite system, respectively. Overall, ferrihydrite and a relatively high Fe/P ratio (2–4) are conducive when vivianite-based phosphorus recovery technology is utilized in wastewater.