Enhancing phosphorus removal: the impact of alkaline environment in eutrophic water systems

Abstract Excessive phosphorus input leads to poor water quality and eutrophication. However, limited research has directly explored the influence of pH on phosphorous in actual aquatic systems. This study investigated the effect of pH on phosphorus removal in synthetic, eutrophic, and black-odorous water. The pH levels ranging from 3.5 to 12.0 were adjusted using H 2 SO 4 , NaOH, and cement with a 0.5 ± 0.03 interval, followed by a 25 ± 1 °C static water bath for 24 h. Results showed that NaOH-adjusted pH removed >65% TP from eutrophic water (pH ≥9.50) and black-odorous water (pH ≥11.0). Meanwhile, cement-adjusted pH removed >84%, >90%, and >82% TP from the synthetic solution (pH ≥11.0), eutrophic water (pH ≥9.5), and black-odorous water (pH ≥9.5), respectively. The alkaline environment enhanced the formation of Ca-P in eutrophic water and black-odorous water, and cement strengthened the chemical precipitation of phosphorus by providing additional Ca 2+ . This study lays the groundwork for pH adjustment strategies in eutrophic water, holding significant implications for water resource management and environmental protection.