Effects of competitive ions, humic acid, and pH on removal of ammonium and phosphorous from the synthetic industrial effluent by ion exchange resins

The removal of the ammonium and phosphorous from the synthetic industrial effluent by the ion exchange resins was studied in this paper, aiming at the determination of the effects of competitive ions, humic acid, pH and resin amount. The kinetic experiments show that the equilibrium time for the removal of both contaminants in the absence and presence of the competing matters was 4 h. Na⁺ and K⁺ significantly reduced the ammonium removal percentage, while the existence of Mg²⁺, Ca²⁺ and humic acid also had a negative influence. Adsorption of ammonium ions in both absence and presence of Na⁺ and K⁺ observed the linear isotherm, however, it did not follow commonly used isotherms in the presence of Na⁺, K⁺, Mg²⁺, Ca²⁺ and humic acid. The phosphorous removal decreased in the presence of the competitive matters, such as Cl^-, CO₃^2-, SO₄^2- and humic acid. Higher pH can cause higher phosphorous removal percentage. A decrease in the solution pH was observed in the phosphorous removal experiments, possibly due to the ion exchange and the adsorption of OH^-. Uptake of humic acid by the resins was observed. Finally, a series of fixed-bed experiments were performed, showing that the performance was dependent on the empty bed contact time (EBCT). Higher EBCT would cause higher bed volumes of both treated ammonium and phosphorous.