Enhancement of nitrogen and phosphorus removal in landscape water using polymeric ferric sulfate as well as the synergistic effect of four kinds of natural rocks as promoter

Abstract

Eutrophication in lakes and rivers caused by the nitrogen (N) and phosphorus (P) is urgent since the accumulation of N and P can possibly cause the algal blooms and devastation to the water ecological system. The removal of N and P in the landscape water would be an efficient way to reduce the enrichment of nutrition before they reach the large water system. The N and P removal efficiency of PFS as well as the synergistic effect of natural rocks (four types of purple parent rock (J₃p, J₂s, T₁f, and J₃s)) as promoter was examined under laboratory conditions. The results indicated that TN and TP removal efficiency of the composite coagulant was significantly better than that of PFS or purple parent rock alone and J₃p + PFS (combination of PFS and J₃p purple parent rock) showed the best TN and TP removal efficiency. TN and TP removal efficiency of 53.53 and 86.48%, respectively, were achieved with coagulant dosage of 6 g L⁻¹ J₃p and 30 mg L⁻¹ PFS, water temperature of 30 °C, and wastewater initial pH of 9. In addition, Fourier transformed infrared (FTIR) spectrophotometer, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis (EDX), and the water quality index analysis revealed that the treatment of TN and TP by using J₃p + PFS was taking advantage of the flocculation function of PFS and the adsorption function of PFS and J₃p. In which, the flocculation mechanism was mainly charge neutralization; adsorption mechanism was mainly physical and chemical adsorption.