Resource recovery of water treatment plant sludge and river sediment as phosphorus removal material: feasibility and mechanisms

ABSTRACT Excessive phosphorus is a critical contributor to eutrophication, necessitating the use of substantial amounts of phosphorus removal materials. To address the challenge of managing water treatment plant sludge and river sediment while also supplying mass-produced phosphorus-removing materials for projects targeting phosphorus removal in water bodies, this paper attempted to study the feasibility of preparing phosphorus removal materials by mixing and calcining water treatment plant sludge and river sediment (C-WTPS/RS). The study examined the transformation of phosphorus forms in C-WTPS/RS before and after adsorption. Furthermore, X-ray fluorescence spectrometer, zeta potential, scanning electron microscope, Brunauer–Emmett–Teller equation, Barrett–Joyner–Halenda model, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy were employed to elucidate the phosphorus removal mechanisms. The results showed that C-WTPS/RS was effective in removing phosphorus from water and preventing the release of phosphorus from the sediment. Additionally, C-WTPS/RS had a low risk of releasing phosphorus and metals within the pH range of natural water bodies. These proved that it is feasible to remove phosphorus by C-WTPS/RS. After adsorption, the increased phosphorus in C-WTPS/RS was mainly dominated by the non-apatite inorganic phosphorus within inorganic phosphorus. The main phosphorus removal mechanisms of C-WTPS/RS were physical adsorption, electrostatic adsorption, chemical precipitation, and ligand exchange.