Removal of ammonia nitrogen and phosphorus by porous slow-release Ca2+ ceramsite prepared from industrial solid wastes

An environmentally friendly ceramsite with slow-release ability was prepared using industrial solid wastes through sintering method. Ca2+ release was mainly evoked by wollastonite, and the porous structure ensured the release process slow but persistent. P removal efficiency of the ceramsite was verified by static and dynamic adsorption, respectively. By regulating pH to a highly alkaline condition independently and releasing sufficient Ca2+, P was efficiently removed by forming hydroxyapatite, with an equilibrium adsorption capacity of 0.2425 mg/g and removal efficiency of 97 %. Meanwhile, the ceramsite was applied to a BAF to investigate the feasibility of the simultaneous removal of NH4+-N and P. Results indicated their average removal efficiencies could be stabilized above 90 % over a long-term operation. The high-efficiency NH4+-N removal was ensured by the nitrification and the intensification of diatoms photosynthesis, while P removal was a result of chemical and physical adsorption.