Synthesis and performance of iron oxide-based porous ceramsite in a biological aerated filter for the simultaneous removal of nitrogen and phosphorus from domestic wastewater

• Novel iron-oxide-based porous ceramsite was prepared and investigated.
• Thin sections of the iron-oxide-based porous ceramsite were analyzed for porosity.
• Micro-computed tomography was used to analyze structural characteristics and porosity of IPC.
• Microscopic observation was undertaken to investigate protozoa and metazoa.

A novel iron oxide-based porous ceramsite (IPC) was synthesized and applied as a microbial biofilm carrier in a biological aerated filter (BAF) to treat domestic wastewater and compared to commercially available ceramsite (CAC). The results indicate that IPC has a higher porosity in comparison to CAC. The uniformity and interconnectivity of pores, as well as the rough surface of the IPC are suitable for microbial biofilm growth. Biofilm growth occurs in the internal pores of the media and promotes nitrogen and phosphorus removal. The effect of air-water ratio (A/W) on the removal of total organic carbon, ammonia nitrogen, total nitrogen, and phosphorus were investigated. The results show that the performance of IPC BAF is much better than CAC BAF. For instance, at an A/W ratio of 3:1, the total nitrogen removal was 46.26% with IPC and 15.64% with CAC, and the PO43− removal was 72.25% with IPC compared with only 33.97% with CAC. An analysis of the microbial community in the IPC BAFs by polymerase chain reaction denaturing gradient gel electrophoresis identified Dechloromonas sp., Sphaerotilus sp., and Nitrospira sp. microbes. The diversity on microbial population, along with the attached growth benefit from the morphological properties of IPC, allows enhancement in the simultaneous nitrification and denitrification performance in IPC BAF. Hence, IPC can be considered a very effective novel media material in BAF for the simultaneous removal of nitrogen and phosphorus.