Optimization, Characterization, and Ammonia Nitrogen Adsorption Study of Novel PVA-SA-VMT Composite Carrier

To address the low ammonia nitrogen removal efficiency of traditional activated sludge processes under low-temperature conditions, this study developed a novel PVA-SA-VMT composite immobilization carrier using polyvinyl alcohol (PVA), sodium alginate (SA), and vermiculite (VMT). The optimal formulation (7% PVA, 2.5% SA, and 2% VMT) was determined through single-factor experiments. The results indicate that the composite carrier possesses high mechanical strength and excellent chemical stability, with a 24-hour TOC leaching amount of only 14.1 mg/L, 72% lower than that of the pure PVA-SA carrier. The interior of the composite carrier features a porous structure, which enhances the effective diffusion coefficient of ammonia nitrogen. Its adsorption mechanism follows second-order kinetics and the Freundlich isotherm, with vermiculite interlayer ion exchange being a spontaneous endothermic process. The synergistic mechanism of ’scaffold support–adsorption enrichment’ provides a solid material foundation for constructing an efficient low-temperature nitrification system in wastewater treatment.