Nitrogen removal and microbial diversity of activated sludge entrapped in modified poly(vinyl alcohol)–sodium alginate gel

Abstract

We investigated nitrogen removal from secondary effluent via microbial entrapment with poly (vinyl alcohol)–sodium alginate gel modified with alumina nanoparticles. Fourier transform infrared spectroscopy (FT–IR) and Raman spectroscopy revealed changes in functional groups on the embedding beads with the modification and the Brunauer–Emmett–Teller (BET) demonstrated that the mechanical strength of beads improved. Batch experiments were conducted to investigate nitrogen removal in synthetic wastewater with initial total nitrogen concentrations of 10–45 mg L−1. The maximum ammonia removal loads ranged from 9.63 to 59.58 mg L−1 h−1. Scanning electron microscope (SEM) observations showed that the beads were highly porous and conducive for microorganism adhesion. Microbial diversity analysis (High throughput sequencing) demonstrated that the microbial community structure inside the beads changed significantly after acclimation to the reactor environment and the reaction process. Alcaligenaceae_uncultured and Comamonadaceae_unclassified, which can conduct both heterotrophic nitrification and aerobic denitrification, were identified. They may facilitate pathways for non-traditional biological denitrification inside embedding beads.