System characteristics of integrated continuous flow simultaneous partial Nitrification, Anammox and Denitrification (SNAD) for NH-rich wastewater: performance, sludge evolution, metagenomic sequencing analysis.

The integrated process of simultaneous partial nitrification, anammox, and denitrification (SNAD) is designed to achieve efficient nitrogen removal and carbon reduction. This study details the design and successful implementation of an innovative, single-piece continuous flow SNAD system for treating high concentration NH wastewater. The system leverages simultaneous anammox and denitrification (SAD) granular sludge and employs a strategy of dosing partial nitrification sludge, alongside meticulous control of pH, dissolved oxygen (DO), free ammonia (FA), and free nitrous acid (FNA) was applied to initiate the SNAD process. The spectral analysis results suggest a marginal reduction in the stability and flocculation properties of the SNAD granular sludge. Molecular analysis via 16S rRNA gene sequencing revealed ammonia-oxidizing bacteria, anaerobic ammonia-oxidizing bacteria, and denitrifying bacteria as the predominant microbial populations within the SNAD system. A marked increase in the abundance of related functional genes was observed, alongside a reduction in quorum sensing (QS) and ATP-Binding Cassette (ABC) transporter proteins. These findings suggest a possible attenuation in the secretion of native signaling proteins within the SNAD system.