Inoculation with Acinetobacter indicus CZH-5 in internal circulation airlift zeolite spheres sequencing batch reactor to augment simultaneous removal of nitrogen, phosphorus, and tetracycline

Abstract

Inoculating functional bacterial strains is a cost-effective strategy for enhancing treatment of anaerobic digestion liquids in swine wastewater. This study systematically evaluated inoculation of heterotrophic nitrification aerobic denitrification strain Acinetobacter indicus CZH-5 in an internal circulation airlift zeolite sphere-based sequencing batch reactor (IR) for aerobic removal of nitrogen (N), phosphorus (P), and tetracycline (TEC). Inoculation with CZH-5 promoted secretion of quorum sensing signaling molecules, specifically N-acyl-homoserine lactones (C6-HSL and C10-HSL). These signaling molecules enhance quorum sensing and reinforce cooperation among functional bacteria. Under optimal conditions, average removal efficiencies of total nitrogen, total phosphate, and TEC were 92.8 %, 88.4 %, and 93.1 %, respectively. The removal performance in IR exceeded that of the control by 26 %–71 %. N removal involved complete nitrification-denitrification, while accumulated P was transformed into phosphate monoesters within biofilm. Metagenomic analysis identified Thauera and Acinetobacter as the dominant genera, and Acinetobacter indicus as predominant species. Inoculation enhanced microbial richness and diversity to improve system operational stability. The abundance of functional genes associated with N, P, and TEC transformations significantly increased compared to the control. This study aimed to investigate the characteristics and mechanisms of inoculating a heterotrophic nitrification aerobic denitrification strain into an aerated biofilm system for swine wastewater remediation.