Enhanced nitrogen removal through rapid biofilm formation by Paracoccus sp. XN-1 immobilized carriers in sequencing batch biofilm reactor

Abstract

Biofilm formation is critical for wastewater treatment efficiency, but slow biofilm development often limits system startup and performance. In this study, a sequencing batch biofilm reactor (SBBR) was established to evaluate Paracoccus sp. XN-1's capability to accelerate biofilm formation for treating aquaculture wastewater. Results showed that XN-1 inoculation (T-SBR) significantly enhanced biofilm formation, achieving mature biofilm development within 36 days compared to 48 days in conventional activated sludge (SBR). This rapid startup is particularly valuable for aquaculture facilities that require efficient and stable wastewater treatment systems to maintain water quality during intensive farming. High-throughput sequencing revealed distinct microbial community structures between the two systems, with T-SBR showing enrichment of key functional groups, particularly Methyloparacoccus (4.8 %) and Lysinibacillus (21.4 %). Network analysis demonstrated complex ecological interactions within T-SBR, with Methyloparacoccus forming a central hub coordinating nitrogen transformation processes. Functional prediction indicated enhanced nitrogen metabolism and oxidative phosphorylation pathways in T-SBR, contributing to superior NH₄⁺-N (99.27 %) and TN (83.14 %) removal efficiencies. These results demonstrate that XN-1 inoculation optimizes microbial community assembly for enhanced nitrogen removal, providing a practical solution for sustainable aquaculture wastewater treatment.