Efficient nitrogen removal in real aquaculture wastewater by immobilized Pseudomonas fluorescens JSRD-3

Efficient nitrogen removal from aquaculture wastewater is critical for sustaining aquatic ecosystem sustainability. In this study, a highly efficient heterotrophic nitrification-aerobic denitrification (HN-AD) bacterium was isolated from aquaculture sediment. The strain was identified as Pseudomonas fluorescens JSRD-3 and evaluated for its nitrogen removal performance. Sodium citrate was determined as the optimal carbon source. Strain JSRD-3 exhibited excellent nitrogen removal across wide ranges of C/N ratio, pH, dissolved oxygen (DO), temperature, and salinity. With single nitrogen sources, complete removal of ammonium (NH₄⁺-N), nitrate (NO₃^--N), and nitrite (NO₂^--N) was achieved within 12 h. Mixed nitrogen experiments further confirmed that strain JSRD-3 could simultaneously and efficiently transform multiple inorganic nitrogen species. It showed a significant preference for NH₄⁺-N utilization. Response surface methodology (RSM) identified pH, temperature, and shaking speed as the key influencing factors. Under the optimized conditions, NH₄⁺-N removal reached 98.90% at 9 h. Microbial immobilization further enhanced the NO₃^--N removal efficiency and operational stability of the strain. Polyurethane foam immobilization outperformed loofah sponge. Notably, polyurethane foam-immobilized JSRD-3 completely removed NH₄⁺-N, NO₂^--N, and NO₃^--N from real non-sterile aquaculture wastewater within 16 h. These results highlight JSRD-3 as a promising candidate for rapid, efficient, and interference-resistant nitrogen removal in practical aquaculture wastewater treatment.