Nanobubble-mediated high-density growth and enzyme activity enhancement of petroleum degrading bacterium Rhodococcus...

In petroleum refinery wastewater treatment, bioaugmentation technology is hindered by factors such as the difficulty in colonization of exogenous microorganisms. This study developed a nanobubble Luria-Bertani medium bacterial inoculant (N-LB) using Rhodococcus erythropolis KB1, and evaluated its performance in sequencing batch reactors (SBRs) treating actual refinery wastewater, comparing it with the conventional Luria-Bertani medium bacterial inoculant (C-LB) and the unamended blank control group. Results demonstrated the distinct superiority of N-LB. Specifically, N-LB exhibited explosive proliferation, with the total bacteria count 7.6-fold higher than that of C-LB, characterized by bacterial miniaturization coupled with high-density growth, while achieving an approximately 20% increase in dehydrogenase (DHA) activity and an approximately 30% higher VS/TS ratio of centrifugation relative to C-LB. Notably, H2 (N-LB) reduced effluent oil concentration, TN, and TP by 3.12 mg L^-1, 2.48 mg L^-1, and 0.05 mg L^-1 under real wastewater stage, respectively, alongside 31.46% and 14.40% increased in ammonia monooxygenase (AMO) and polyphosphate kinase (PPX) activities. H2 exhibited a higher Rhodococcus relative abundance (1.13‱) compared with H1 (0.91‱), and promoted synergistic interactions among functional microbial communities. Furthermore, N-LB elevated the relative abundance of key genes involved in carbon (maxF, acs), nitrogen (nirS), and phosphorus (phnW) cycling. This study provides an effective bioaugmentation strategy that can simultaneously enhance microbial activity, community synergy, and metabolic pathway efficiency, thereby achieving efficient treatment of petroleum refinery wastewater.