Efficient biodegradation of phenol at high concentrations by Acinetobacter biofilm at extremely short hydraulic retention times

Efficient biofilm-forming bacteria are crucial for biofilm wastewater treatment reactors. Nevertheless, finding a suitable bacterial culture with high biodegradation capabilities and ability to grow a stable and effective biofilm that can survive the reactor environment poses a challenge. Here, we present a newly isolated bacterium Acinetobacter EMY that exhibits excellent growth rate, biofilm formation capability, and ability to biodegrade phenol at high concentrations. The phenol degradation rate of Acinetobacter EMY immobilized on polyethylene biocarriers in batch and continuous moving bed bioreactors (MBBRs) treated with phenol as the sole carbon source was significantly higher than that of a bacterial suspension. The continuous MBBR demonstrated impressive phenol removal rates (8.11 and 10.95 kg/m3/d at extremely short hydraulic retention times of 0.5 and 0.25 h, respectively). The phenol removal efficacy was 100% for hydraulic retention times of & GE;0.5 h and 67.25% at 0.25 h. The Acinetobacter EMY biofilm batch bioreactor loaded with 165, 330, 665, 1150, and 2100 mg/L phenol achieved the maximum biodegradation rates of 7.65, 7.03, 9.15, 4.48, and 4.16 kg/m3/d, respectively. The new Acinetobacter EMY isolate showed enhanced phenol biodegradation capabilities compared with other isolates in similar studies. Chemical oxygen demand measurements proved that Acinetobacter EMY also consumed the intermediates of phenol degradation. In summary, Acinetobacter EMY is a promising bacterium for use in MBBR systems that treat water containing phenols.