Antibiotic resistant bacteria removal in stormwater bioretention cells through the combination of biochar with intermittent aeration

Recently, there has been increasing information about the removal of chemical pollutants through biochar and intermittent aeration. However, little attention was paid to the application of biochar and intermittent aeration for the improvement of antibiotic resistant bacteria (ARB) removal in stormwater bioretention cells. Target ARB ( E. coli K-12 carrying bla TEM, tet R and aph A) was used in batch experiments for bioretention cells with different biochar contents, ratios of air to water (A/W) and aeration time (AT). ARB removal decreased with the increase of M/B in bioretention cells, where the highest ARB removal (3.73 Log) was found under 10 % of biochar, while intermittent aeration could contribute to the enhancement of ARB removal with the largest (3.94 Log) under A/W of 40:1 and AT of 4 hr/d. Both biochar chemisorption and H 2 O 2 oxidation were responsible for ARB removals with the maximal adsorption capacity of 33843 CFU/g, and the highest ARB removal less than 0.20 Log due to H 2 O 2 yields (0.021–0.042 mmol/L). ARGs conjugation frequencies tended to decrease with the increase of biochar levels and AT, and ARGs transformation decreased obviously under A/W of 40:1 and 20:1. There were around 1.13-fold changes for both intracellular reactive oxygen species (ROS) and cell membrane permeability (CMP) in bioretention cells with the combination of biochar and intermittent aeration, suggesting the slightly increasing risks for both conjugation and transformation when the application of the combined method on ARB removals.