Phenol biodegradation by bacterial cultures encapsulated in 3D microfiltration-membrane capsules

The aim of the study was to evaluate the performance of batch and semi-continuous treatment systems for phenol degradation using a consortium of bacterial cultures that were encapsulated using the 'Small Bioreactor Platform' (SBP) encapsulation method. The maximal phenol biodegradation rate was 22 and 48 mg/L/h at an initial phenol concentration of 100 and 1000 mg/L in the batch and semi-continuous bioreactors, respectively. The initial phenol concentration played an important role in the degradation efficiency rates. The batch bioreactor results could be described by the Haldane model, where the degradation rate decreased under low as well as under very high initial phenol concentrations. Concentration equalization between the two sides of the SBP capsule's membrane occurred after 80 min. The microfiltration membrane is perforated with holes that have an average diameter of 0.2-0.7 µm. It is therefore suggested that the capsule's membrane is more permeable compared to other polymeric matrixes used for bacterial encapsulation (such as alginate). This study shows that the encapsulation of phenol degraders within microfiltration-membrane capsules which create a confined environment has a potential for enhancing phenol removal in phenol-rich wastewaters.