Emerging investigator series: Quaternary treatment with algae-assisted oxidation for antibiotics removal and refractory organics degradation in livestock wastewater effluent

In this study, we investigated the combination of algal treatment and subsequent oxidation to improve the antibiotics removal and refractory organics degradation in livestock wastewater effluent. We also proposed a better combination of oxidation processes for robust treatment of recalcitrant wastewater, mainly focusing on the removal of antibiotics. Stand-alone processes of O3, O3/H2O2, ultraviolet C (UVC), and UVC/H2O2 as well as their combined effects were evaluated as a downstream oxidation process. Prior to those oxidation processes, the effluent was treated with microalgae under continuous light illumination, which turned it into alkaline wastewater (pH > 10). The algal treatment was feasible not only to directly remove antibiotics resistant to a specific oxidation method, but also to improve the degradation of antibiotics and effluent organic matter in the alkaline wastewater upon subsequent oxidation. The alkaline wastewater was more favorable for the removal of antibiotics (especially for clopidol) with UVC treatment (UVC and UVC/H2O2). The algal treatment promoted ozonation to some extent for the degradation of florfenicol in the effluent. The removal of antibiotics by ozonation decreased with added H2O2, whereas the UVC performance was improved by adding H2O2. For ozonation followed by UVC treatment, the ozonation dominated the degradation of selected antibiotics.