Sustainable removal of contaminants of emerging concern from wastewater by the living membrane bioreactor: effect of the co-occurrence of microplastics and antibiotics

Wastewater treatment plants (WWTPs) have been considered as sinks of contaminants of emerging concern (CECs) including antibiotics and microplastics. If not well-retained in the WWTPs, these CECs are discharged to the environment. The co-presence of these CECs in wastewater lead to further environmental impacts since MPs can act as adsorbents and carriers of antibiotics. The study aims to investigate the efficiency of a living membrane bioreactor (LMBR) in the treatment of urban wastewater containing ofloxacin and oxidized polyethylene microplastics (PE MPs). The living membrane (LM), in which a series of biological layers (an external sludge cake and an encapsulated biofilm between two coarse-size mesh sheets) function as a membrane filter, is utilized. This study aimed to investigate the effects of the presence of both ofloxacin and PE MPs to the contaminant removal and to the alleviation of membrane fouling. The influence of the presence of the PE MPs on the prevalence of antibiotic-resistant genes in the reactor will also be examined. The experiment was conducted using two parallel LMBRs, which were fed with synthetic urban wastewater with the antibiotic Ofloxacin at a concentration of 0.2 mg L influent-1. One reactor was dosed with 15 µm PE MPs (10 mg L influent -1) daily. The other reactor without added PE MPs acted as the control. Results showed that the permeate turbidity of the reactor with PE MPs was slightly higher at 1.14 NTU. This implied that the presence of PE MPs potentially affected the formation of the LM layer. Despite this, the average permeate turbidities in both reactors were lower than 5 NTU. Consistently high removals of COD and NH4-N were obtained in both reactors. However, the removal of Ofloxacin decreased over time in both cases. The removal of Ofloxacin was slightly higher in the reactor without PE MPs (77%). This ongoing work will contribute to the development of membrane technologies for the sustainable treatment of wastewater containing micropollutants including antibiotics and microplastics.