Bioelectrical power generation coupled with high-strength nitrogen removal using a photo-bioelectrochemical fuel cell under oxytetracycline stress

Abstract

Photo-bioelectrochemical fuel cell shows great potential as an environmental-friendly technology for converting solar energy and bioenergy into electricity with simultaneous wastewater treatment. The present work aims to assess the performance of an algal-bacterial biocathode photo-bioelectrochemical fuel cell (ABPBFC) operated with daily light/dark cycle for simultaneous bioelectrical power generation and high-strength nitrogen removal under oxytetracycline (OTC) stress by adding different concentrations of OTC into the biocathode. The results showed that the power generation of the ABPBFCs was significantly enhanced by the presence of OTC at all levels tested (5–50 mg/L) due to enhanced electron transfer from cathode to oxygen and nitrate mediated by degradation products of OTC, but the enhancement was not proportional to the rise in OTC concentration. The largest maximum power density of 54 mW/m2 was achieved at 5 mg/L OTC during light period and 8.5 mW/m2 was produced at 20 mg/L OTC during dark period, corresponding to a 1.8 and 7.5 fold increases compared to that of the ABPBFC without addition of OTC. The removal of nitrate was obviously accelerated by the addition of OTC with an initial OTC concentration lower than 20 mg/L. Increases in the concentration of OTC added to the biocathode did not result in continuous enhancement in power generation and nitrate removal due to the toxicity of OTC to biocathodic microbial community. Cathodic bioelectrochemical process enhanced photolysis of OTC, which was attributed to its contribution to basification of catholyte. The growth of some dominated genus related to biocathodic electron transfer, nitrogen removal and OTC degradation were stimulated at OTC concentrations less than 20 mg/L but inhibited at 50 mg/L, except for some OTC-resistant bacteria.