Research on removal of fluoroquinolones in rural domestic wastewater by vertical flow constructed wetlands under different hydraulic loads

Antibiotics had attracted more and more attention in recent years due to their harmfulness. Fluoroquinolones (FQs), one class of antibiotics widely used in human and veterinary medicine, were found in various water bodies in China. Therefore, in order to found an efficient method for removing FQs in rural domestic wastewater and optimize the process parameters, ceramsite and soil were applied in vertical flow constructed wetlands (VFCWs) to study the effects of different hydraulic loads and different substrates on the removal of FQs and conventional pollutants. The results showed the VFCW-D filled with 45 cm soil layer and 15 cm ceramasite layer had the highest removal efficiency of conventional pollutants and FQs under low hydraulic load. Nevertheless, the removal efficiency of conventional pollutants was significantly declined for the VFCWs which contained soil substrates under high hydraulic load due to the soil pores were clogged by the accumulation of organic matter. Finally, VFCW-A filled with 60 cm ceramasite layer revealed good ability to remove conventional pollutants and FQs under high hydraulic load. Deinococcus played a vital role here due to its excellent removal effect on conventional pollutants. The microbial composition in the substrate changed greatly after adding antibiotics under high hydraulic load. Devosia, Pseudorhodoferax, Cellvibrio, Bosea, Caulobacter, Acinetobacter, Zoogloea, Arcobacter, Dechloromonas, Flavobacterium, Nakamurella, Chloroplast, Clostridium_sensu_stricto_1, Pelosinus, UTCFX1 and Hypnocyclicus became the new dominated genera and were essential to remove pollutants. In summary, VFCW was an effective system to remove fluoroquinolones in rural domestic wastewater.

Automated summary

The study found that using ceramsite and soil as media in VFCWs can effectively remove fluoroquinolones and conventional pollutants in rural domestic wastewater. Under low hydraulic load, VFCW-D filled with 45 cm soil layer and 15 cm ceramsite layer had the highest removal efficiency. However, under high hydraulic load, the removal efficiency of conventional pollutants significantly declined due to the clogging of soil pores by organic matter accumulation. Nevertheless, VFCW-A filled with 60 cm ceramsite layer showed good ability to remove both conventional pollutants and fluoroquinolones under high hydraulic load.