High-Throughput Profiling of Antibiotic Resistant Genes in a Novel Tridimensional Eco-Biological WWTP with High Discharge Standards for Reuse

Antibiotic resistome is a raising concern around the world, especially considering reclaimed wastewater. In this study, a novel tridimensional eco-biological wastewater treatment plant (TEB-WWTP) with high discharge standard (CODcr < 20 mg/L, ammonia < 1 mg/L, TP < 0.2 mg/L, third sort of Environmental quality standards for surface water in China) for reuse was selected. The bioreactors were characterized by adding internal bio-modules and planting various macrophytes which were fixed by stainless steel cages with additional bio-ceramsites on the top of bioreactors to purify odor gas. WWTPs are considered as hotspots of antibiotic resistant genes (ARGs). High-throughput qPCR (HT-qPCR) was applied here to profile ARGs in the TEB-WWTP and receiving stream. A total of 228 ARG subtypes were detected in the TEB-WWTP system which exhibited good performance for the removal of ARGs with the number, relative abundance and absolute abundance of ARGs largely decreased in the final effluent. Surprisingly, we found that the number and relative abundance of ARGs in the rhizosphere of three macrophytes (Canna indica, Cyperus alternifolius and Musa basjoo) were lower than that of biological reactor effluent. Aquatic plants probably play an important role in the inhibition of ARGs dissemination. Most of ARGs have significant correlations (p < 0.001) with total abundance of mobile genetic elements (MGEs), suggesting that horizontal gene transfer was the main mechanism for ARGs propagation. More attention should be paid to excess sludge with high relative abundance of ARGs for further dispose or farmland application. The final effluent was discharged to a stream for ecological reuse. The number and relative abundance of ARGs in the sediment of downstream were much higher than that of upstream, indicating that the risk of ARGs can’t be overlooked when considering wastewater reuse.