Fates of nutrients, bacteria community, and antibiotic resistance genes during membrane separation of biogas slurry at industrial scale

Abstract

The swine wastewater was rich in nutrients, microbes, and antibiotic resistance genes (ARGs), thus the discharge without treatment could inevitably pose numerous harms to environment. Multistep membrane separation has been developed as a promising strategy to achieve nutrient recovery and harmful contaminants removing. Here, an integrated membrane separation system including ultrafiltration and reverse osmosis was used to treat the biogas slurry produced from swine wastewater, and samples were gathered from different points. Then, a series of physicochemical parameters were analyzed, and 16S rRNA gene amplicon sequencing and real-time qPCR was used to research the bacteria communities and the abundance of ARGs in each sample, respectively. Results showed that the integrated membrane filtration could reject most of conventional pollutants, and the final permeate, which has extremely low levels of nutrients and metal elements, could be reused to wash the piggery or meet the Chinese national discharge standard. Moreover, the membrane filtration also could reduce 99.99 % of the detected ARGs, and the bacterial abundance and diversity in the final permeate significantly decreased compared with the feed biogas slurry. Redundancy analysis and network analysis indicated that the size exclusion and the adaptation to the different water quality were the common driving forces for the variation of bacterial community and ARGs during the membrane separation processes. In addition, our results also revealed the variety of putative pathogen and abundance of ARGs except for nutrients in the reverse osmosis concentrate, thus further disinfection procedures should be implemented before resource utilization of the concentrate.