Comprehensive assessment for the seasonal variations of organic compounds and core soil microbiome in the simulated pilot-scale aquifer storage and recovery (ASR) system

Soil microbiome is responsible for crucial biochemical reactions by interacting with organic compounds in the injection wells in aquifer storage and recovery (ASR) processes. This study investigated seasonal variations in organic compounds and microbial communities in a simulated ASR system. For this purpose, eleven pilot-scale soil columns were operated in ASR mode over 13 months. River water was intermittently fed into the simulated ASR system after sedimentation pretreatment. As a result, the sand ratios in soil texture were slightly increased from 93.2-93.4 % to 96.6-98.1 % while the total organic carbon content in the soil was accumulated and maintained at < 0.2 % during the ASR operation. During the sedimentation process, 9-31 % of dissolved organic carbon (DOC) was removed in the water, while during the storage in the soil column, the DOC in water was fluctuated. However, the DOC concentration (less than 4 mg/L) in the effluent was stably maintained until the end of operational periods. High-throughput sequencing results showed that the predominant phylum was Proteobacteria. Interestingly, at the species level, the microbial community structure clearly shifted with elapsed time and column location; various organic degrading soil microbiome having different physiological characteristics (e.g., oxygen, substrate, and temperature) became predominant. Outcomes of this study suggest that soil microbiome can facilitate the establishment of stable ASR processes for river water treatment by contributing to bioattenuation.