Rapid Start-Up of a Biological Filter for Simultaneous Manganese and Ammonia Removal at Low Temperature Through Combined Bioaugmentation and a Dual-Media Filter

Groundwater in northeastern China is characterized by low temperature and the coexistence of manganese (Mn), ammoniacal nitrogen, and organic pollutants, resulting in prolonged start-up of biological Mn removal filters. To address this challenge, combined bioaugmentation with heterotrophic nitrifying bacteria (HNB) and manganese-oxidizing bacteria (MnOB) was employed. The optimal inoculation ratio was determined, and the effects of manganese sand and activated carbon on Mn and ammoniacal nitrogen removal were evaluated. Under bioaugmentation conditions, manganese sand promoted the rapid establishment of ammonia oxidation, whereas activated carbon exhibited superior Mn2+ oxidation performance. A dual-media filter consisting of an upper manganese sand layer and a lower activated carbon layer was subsequently developed. Compared with the conventional manganese sand filter, the bioaugmented composite filter shortened the start-up period by 21 days and reached stable operation on day 24. High-throughput 16S rRNA gene sequencing revealed that activated carbon enriched norank_f__Beggiatoaceae and enhanced synergistic interactions among functional microbial groups. This study provides a promising strategy for the efficient simultaneous removal of Mn and ammoniacal nitrogen from groundwater in cold regions.