Initial stage of innovative cell-entrapped biofilter start-up for removal of manganese in water: Treatment performance, manganese speciation, and microbial community

Manganese-contaminated groundwater as a drinking water source causes colored water, pipe clogging, and health problems. Manganese removal using biofilters is an effective process, but microbial acclimatization during the start-up period takes time. The aim of this study is to investigate the initial stage of an innovative cell-entrapped biofilter start-up for manganese removal. Streptomyces violarus SBP1 (SBP1) entrapped in barium alginate was incorporated into the biofilter to enhance manganese removal and cell retention. The manganese removal performance, microbial community, and manganese transformation were examined through dual media columns representing free cell-augmented (FC), entrapped cell-augmented (EC), and conventional biofilters at an initial manganese concentration of 1 mg/L. In a filtration experiment, EC achieved better removal performance (53 %) than FC (45 %) and conventional biofilter (39 %) because of higher manganese bio-oxidation. During the beginning period, manganese adsorption was predominant, whereas manganese bio-oxidation played a main role thereafter. A synchrotron-based analysis confirmed that most Mn(II) was oxidized to Mn(III) and Mn(IV). The amplicon sequencing results revealed that Proteobacteria-dominated natural biofilm in all three filters, while Streptomyces (expected as SBP1) was the major bacterial group in EC. This study demonstrated the feasibility of developing an innovative cell-entrapped biofilter.