Implication on selection and replacement of granular activated carbon used in biologically activated carbon filters through meta-omics analysis

Biologically activated carbon (BAC) filters are widely used in China and worldwide as an essential part of advanced water treatment. However, it is unclear how to properly select the granular activated car-bon (GAC) used in BAC filters and to determine when GAC should be replaced. In this study, five BAC filters, each filled with a different coconut-or coal-based GAC with different physicochemical proper-ties, were run continuously for 400 days. The structure and function of the microbial community and the quantity of specific enzymes in the BAC filters were investigated through an integrated metage-nomic/metaproteomic analysis. The results indicated that GAC adsorption still played a major role in removing organic matter once the filters reached a steady-state, which was attributed to bioregenera-tion, and the contribution of adsorption might be relatively greater than that of biodegradation. GAC with strong adsorption capacity and high bioregeneration potential selected bacterial communities more phylogenetically closely-related than others. The iodine value could be used as an indicator of BAC per-formance in terms of organic matter removal in the initial stage of the filters, which is dominated by adsorption. However, it could not be used to assess performance at a later stage when adsorption and biodegradation occurred simultaneously. Pore-size distribution characteristics could be chosen as a poten-tial better indicator compared with the current adsorption indicators, dually representing the adsorption performance and the microbial activity, and the proportion of important pore-size of GAC that is more suitable for BAC filter is suggested. GAC with strongly polar terminal groups is more conducive to the removal of ammonium-nitrogen. (c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The study found that once BAC filters reach a steady state, GAC adsorption still plays a major role in removing organic matter due to bioregeneration. Iodine value can be used as an indicator of BAC performance in the initial stages, dominated by adsorption, but not in later stages. Pore-size distribution characteristics may be a better indicator, representing both adsorption performance and microbial activity.