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Abstract: Ozonation followed by granular activated carbon (GAC) is one of the advanced drinking water treatments. During GAC treatment, ammonia can be oxidized by ammonia-oxidizing microorganisms associated with GAC. However, there is little information on the abundance and diversity of ammonia-oxidizing microorganisms on GAC. In this study, the nitrification activity of GAC and the settlement of ammonia-oxidizing archaea (AOA) and bacteria (AOB) in GAC were monitored at a new full-scale advanced drinking water treatment plant in Japan for 1 year after plant start-up. Prechlorination was implemented at the receiving well for the first 10 months of operation to treat ammonia in raw water. During this prechlorination period, levels of both AOA and AOB associated with GAC were below the quantification limit. After prechlorination was stopped, 105 copies g-dry−1 of AOA amoA genes were detected within 3 weeks and the quantities ultimately reached 106–107 copies g-dry−1, while levels of AOB amoA genes still remained below the quantification limit. This observation indicates that AOA can settle in GAC rapidly without prechlorination. The nitrification activity of GAC increased concurrently with the settlement of AOA after prechlorination was stopped. Estimation of in situ cell-specific ammonia-oxidation activity for AOA on the assumption that only AOA and AOB determined can contribute to nitrification suggests that AOA may account for most of the ammonia-oxidation. However, further validation on AOB contribution is required. [ABSTRACT FROM AUTHOR]

The effects of different placements of rapid sand filtration on nitrification performance of BAC treatment in a pilot-scale plant were evaluated. In this plant, rapid sand filtration was placed after ozonation-BAC treatment in Process (A), while it preceded ozonation-BAC treatment in Process (B). Analysis of amoA genes of ammonia-oxidizing archaea (AOA) and bacteria (AOB) combined with nitrification potential test was conducted. BAC from Process (A) demonstrated slightly higher nitrification potential at every sampling occasion. This might be due to higher abundances of AOB on BAC from Process (A) than those on BAC from Process (B). However, AOA rather than AOB could be predominant ammonia-oxidizers in BAC treatment regardless of the position of rapid sand filtration. The highest nitrification potential was observed for BAC from both processes in February when the highest abundances of AOA-amoA and AOB-amoA genes were detected. Since rapid sand filtration was placed after BAC treatment in Process (A), residual aluminum concentration in BAC influent was higher in Process (A). However, adverse effects of aluminum on nitrification activity were not observed. These results suggest that factors other than aluminum concentration in different treatment processes could possibly have some influence on abundances of ammonia-oxidizing microorganisms on BAC. [ABSTRACT FROM AUTHOR]