Predominance of ammonia-oxidizing archaea on granular activated carbon used in a full-scale advanced drinking water treatment plant

Ozonation followed by granular activated carbon (GAG) is one of the advanced drinking water treatments. During GAG treatment, ammonia can be oxidized by ammonia-oxidizing microorganisms associated with GAG. However, there is little information on the abundance and diversity of ammonia-oxidizing microorganisms on GAC. In this study, the nitrification activity of GAG and the settlement of ammonia-oxidizing archaea (AOA) and bacteria (AOB) in GAG 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 GAG were below the quantification limit. After prechlorination was stopped, 10(5) copies g-dry(-1) of AOA amoA genes were detected within 3 weeks and the quantities ultimately reached 10(6)-10(7) copies g-dry(-1), while levels of AOB amoA genes still remained below the quantification limit. This observation indicates that AOA can settle in GAG rapidly without prechlorination. The nitrification activity of GAG 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. (C) 2010 Elsevier Ltd. All rights reserved.