Quantification of Ammonia- and Nitrite-oxidizing bacteria using competitive PCR in Bench Scale Wastewater Treatment Reactors at Different Biological Solids Retention Times
Abstract:The effect of solids retention time on ammonia- and nitrite-oxidizing bacteria was measured by amoA and Nitrospira 16S rDNA competitive PCR assays in a completemix, bench-scale, activated sludge system. During steady-state operation, nitrification was complete in 20-and 10- day BSRT reactors, nearly complete in the 5-day BSRT reactor and incomplete in the 2-day BSRT reactor (80% ammonia removal and 80% nitrite oxidation). Total bacterial 16S rDNA, measured by dot blot hybridizations, ranged from 4.0 × 1013 to 1 × 1012 copies per liter, and decreased with decreasing solids retention times. Nitrospira 16S rDNA was 5 to 40 fold higher than amoA and ranged from 3.3 × 1010 to 2 × 109 Nitrospira copies per liter and 1 × 1010 to <8 × 107 amoA copies per liter. The data suggest a minimum of 1 × 1010 Nitrospira 16S rDNA and 9 × 108 amoA copies per liter are need for complete nitrification.
Document Type: Research Article
Publication date: January 1, 2001
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