Quantification of Ammonia- and Nitrite-oxidizing bacteria using competitive PCRin Bench Scale Wastewater Treatment Reactors at Different Biological SolidsRetention Times

摘要

The effect of solids retention time on ammonia- and nitrite-oxidizing bacteria wasmeasured by amoA and Nitrospira 16S rDNA competitive PCR assays in a completemix,bench-scale, activated sludge system. During steady-state operation, nitrificationwas complete in 20-and 10- day BSRT reactors, nearly complete in the 5-day BSRTreactor and incomplete in the 2-day BSRT reactor (80% ammonia removal and 80%nitrite oxidation). Total bacterial 16S rDNA, measured by dot blot hybridizations, rangedfrom 4.0 x 1013 to 1 x 1012 copies per liter, and decreased with decreasing solids retentiontimes. Nitrospira 16S rDNA was 5 to 40 fold higher than amoA and ranged from 3.3 x1010 to 2 x 109 Nitrospira copies per liter and 1 x 1010 to <8 x 107 amoA copies per liter.The data suggest a minimum of 1 x 1010 Nitrospira 16S rDNA and 9 x 108 amoA copiesper liter are need for complete nitrification.