Fate of faecal indicator organisms and bacterial diversity dynamics in a series of continuously fed aerated tank reactors treating dairy manure

Abstract

This study aimed to investigate the fate of faecal indicator organisms and to characterize microbial diversity dynamics in dairy manure and in aerated liquid manure in different treatment reactors in a series of continuously fed aerated tank reactors using low intensity aeration and ammonia-reduced feedback. The bacterial diversity in the treatment reactors was also compared with that in the soil from which the process inoculant originated. The fate of enteric indicator organisms was studied by the enumeration of viable counts. Total bacterial community DNA was extracted, amplified using 16S rRNA primers, cloned, sequenced and identified by comparison to known sequences. At best over 90% reduction was observed in the numbers of enteric indicator organisms. However, the result obtained varied depending on treatment run and indicator organism. Firmicutes were the dominating phyla of the untreated slurry; whereas; Proteobacteria and Deinococcus-Thermus dominated in the treatment tanks. Soil had the broadest phylogenetic diversity: the major phylums were Acidobacteria, Proteobacteri and Gemmatimonadetes. At the genus level, raw manure and treatment tanks shared a number of sequences. Soil, the origin of the inoculant, and treatment tanks did not share any sequence at the genus level, although some was observed at the family level.