Structure of archaeal communities in membrane-bioreactor and submerged-biofilter wastewater treatment plants.

A cultivation independent approach (PCR-TGGE) was used to evaluate the occurrence of Archaea in four wastewater treatments based on technologies other than activated sludge, and to comparatively analyze their community structure. TGGE fingerprints (based on partial archaeal 16S-rRNA amplicons) were obtained from sludge samples taken from a pilot-scale aerated MBR fed with urban wastewater and operated under two different sets of conditions (MBR1 and MBR2 treatments), and also from biofilms sampled from two pilot-scale submerged biofilters (SBs) consisting of one aerated and one anoxic column each, fed with urban (USB treatment) or industrial (ISB treatment) wastewater, respectively. Analysis of TGGE fingerprints revealed clear and significant differences of the community structure of Archaea between the wastewater treatments studied, primarily according to wastewater origin and the type of technology. Thirty-two different band classes were detected among the 23 sludge and biofilm samples analyzed, from which five were selected as dominant or distinctive of the four treatments studied. Sixteen predominant TGGE bands were identified, revealing that all of them were related to methanogenic Archaea. Neither other Euryarchaeota groups nor Crenarchaeota members were identified amongst the 16S-rRNA fragments sequenced from separated TGGE bands.