Comparative analysis of the composition of bacterial communities from two constructed wetlands for municipal and swine wastewater treatment Paula Arroyo, Gemma Ansola, Ivan Blanco, Patricia Molleda, Estanislao de Luis Calabuig and Luis E. Sa ´ enz de Miera ABSTRACT Paula Arroyo Ivan Blanco Patricia Molleda IMARENABIO, Universidad de Leo ´ n, Leo ´ n 24071, Spain Gemma Ansola (corresponding author) Estanislao de Luis Calabuig A ´ rea de Ecologı ´a, Universidad de Leo ´ n, Campus de Vegazana, 24071 Leo ´ n, Spain E-mail: gemma.ansola@unileon.es Luis E. Sa ´ enz de Miera A ´ rea de Gene ´ tica, Universidad de Leo ´ n, Leo ´ n 24071, Spain This work provides information about bacterial community structure in natural wastewater treatment systems treating different types of wastewater. The diversity and composition of bacterial communities associated with the rhizosphere of Typha latifolia and Salix atrocinerea were studied and compared among two different natural wastewater treatment systems, using the direct sequencing of the 16S ribosomal RNA codifying genes. Phylogenetic affiliations of the bacteria detected allowed us to define the main groups present in these particular ecosystems. Moreover, bacterial community structure was studied through two diversity indices. Ten identified and five non-identified phyla were found in the samples; the phylum Proteobacteria was the predominant group in the four ecosystems. The results showed a bacterial community dominated by beta-proteobacteria and a lower diversity value in the swine wastewater treatment system. The municipal wastewater treatment system presented a high diverse community in both macrophytes (Typha latifolia and Salix atrocinerea), with gamma-proteobacteria and alpha-proteobacteria, respectively, as the most abundant groups. Key words | bacterial diversity, municipal wastewater treatment, swine wastewater treatment, 16S rRNA gene ABBREVIATIONS BOD 5 biochemical oxygen demand HMAE w Hierarchical Mosaic of Artificial Ecosystems HRT hydraulic retention time MWWS municipal wastewater system PCR polymerase chain reaction SWWS swine wastewater system INTRODUCTION The operation of wastewater treatment technologies relies on a combination of physical, chemical and biological factors. For many decades, these systems have been based mainly on information about chemical and physical parameters, having been quite successful in using the advantages of the amazing metabolic potential of microbial communities without detailed available knowl- edge about the organisms involved (Gilbride et al. 2006). The development of more stringent disposal limits to protect the environment demands an in-depth acquain- tance with the parameters involved in wastewater treatment systems in order to improve and optimize their performance. Secondary treatment is one of the key components of a wastewater treatment plant. It involves the biological reduction of organic matter, suspended solids and toxicity of industrial wastewaters, together with the production of doi: 10.2166/wh.2009.123 147 Q IWA Publishing 2010 Journal of Water and Health | 08.1 | 2010