Influence of Biological Treatment and Ultraviolet Disinfection System on Pseudomonas spp. Diversity in Wastewater as Assessed by Denaturing Gradient Gel Electrophoresis

Biological treatment methods use natural processes of ubiquitous living organisms to improve or upgrade the quality of a wastewater. To investigate the dominance of Pseudomonas spp. community in untreated and treated wastewater from full‐scale bio‐discs treatment plant, PCR–denaturing gradient gel electrophoresis coupled with sequence analysis of 16S rRNA gene fragments from dominant bands, were performed. The Pseudomonas species distribution over the total treatment process and over seasons (summer and winter) was obtained by comparing the denaturing gradient gel electrophoresis (DGGE) patterns to a normalized mix of nine reference Pseudomonas strains. Results indicated that Pseudomonas putida and Pseudomonas fluorescens strains showed dominance in wastewater, remarkable stability in the biofilm and resistance to UV irradiation. A reduction of Pseudomonas aeruginosa in treated wastewater was also observed. In addition, climatic and operational conditions results in selection of microbial community. The high temperature and intense solar radiation contribute to the total absence of the Pseudomonas syringae strain. In this work, the effect of increasing UV254 germicidal dose on the Pseudomonas community in secondary treated wastewater effluent was also tested. At a dose of 1200 mWs/cm2, total disappearance of the band corresponding to P. aeruginosa, was noted. The DGGE approach can be used as an effective method to assess directly the Pseudomonas community shifts in studied wastewater treatment plant.