Purple anoxygenic phototrophic bacteria distribution in Tunisian wastewater stabilisation plant exhibiting red water phenomenon

Both eutrophication and thermal stratification lead to degradation of wastewater treatment efficiency and have a major effect on the wastewater pond biology, but their effects on phototrophic anoxygenic bacterial community is not as well understood. Terminal restriction fragment length polymorphism analysis proved to be a valuable technique that could resolve the diversity and shift of the purple anoxygenic phototrophic community composition in three stage wastewater stabilization ponds (WSP) exhibiting periodically red water phenomenon. Chemical and biological parameters confirmed the eutrophic state during the appearance of the red water. Concomitantly a decrease of ponds performances is reported with total removal percentage of 27, 36 and 43% for Total suspended solid (TSS), DBO(5) and DCO, respectively. By targeting the pufM gene, 74 Terminal restriction fragments (TRFs) were detected in the three studied ponds which 78% were located in the anaerobic and facultative ponds. Simpson (D) and Shannon (H') diversity index showed a loss of phototrophic bacterial diversity from the anaerobic to the maturation pond, especially in the water phase. Principal coordinate analysis (PCoA) of both HpaII and HaeIII - T-RFLP profiles, allowed deducting a differential distribution between the water and sediments samples.