Prevalence of Nitrosomonas cluster 7 populations in the ammonia-oxidizing community of a submerged membrane bioreactor treating urban wastewater under different operation conditions.

A pilot-scale ultrafiltration membrane bioreactor (MBR) was used for the aerobic treatment of urban wastewater in four experimental stages influenced by seasonal temperature and different sets of operation conditions. The structure of the ammonia-oxidizing bacteria (AOB) community was profiled by temperature gradient gel electrophoresis (TGGE), based on the amplification and separation of partial ammonia-monoxygenase subunit A (amoA) genes. Canonical correspondence analysis revealed that temperature, hydraulic retention time and percentage of ammonia removal had a significant effect on the fingerprints of AOB communities. Phylogenetic analysis conducted on amoA/AmoA sequences of reamplified TGGE bands showed, however, that closely related ammonia-oxidizing populations inhabited the sludge of the MBR in all experimental stages. Nitrosomonas cluster 7 populations (N. europaea-N. eutropha cluster) prevailed under all conditions tested, even when the MBR was operated under complete biomass retention or at low temperatures, suggesting that the high ammonia concentrations in the system were determinant to select r-strategist AOB.

Effect of salinity on enzymatic activities in a submerged fixed bed biofilm reactor for municipal sewage treatment.

The effect of salinity on the hydrolytic enzymatic activities (acid phosphatase, alkaline phosphatase, glucosidase, protease and esterase) released by the microorganisms in a submerged fixed bed bioreactor for real urban wastewater treatment was investigated. The influence of salt (NaCl) on the enzymatic activities was evaluated in four different experiments with concentrations of NaCl of 0, 3.7, 24.1 and 44.1g/L, remaining constant all other operating parameters of the bioreactor. The results show that enzymatic activities were reduced when the salinity was increased in the influent and consequently the biotransformation of organic matter in the submerged fixed bed bioreactor significantly decreased. A redundancy analysis was performed to evaluate the relationships between enzymatic activities and physic-chemical parameters analyzed in the influent. According to the results obtained with the Monte Carlo permutation test, salinity and sampling day significantly contributed to explain the variation of enzymatic activities, showing a negative correlation.

Analysis of community composition of biofilms in a submerged filter system for the removal of ammonia and phenol from industrial wastewater.

The bacterial diversity of a submerged filter, used for the removal of ammonia and phenol from an industrial wastewater with high salinity, was studied by a cultivation-independent approach based on PCR/TGGE (temperature-gradient gel electrophoresis). The wastewater treatment plant (laboratory scale) combined the nitrification and denitrification processes and consisted of two separated columns (one anoxic and one aerated) connected through a valve. The spatial diversity of bacterial communities in the plant biofilms was analysed by taking samples at four different heights in the system. TGGE profiles of PCR-amplified sequences of the 16 S rRNA gene (V3-hypervariable region) showed significant variations of the bacterial diversity, mainly depending on the concentration of O(2) along the system. Several bands separated by TGGE were reamplified and sequenced, in order to explore the composition of the microbial communities in the biofilms. Most of the sequenced bands (10 out of 13) were closely related to the 16 S rRNA gene of marine alpha-proteobacteria, mainly grouping in the periphery of the genus Roseobacter. Other sequences were related to those of gamma-proteobacteria, the nitrite oxidizer Nitrospira marina and anaerobic phenol-degrading bacteria of the Desulfobacteraceae.