Microbial community dynamics in a submerged fixed bed bioreactor during biological treatment of saline urban wastewater
Cortés-Lorenzo, C. ; Sipkema, D. ; Rodríguez-Díaz, M. ; Fuentes, S. ; Juárez-Jiménez, B. ; Rodelas, B. ; Smidt, H. ; González-López, J. - \ 2014
Ecological Engineering 71 (2014). - ISSN 0925-8574 - p. 126 - 132.
activated-sludge - treatment plants - bacterial diversity - sewage-treatment - biofilm reactor - gradient - denitrification - sea
The influence of salt (NaCl) on bacterial and archaeal communities in a submerged fixed bed bioreactor system for the treatment of urban wastewater was determined by DGGE and 454 pyrosequencing of PCR-amplified 16S ribosomal RNA gene fragments. Cluster analysis of DGGE fingerprints showed significant differences in the community structure dependent on the salt concentration in the influent. Proteobacteria was found to be the dominant bacterial phylum in all experiments, with a-Proteobacteria being the main order at low salinity and ¿-Proteobacteria the dominant order at high salinity. Euryarchaeota was the main archaeal phylum in all experiments, with all microorganisms corresponding to methanogenic archaea. Whereas bacterial a-diversity decreased as salinity increased, archaeal a-diversity increased with higher NaCl concentrations.
Potential of mechanical cleaning of membranes from a mebrane bioreactor
Brink, P. van den; Vergeldt, F.J. ; As, H. van; Zwijnenburg, A. ; Temmink, H. - \ 2013
Journal of Membrane Science 429 (2013). - ISSN 0376-7388 - p. 259 - 267.
drinking-water - biofilm reactor - critical flux - waste-water - exopolysaccharides - denitrification - precipitation - communities - limitation - bacteria
Several membrane fouling mechanisms have been identified in membrane bioreactors. While cake layers can be removed by physical cleaning, irreversible fouling such as a gel layer is difficult to remove by physical cleaning during filtration. Harsh mechanical cleaning was applied in this study to evaluate how much fouling could be maximally removed and distribution of remaining fouling was investigated. The fouling resistance of several membranes operated at different relatively low fluxes was followed during long term continuous flux operation. Remaining fouling was observed with scanning electron microscopy (SEM) and magnetic resonance imaging (MRI). Dead-end filtration tests with mechanically cleaned membranes showed a decreased permeability. To determine whether bacteria were present in the remaining fouling, oxygen consumption was quantified. Even after harsh mechanical cleaning, membrane samples showed considerable oxygen consumption. SEM did not show fouling inside the membrane. Of several membranes operated for at least 1 year, the permeate side was covered with bacteria and extracellular polymeric substances (EPS). These results show that fouling cannot be removed completely by harsh mechanical cleaning and that both feed and permeate side of the membrane contains biofouling. This fouling on the permeate side should not be neglected when designing membrane cleaning.
Toxic effects exerted on methanogenic, nitrifying and denitrifying bacteria by chemicals used in a milk analysis laboratory
Lopez-Fiuza, J. ; Buys, B. ; Mosquera-Corral, A. ; Omil, F. ; Mendez, R. - \ 2002
Enzyme and Microbial Technology 31 (2002)7. - ISSN 0141-0229 - p. 976 - 985.
industrial waste-water - nitrification inhibition - biofilm reactor - oxygen-uptake - denitrification - biodegradation - nitrobacter - respiration - kinetics - system
The toxic effects caused by the chemicals contained in wastewaters generated by laboratories involved in raw milk analyses were assessed using batch assays. These assays were carried out separately with methanogenic, ammonium-oxidizing, nitrite-oxidizing and denitrifying bacteria. Since sodium azide is one of the main components of the chemical mixture present in these streams, a set of assays was carried out with the whole chemical mixture, and another one was performed only with azide as the sole toxicant. The concentrations of all chemicals in the raw wastewaters (100%) were the fundamental references used to assess the relative concentrations corresponding to a decrease of 50% in bacterial activity (IC50). The results obtained showed that nitrite-oxidizing bacteria were the most sensitive microorganisms, with IC50 relative concentrations around 0.04%. The values obtained for the other groups were: 20, 20 and 33% for methanogenic, ammonium-oxidizing and denitrifying bacteria, respectively