Proposing a method for online permeability monitoring in membrane bioreactors.

Reliable and efficient operation of membrane bioreactors (MBR) for centralized municipal wastewater treatment strongly depends on a good monitoring of the membrane permeability, a value often used to quantify the transmissibility (i.e. the inverse of the flow resistance) of the membrane. By directly or indirectly evaluating this parameter the operator normally plans on the necessity and effectivity of maintenance activities. To allow the operator monitoring the membrane performance closely, the present paper proposes a method for online permeability based on the measurements of permeate flow, transmembrane pressure and water temperature. The theoretical background of the method is discussed and a data set of 250 days of continuous pilot operation of a municipal MBR equipped with three different standard membrane modules is used for testing. The method is numerically simple enough to allow being implemented on any programmable logical controller.

Development of an rRNA-targeted oligonucleotide probe specific for the genus Acinetobacter and its application for in situ monitoring in activated sludge.

Enhanced biological phosphate removal in an anaerobic-aerobic activated sludge system has generally been ascribed to members of the genus Acinetobacter. A genus-specific 16S rRNA-targeted oligonucleotide probe was developed to investigate the role of Acinetobacter spp. in situ. Nonisotopic dot blot hybridization to 66 reference strains, including the seven described Acinetobacter spp., demonstrated the expected probe specificity. Fluorescent derivatives were used for in situ monitoring of Acinetobacter spp. in the anaerobic and aerobic compartments of a sewage treatment plant with enhanced biological phosphate removal. Microbial community structures were further analyzed with oligonucleotide probes specific for the alpha, beta, or gamma subclasses of the class Proteobacteria, for the Cytophaga-Flavobacterium cluster, for gram-positive bacteria with a high G + C DNA content, and for all bacteria. Total cell counts were determined by 4',6-diamidino-2-phenylindole staining. In both the anaerobic and the aerobic basins, the activated sludge samples were dominated by members of the class Proteobacteria belonging to the beta subclass and by gram-positive bacteria with a high G + C DNA content. Acinetobacter spp. constituted less than 10% of all bacteria. For both basins, the microbial community structures determined with molecular techniques were compared with the compositions of the heterotrophic saprophytic microbiota determined with agar plating techniques. Isolates on nutrient-rich medium were classified by whole-cell hybridization with rRNA-targeted probes and fatty acid analysis.(ABSTRACT TRUNCATED AT 250 WORDS)