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N C Holm

Publications and source records attributed to N C Holm.

4 recordsLinked to original sources
PubMed2006

Specific SBR population behaviour as revealed by comparative dynamic simulation analysis of three full-scale municipal SBR wastewater treatment plants.

Three full-scale municipal sequential batch reactor (SBR) wastewater treatment plants (WWTPs) were investigated by dynamic simulation studies using ASM1. All three WWTPs showed similar kinetic and stoichiometric conditions in the SBR population behaviour after calibration of the models. The simulation results detected only a discrepancy to the ammonia online data during and shortly after shock loading under anoxic and anaerobic conditions that so far could not be adjusted by the ASM1 model. However, these differences did not severely affect the quality of the simulations nor the effluent flows. Additionally, in all cases a dynamic alpha factor curve occurred during the aeration phases that was verified by further oxygen transfer measurements. This might reveal new aspects for the process control, design and simulation of SBR WWTPs. A short lag phase was detected in many cases at the beginning of the first aeration phase.

Calibration↗
PubMed1996

Diversity and structure of hyphomicrobium populations in a sewage treatment plant and its adjacent receiving lake.

Budding methylotrophic bacteria resembling Hyphomicrobium spp. were counted for 12 months in a German sewage treatment plant by most-probable-number (MPN) methods. Influent samples contained up to 2 x 10(sup4) cells ml(sup-1), activated sludge consistently contained 1 x 10(sup5) to 5 x 10(sup5) cells ml(sup-1), and the effluent contained 1 x 10(sup3) to 4 x 10(sup3) cells ml(sup-1). The receiving lake had only 2 to 12 cells ml(sup-1). Six morphological groups with different growth requirements could be observed among 1,199 pure cultures that had been isolated from MPN dilutions. With dot blot DNA hybridizations, 671 isolates were assigned to 30 hybridization groups (HGs) and 84 could not be classified. Only HG 22 hybridized with a known species, Hyphomicrobium facilis IFAM B-522. Fourteen HGs (HGs 8 to 20 and HG 22) were specific for the lake; most others occurred only in the treatment plant. HGs 1, 3, and 26 were found in the activated sludge tank throughout the year, and HGs 27 and 28 were found for most of the year. In summary, it was demonstrated that bacteria with nearly identical and specific morphologies and nutritional types showed a high level of genetic diversity, although they were isolated under the same conditions and from the same treatment plant or its receiving lake. A directional exchange of these genetically different populations was possible but less significant, as was shown by the establishment of distinct populations in specific stations.

Journal Article↗
PubMed1988

New bacteriophages active on strains of Hyphomicrobium.

Fifty-five lytic bacteriophages isolated from water and soil samples were active on many strains of the genus Hyphomicrobium. The optimal isolation procedure was an adsorption method in which samples from a habitat similar to that of the respective host bacterium were used as the phage inoculum. According to the morphology and nucleic acid type these bacteriophages belonged to different families: Myoviridae (type A1: five phages); Styloviridae (type B1: 33 phages; type B2: eight phages) and Podoviridae (type C1: nine phages). The Styloviridae (type B1) appeared in two morphological variants (tails flexible or rigid). All phages investigated were specific for the genus Hyphomicrobium and were unable to lyse members of other genera of hyphal, budding bacteria (e.g. Hyphomonas, Pedomicrobium, genus D, genus T). The host specificity of 42 phages was tested with 156 Hyphomicrobium strains: 122 strains were lysed by at least one of these phages, but 34 Hyphomicrobium strains were not susceptible. Morphotype B1 phages with identical morphology could be distinguished according to their host-range properties on prophage-containing Hyphomicrobium strains. With regard to differences in morphology and host range, 25 phages were selected for more detailed investigations. From these phages DNA was isolated; the melting transition midpoints (Tm) ranged from 67 to 93 degrees C. The upper and higher values suggested the presence of DNA modifications. Six different adsorption patterns could be distinguished among the Hyphomicrobium phages. Preferred attachment sites were the proximal pole of the mother cell, the hyphal tip, the distal pole of the bud, and the distal pole of the swarmer cell.

Bacteria↗