Loredana Stante | PubMed Health

PubMed2005

Sequencing batch reactor performance treating PAH contaminated lagoon sediments.

The applicability of sediment slurry sequencing batch reactors (SBR) to treat Venice lagoon sediments contaminated by polycyclic aromatic hydrocarbons (PAHs) was investigated, carrying out experimental tests. The slurry, obtained mixing tap water and contaminated sediments with 17.1 mg kg(-1) TS total PAHs content, was loaded to a 8l lab-scale completely stirred reactor, operated as a sequencing batch reactor. Oxygen uptake rate exerted by the slurry, measured by means of a DO-stat titrator, was used to monitor the in-reactor biological activity and to select the optimal operating conditions for the sediment slurry SBR. The PAHs removal efficiency was evaluated in different operating conditions, obtained changing the hydraulic retention time (HRT) of the lab-scale reactor and adding an external carbon source to the slurry. HRT values used during the experiments are 98, 70 and 35 days, whereas the carbon source was added in order to evaluate its effect on the biological activity. The results have shown a stable degradation of PAHs, with a removal efficiency close to 55%, not dependent on the addition of carbon source and the tested HRTs.

Biodegradation, Environmental↗

PubMed2004

Emended description of the species Lampropedia hyalina.

Three Lampropedia hyalina strains from different habitats were compared by phenotypic, chemotaxonomic and molecular characteristics. All strains form coccoid cells and have been reported to grow as square tablets of eight to 64 cells. However, two of these strains (ATCC 11041T and ATCC 43383) have apparently lost this ability, and the third strain may temporarily lose this capacity under certain cultivation conditions. The three strains showed only minor differences in metabolic characteristics: the main significant physiological difference was the ability to accumulate polyphosphate under alternating anaerobic-aerobic conditions found for DSM 15336. The three strains showed high similarity in fatty acid composition and only slight differences in the G + C content (63-67 mol%) and DNA-DNA reassociation (90-95 % relatedness). Comparative 16S rRNA gene sequence analyses on these three strains and three Lampropedia hyalina 16S rRNA gene sequences deposited at NCBI showed that they are all very similar (> 98.8 %) and that they form a distinct group among the 'Betaproteobacteria', showing between 94.6 and 93 % 16S rRNA gene similarity to members of various genera such as Acidovorax, Aquaspirillum, Brachymonas, Comamonas, Delftia and Xenophilus. Fluorescent in situ hybridization with oligonucleotide probes targeting betaproteobacteria on the 16S rRNA and 23S rRNA gene level further supported the conclusion that all investigated strains are members of the 'Betaproteobacteria'. Two oligonucleotide probes were designed and successfully applied for culture-independent identification of Lampropedia hyalina by means of fluorescent in situ hybridization.

Aerobiosis↗