Investigation of airflow patterns in a microclimate by particle image velocimetry (PIV)

Problems with mould growth in dwellings usually occur in bedrooms in the microclimate behind closets placed next to exterior walls with poor insulation. It is anticipated that the problems are caused by lack of airflow behind the furniture in combination with a colder surface temperature and a high moisture production. The lack of air circulation decreases the surface temperature, which can cause problems. A particle image velocimetry (PIV) investigation was performed of the airflow patterns in such a microclimate. This paper describes the experimental set-up and the results. The results indicate that the flow rates behind the furniture will increase with increased distance between the closet and the wall, and even higher airflow rates are seen when the furniture is elevated by legs.     

Effect of periodic feeding in sequencing batch reactor on substrate uptake and storage rates by a pure culture of Amaricoccus kaplicensis

A pure culture of Amaricoccus kaplicensis was aerobically cultured at a long culture residence time (Theta(C)>12d), under periodic acetate feeding in a sequencing batch reactor (SBR). The cycle length and, correspondingly, the volumetric organic load rate (vOLR) were varied in the range 4-24h and 0.76-0.12gCODl(-1)d(-1), respectively. The transient response of the microorganism to the acetate spike was investigated throughout batch tests, as a function of SBR cycle length and vOLR. In all tested conditions, a rapid transient response was observed, mainly due to acetate storage in the form of polyhydroxybutyrate, since growth (production of active biomass) played a minor role. Apart from this general trend, the maximum rates under transient conditions increased as the cycle length increased from 4 to 24h. In the SBR, the longest cycle also caused a decrease in floc size and settleability as well as an increase in the observed yield. The observed effect of SBR operating conditions on the physiological state of cells and their related transient response may have great significance on the performance of full scale activated sludge processes.     

Evaluation of the metabolic diversity of microbial communities in four different filter layers of a constructed wetland with vertical flow by Biolog™ analysis

The community-level substrate utilization test based on direct incubation of environmental samples in Biolog EcoPlates™ is a suitable and sensitive tool to characterize microbial communities. The aim of this study was to investigate the influence of plant roots and soil structure on the metabolic diversity of microorganisms in a constructed wetland with vertical flow.Sediment samples were taken from different filter depths representing specific filter layers. The color development representing the substrate utilization was measured with the samples over a period of 10 days. The average well color development (AWCD) for all carbon sources was calculated as an indicator of total activity and in order to compensate the influence of the inoculum's density on the color development in the plates. After transformation by dividing by the AWCD, the optical density data were analysed by principal component analysis (PCA). An analysis of the kinetic profile of the AWCD was carried out to increase the analytical power of the method. The corrected data have been successfully fit to the logistic growth equation. Three kinetic model parameters, the asymptote (K), the exponential rate of color change (p) and the time to the midpoint of the exponential portion of the curve (s), were used for statistical analysis of the physiological profile of the microbial community in the different filter layers of the constructed wetland.We found out that in the upper two horizons, which were rooted most densely, mainly easily degradable materials like specific carbohydrates were utilized, while in the lower layers, where only single roots occur, more biochemically inert compounds, e.g. 2-hydroxy benzoic acid, were utilized. Furthermore it could be shown that microorganisms in the surface layer benefited from the plant litter because they can utilize decay products of these. In the lower filter layers specialists took advantage because they had to cope with the biochemically inert materials and the lower nutrient supply.