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  • Author: David Stransky x
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Suitability of combined sewers for the installation of heat exchangers

Abstract

The present paper deals with the classification of the suitability of combined sewers for the installation of heat exchangers and with assessment of the theoretical potential of wastewater in the sewer system for heating of buildings. A classification scheme involving criteria like theoretically available heat, sewer diameter, number of the heat exchanger parallel modules in the sewer cross-section, hydraulic conditions (hydraulic capacity of the sewer, pressurized flow), and potential fouling by biofilm growth was developed. First, individual sewers in the pilot catchment were assessed based on monitoring the flow characteristics and wastewater temperatures and on pipe flow modelling. Second, connectivity of the suitable and partly suitable sewers was examined with respect to the length necessary for the installation of the heat exchanger with the minimum required power of 100 kW. For the continuous sewer sections, the maximum potential power was calculated. The presented approach is generally applicable, however, for other heat exchanger types and other climatic and economic conditions, values of the suitability criteria for the heat exchanger installation must be adapted.

Open access
Methods Applied for Measurement and Visualization of Changes in Biodiversity

Abstract

The article presents the possible methods for determining biological or statistically significant differences between taxocenoses compared with respect to biodiversity. To obtain a complete description of biological differences between the compared hypothetical communities, the following indices were calculated: S (taxon richness), H (the Shannon index), Hmax (the maximum value of the Shannon index for the richness of taxa represented by the same number of individuals), Vd (a percentage value of covering the structural capacity of community, “evenness deficiency”), E (the MacArthur index - a taxon number (S) in a community for which the observed value of H equals Hmax), and Ps (a taxon richness shortage in percents). Moreover, a graphic profile method (Дд, Tj, and Lj profiles) was used for comparing the diversity of the communities. To obtain information about statistically significant differences in biodiversity between the analysed communities, rarefaction curves were applied. The curves are based on the null models and the Monte Carlo method. The rarefaction method resulted in determination of the statistical significance of the differences between taxon richness and Shannon's index values for the compared communities. The Vd and Ps indices and the profile method allowed concluding about the significance of the biological differences between taxocenoses, even when their values of Shannon's H indices were numerically similar.

Open access