Entrepreneurial capabilities

The aim of this article is to analyse entrepreneurship from an action research perspective. What is entrepreneurship about? Which are the fundamental capabilities and processes of entrepreneurship? To answer these questions the article includes a case study of a Danish entrepreneur and his networks. Finally, the article discusses how more long term action research methods could be integrated into the entrepreneurial processes and the possible impacts of such an implementation.     

Analysis of rainfall series in the design of urban drainage control systems

Intensity-duration-frequency curves are traditionally used in the design of urban runoff treatment and management systems. The uniform intensity for a specified duration and return period is selected for a design storm without consideration of the inter-event dry periods between two successive rainfall events. For many purposes, especially those related to urban storm pollution control and receiving water impacts, the cumulative effects of successive storm events must be taken into account. This fact requires the selection of design storms where the minimum inter-event dry periods are adjusted to the effect in question. This paper will discuss the concept of inter-event dry periods for evaluation of design storms derived from a rainfall record. As an example the rainfall record for the city of Odense, Denmark, has been analyzed. The basic statistics as well as the importance of the concept will be illustrated.     

Effect of Temperature on Air-Water Transfer of Hydrogen Sulfide

The extent of hydrogen sulfide transfer across the air-water interface plays a major role for odor and corrosion problems in sewer networks. One significant physical factor affecting the air-water transfer process is temperature. This study describes the temperature dependence of air-water transfer of hydrogen sulfide in terms of a temperature correction factor (temperature coefficient). The air-water transfer rate was found to increase with increasing temperature at a constant turbulence level. A mathematical expression for the transfer rate versus temperature was addressed following the Arrhenius equation. The temperature coefficient for air-water transfer of hydrogen sulfide was observed under acidic and neutral conditions (pH 4.5, 6.5, and 7.0), i.e., under conditions where only the molecular form of hydrogen sulfide was present (pH 4.5) and under conditions where both the molecular form and the ionized form existed (pH 6.5 and 7.0). The effect of temperature on air-water transfer of hydrogen sulfide decreased with increasing pH. The temperature coefficients found in this study were within the range reported in the literature for other substances transferring across the air-water interface such as oxygen, ozone, and krypton-85.     

Kinetics and stoichiometry of sulfide oxidation by sewer biofilms

Oxidation of sulfide under aerobic conditions by biofilms grown on municipal wastewater in 6 identical pipe reactors was investigated. The biofilms were grown at pH 7.6 and temperatures of 20 and 25 degrees C under aerobic-anaerobic transient conditions with pulse dosing of sulfide in the bulk water. The pulse dosing of sulfide served to simulate conditions in a gravity sewer located downstream of a pressure main. During growth of the biofilms, sulfide was pulse dosed in concentrations of 0, 0.5, 2.0 and 5.0 g Sm(-3) with a frequency of 1h(-1). Based on a series of batch experiments, kinetics and stoichiometry of sulfide oxidation by the sewer biofilms was investigated and a rate equation and a stoichiometric constant proposed. Sulfide oxidation kinetics was significantly faster for biofilms grown at sulfide loadings of 0.5, 2.0 and 5.0 g Sm(-3)h(-1) than for biofilms grown in the absence of sulfide. However, the kinetics of sulfide oxidation was relatively constant for biofilms grown at sulfide loadings above 0.5 g Sm(-3)h(-1). Mass balance calculations of dissolved oxygen and sulfur compounds suggested the oxidation product to be elemental sulfur. Further oxidation of elemental sulfur could not be documented.     

Chemical sulfide oxidation of wastewater--effects of pH and temperature.

In this study, the kinetics and stoichiometry of chemical sulfide oxidation of wastewater from sewer networks were investigated. Based on experiments, it was shown that the stoichiometry could be considered identical for wastewater from two sampling sites. However, the kinetics differed significantly among the wastewaters from the two sites. Effects of pH and temperature were investigated in the pH and temperature ranges 5-9 and 5-25 degrees C, respectively. The rate of chemical sulfide oxidation could be related to the dissociation of H2S to HS-, with HS- being oxidized at a higher rate than H2S. The temperature dependency of the chemical sulfide oxidation rate was described using an Arrhenius relationship. The oxidation rate was found to double with a temperature increase of 12 degrees C. The stoichiometry of the chemical oxidation was not significantly affected by varying pH and temperature. Based on the experiments, a general rate equation, including a stoichiometric coefficient describing chemical sulfide oxidation in wastewater was proposed, enabling the process to be incorporated into sewer process models that can predict odor and corrosion problems.     

Chemometric strategies to assess metabonomic imprinting of food habits in epidemiological studies

Application of metabonomics to nutritional sciences, also termed as nutrimetabonomics, offers the possibility to measure metabolic responses associated with the consumption of specific nutrients and foods. As dietary differences generally only lead to subtle metabolic changes, measuring diet associated metabolic phenotypes is a challenge, and also an opportunity to develop and test new chemometric strategies that can highlight metabolic information in relation to different dietary habits. While multivariate statistical techniques have long been used to analyse dietary data from diet records and questionnaires, to date no attempt has been made to link dietary patterns with metabolic profiles. Using a three-step strategy, it was possible to merge ¹H NMR plasma metabolic profile data with specific dietary patterns as assessed by Principal Component Analysis (PCA) and Partial Least Squares-Discriminant Analysis (PLS-DA). Five dietary patterns (energy intake, plant versus animal based diet, “traditional diet” versus sugar-rich diet, “traditional” versus “modern” diets, and consumption of skim versus whole dairy products) were found by applying PCA to the food frequency questionnaire data which explained 50% of the variation. Metabolic phenotypes associated with these dietary patterns were obtained by PLS-DA and were mainly based on differences in lipids and amino acid profiles in plasma. This new approach to assess relationships between dietary intake and metabolic profiling data will allow greater steps to be made in merging nutritional epidemiology with metabonomics.     

Influence of pipe material and surfaces on sulfide related odor and corrosion in sewers

Hydrogen sulfide oxidation on sewer pipe surfaces was investigated in a pilot scale experimental setup. The experiments were aimed at replicating conditions in a gravity sewer located immediately downstream of a force main where sulfide related concrete corrosion and odor is often observed. During the experiments, hydrogen sulfide gas was injected intermittently into the headspace of partially filled concrete and plastic (PVC and HDPE) sewer pipes in concentrations of approximately 1000 ppm_v. Between each injection, the hydrogen sulfide concentration was monitored while it decreased because of adsorption and subsequent oxidation on the pipe surfaces. The experiments showed that the rate of hydrogen sulfide oxidation was approximately two orders of magnitude faster on the concrete pipe surfaces than on the plastic pipe surfaces. Removal of the layer of reaction (corrosion) products from the concrete pipes was found to reduce the rate of hydrogen sulfide oxidation significantly. However, the rate of sulfide oxidation was restored to its background level within 10-20 days. A similar treatment had no observable effect on hydrogen sulfide removal in the plastic pipe reactors. The experimental results were used to model hydrogen sulfide oxidation under field conditions. This showed that the gas-phase hydrogen sulfide concentration in concrete sewers would typically amount to a few percent of the equilibrium concentration calculated from Henry's law. In the plastic pipe sewers, significantly higher concentrations were predicted because of the slower adsorption and oxidation kinetics on such surfaces.     

European Research into Sewer Sediments and Associated Pollutants and Processes

Research investigating all aspects of solids in sewer systems has been underway in Europe for nearly two decades. Due to the early development of European sewer systems, originally as part of the industrialization process more than 100 years ago, urbanization has caused the original sewer networks to become overloaded and unable to function efficiently. Operational problems of interest include loss of ability to convey (designed) flows and the performance of “overflows” to relieve the high flows discharging directly into rivers and other watercourses. Research has characterized the nature of the solids getting into sewer systems, how they behave in terms of transport, and some of the main aspects of their effects. It has been possible to demonstrate that much of the pollutants found in suspension during storms, and likely to be discharged from overflows, originate from the predominantly organic “near bed solids” which accumulate in systems during dry weather. New ideas for the way in which the sediments are transported and the importance of the transformation processes, are leading toward the development of a unified and integrated understanding of the way in which sewer solids behave and the associated biochemical transformation processes.