Open Access

The enhancement of standard dense phase carbon dioxide (DPCD) pasteurization by additional mechanical effects was assessed in this work. These effects were induced during pasteurization by the sudden depressurization in a narrow minitube. The high flow velocities, moderate pressures (40–80 bar) and low temperatures (25–45 °C) lead to intense degasification and shear stress. The inactivation of the test microorganism Escherichia coli DH5α (E. coli DH5α) was determined before and after depressurization in the minitube, representing entirely chemical DPCD via dissolved CO2 and total inactivation comprising the effects of dissolved CO2 and mechanical effects, respectively. Compared to conventional DPCD pasteurization, which is mostly attributed to chemical effects, the additional mechanical effects increased the inactivation efficiency considerably.

Wetlands offer different ecosystem services that contribute to human well-being (Kovács et al., 2015). According to the Ramsar Convention Secretariat (2018) wetland located in urban areas have been threatened by several activities such as drainage, pollution, encroachment, agriculture, among others. On the other hand, wetland degradation reduces the resilience of hazards like floods and storm surges (Kumar et al., 2017). For that reason, ecosystem-based disaster risk reduction (Eco-DRR) is an important strategy which enhances the conservation and restoration of ecosystems to reduce disaster risk aiming to sustainable development and resilience (Estrella & Saalismaa, 2013). Despite international recognition of the importance of wetlands, urban wetlands have diminished their capacity to cope with flood threats (Boyer and Polasky, 2006) due to the aforementioned human impacts. That is why this thesis aimed to identify the role of urban wetlands in Bogota, Colombia, that has an urban wetland complex that is recognised as a Ramsar site in 2018. However, wetlands in the city reduced its area from 50.000 hectares to less than 800, approximately, in less than 40 years, mainly because of urban expansion and encroachment (IDIGER, 2018). To achieve this objective, an analysis of the city’s risk management framework was conducted, as well as a stakeholder analysis based on semi-structured interviews and a spatial-temporal analysis for the period 1998-2017, for which the Jaboque wetland was used as a case study. This wetland is located near the Bogotá River and is in the area threatened by flooding. It was possible to determine that national and district policies on wetlands, biodiversity, and climate change adaptation address some ecosystem functions. Still, disaster risk reduction is not strongly linked to them. Thus, based on the case study, the wetlands in Bogota have not played a decisive role in flood risk management in the city.

Urbanization processes are one of the main factors for habitat loss and fragmentation, driving global biodiversity loss and species extinction. The neotropical Atlantic forest in Brazil is considered a global key biodiversity hotspot and used to be one of the most extensive forests of the Americas. Due to substantial deforestation over centuries, its landscape was transformed into a mosaic of small forest fragments surrounded by a predominantly agricultural matrix. Urban expansion and rural urbanization have created peri-urban zones, which still can harbor natural habitat remnants, contributing to biological diversity and thus providing essential ecosystem services to urban and rural areas. The maintenance of such ecosystem services requires an understanding of the ecological processes in the ecosystem. A prerequisite for such an in-depth insight is the quantification of the underlying ecosystem functions. The ecosystem function pest control, a trophic interaction between insectivorous birds and herbivorous arthropods, was quantified in an empirical study using artificial caterpillars as prey models. This technique allows the identification of predator groups and the assessment of their predation rates. A total of 888 plasticine caterpillars were distributed at eight sites in secondary forest fragments surrounding the university campus of the federal university of São Carlos (UFScar) in peri-urban Sorocaba, southeastern Brazil. In sixteen point counts, 72 insect-eating birds, belonging to 19 species, were identified as possible artificial caterpillar attackers. Local habitat variables were measured to describe the forest vegetation structure and the landscape context. The study aimed to assess which structural components of the forest fragments, together with the recorded bird community variables (abundance, richness, αdiversity), best explain the estimated predation rates by birds. The mean predation rate for birds was 8.25 ± 6.3 % for a reference period of eight days, representing the first quantification of the ecosystem function pest control for the study area. The three treatments of caterpillar placement heights (ground, stem: 0.5 -1.0 m, leaf: 1.5 - 2.0 m) were the best and only estimator to explain bird predation rates. The little dense understory and ground vegetation might have facilitated the accessibility of artificial caterpillars, especially for carnivorous arthropods and birds. The detected contrast in their foraging and predation patterns suggests that arthropods and birds complement each other in their function of pest control. Bird predation rates were found to be negatively related to the vegetation structure. Thus, more open habitats, with less understory and low tree density, but high canopy cover and including dead trees were correlated with the highest predation rates and also exhibited more specialized forest-dependent bird species. This study confirms the importance of the maintenance of forest fragments in peri-urban areas, even if they are small, to preserve forest-associated birds, to contribute to the biological diversity on a broader scale, and to prevent the loss of ecosystem functions and services, mitigating some of the adverse effects of urbanization. Further investigation of the effect among the three treatments of caterpillar placement on the predation rates is encouraged, including comparative studies among different habitat types. For future studies, it is recommended to model the avian community variables with the vegetation structure measures to predict habitat preferences of insectivorous birds. Therefore, the sampling of more units and on a bigger scale, including over a more extended period, is necessary to improve the robustness of the results, which could provide the basis for a monetary analysis of the ecosystem service pest control by birds.

Resilience in relation to flood risk management (FRM) is not a new concept, yet parts of the FRM community are still struggling to apply it. The main challenge this study addresses is the question as to whether parts of the FRM community should still adopt, or rather “leap‐frog,” resilience. The main purpose is to evaluate whether resilience is a still on‐going trend or, already subsiding. Research suggests that resilience is an on‐going trend that connects research and policy and has gained international recognition as expressed by international guidelines and bodies promoting its research but also its operationalization. Academic literature in the area of FRM also shows a significant continuing development. Resilience enables to analyze dynamics and transformations of riverine areas, or coastal zones in connection to an integrated social‐environmental system approach with more emphasis and conceptual basis than previous concepts. Resilience is more than a short‐lived notion and it appears that FRM researchers cannot avoid addressing it. Resilience often is a convergence of ideas and mainstreaming of efforts, which in many venues is absolutely necessary and can help, for example, to decrease silo‐thinking. But as academics, we have a mandate to remain skeptical and remain on the look‐out for novel ideas, too. This article is categorized under: Engineering Water > Planning Water

Anaerobic digestion plants have the potential to produce biogas on demand to help balance renewable energy production and energy demand by consumers. A proportional integral (PI) controller is constructed and tuned with a novel tuning method to control biogas production in an optimal manner. In this approach, the proportional part of the controller is a function of the feeding rate and system's degree of stability. To estimate the degree of stability, a simulation‐based soft sensor is developed. By means of the PI controller, the requirement for gas storage capacity of the digester is reduced by approximately 30 % compared to a constant, continuous feeding regime of the digester.