Potentials for Sponge City Implementation in Sub-Saharan Africa

Despite the growing interest in implementing sponge cities (SPC), their potential is not yet being tapped in many fast-growing Sub-Saharan African cities. This is remarkable because SPC interventions can contribute considerably to increasing water safety and availability in a city. By means of a three-stage potential assessment, this study provides the first analysis of what concrete options can be identified for implementing the SPC concept in Sub-Saharan cities. The methodology was filled with information obtained especially from expert interviews, literature reviews, and satellite imagery. Thus, the analysis also considers what obstacles impede SPC implementation, and, in particular, what technical and socioeconomic constraints need to be taken into account. The cities of Hawassa (Ethiopia), Beira (Mozambique), Kigali (Rwanda), Ouagadougou (Burkina Faso), and Cotonou (Benin) are examined in detail. Additionally, a local SPC implementation was conceptualized and evaluated for two districts in Ouagadougou and Cotonou. The first finding is that, when geographical and socioeconomic aspects such as climatic patterns, migration flows, health risks, and existing infrastructure are sufficiently taken into account, SPC interventions would massively help African cities to mitigate current and urgent challenges such as water scarcity and urban flooding. In terms of water safety, the second key finding is that rainwater harvesting solutions at the household level could be implemented quickly; however, there would be substantial difficulties such as lack of financing and maintenance as well as claims of ownership, especially in informal settlements and slums. Thus, it seems quite promising to directly strive for a rapid “centralization” of SPC implementation in individual neighborhoods. This neighborhood approach paves the way for SPC measures to receive public acceptance and constant maintenance. When this mosaic of implementations comes together, many individual instances of SPC implementation can help to improve urban resilience and living conditions for the city dwellers as is here demonstrated for the districts in Cotonou and Ouagadougou

Investigation of the Degradation of Chelate Complexes in Liquid Redox Desulfurization Processes

Metal complexes such as Fe‐EDTA, which are used as pseudo‐catalysts or oxygen carriers in wet oxidative desulfurization processes, are subject to a degradation mechanism that significantly influences the economics of such processes. Therefore, this study presents a methodology for determining the degree of degradation during the reactive hydrogen sulfide absorption in a Fe‐EDTA solution within a continuously operating semi‐batch reactor system. For this purpose, the reactive conversion of H2S in the liquid phase was used as a reference, and a clear dependence of the degradation on the pH could be shown. In addition, indicators are introduced that evaluate the observed pH dependency of the degradation and distinguish pH‐induced effects such as the pH‐dependent absorption performance of H2S.TU Berlin, Open-Access-Mittel - 202

Biogas potential of organic waste onboard cruise ships : A yet untapped energy source

To tap the organic waste generated onboard cruise ships is a very promising approach to reduce their adverse impact on the maritime environment. Biogas produced by means of onboard anaerobic digestion offers a complementary energy source for ships’ operation. This report comprises a detailed presentation of the results gained from comprehensive investigations on the gas yield from onboard substrates such as food waste, sewage sludge and screening solids. Each person onboard generates a total average of about 9 kg of organic waste per day. The performed analyses of substrates and anaerobic digestion tests revealed an accumulated methane yield of around 159 L per person per day. The anaerobic co-digestion of sewage sludge and food waste (50:50 VS) emerged as particularly effective and led to an increased biogas yield by 24%, compared to the mono-fermentation. In the best case, onboard biogas production can provide an energetic output of 82 W/P, on average covering 3.3 to 4.1% of the total energy demand of a cruise ship. © 2021, The Author(s)

Using Stormwater in a Sponge City as a New Wing of Urban Water Supply—A Case Study

Rapid and even disruptive innovations are needed to make cities fit for the future. The particular challenge will be to transform existing urban spaces in order to increase climate resilience. Along these lines, rainwater harvesting has taken place insufficiently to date, even when Sponge City concepts are implemented. Thus, the concept presented here addresses existing urban neighborhoods and proposes to collect rainwater from nearby rooftops and treat it in decentral treatment units called “City Water Hubs” (CWH) equipped with modular coupled low-energy technologies to produce various customized “City Water” qualities, and store it until it can be used or distributed. A feasibility study with a focus on the campus area at the main building of the Leibniz University of Hannover, the determined rainwater qualities, and the results from investigations with two laboratory test plants provided the basis for the technical design of the pursued concept. The feasibility study showed how sufficient rainwater for irrigation purposes can be made available for the listed large university park even under extreme dry and heat wave conditions. If large portions of the roof area (11,737 m2) of the university’s main building were activated, even in a dry year with only 49.8% of the average precipitation, only 19.8% of the harvested stormwater would be needed for irrigation. The rainwater samples showed TSS concentrations of up to 7.54 mg/L, COD of up to 58.5 mg/L, and NH4 of up to 2.21 mg/L, which was in line with data reported in the literature. The treatment technologies used for the two pilot plants are proven approaches for stormwater treatment and were composed as follows: (1) gravity-driven membrane filtration (GDM) and (2) slow sand filter with integrated activated carbon (AC) layer. The treatment with both (1) and (2) clearly improved the rainwater quality. The GDM reduced turbidity by 90.4% and the Sand/AC filter by 20.4%. With regard to COD, the studies for GDM did not show a clear elimination trend; the Sand/AC filter reduced the COD by 77%. Taken together, decentralized low-energy rainwater treatment can reliably provide quality-assured City Water for any specific use. Regarding the treatment design, GDM is preferable and can be better operated with downstream UV disinfection, which might be needed to reduce the pathogenic load, e.g., for local heat control measures. The research steps presented here will pioneer the development of a city-wide rainwater harvesting infrastructure on the way of establishing stormwater as a resource for a new wing of urban water supply. The presented findings will now result in the implementation of a full-scale CHW on the campus to ensure long-term irrigation of the listed park, relieving the public drinking water supply

Wasser in der Stadt : Transformation städtischer Bestandsquartiere

Wie können Siedlungsräume fit für die Zukunft gemacht werden? Damit hat sich das BMBF-Projekt TransMiT – federführend geleitet vom Institut für Siedlungswasserwirtschaft und Abfalltechnik – beschäftigt. Explizites Ziel war es, neben der Entwicklung innovativer (Entwässerungs-) Infrastrukturen (smart, multifunktional und damit emissionsarm und ressourceneffizient) die Institutionalisierung den Transformationsprozess unterstützender kommunaler (Planungs-) Prozesse

Erweitertes Schwammstadtkonzept : Ausreichend Wasser für eine lebenswerte Stadt

Eine Stadt wie ein Schwamm: Stephan Köster und Maike Beier, Wissenschaftler*innen am Institut für Siedlungswasserwirtschaft und Abfalltechnik der Leibniz Universität Hannover arbeiten mit einem Forschungsteam seit vielen Jahren an Lösungen, um mit besonderem Blick auf die städtische Wasserwirtschaft praxistaugliche Transformations- und Entwicklungspfade für Städte und ihre Wasserinfrastrukturen aufzuzeigen

Zukunftslabor Wasser : Kostbare Ressourcen managen – Ökosysteme nachhaltig nutzen

[no abstract available