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Frischer Fisch und frisches Gemüse direkt vom Dach produziert mit aufbereitetem Wasser aus dem Gebäude, das ist die Vision von ROOF WATER-FARM. Das vom Bundesministerium für Bildung und Forschung geförderte Verbundprojekt untersuchte erstmalig, wie sich Leichtbaufarmtechnologien wie Aquaponik und Hydroponik mit dezentralen Technologien zur Betriebswassernutzung und Düngemittelproduktion im und am Gebäude kombinieren lassen. Die ROOF WATER-FARM Handlungsempfehlungen sind eine aktualisierte Fassung der bereits im ROOF WATER-FARM Handbuch 2018 veröffentlichten Praxisempfehlungen Hygiene von kombinierten Wasserrecycling- und Farmsystemen. Sie sind neben gesundheitsrelevanten Fragen die Voraussetzung für die Vermarktungsfähigkeit der Produkte und eine breite praktische Umsetzung dieser zukunftsweisenden Kreislauftechnologien. Fresh fish and fresh vegetables directly from the roof, produced with treated water from houses, that is the vision of ROOF WATER-FARM. The research project, funded by the German Federal Ministry of Education and Research from 2013-2016, investigated for the first time how lightweight farm technologies such as aquaponics and hydroponics can be combined with decentralized technologies for the use of process water and fertilizer production from domestic wastewater streams in buildings. The ROOF WATER-FARM recommendations for action on hygienic aspects complement the recommendations for the implementation of combined water recycling and farming systems already published in the ROOF WATER-FARM Handbook 2018. Controlling the hygienic safety of the systems is a prerequisite for the marketability of the products and thus paves the way for a broad practical implementation of such innovative projects.

Protozoan grazing on bacteria is among the oldest predator-prey interactions in nature. While bacteria developed different defence strategies such as toxicity and microcolony formation to prevent grazing losses, protozoa developed different feeding mechanisms to compass these strategies. One important mode of grazing protection is biofilm formation. Its characteristics such as high bacterial densities and thus possible toxin production, as well as excretion of an extracellular matrix provide bacteria in biofilms with advantages in grazing protection compared to suspended bacteria. However, despite its importance, studies of protozoan grazing on biofilms are rare. This is partly due to the lack of appropriate methods to test mechanisms under complex field conditions. Here, different laboratory as well as field experiments were developed to investigate defence mechanisms of bacterial biofilms against protozoan grazers. The first part of this thesis demonstrates the impact of the ciliate Tetrahymena pyriformis on biofilms of the microcolony forming bacterial strain Acinetobacter sp. C6 and toxigenic and non-toxigenic strains of Vibrio cholerae, respectively. The grazer had a strong impact on the morphology of Acinetobacter sp. biofilms grown under various nutrient conditions. Microcolony formation did not protect the biofilms as such. However, biofilm biovolume of the grazed treatments stayed the same or increased during the course of the experiment indicating possible nutrient recycling. In a comparative study with T. pyriformis grazing on a toxigenic wild-type Vibrio cholerae strain A1552 and a genetically modified, non-toxigenic V. cholerae strain hapR it could be demonstrated that biofilms of the toxic V. cholerae A1552 supported less ciliates than biofilms of the non-toxic V. cholerae hapR. Microcolony abundances and active bacterial cells within the biofilms of V. cholerae A1552 increased compared to non-grazed control biofilms arguing for a mutual benefit for grazer and bacteria possibly due to nutrient recycling and chemical cues. In the second part of this thesis two new tools for environmental biofilm experiments are presented. (i) Diffusion chambers were successfully modified to expose toxigenic and non-toxigenic V. cholerae strains into the natural environment. The toxicity of wild-type V. cholerae A1552 for the flagellate Rhynchomonas nasuta could be verified. However, in comparison with the natural hapR mutant strain V. cholerae N16961, the level of toxicity impact on the flagellate varied dependent on seasonal background. The importance of nutrient concentration on V. cholerae toxicity could be demonstrated in subsequent laboratory experiments. This suggested a separate toxicity pathway beside the beforehand known hapR pathway. (ii) Two established methods of biofilm and protozoa observation were combined to quantify grazing interactions. The coupling of natural biofilm establishment in flow cells and video microscopic analysis of individual flagellate feeding revealed inter- as well as intra-specific differences and similarities in feeding behaviour and food preferences in three flagellate species. Whereas the three species showed distinct feeding behaviour, individuals of all species were only able to ingest single prey cells. Although microcolonies were contacted no cells were ingested. Thus, microcolony formation did protect bacteria against flagellate grazing. Taken together these experiments demonstrate the complex interactions of protozoa and bacteria on biofilms. Nutrient recycling, chemical and structural defence strategies of the bacterial community and the physical presence of the grazer have a major impact on biofilms. The presented methods such as the modified diffusion chambers and video microscopy in combination with the flow cell system are powerful tools to unravel the dynamics of predator-prey interactions on biofilms.

The Earth’s Critical Zone ranges from deep, unweathered rock to the canopy of the highest trees and is the zone, where rock meets life. Physical, chemical, and biological processes shape this zone. Over timescales that can range from minutes to millennia, they form habitats for myriads of organisms. Weathering converts pristine rock into regolith (comprised of weathered rock, saprolite and soil) by means of inorganic and biogenic disintegration. These processes include physical and chemical alteration of rock and provide nutrients which are necessary to fulfill plants’ physiological needs. Terrestrial plants act as a gigantic geochemical pump that continuously passes water and mineral-derived nutrients from the rooting zone towards the soil and the top of the canopy. In doing so, they directly and indirectly modulate the shape and architecture of the Critical Zone. One widely accepted paradigm is that plants enhance weathering to constantly liberate nutrients by (1) mechanically weakening rock and regolith, (2) directing photosynthetic energy to soil microbiota, (3) increasing the solubility of minerals through acidification, and by (4) regulating surface runoff and water residence times at depth. Regardless of whether the resulting weathering serves to fulfill plant-physiological needs or is merely a side effect of the presence of plants, the question arises whether we can identify the geochemical imprints of plant nutrition. This is the central topic of this thesis. I focus on the below-ground geochemical characterization of four different ecosystems and of the associated above ground vegetation. I further use radiogenic and stable Sr isotopes as a proxy for mineral nutrient sources and geochemical mass balances to quantify the fluxes and sources from rock weathering into plants. How the architecture and chemistry of the Critical Zone varies along a gradient of mean annual precipitation (MAP; 10–1100mm yr−1) and net primary productivity (NPP; 30– 500 gC m−2 yr−1) was explored in the four “EarthShape: Earth Surface Shaping by Biota” (DFG-SPP 1803) study sites. These are situated along the Chilean Coastal Cordillera in arid (Pan de Azúcar), semi-arid (Santa Gracia), mediterranean (La Campana), and humid- temperate (Nahuelbuta) climate conditions. These sites were chosen to isolate the effect mean annual precipitation (MAP) and net primary productivity (NPP) and to minimize variabil- ity in confounding variables on weathering. Accordingly, all sites are underlain by granitoid rock and with roughly uniform rock uplift rates. In contrast, mantling soils range from poorly developed Regosol in the arid site to mature umbric Podzol in the humid-temperate site. Vegetation cover increases along this gradient from 5% to 100% ground cover and the prevailing plant species change from desert shrubs to deciduous and evergreen species. At all sites, I quantified the rate and the degree of chemical weathering, and hence the release and availability of mineral-derived nutrients to terrestrial ecosystems. Weathering rates are lowest in the arid and sparsely vegetated site and highest in the mediterranean site with almost complete vegetation cover. In the semi-arid and humid-temperate site however, weathering rates are similar despite massive differences in MAP, NPP, and vegetation cover. A trend similar to that observed for weathering rate applies to the relative degree of chemical weathering among the four sites: It is lowest in the arid site and highest in the mediterranean site. Due to differences in mineralogy, however, the degree of chemical weathering in the semi-arid site is higher than in the humid-temperate site. Yet, at none of the sites the regolith is entirely depleted in its stock of primary minerals, such that mineral nutrients remain available for plant nutrition. The absence of statistically significant differences in the degree and rate of chemical weathering between the sites (excluding the arid Pan de Azúcar) does not allow for distinguishing the abiotic (purely climate-related) from the biotic (climate- and bio-related) drivers of weathering. After quantifying the nutrient availability in these sites, I quantified their accessibility to plants and the fluxes into and out of the different ecosystems. These fluxes characterize the geogenic nutrient pathway (i.e. long-term nutrient supply through weathering) and the organic nutrient cycle (i.e. nutrient uptake by plants and subsequent recycling of leaf litter). Key to this characterization is knowledge of the weathering release fluxes, the size of the nutrient-reservoir available to plants, and a representative chemical composition of the ecosystem dominant plant taxa. The latter information is nearly impossible to acquire purely by means of sampling and chemical analysis of plants. Thus, I applied an allometric model which allocates relative growth rates between stems/ twigs and leaves to estimate bulk plants’ representative chemical composition. Bio-availability of most elements in soil, bar a few exceptions, increase from the arid to mediterranean site. However, despite featuring the thickest soils, element bio-availability is lowest in the humid-temperate site. The pattern of elemental release is rather uniform across the different climate regimes and levels of NPP, and so does not correlate with the size of the bio-available pool. In contrast, plants’ nutrient uptake rates increase in spite of the rather uniform weathering release rates from the semi-arid to the humid-temperate site. Hence, recycling rates (RecX) increase along this gradient and the ecosystems with high NPP maintain their nutrient supply by increasing recycling rather than increasing weathering. The organic nutrient pathway thus intensifies, whereas the geogenic nutrient pathway stays steady despite increasing MAP and NPP. Weathering and ecosystem nutrition are intimately linked through the supply of fresh mineral nutrients from regolith and bedrock (i.e. the “geogenic nutrient pathway”) that must replace any nutrient leakage. This link is muted if re-utilization of nutrients from plant litter during re-mineralization is efficient (i.e. the “organic nutrient cycle”). The shifting balance between these two cycles along the EarthShape climate and vegetation gradient was quantified by applying Sr isotope geochemistry in combination with mass balance calculations. Radiogenic and stable Sr isotope ratios as well as molar Ca/Sr ratios in the different compartments of the Critical Zone (bedrock, bulk regolith, the bio-available fraction being representative for regolith fluid, and vegetation) were measured to define the Sr sources and to quantify its fluxes. Sr is released through weathering over the entire depth of the regolith profiles. This release is isotopically congruent and no shift in isotope ratios of the released Sr occurs during secondary mineral formation and its initial transfer into the bio-available pool. However, Sr contained in the bio-available fraction is isotopically heavier than in rock and regolith. The cause of this offset was found in the plants ability to fractionate Sr. Although 88Sr/86Sr in organs of plants at all four study sites systematically increases from roots towards their leaves, bulk plants preferentially take up Sr with low 88Sr/86Sr. The shift in 88Sr/86Sr in the bio-available pool occurs after preferential uptake of isotopically light Sr into plants and its subsequent export in the form of fractionated organic solids (i.e. leaf litter) from the ecosystems. This export effectively diminishes the litter pool that is available for nutrient re-utilization and decreases the “net” nutrient recycling factor (RecX). Accordingly, RecX is essentially unaltered in the arid and semi-arid site where Sr export fluxes are low but shifts from 1 to almost zero recycling in the mediterranean site, and roughly halves recycling from 5 to 2 – 3 in the humid-temperate site. The major outcomes of this thesis are that (1) Ecosystems exert a substantial control over weathering by both directly and indirectly modulating processes which either enhance or reduce weathering fluxes. The silicate-weathering fluxes become effectively decoupled from the ultimate nutrient demands of biota by intensifying the organic nutrient cycle; and (2) Organic solids proving a significant export path of elements released during weathering. This export potentially impairs the ability for direct nutrient (re-) acquisition from leaf litter and thus reduces the recycling factor.

Eine Anpassung von Wasserversorgungs- und Abwasserentsorgungssystemen im ländlichen Raum kann aufgrund vielfältiger Herausforderungen wie demografischen, siedlungsstrukturellen und klimatischen Veränderungen erforderlich werden. Im Zuge dessen können auch die Nachhaltigkeit und Ressourceneffizienz der bestehenden Systeme gesteigert werden. Das Ziel dieser Arbeit ist die Ableitung von Handlungsempfehlungen zur Unterstützung der notwendigen Anpassungsprozesse der Abwasserentsorgung ländlicher Gemeinden. Dazu werden verschiedene Transformationspfade für Abwassersysteme aufgezeigt und analysiert. In dieser Arbeit wird ein softwaregestütztes Entscheidungs- und Optimierungssystem angewendet und evaluiert, dass optimale Anpassungsmöglichkeiten aufgezeigt. Das gemischt-ganzzahlige lineare Optimierungsmodell berechnet für jede Gemeinde in Abhängigkeit von dem ausgewählten Szenario und vorgegebenen Zielen den optimalen Transformationspfad mit seiner zeitlichen und räumlichen Umsetzung. In den Szenarien werden zukünftige Entwicklungen der Bevölkerung, der Siedlungsstruktur, des Wasserbedarfs, der Kosten technischer Anlagen und des Klimawandels berücksichtigt. Die Zielfunktion bildet sich aus der gewichteten Summe ökonomischer, ökologischer und sozialer Bewertungskriterien. Die beispielhafte Anwendung des Modells erfolgt für zwei repräsentative ländliche Modellkommunen in Rheinland-Pfalz. Durch eine detaillierte Auswertung und Evaluierung von ausgewählten Kombinationen von Szenarien und Bewertungskriterien kann das Spektrum an möglichen Transformationspfaden von der Erhaltung des zentralen Systems bis hin zu dezentralen und ressourcenorientierten Systemen aufgezeigt werden. Sensitivitätsbetrachtungen zeigen, dass die Auswahl und Gewichtung der Bewertungskriterien und die lokalen Randbedingungen der Gemeinde einen größeren Einfluss auf die resultierende Transformationspfade haben als die Auswahl der Szenarien. Der Zustand des Entwässerungssystems wie der Anteil alter Kanäle, ein großer Anteil Mischsystem, große Durchmesser und eine große Kanallänge pro Einwohner sowie eine niedrige Siedlungsdichte fördern dezentrale Strukturen und sind geeignete Voraussetzungen für einen Systemwechsel. Bei der Priorisierung der Ziele Flexibilität, Wasserbilanz und Wasserrecycling wird die Dezentralisierung eines Systems mit Kleinkläranlagen favorisiert. Ein ressourcenorientiertes System mit einer Grau- und Schwarzwassertrennung ist nur zukünftig vorteilhaft, wenn die Ziele Wasserrecycling, Nährstoffrecycling und/oder Energieeffizienz priorisiert werden. Wenn ein Systemwechsel vollzogen werden soll, müssen auch die Auswirkungen auf die Wasserversorgung und Abwasserreinigung untersucht werden. Es kann gezeigt werden, dass bei einer abnehmenden Bevölkerung dezentrale und ressourcenorientierte Systeme im ländlichen Raum eine Alternative darstellen. Zur Begleitung von Transformationsprozessen ist die Verwendung einer adäquaten Methodik zum Aufzeigen von verschiedenen Systemalternativen (z.B. mathematische Optimierung) zielführend. Adaptations of water supply and wastewater systems in rural areas may be necessary due to a variety of challenges such as demographic change, changes in the settlement structure or climate change. By adapting an existing system the sustainability and resource efficiency can also be increased. The objective of this thesis is to derive recommendations for the required adaptation processes of wastewater systems in rural areas. Various transformation paths for wastewater systems are identified and analysed. A software-based decision support and optimisation system to demonstrate optimal adaptation possibilities is used. The mixed-integer linear model calculates optimal transformation paths for each municipality, depending on the selected scenario and given objectives. The chronological and spatial implementation of adaptation measures is shown. Considered scenarios take into account future developments of population, settlement structure, water demand, costs of the technical facilities, and climate change. The objective function consists of the weighted sum of economic, ecological, and social evaluation criteria. The model is applied to two rural municipalities in Rhineland-Palatinate. By means of a detailed analysis and evaluation of selected combinations of scenarios and objectives, possible transformation paths can be shown. The existing system can be maintained or it can be transformed to a decentral or a resource-oriented system. Sensitivity analyses show that the selection and weighting of the objectives and the local boundary conditions of the municipality have a greater influence on the resulting transformation path than the selection of scenarios. The condition of the drainage system, such as the proportion of old sewers, a higher share of combined sewers, large sewer diameters and a large sewer length per capita as well as a low population density support decentralised structures and are suitable prerequisites for a system change. By prioritising the objectives flexibility, water balance, and water recycling, the decentralisation of a system with small wastewater treatment plants is favoured. A resource-oriented system with a grey- and blackwater separation will only be advantageous in the future if the objectives water recycling, nutrient recycling, and/or energy efficiency are prioritised. If a wastewater system is changed, the effects on water supply systems and the wastewater treatment plant have to be examined. It can be shown that with a declining population, decentralised and resource-oriented systems in rural areas represent an alternative. To accompany transformation processes, the use of an adequate methodology to identify different system alternatives (e. g. mathematical optimisation) is purposeful.

Organische Dünger und organische Reststoffe leisten einen entscheidenden Beitrag für die Humusreproduktion von Böden und das Recycling von Pflanzennährstoffen. Im Hinblick auf deren Anfall und Nutzung sind in den vergangenen Jahren zwei gegenläufige Trends festzustellen. Einerseits hat das Volumen der in der Landwirtschaft anfallenden und der in die Landwirtschaft eingetragenen organischen Dünger regional stark zugenommen, andererseits hat sich gleichzeitig eine starke außerlandwirtschaftliche Nachfrage nach bisher für den Humusersatz genutzter Biomasse entwickelt. Ziel dieser Stellungnahme ist es, den nationalen und regionalen Bedarf von Stickstoff, Phosphat und Kalium sowie von organischem Kohlenstoff für den Humusersatz abzuschätzen und dem nationalen und regionalen Anfall dieser Stoffe mit organischen Düngern und organischen Reststoffen gegenüberzustellen. Dabei soll eine Bewertung der organischen Dünger und organischen Reststoffe im Hinblick auf Nährstoffgehalte und Nährstoffverfügbarkeit, Schadstoffgehalte, Nähr- und Schadstofffrachten sowie hygienische Risiken bei der landwirtschaftlichen Verwertung vorgenommen werden. Auf der Basis des geschätzten Bedarfs, des Anfalls und der Bewertung von Nutzen und Risiken sollen Nutzungsempfehlungen für Landwirtschaft, Verwaltung, Politik und Rechtsetzung abgeleitet werden. Use of organic fertilizers and organic wastes in agriculture Organic fertilizers and organic wastes contribute significantly to humus reproduction in soil and to plant nutrient recycling. As regards their generation and usage, two opposing trends have appeared over the past few years. On the one hand, there has been a marked regional increase in the volume of organic fertilizers produced and used in agriculture, on the other, the non-agricultural demand for biomass previously used as a humus substitute has risen significantly. This article intends to estimate the national and regional demand for nitrogen, phosphates and potassium as well as for organic carbon for humus substitution and to compare it to the national and regional volume of these substances that arises with organic fertilizers and organic wastes. This includes an assessment of organic fertilizers and organic wastes in terms of their nutrient content and nutrient availability, pollutant content, nutrient and pollutant load and any health risks associated with their use in agriculture. Based on the estimated demand, the available amount and the assessment of risks and benefits, recommendations for use are derived for the agricultural, administrative, political and legislative sectors. L’utilisation d’engrais et de déchets organiques dans l’agriculture Les engrais et les déchets organiques contribuent de manière significative à l’humification des sols et au recyclage des substances nutritives pour les plantes. Quant à leur production et leur utilisation, deux tendances opposées se sont manifestées au cours des dernières années. D’une part, le volume des engrais organiques produits et utilisés dans l’agriculture a fortement augmenté au niveau régional; d’autre part, la demande extra-agricole de biomasse, jusqu’alors utilisée pour remplacer l’humus, a fortement augmenté. L’objectif de la présente contribution est d’estimer les besoins nationaux et régionaux en azote, en phosphate, en potassium et en carbone organique pour remplacer l’humus et de comparer la production nationale et régionale de ces substances avec les engrais et déchets organiques. À cet effet, il convient d’évaluer la teneur en nutriments et leur disponibilité, la teneur en polluants, les charges de nutriments et de polluants, ainsi que les risques hygiéniques lors de la valorisation agricole. Sur la base de l’estimation des besoins et de la production ainsi que de l’évaluation des bénéfices et des risques, il convient de déduire des recommandations d’utilisation pour les secteurs agricole, administratif, politique et législatif., Berichte über Landwirtschaft - Zeitschrift für Agrarpolitik und Landwirtschaft, Band 94, Heft 1, Mai 2016