Gülle und Gärreste werden häufig als Wirtschaftsdünger in der Landwirtschaft eingesetzt. Sie liefern sowohl organisches Material für den Boden als auch Stickstoff, der ein wichtiger Nährstoff für Pflanzen ist. Oft stimmt jedoch die gesetzlich vorgeschriebene, saisonale Ausbringung der Gülle nicht mit dem Zeitpunkt des tatsächlichen Stickstoffbedarfs der Pflanzen überein. Dies führt zu einem unerwünschten Verlust des Stickstoffs für die Pflanzen durch Emissionen ins Grundwasser (Nitrat) oder in die Atmosphäre (Ammoniak und/oder Lachgas). Besonders in Regionen mit einem hohen Gülleaufkommen und einer hohen Ausbringungsrate der Gülle kann es zu starken Umweltbelastungen kommen. Um die Zufuhr des organischen Materials für den Boden von der Stickstoffzufuhr aus der Gülle für die Pflanzen zu entkoppeln, wurde in dem EU geförderten Projekt Circular Agronomics (www.circularagronomics.eu) eine Pilotanlage entwickelt und konstruiert. Die Pilotanlage soll eine „stickstoffabgereicherte Gülle“ produzieren, die als Bodenverbesserer eingesetzt werden kann. Cirular Agronomics zielt darauf ab, zwischen 80 % und 90 % des Stickstoffs, der ursprünglich als Ammonium vorlag, aus der Gülle bzw. dem Gärrest zurückzugewinnen. In einem anschließenden Gaswäscher reagiert das Ammoniakgas mit Schwefelsäure zu einer Ammoniumsulfatlösung, welche ein typischer mineralischer Stickstoffdünger ist. Dieser kann dann ausgebracht werden, wenn die Pflanze den Stickstoff benötigt und umsetzen kann. Um den Prozess der Vakuumentgasung besser zu verstehen und die optimalen Prozessbedingungen zu untersuchen, wurden im Vorfeld Laborexperimente durchgeführt. In den Versuchen wurden der pH-Wert, die Druckbedingungen und die Prozesstemperatur variiert. Die Experimente zeigten, dass bei einem pH-Wert von 9.0, einer Temperatur von 60 °C und einem absoluten Druck von 190 mbar bis zu 88 % des Ammoniums aus dem Gärrest in Form von Ammoniak abgereichert wurden. Eine CO2-Strippung vor Anhebung des pH-Wertes auf pH 9.0, verringerte zudem die notwendige Natronlaugenzufuhr zur pH-Wert-Anhebung um 30 %. Basierend auf den Ergebnissen der Experimente wurden Schlussfolgerungen für ein optimales Design der Pilotanlage abgeleitet. Derzeit wird die Pilotanlage in Betrieb genommen und erste Versuche durchgeführt, deren Ergebnisse ebenfalls im Vortrag präsentiert werden.

Circular Agronomics (CA) provides a comprehensive synthesis of practical solutions to improve the current carbon, nitrogen and phosphorus cycling in European agro-ecosystems and related up and downstream processes within the value-chain of food production. CA is a frontrunner project exploiting affordable solutions to meet, among others, the requirements of agriculture, water and waste legislations as well as the EU policy targets regarding emission reduction (mainly NH3, NOx and GHG: CO2, CH4, N2O). The policy analysis contributes to market innovations, to sustainability and European initiatives and finally also to the development of effective joined up policy - further steps towards integrating agriculture in circular economy.

The types and objectives to apply managed aquifer recharge (MAR) are manifold and so are the risks that can arise during the planning, implementation and operation of a MAR facility. In general, operational, regulatory, business, human health, and environmental risks can occur and should be identified already during the planning and implementation stage to apply preventive measures and secure the safe and realibale operation of a MAR facility. This report represents risk assessment based on recommendations of international guidelines (AlcaldeSanz and Gawlik, 2017; NRMMC-EPHC-NHMRC, 2008; WHO, 2009, 2011) at six MAR sites which are at different stages of development. Three case studies are at the feasibility or pilot stage: two ASR systems in João Pessoa and Recife, Brazil and one induced bank filtration site at the Beberibe River in Brazil, and three case studies at the operational stage: one SAT system in the Ezousa catchment in Cyprus, and two infiltration basin systems in Hyères, France (Aquarenova site) and Berlin-Spandau, Germany. The entrylevel assessment according to the Australian guidelines (NRMMC-EPHC-NHMRC, 2009) has been conducted for the feasibility or pilot scale schemes For fully operational MAR schemes, in addition to the entry-level assessment, the degree of difficulty assessment and the maximal risk assessment were carried out. At all stages of site development, risk assessment helps to identify and characterize potential hazards that may cause risks to human health and the environment. This report may be used to assist in clarifying which actions or further investigations are required to identify and reduce the uncertainty of risks and to implement remediation measures if necessary. In addition, this report intends to show how sitespecific hazards have been assessed to varying degrees depending upon the level of risk assessed at each project development stage.

Durch die Klärschlammverordnung (AbfKlärV) wird die Phosphor(P)-Rückgewinnung aus Klärschlämmen bzw. Klärschlammaschen für Klärwerke mit einer genehmigten Ausbaugröße ab 100.000 Einwohnerwerten (EW) ab dem Kalenderjahr 2029 gesetzlich vorgeschrieben. Dies betrifft alle sechs Klärwerke, welche von den Berliner Wasserbetrieben (BWB) betrieben werden. Die vorliegende Studie diskutiert verschiedene Möglichkeiten der Phosphorrückgewinnung mit Blick auf die Vorgaben der AbfKlärV, die Wirtschaftlichkeit der verschiedenen Ansätze und dient den BWB als Konzeptpapier für eine weitergehende Planung Ihrer Strategie zur P-Rückgewinnung.

The sewage sludge ordinance forces wastewater treatment plants to ensure the recovery of phosphate from the produced sewage sludge. In most cases, this obligation is transferred to the company in charge of the sludge disposal. For the recovery process, technology-specific but not product-specific specifications are made. The present article gives an overview of the products of different processes and their possible marketing in two routes: direct marketing and integration into the fertilizer industry. Possibilities, limits, requirements and potential product revenues for selected products are discussed against the background of current world market prices. Finally, the chemical expenditure of certain processes and logistical considerations are addressed. The considerations suggest that wet chemical ash processes should best be integrated in chemical parks.

In this master thesis the redissolution and recovery of phosphorus (P) and other valuable materials from Ruhleben sewage sludge ash (R-SSA) with HCl and H2SO4 was investigated using experimental laboratory tests. The parameters acid amount, solid liquid ratio (s/l ratio) and reaction time were varied and their influence on the redissolution of Ca, P, Al, Fe and SO4 was measured. Results showed that HCl(37%) resolved 91 ± 4 % P with an acid amount of 4 mL on 5 g R-SSA, a s/l ratio of 1:20 (acid concentration 0.46 mol/L) and a reaction time of 60 min. H2SO4(30%) on the other hand resolved 89 ± 3 % P at 6 mL on 5 g R-SSA, a s/l ratio of 1:10 (acid concentration 0.6 mol/L) and a reaction time of 60 min. Ca and SO4 showed very good redissolution of up to 100 % with HCl. The Ca redissolution with H2SO4 is clearly below that of HCl and is 63%. Al resolved to a lesser extent and reaches 65% with H2SO4 and 53% with HCl. Fe shows the lowest redissolution of 14% with HCl and 12% with H2SO4. The H2SO4 leaching experiments also showed that it is possible to separate the gypsum from the R-SSA if the leaching liquid is separated from the R-SSA after short contact times with H2SO4. The contact time, the acid amount and the s/l ratio have a big impact on the precipitation. It was possible to recover 75% of the total amount of gypsum that can be precipitated from R-SSA. In addition to this, the gypsum-free leaching liquid was then added to the R-SSA again which had already been leached, in order to dissolve P. There was no loss of P redissolution when the gypsum was extracted. This approach could not be observed in any other study. Based on the results, a recovery of 2,114 ± 130 t P/a with HCl and 2062 ± 130 t P/a with H2SO4 are possible if an amount of 30,000 t R-SSA/a is treated, which are forecasted for Berlin in the future. Since the redissolution of 91 ± 4% P requires an acid amount of 946 kg HCl(37%)/t R-SSA, this would result in an absolute annual acid requirement of 28,380 t HCl(37%) for 30,000 t R-SSA/a. H2SO4 experiments showed that 725 kg H2SO4(90%)/t R-SSA would be required for 89 ± 3% P redissolution, resulting in an absolute acid requirement of 21,750 t H2SO4(90%). Since H2SO4 has a lower consumption due to the higher concentration, is the cheaper acid of the two and has the possibility of recovering gypsum, H2SO4 would be preferred for leaching R-SSA from an economic point of view. In addition, about 75% of the gypsum can be precipitated with H2SO4, which corresponds to a quantity of 255 kg of gypsum(dry)/t R-SSA. At 30,000 t R-SSA/a, this results in an annual amount of 6630 ± 51 t gypsum that can be recovered.

Vacuum degasification (VD) of ammonia from waste streams and subsequent production of nitrogen fertilizer can be one element of the effort towards closing the nitrogen (N) cycle and thus avoiding emissions harmful to the environment. This master’s thesis comprises a literature research for suitable substrates and laboratory experiments for the optimization of a design and experimental design of a VD pilot plant for ammonia recovery. Eight streams among the top 20 food waste streams in Europe and their associated streams, all digestates from digestion or co-digestion of animal waste streams, agricultural digestates and manures were identified as suitable substrates for N-recovery with VD. During 120 min of VD at pH 9.0, 190 mbar and 60 °C a total ammonia-N (TAN) removal rate of 0.81 ± 0.03 was achieved with an NaOH load of about 80 ml (L substrate)-1 in biogas digestate. The TAN removal rate during VD at 190 mbar and 60°C was dependent on pH with a dose response function. For efficient ammonia removal pH = 9.0 was necessary. Evidence for an ammonia volatilization inhibition at pH = 8.5 not explicable by the ammonia dissociation was found. At 158 % of the boiling pressure, 69 % of the TAN removal rate at boiling pressure was reached. Air stripping the hot substrate for 60 min lowered the NaOH load for maintaining pH 9.0 during VD by 30 %. Electrical conductivity (EC) and pH during the degasification treatment did not correlate. Alkaline hydrolysis could be the reason for pH decrease during VD at pH 9.5. In the pilot plant a pH sensor and a possibility to adjust the pH continuously should be installed. The pH for VD experiments at 60°C should be in the range 8.75–9.5. Pressures below the boiling pressure should not be excluded. Experiments with CO2 stripping should be conducted to exhaust the potential for NaOH saving.

Weltweit stehen Kommunen vor der Aufgabe, Wassersysteme mittelfristig an neue Gegebenheiten anzupassen und sie resilienter gegen unvorhersehbare Ereignisse zu machen. Digitale Lösungen für das Abwasser- und Wassermanagement werden dafür immer bedeutsamer.