Für die Klärschlammbehandlung und -entsorgung von vier Kläranlagen (Ruhleben, Waßmannsdorf, Schönerlinde und Münchehofe) in Berlin wurden Energie- und Treibhausgasbilanzen jeweils mit und ohne Einbindung der Hydrothermalen Karbonisierung (HTC) erstellt. Als Methode diente die Ökobilanz mittels der Software Umberto 5.6. Hierzu wurden Stoffstrommodelle zur Quantifizierung der relevanten Stoff- und Energieströme bei der Schlammbehandlung, Prozesswasserbehandlung und Faulgasverwertung jeweils ohne und mit HTC (Reaktor, Entwässerung, Prozesswasserrückführung in Faulung bzw. Klärwerk) erstellt. Als Input-Daten dienten Messwerte der BWB, Laborversuche und Herstellerangaben. Aus den Ergebnissen wurden der kumulierte fossile Energieaufwand und das Treibhauspotential berechnet. Neben der Frage, inwieweit und durch welche wesentlichen Parameter die HTC die Bilanzen verbessert, wurde die Auswirkung der Ansäuerung bei der HTC, der Unterschied zwischen zwei HTC-Verfahren (TerraNova- und AVA-CO2) sowie die Ergebnisse einiger Pilotversuche hinsichtlich der Bilanzen ausgewertet. Bei den Klärwerken mit Faulung wurde eine deutliche Verbesserung der Energieund Treibhausgasbilanz durch die HTC bei Annahme einer guten Entwässerbarkeit (TR 65 %) festgestellt, in Ruhleben allerdings nur bei Ergänzung einer anaeroben HTC-Prozesswasserbehandlung mit Faulgasnutzung, dafür jedoch mit der größten Verbesserung. Hier kann der HTC-Wärmebedarf durch effiziente BHKWAbwärmenutzung zu 35 % gedeckt werden, bei den übrigen Klärwerken sind es >90 %. Die Verbesserung der Bilanzen kommt primär durch die zusätzliche Stromproduktion bzw. Braunkohlesubstitution bei der Verbrennung infolge des höheren Heizwertes, die Stromgewinnung durch das zusätzliche Faulgas (+16-19 %) und die reduzierten N2O-Emissionen bei der Monoverbrennung zustande. Die Coverbrennung zeigt stets deutlich bessere Energiebilanzen als die Monoverbrennung. Die Ansäuerung bei der HTC bewirkt eine geringere Methanausbeute aus dem Prozesswasser sowie eine geringe HTC-Kohle-Massenausbeute und damit eine Verschlechterung der Bilanzen. Bezüglich der Ursachen besteht noch Klärungsbedarf. Das AVA-CO2-Verfahren hat nur eine geringfügige Methanausbeute, verbunden mit einem höheren Erdgasbedarf, jedoch einen höheren Heizwert und Massenausbeute der HTC-Kohle. Dadurch ist es dem TerraNova-Verfahren hinsichtlich der Bilanzen nur bei der Coverbrennung überlegen, bei der Monoverbrennung ist es umgekehrt. In den Pilotversuchen fiel der Entwässerungsgrad geringer aus als angenommen (TS 44-51 %). Dadurch sinkt der nutzbare Heizwert und die Bilanzen verschlechtern sich entsprechend. Weitere Pilotversuche sind empfehlenswert. Refraktäre Verbindungen im Prozesswasser verursachen eine zusätzliche CSBBelastung des Ablaufs (+7-12 mg/l). In Waßmannsdorf würde der Überwachungswert überschritten, in den übrigen Klärwerken würde er im Mittel eingehalten.

Für die Gewinnung von Braunkohle ist die Absenkung des Grundwasserspiegels im Rheinischen Braunkohlerevier notwendig. Die große Ausdehnung der Tagebaue, sowohl in der Fläche als auch in der Tiefe, erfordert dabei eine über mehrere Jahrzehnte anhaltende Entwässerung der Lockergesteinsschichten. Hierfür werden Sümpfungsbrunnen verwendet, die bis in eine Tiefe von 750 m reichen. Im gesamten Rheinischen Braunkohlerevier werden von der RWE Power AG ca. 1.500 solcher Brunnen zur Entwässerung der Tagebaue eingesetzt.

The recovery of phosphorus (P) from sewage sludge, sludge liquor, or ash from monoincineration can be realized with different processes which have been developed, tested or already realized in full-scale in recent years. However, these pathways and processes differ in their amount of P that can be recovered in relation to the total P content in sludge, in the quality of the recovered P product, and in their efforts in energy, chemicals, fuels, and infrastructure required for P recovery. This study analyses selected processes for P recovery from sludge, liquor, or ash in their potential environmental impacts, following the method of Life Cycle Assessment (LCA, ISO 14040/44). Based on available process data from technology providers and end users, these processes are implemented in a hypothetical reference system for sludge digestion, dewatering and disposal in mono-incineration, including potential side-effects on mainstream wastewater treatment with the return load from sludge dewatering. Recovered products (e.g. P or N fertilizer, electricity, district heating) are accounted as credits for substituting equivalent industrial products. Depending on the maturity of the investigated process, collected process data of process efficiency, product quality, and energy and material demand originates from full-scale plants, pilot trials, or prospective modeling (status in 2014). This data is validated with the technology providers, transferred to the reference system and evaluated with a set of environmental indicators for energy demand, global warming, acidification, abiotic resource depletion, eutrophication, and human and ecotoxicity. Results show that pathways and processes for P recovery differ heavily in their amount of recovered P, but also in energy and related environmental impacts (e.g. greenhouse gas emissions). As direct struvite precipitation in sludge or liquor relies on the dissolved amount of P in digested sludge, these processes are only applicable in wastewater treatment plants with biological P removal. Here, they can recover 4-18% of total P in sludge with a relatively low effort in energy and chemicals, reducing return load to the mainstream process and eventually improving sludge dewaterability in case of direct precipitation in sludge. Acidic leaching of P from digested sludge can yield up to 48% of P for recovery, but requires a significant amount of chemicals for control of pH (leaching and precipitation) and for minimizing heavy metal transfer into the product. The quality of products from sludge and liquor is good with low content on heavy metals, leading to a low potential toxicity for humans and ecosystems. Leaching of monoincineration ash with sulphuric acid yields 70% P with moderate chemical demand, but the leached ash and co-precipitated materials have to be disposed, and the product contains some heavy metals. Complete digestion of ash in phosphoric acid and multi-stage cleaning with ion exchangers yields high recovery of 97% P in a high-quality product (H3PO4) and several coproducts, having an overall low environmental impact. Thermo-chemical treatment of ash can recover up to 98% P with moderate energy input in case of integration into an existing monoincineration facility, but the product still contains high amounts of selected heavy metals (Cu, Zn). Metallurgic treatment of dried sludge or ash can also recover up to 81% of P, but the process has still to be tested in continuous pilot trials to validate product quality, energy demand, and energy recovery options. Sensitivity analysis shows that other pathways of sludge disposal (e.g. co-incineration combined with upstream P extraction, direct application in agriculture) may also be reasonable from an environmental point of view depending on local boundary conditions and political targets. In general, the use of life-cycle based tools is strongly recommended to evaluate and select suitable strategies for regional or national concepts of P recovery from sewage sludge.

This paper provides an overview of promising technologies for phosphorus recovery from waste streams in the context of real nutrient recycling and discusses aspects regarding their wide-spread application but also limitations. Not only the technologies themselves, also the recovered materials and their valorization options are addressed. Results of the EU FP7 project P-REX titled “Sustainable sewage sludge management fostering phosphorus recovery and energy efficiency” will be discussed. Since innovation always needs an enabling environment for market penetration, barriers set by the existing legal framework and measures to resolve them will be concluded. To finally achieve a closed loop, the gap between phosphorus recovery and actual recycling has to be bridged. Finally, Goethe’s words are true more than ever: “Knowing is not enough, we must apply! Willing is not enough, we must do!”

This project report summarizes work conducted in work package 12 of the DEMEAU project. Along with Deliverable 12.1 it covers all tasks from work package 12 as formulated in the Description of Work (DoW). This report contains information about (pre-) feasibility studies, design recommendations and pre-treatment options for different types of MAR. The wide range of hydrogeological features encountered in reality makes a site-by-site approach indispensable. As part of this effort the hydrogeological pre-requisites for surface spreading and deep well injection techniques are described in detail. In chapter 2, ten essential hydrogeological parameters are defined by objective criterias. The following chapter outlines and describes how to obtain these essential hydrogeological parameters. This feasibility assessment starts with the screening of the potential site based on a structured procedure. Site investigations start with relatively cheap but numerous field and laboratory testing and continue to more cost-demanding but less numerous tests. With this procedure it is possible to carry out technical site feasibility in a costand time efficient way. The fourth chapter investigates the International Hydrogeological Map of Europe (IHME 1500) as a planning basis for pre-feasibility of new MAR sites. It was found that the IHME 1500 is useful for a pre-assessment, but detailed regional and local scale maps (and investigations) are additionally necessary to effectively assess hydrogeological features. The final chapter deals with pre-treatment options for MAR. Pre-treatment is necessary to remove critical contaminants from the source water to i) enhance system performance and removal efficiencies, ii) ensure the long-term functioning of the system, iii) meet regulatory demands and iv) ensure beneficial uses of the aquifer beyond the attenuation zone. Available pre-treatment methods in relation to source water type and intended end-use are described. Based on chemical concentrations in source water and intended end-use the most appropriate pre-treatment method can be assessed from a table. Altogether this report thus provides guidance in designing new MAR systems based on a sound hydrogeological site characterisation and pre-feasibility assessment based on available information and parameters obtained from structured investigations.

Within Work Area 5 of the DEMEAU project, selected innovative technologies and tools for emerging contaminants removal and monitoring are assessed in their environmental and economic benefits and impacts by using life-cycle based tools such as environmental Life Cycle Assessment (LCA) and economic Life Cycle Costing (LCC). Six case studies were assessed to quantify their environmental and economic profiles and formulate unique selling propositions to promote market uptake and implementation. These case studies include managed aquifer recharge for groundwater replenishment or for drinking water production in combination with advanced oxidation process, hybrid ceramic membrane filtration with powdered activated carbon for tertiary wastewater treatment, automatic neural net control systems to optimize membrane operation, ozonation of wastewater treatment plant effluent, and bioassays as screening tool for water quality monitoring. This report summarizes the study layout, input data, and results of LCA and LCC for all case studies and indicates unique selling propositions based on the outcomes of the assessment.