Risk-based management approaches are more and more used in the water sector and are promoted by the WHO. As a first step towards an overall risk-based management approach of the agricultural wastewater reuse concept of Braunschweig a quantitative microbial risk assessment (QMRA) is conducted. A 1000 trial Monte Carlo Simulation is used for the assessment of microbial risks for fieldworkers and nearby residents. As a tolerable value of risk an additional disease burden of 1 µDALY is set following the current WHO guidelines. Concerning microbial risks risk-based targets are set in terms of additional required pathogen reduction in the STP Steinhof. Based on the model results an additional reduction of 1.5log units is derived for viruses, for which the highest annual risks of infection per person per year (pppy) is calculated in all scenarios.

Das vorgestellte modellbasierte Werkzeug bildet Mischwasserüberläufe aus dem Berliner Mischkanalsystem und deren kurzfristige Auswirkungen im Gewässer ab. Es soll für die Massnahmenplanung und die Berechnung von Zukunftsszenarien verwendet werden. Das Werkzeug zeigt eine gute Übereinstimmung mit Messungen bezüglich des Verlaufes der Sauerstoffkonzentration im Gewässer und des Auftretens kritischer Bedingungen für die Fischfauna.

Das vorgestellte modellbasierte Werkzeug bildet Mischwasserüberläufe aus dem Berliner Mischkanalsystem und deren kurzfriste Auswirkungen im Gewässer ab. Es soll für die Maßnahmenplanung und die Berechnung von Zukunftsszenarien verwendet werden. Das Werkzeug zeigt eine gute Übereinstimmung mit Messungen bezüglich des Verlaufes der Sauerstoffkonzentration im Gewässer und des Auftretens kritischer Bedingungen für die Fischfauna. Eine Szenarienuntersuchung für ein Extremjahr zeigt, dass durch die bis zum Jahr 2020 geplante Stauraumvergrößerung die Häufigkeit fischkritischer Bedingungen im Gewässer bereits um ein Drittel reduziert werden kann. Eine Reduktion um ein zusätzliches Drittel wäre durch weitergehende Maßnahmen im Bereich der Entsiegelung möglich. Die verbleibenden fischkritischen Bedingungen sind das Ergebnis von sehr starken Regenereignissen und können kaum verhindert werden. Eine durch Klimaveränderung erhöhte oder reduzierte Regenintensität im Sommer hätte starken Einfluss auf das Auftreten fischkritischer Bedingungen; die erwartete Temperaturerhöhung würde hingegen hauptsächlich die Sauerstoffsituation bei Trockenwetter verschlechtern.

The present laboratory study tests the hypothesis that straw-bark mulch bioreactors are capable of concurrently retaining nitrate (NO3-) and the herbicides atrazine or bentazone at short hydraulic residence times (HRT). In a 1 year column experiment at HRT of ~4h three organic carbon sources, straw of common wheat (Triticum aestivum L.), bark mulch of pine tree (Pinus sp.) and a mixture of both materials, showed high reduction of continuously dosed NO3- (100mgL-1) with average denitrification rates of 23.4g-Nd-1m-3, 8.4g-Nd-1m-3 and 20.5g-Nd-1m-3, respectively. Under denitrifying conditions, fast and substantial retention of continuously dosed atrazine (20µgL-1) was observed with estimated dissipation times (DT50) between 0.12 and 0.49 days in the straw-bark mulch bioreactor. In parallel batch experiments, it could be confirmed that atrazine retention is based on adsorption to bark mulch and on degradation processes supplied by the organic materials as continual sources of carbon. In contrast, bentazone was not significantly reduced under the experimental conditions. While aging of materials was clearly observed in a reduction of denitrification by 60-70% during the experiment, systems still worked very well until the end of the experiment. The results indicate that the combined use of straw and bark mulch could increase the efficiency of mitigation systems, which are installed to improve the quality of drainage water before its release to surface waters. Further, the addition of these materials has the potential of parallel retention of NO3- and less mobile herbicides like atrazine, even during high flow events, as expected at the outlet of agricultural drainage systems. High removal is expected for mitigation system designed to remain saturated most of the time, whereas bioreactors that run periodically dry are not covered by this study. However, further experiments with the tested materials at technical or field scale under more realistic climate conditions need to be carried out.

Being one of the key nutrients, there is no doubt about the importance of phosphorus for all life on Earth. This element is even considered “life’s bottleneck”, as Isaac Asimov, one of the brilliant minds of the last century already stated in 1959 in his essay of the same title. Its importance as plant nutrient is emphasized by the huge amount of about one million metric tons of mineral phosphorus annually imported into Europe to sustain good harvests. Since phosphorus is a limited fossil element and given the strong dependency of Europe on phosphorus imports, its extensive recovery from “secondary deposits” is of paramount importance and follows the principles of the European Roadmap for Resource Efficiency. No matter, if there would be a phosphorus peak in the future or even physical scarcity, pure reason alone should force us to secure this vital resource not only for ourselves but also for future generations. Scarcity itself is not a problem of the future, but an actual thread to many people’s life whose cannot effort fertilizers to grow enough food for themselves. They know the essential or real demand of phosphorus humans need to survive, whereas in Europe we can afford luxury uptake. The availability of phosphorus is dramatically dependent on economical drivers. Looking at the current supply-chain efficiency of phosphorus, only about 20% of mined phosphate rock is finally consumed in form of food (Schröder et al. 2010). Most of the precious element is lost on its way from mine to fork. However, phosphorus does not disappear and can, unlike oil, be recycled once used. In developed countries with proper sanitation and wastewater treatment, the wastewater stream represents a relevant phosphorus reserve. In Germany, more than 50% of the annually imported mineral phosphorus destined to be used as fertilizer (about 120,000 metric tons) could be substituted by recovered phosphorus from the wastewater stream if it were recycled completely. Various technologies have been developed in recent years to tap into this secondary resource. They might also be applicable for other material flows like manure and digestate. The traditional application of sewage sludge in agriculture was the dominating recycling path in the past, but is increasingly refused due to concerns about pollutants being harmful for the environment and public health. Technological alternatives are about to contribute to close the phosphorus cycle again (Kabbe 2013). Although some of these techniques are already feasible, they still need to be implemented onto the market. Three waste material flows, sewage sludge, manure and digestate are all alternatives to industrial fertilizers and compete for the same limited land area. Thus, only solutions that safeguard human health and the environment are viable resulting in a driver for wide-spread application of innovative alternatives when direct valorization on arable land falls short. For successful market implementation, new technologies and their resulting products need to be proven capable and feasible. Within the European project P-REX, novel and available technical solutions for phosphorus recovery and recycling will be demonstrated in full-scale. Their performance and feasibility will be systematically assessed and validated, as well as the quality of obtained recycling products with focus on plant-availability and eco-toxicity. Environmental impacts (LCA) and costs (LCC) will be calculated based on these data. Together with the analysis of the legal framework and existing market barriers and market potentials for novel recycling technologies and their products, strategies and recommendations will be developed for efficient and wide-spread implementation of phosphorus recovery with regards to specific regional conditions. A first overview of legal, societal and market aspects has been elaborated within the first project year and was discussed in the stakeholder workshop “Recycled Phosphorus Fertilizer- Market Chances and Requirements” in Podebrady (CZ) in September 2013. The finalized report (A. Nättorp et al, 2013) is available for download at the project’s website: www.p-rex.eu. Stakeholder workshops in different European regions will be organized in 2014 to ensure the involvement of all relevant stakeholder perspectives and regional conditions and needs. Especially the end-user perspectives (plant operators, fertilizer industry, crop farmers) need to be considered more in the overall discussion in the future. P-REX is aiming to increase the European phosphorus recycling rate from municipal wastewater by closing gaps between science, policy and practice, as it was a key message of the First European Sustainable Phosphorus Conference in March 2013: waste less, recycle more and cooperate smart (www.phosphorusplatform.eu). Besides wastewater and sewage sludge, manure and digestate bear substantial quantities of phosphorus for recovery and possible synergies just wait to be applied.