Nutrients, phosphorus and nitrogen, from municipal and industrial water streams contribute to the pollution or reduce the ecological potential of receiving water bodies. Recovering or reducing the nutrient content of waste streams, thus reducing the amounts of phosphorous and nitrogen that ends up in the water bodies, will contribute to a better environment. The first part of this report describes two tests performed to treat the concentrate of the reverse osmosis process at the Torreele facility. The first test used a natural system based on willows; the second test was based on post-denitrification MBBR. The willows proved able to remove nutrients for more than 30%, resulting in a substantial cost benefit for discharge which could make it economical feasible when installed at full-scale to treat the total volume of RO concentrate. Contrary to the willows, that even remove part of the nitrogen in winter, the post-denitrification MBBR was only efficient when N-NO3- exceeded 30 mg/L. The variable N-NO3- N-NO3- concentration and salinity of RO concentrate seemed to be limiting factors for a good performance. The second part of this report summarizes the activities regarding the optimization of water and nutrient (nitrogen and phosphorus) management at the reuse site Braunschweig, Germany. A detailed analysis of supply and demand of both, water and nutrients, for the reuse site was conducted. The optimization potential is especially high for nitrogen management, since the simultaneous supply via the Braunschweig wastewater treatment plant and additional conventional nitrogen fertilizer application by farmers result in an oversupply of nitrogen, losses to environment and a low efficient reuse compared to the total potential of renewable nitrogen in wastewater or sludge. Following this analysis, two possible solutions are discussed (fertigation and technical nutrient recovery), which are practically relevant for the Braunschweig reuse scheme in mid- and long-term timescale. Results indicate a high potential to increase the efficiency of nitrogen recycling. Simultaneously irrigation adopted on water demand of plants can be achieved.

This report describes different options for tertiary treatment of secondary effluent from municipal wastewater treatment plants for the purpose of water reuse. For each of the treatment trains, associated environmental impact (represented by energy demand and related global warming potential) and risk reduction potential (i.e. removal of chemical and microbial contaminants) are described based on the results of the DEMOWARE case studies. This should inform water professionals about impacts and benefits of different options for producing reclaimed water, enabling an informed decision on an adequate treatment train depending on the water quality targets for the respective reuse purpose.

Whether or not there will be a phosphorus (P) peak within decades, centuries or millennia, (Cordell and White, 2011; Scholz and Wellmer, 2013) one thing is for sure – phosphorus is a limited and, in its function as a nutrient, an essential and irreplaceable resource (Asimov, 1959; Smil, 2000; Filippelli, 2008). The debate on P limitation is often mentioned as motivation to foster activities regarding P recovery and recycling. The ambition of the European Commission (EC) to establish a circular economy in Europe goes far beyond that and is not primarily motivated by limitations of certain raw materials. From the European perspective and in the light of having just one small mine in Finland, the geopolitics and economic vulnerability are issues to be taken seriously. Europe is highly dependent on phosphorus imports (De Ridder et al., 2012) as reflected by the quantities given in figure 1. In contrast to the above mentioned issues, the waste and dissipation of phosphorus that exists in developed countries may lead to a different conclusion. The global resource efficiency for P along the supply chain from mine to fork is only 20% (Schröder et al., 2010). Given the figures of 225 million tons P rock globally mined in 2013 (USGS, 2015) and assuming that 90% of the mined P is used for food production, only 45 million tons of the mined quantity finally ends up in form of food on our tables. So, what can we do to increase the resource efficiency of P? Recently, the implementation of a coherent package of nutrient management strategies and measures to close the European P cycle has been proposed – the 5R strategy (Withers et al., 2015). The five R’s are Realign P inputs, Reduce P losses to waters, Recycle P in bio-resources, Recover P from waste and finally Redefine our food system. So, recovery and recycling can play an important role in improving resource efficiency and sustainable nutrient management. Although, there are various relevant waste streams carrying huge quantities of phosphorus dissolved in liquids or fixed in solids like in manure or organic waste, the focus of P-REX was laid upon P recovery and recycling from wastewater and sewage sludge.

In recent years several ways of recovering phosphorous from municipal wastewater have been developed. Depending on the applied technology the recovered products vary significantly concerning the concentrations of heavy metals and organic residues. Within the boundaries of data quality and present uncertainties a comparative risk assessment of seven secondary phosphorus fertilizers, sewage sludge, raw ash and triple super phosphate has been conducted for PCDD/Fs, PCBs, PAHs, As, Cd, Cr, Cu, Hg, Ni, Pb and Zn. Local exposure assessment was done using the kinetic model of the European Union’s Technical Guidance Document for all substances accounting for both fertilization and average atmospheric deposition. For substances of concern (Cd and Zn) the exposure was additionally refined using a solute transport model (HYDRUS-1D) and a precipitation model (Visual MINTEQ-software). An annual fertilizer amount equivalent to 60 kg P2O5/ ha × year by these products is assumed. In order to account for potential accumulation a time span of 100 years is modelled. Results indicate that out of the selected 11 (groups of) chemicals only cadmium and zinc are of concern. Regarding soil organisms, zinc is of concern for sludge, raw ash and one of the seven secondary phosphate fertilizers in case of soil-pH above pH 6.0. Regarding groundwater, cadmium and zinc are of concern below pH 6.0 since mobilization at this pH level increase significantly. No risk is expected regarding the endpoint humans. Among the investigated products struvites have shown the lowest phosphorus-specific heavy metal contents. For ash related products more data from full scale operations are needed to reduce still existing uncertainties like the influence of raw wastewater quality and WWTP operation on the final product.

Dieser Beitrag vermittelt einen Überblick über die im Rahmen des EU Projektes P-REX erzielten Ergebnisse und Schlussfolgerungen. Neben der Bewertung von praxisrelevanten Verfahren zur Phosphorrückgewinnung aus dem Abwasserpfad und den jeweiligen Recyclaten geht es vor allem auch um Aspekte zur flächendeckenden Implementierung und Marktentwicklung. Vor allem integrative Ansätze, die auf eine bessere Ausnutzung der bereits vorhandenen Infrastruktur zur Optimierung des Phosphorrecyclings abzielen, bieten vielversprechende und vor allem kurzfristig umsetzbare Lösungen. Um jedoch Anreize für deren Umsetzung zu schaffen, bedarf es Entscheidungen und verlässlicher politischer Weichenstellungen. Für den Fall des Phosphorrecycling haben Goethes Worte „Wissen ist nicht genug, wir müssen auch anwenden! Wollen ist nicht genug, wir müssen auch tun!“ höchste Aktualität.

To sustain good harvests, each year more than one million tonnes of mineral phosphorus have to be imported to the European Union (van Dijk et al., unpublished data), while the potential to recover and recycle this essential resource remains untapped or is just inefficiently used as in the case of sewage sludge, manure and food waste. In recent years various technical solutions have been developed to recover phosphorus providing mineral compounds suitable as raw material for fertiliser production or even as ready-to-use fertiliser. Regarding the implementation of these technologies, operational benefits for plant operators like the water utilities in the case of P recovery from wastewater and/or sewage sludge are the strongest argument for their market penetration. Without the provision of direct operational benefits, implementation needs to be motivated or even enforced by suitable and reliable policies. In order to realise a circular economy, it is important not just to focus on the recovery itself. The recovered materials need to match the requirements and needs of their intended users. Therefore, full value-chain solutions have to be promoted instead of isolated technology-focused approaches. Following our principles of sustainability and resource efficiency, the assessment of innovations must also include their environmental impact. This review provides an overview of recently developed and promising technologies for phosphorus recovery from wastewater and discusses aspects regarding their wide-spread application, along with their limitations. It will focus on recovery and recycling from sewage sludge. Not only the technologies themselves, also the recovered materials and their valorisation options are addressed. Results of the EU FP7 funded project P-REX entitled 'Sustainable sewage sludge management fostering phosphorus recovery and energy efficiency' and other recent initiatives will be included. Since innovation always needs an enabling environment for market penetration, barriers set by the existing legal framework and measures to resolve them will be reviewed. Finally, Goethe's words are true more than ever: 'Knowing is not enough, we must apply! Willing is not enough, we must do!'

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!”

In recent years several ways of recovering phosphorous from municipal wastewater have been developed. Depending on the applied technology the recovered products as well as the quality of sewage sludge vary significantly concerning the concentrations of heavy metals and organic residues. Within WA 4 “environmental, economic and risk assessment of P recovery options” of the P-REX project a quantitative risk assessment of substances in phosphorus products for humans and environment is intended. In this deliverable risk assessment is done as a relative risk ranking for PCDD/F, dl-PCB, PAH, As, Cd, Cr, Cu, Hg, Ni, Pb and Zn between seven secondary phosphate fertilizers from wastewater stream, sewage sludge, mono-incinerated ash from sewage treatment and conventional phosphorus fertilizers.