Restoring nutrient circularity across scales is important for ecosystem integrity as well as nutrient and food security. As such, research and development of technologies to recover plant nutrients from various organic residues has intensified. Yet, this emerging field is diverse and difficult to navigate, especially for newcomers. As an increasing number of actors search for circular solutions to nutrient management, there is a need to simplify access to the latest knowledge. Since the majority of nutrients entering urban areas end up in human excreta, we have chosen to focus on human excreta and domestic wastewater. Through systematic mapping with stakeholder engagement, we compiled and consolidated available evidence from research and practice. In this paper, we present ‘Egestabase’ – a carefully curated open-access online evidence platform that presents this evidence base in a systematic and accessible manner. We hope that this online evidence platform helps a variety of actors to navigate evidence on circular nutrient solutions for human excreta and domestic wastewater with ease and keep track of new findings. 

Vid infrastrukturprojekt som innefattar sprängningsarbeten uppstår ett processvatten som kan ha för höga halter av kväve och andra föroreningar för att släppas ut till recipient. Avskiljning av olja, partiklar, metaller samt pH-justering utförs ofta ”on-site”. I dagsläget saknas dock en standardiserad metod för kväveavskiljning. Där det är möjligt kan kväveavskiljning ske genom, exempelvis våtmarker, men vid arbete i urbana miljöer kan de möjligheterna saknas. I sådana fall avleds ofta processvattnet till kommunalt reningsverk för behandling innan utsläpp. Avskiljning av kväve från olika typer av spillvatten utförs ofta med biologisk behandling, exempelvis på kommunala reningsverk. På grund av processvattnets innehåll samt variation över tid av både innehåll och flöde är en biologisk process olämplig. Detta framkom i tidigare projekt där biologisk behandling av processvattnet studerades i laboratoriemiljö. I detta projekt har ett principförslag för en demonstrationsanläggning med kväveavskiljning på aktiv entreprenad tagits fram, i syfte att bidra till mer långtgående behandling av processvattnet på plats. Arbetet har inkluderat studiebesök och provtagning av processvatten för att komplettera befintligt analysunderlag och öka förståelsen för hur processvattnet uppstår, varierar och hanteras. Med projektets referensgrupp bestående av experter hos Trafikverket och representanter från entreprenör, kommunalt va-bolag och tillsynsmyndighet har det diskuterats krav på anläggningen, krav på utgående vatten samt praktiska förutsättningar för demonstrations- och fullskaleanläggning. För kravställningen har även juridiska underlag samt kommunala riktvärden granskats för att ställa ett generellt krav på utgående vatten gällande kväveinnehåll. Vid framtagande av principförslaget har leverantörer av tekniska lösningar och komponenter inkluderats. Genomförd provtagning finns rapporterad i PM som utgjort delleverans till projektet. Principförslaget presenteras i CAD-ritning och flödesschema baserat på P&ID. Föreslagen demonstrationsanläggning utgörs av en container som placeras efter befintlig anläggning med kemisk fällning och partikelavskiljning. Demonstrationsanläggningen använder ett delflöde som efter behandling släpps till befintligt utlopp. Vald behandlingsteknik är omvänd osmos följt av elektrokemisk behandling, där den senare visade god avskiljning i tidigare laboratorieförsök. Denna konfiguration innebär att två processer kan utvärderas, var för sig eller i kombination. Vidare kan vattnet recirkuleras genom en eller båda processerna för att uppnå högre avskiljning. Till principförslaget hör även förslag till drift och provtagning för dess utvärdering samt komponentlista och kostnadsuppskattning. En utmaning som lyftes är de påfrestningar på teknisk utrustning som miljön på en aktiv entreprenad leder till. Potentiellt kan mycket höga flöden uppstå, men även förhöjda partikelhalter. För att skydda de känsligare delarna i anläggningen, som membran, behövs åtgärder för att övervaka och hantera oväntat höga partikelhalter. I principförslaget ingår därför en förfiltrering. Kväveavskiljningen innebär att en koncentrerad volym kväverikt vatten produceras som restflöde. Det finns olika sätt för kvittblivning eller tillvaratagande av detta vatten, vilka inte har studerats i detalj i detta projekt. Volymminskningen underlättar dock transport och kväveinnehållet innebär att det kan finnas aktörer intresserade av att återvinna kvävet.

Principal design of demonstration plant for treating nitrogen rich construction water Constructing roads and railways may involve rock blasting. Process water from such activities may contain too high levels of nitrogen and pollutants to be directly discharged to receiving waters. Such process water is being treated on site to remove oil, particles, metals, and pH adjustments. There is no currently standardized method for treating the nitrogen. Where possible, area intensive methods such as wetlands can be used. In urban areas such methods are unfeasible, instead the process water is usually led to a municipal wastewater treatment plant. The process water varies significantly from other types of wastewaters, such as municipal. Common treatment methods for wastewater may not be suitable for this rock blasting process water. Furthermore, the characteristics of the process water can vary greatly over time. In this project, a principal design is presented for a demonstration plant for nitrogen treatment at an active construction site. The purpose is to contribute to a more advanced treatment of process water on site. This has included study visits and sampling of the process water to increase the understanding of its origin, variations, and current management. Together with the project’s reference group, discussion have been held regarding requirements on the treatment unit, demands for its treatment efficiency and practical aspects during both demonstrational and full-scale use. For the requirements, regulatory documents and guideline values have been studied to present a general treatment efficiency goal. For the principal design, technology suppliers have been involved. The results of water sampling and analyses are presented in a separate PM. The principal design is comprised of a CAD-drawing and process scheme based on P&ID. The suggested demonstration plant is comprised of a container which will be placed after the current water treatment. It treats a partial flow and uses the current outlet. The technological processes selected are reverse osmosis followed by electrochemical treatment. This process design enables evaluation of the technologies separately and combined, as well as option to reach higher and lower discharges values by recirculation within the treatment facility. Suggestions for running the treatment and sampling to evaluate its effectiveness is included, as well as list of components and cost estimates. A challenge that has been frequently discussed throughout the project is the strain the environment of an active construction site puts on technical components. Problematically high flows of water can arise, followed by a substantial increase in particulate matter in the process water. To protect the sensitive equipment in the nitrogen treatment, such as membranes, a pre-filtration. The nitrogen treatment renders a concentrate, which has a smaller volume and higher nitrogen concentrations. This residual flow needs to be managed, with several potential options for deposition. The smaller volume means easier transportation to an offsite facility for further treatment, and the nitrogen concentrations could make it suitable for nitrogen recovery.

Ecotechnologies have the potential to reduce the use of finite resources while providing a variety of co-benefits to society, though they often lack in market competitiveness. In this study, we investigate the sustainability of ecotechnologies for recovering carbon and nutrients, and demonstrate how a so-called “bottom-up” approach can serve as a decision-making instrument. Based on three case study catchments with a focus on domestic wastewater in Sweden and Poland, and on manure, grass and blackwater substrates in Finland, we apply a cost–benefit analysis (CBA) on system alternatives derived from a participatory process. After drawing on an initial systematic mapping of relevant ecotechnologies, the scope of the CBA is determined by stakeholder suggestions, namely in terms of the considered assessment criteria, the physical impacts and the utilised data. Thus, this CBA is rooted in a localised consideration of ecotechnologies rather than a centralised governmental approach to systems boundaries. The key advantage of applying such a bottom-up approach is that it has gone through a robust participatory selection process by local stakeholders, which provides more legitimacy to the decisions reached compared with traditional feasibility studies. Despite considering the revenues of the recovered products as well as the provision of the non-market goods CO2 mitigation and reduced eutrophication, findings from this study indicate that the benefits of the considered ecotechnologies are often outweighed by their costs. Only anaerobic digestion of agricultural wastes appears to be economically feasible under the current conditions, highlighting that further efforts and incentives may be required to mainstream ecotechnologies. © 2021, The Author(s), 

Rapporten beskriver etablerade och nya tekniker för kväveåtervinning ur avloppsvatten, och jämföråtervinningsmetoderna med andra sätt att tillverka kvävegödsel när det gäller klimatpåverkan ochkostnader. Rapporten innehåller också en kort genomgång av möjligheter för återvinning av kalium ochsvavel och en statusuppdatering av metoder för återvinning av fosfor.

Background: Research and development on the recovery and reuse of nutrients found in human excreta and domestic wastewater has intensified over the past years, continuously producing new knowledge and technologies. However, research impact and knowledge transfer are limited. In particular, uptake and upscaling of new and innovative solutions in practice remain a key challenge. Achieving a more circular use of nutrients thus goes beyond technological innovation and will benefit from a synthesis of existing research being readily available to various stakeholders in the field. The aim of the systematic map and online evidence platform described in this protocol is threefold. First, to collate and summarise scientific research on technologies that facilitate the recovery and reuse of plant nutrients and organic matter found in human excreta and domestic and municipal wastewater. Second, to present this evidence in a way that can be easily navigated by stakeholders. Third, to report on new relevant research evidence to stakeholders as it becomes available. Methods: Firstly, we will produce a baseline systematic map, which will consist of an extension of two previous related syntheses. In a next stage, with help of machine learning and other automation technologies, the baseline systematic map will be transformed into ‘living mode’ that allows for a continually updated evidence platform. The baseline systematic map searches will be performed in 4 bibliographic sources and Google Scholar. All searches will be performed in English. Coding and meta-data extraction will include bibliographic information, locations as well as the recovery and reuse pathways. The living mode will mostly rely on automation technologies in EPPI-Reviewer and the Microsoft Academic database. The new records will be automatically identified and ranked in terms of eligibility. Records above a certain ‘cut-off’ threshold will be manually screened for eligibility. The threshold will be devised based on the empirically informed machine learning model. The evidence from the baseline systematic map and living mode will be embedded in an online evidence platform that in an interactive manner allows stakeholders to visualise and explore the systematic map findings, including knowledge gaps and clusters. © 2021, The Author(s).

There exist numerous ecotechnologies for recovery and reuse of carbon and nutrients from various waste streams before they are lost to runoff. However, it remains largely unknown how growing implementation of such ecotechnologies affect nutrient emissions to surface waters at catchment scale. Here, this knowledge gap is addressed by application of SWAT model in three case study catchments draining to the Baltic Sea: Vantaanjoki (Finland), Fyrisån (Sweden) and Słupia (Poland). Sustainability analysis with Multi-Criteria Analysis was applied in the stakeholder workshops in the case study areas to assess different ecotechnology alternatives. The following ecotechnologies received the highest sustainability scores: in Vantaanjoki anaerobic digestion, based on mostly agricultural residues; in Fyrisån source-separation of wastewaters; in Słupia nutrient extraction within the wastewater treatment process. The effect of application of digestate on agricultural soils in the Vantaanjoki catchment was simulated by adjusting the model parameters describing the organic carbon content and physical properties of soil. The results showed small reductions of nutrient loads to the Gulf of Finland. Larger reductions of nutrient loads to Lake Mälaren in Sweden and the Baltic Sea in Poland were achieved as a result of the wastewater treatment upgrades. In the Fyrisån catchment, higher relative reductions were simulated for TN than TP, and in dry years than in wet years. Although the studied ecotechnologies did not show as high effectiveness in nutrient load reduction as combinations of traditional Best Management Practices reported in literature, they do have other multiple benefits including crop yield increase, electricity, heat and bio-based fertilizer production.

This paper summarizes key findings from a series of systematic reviews and comprehensive efforts to collate evidence and expert opinions on circular solutions for recovery and reuse of nutrients and carbon from different waste streams in the agriculture and wastewater sectors. We identify established and emerging approaches for transformation towards a more circular nutrient economy with relevance to SDGs 6 and 14. The paper cites the example of the Baltic Sea Region which has experienced decades of fertilizer overuse (1950s–1990s) and concomitant urban sources of excessive nutrients. Regulations and incentive policies combining the nitrogen, phosphorus and carbon cycles are necessary if circular nutrient technologies and practices are to be scaled up. Pricing chemical fertilizer at levels to reflect society's call for circularity is a central challenge.

Background: Eutrophication of the Baltic Sea, and many other water bodies, is partly the result of point-source emissions of nutrients and carbon from wastewater. At the same time, nitrogen and phosphorus planetary boundaries have been breached. There is a need for more efficient resource management, including the recovery and reuse of nutrients and carbon in waste. The aim of this paper is to collate evidence on ecotechnologies intended for use in the wastewater sector globally to facilitate the recovery or reuse of carbon and/or nutrients. Methods: Searches were performed on literature published between 2013 and 2017 and in 5 bibliographic databases, 1 search engine, and 38 specialist websites. Database searches were performed in English. Searches in specialist websites were also performed in Finnish, Polish and Swedish. There was no geographical limitation. Screening was conducted at title and abstract level, and on full texts. Apart from bibliographical information, we extracted information on ecotechnology type, intervention, details of the recovery or reuse, the type of wastewater stream to which the ecotechnology is applied, the study location, type and design. Prior to screening and coding, we conducted consistency checks amongst reviewers. We generated a searchable database of coded studies. Findings were synthesised narratively and visualised in a geographical information system (i.e. an evidence atlas). We identified a series of knowledge gaps and clusters that warrant further research. Results: The search resulted in 4024 records, out of which 413 articles were retained after the screening process. In addition, 35 pre-screened studies from the specialist website searches were added. Together, these 448 articles contained 474 individual studies of 28 types of ecotechnologies. A combination of ecotechnologies (16.7%), followed by microalgae cultivation (14.1%) were the most frequent ecotechnologies in the evidence base. Ecotechnologies for recovery composed 72.6% of the evidence base. The most common wastewater streams for recovery were mixed wastewater and sludge (73.8%). There was a relative lack of studies on recovery from source-separated wastewater. The most common type of recovery was energy (27.3%), followed by simultaneous recovery of nitrogen and phosphorus (22.1%). Reuse of recovered substances was described in 22.8% of the studies. The most common type of reuse was of nitrogen and phosphorus (57.4%), followed by joint reuse of organic carbon, nitrogen and phosphorus (35.2%). Reuse ecotechnologies were mostly focused on the use of wastewater for irrigation or reuse of biosolids, and not on the nutrients that had been extracted through e.g. precipitation of struvite. In 22 studies both recovery and reuse were described. In total, 60 different study countries were reported in the evidence base, and the most common study location was China. Conclusions: We found substantial evidence for the recovery and reuse of nutrients and carbon from wastewater sources. The relative abundance of studies where substances are recovered compared to studies where they are reused, suggests a knowledge gap on reuse of recovered nutrients and carbon. The majority of studies on reuse were on irrigation with treated wastewater or reuse of biosolids, and not on reuse of extracted nutrients such as struvite. © 2020 The Author(s).