An innovative circular economy (CE) system was implemented at the wastewater treatment plant (WWTP) in Brunswick. The performance of the CE system was evaluated for 4 years: the thermal pressure hydrolysis enhanced the methane production by 18% and increased the digestate dewaterability by 14%. Refractory COD formed in thermal hydrolysis and increased the COD concentration in the WWTP effluent by 4 mg L−1 while still complying with the legal threshold. Struvite production reached high phosphorus recovery rates of >80% with a Mg:P molar ratio ≥0.8. Nitrogen was successfully recovered as ammonium sulfate with high recovery rates of 85–97%. The chemical analyses of secondary fertilizers showed a low pollutant content, posing low risks to soil and groundwater ecosystems. The total carbon footprint of the WWTP decreased due to enhanced biogas production, the recovery of renewable fertilizers and a further reduction of nitrous oxide emissions. Using green energy will be crucial to reach carbon neutrality for the entire WWTP.

A new generation of integrated fixed-film activated sludge (IFAS) systems, merging the biofilm of the root zone from aquatic plants into the activated sludgeprocess, has increasingly gained attention in recent years as a potential alternative to conventional wastewater treatment systems. However, there is a lack of understanding of the broader environmental impact of this emerging technology and how it compares to traditional concepts of wastewater treatment. In this research, we address this gap by conducting a comparative Life Cycle Assessment (LCA) with three reference scenarios, based on design simulations in seven midpoint impact categories. The entire novel wastewater treatment system at a small to medium-sized brewery in the Netherlands, including sludge disposal, resulted in net values of 29.2 MJ, 1.9 kg CO2-eq., 3.4 g  OX-eq., 0.1 mg CFC11- eq., 4.0 g SO2-eq., 0.3 g P-eq., and 1.9 N-eq. per m3 wastewater treated, under categories CED, GWP, POFP, ODP, TAP, FEP, and MEP, respectively. Compared to aerated SBR systems, the new system demonstrated higher environmental burdens in CED (120%), GWP (122%), POFP (125%), ODP (123%), and TAP (133%). This study provides evidence that these impacts on the environment mainly depend on the technology’s current electricity demand, while additional improvements can also be achieved by lowering the chemical and nutrient demand of the system. The comparison to a potential anaerobic treatment opportunity for the brewery wastewater with an EGSB reactor, exacerbated the previously identified shortcomings of the new technology, since the crediting of biogas allowed a complete offset of the total environmental impact measured by the GWP, CED, and ODP. Our findings suggest that additional water recovery concepts with subsequent nanofiltration systems, aimed at preserving natural water resources, may offer no competitive advantage for the GWP, CED, POFP, OPD, and TAP, if the electricity demand (1.17 kWh per provided m3 reused water) surpasses the benefit of water reuse. However, it is important to note that the new technologies provide their own set of benefits, such as a reduced impact on freshwater and marine eutrophication, due to the high  nutrient uptake capability. Our research provides implications for practitioners and researchers seeking to understand the environmental impact associated with plant root equipped IFAS, while implicit design assumptions may limit the ability to generalise findings on real-world scenarios.

In the European Union (EU) Horizon 2020 (H2020) project NextGen, 24 technologies related to circular economy in the water sector were investigated at 10 case studies distributed across Europe. The technologies are involved in water management and recovery, material recovery and energy recovery. In this context, a database containing information and data referring to those technologies was developed. The database is called technology evidence base (TEB), is open access and hosted by Water Europe as part of the Marketplace (https://mp.watereurope.eu/).

As a potential solution to better use water-embedded resources, the transition to circular water systems and services requires technology-focused approaches that can enhance a positive reception by organizations in the public, business and government sectors. NextGen focuses on water, energy and nutrients/material cycles in the water and wastewater sector to make them economically and environmentally attractive. This report addresses new approaches and best practices for closing the energy cycle in the water sector. Five NextGen case studies developed and demonstrated a wide range of innovative energy recovery technologies/approaches: Athens (EL), Filton Airfield (UK), Braunschweig (DE), Spernal (UK) and Westland (NL).

This Handbook provides a comprehensive overview of how water, energy and food are interconnected, comprising a coherent system: the nexus. It considers the interlinkages between natural resources, governance processes seeking coherence among water, energy and food policies, and the adoption of transdisciplinary approaches in the field.

With contributions covering a broad range of disciplinary perspectives and cross-cutting themes, the Handbook has a well-balanced mix of conceptual chapters and empirical studies. It includes a state-of-the-art analysis of the concepts and experiences in implementing the nexus in different policy environments, providing examples of successful integrated decision-making across the domains of water, energy and food. Offering a global perspective on water, energy and food security, the Handbook contains insights into achieving both national development goals and the Sustainable Development Goals. Chapters further highlight how to understand the concepts of the nexus in practice, impacts of the nexus in governance, policy and business, and methods and tools to strengthen the nexus.

Interdisciplinary and thorough, this Handbook will be critical reading for environmental management, public policy and human geography scholars. It will also be a useful tool for policymakers looking for successful examples of policy coherence towards an integrated management of water, energy and food resources.