The recovery of resources, including water reuse, has been presented as a solution to overcome scarcity, and improve the economic and environmental performance of water provision and treatment. However, its implementation faces non-technical challenges, including the need to collaborate with new stakeholders and face societal acceptance issues. Looking at the prominence of the circular economy in current policy developments and the challenges to resource recovery, exploring these issues is urgently needed. In this work, we reviewed a broad range of literature to identify societal values relevant to the recovery of water and other resources from wastewaters, particularly urban and industrial wastewater and desalination brines. We discuss tensions and uncertainties around these values, such as the tension between socio-economic expectations of resource recovery and potential long-term sustainability impacts, as well as uncertainties regarding safety and regulations. For addressing these tensions and uncertainties, we suggest aligning common methods in engineering and the natural sciences with Responsible Innovation approaches, such as Value Sensitive Design and Safe-by-Design. To complement Responsible Innovation, social learning with a Sustainability Transitions or Adaptive Governance perspective is suggested.

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In the current linear take-make-waste pattern the production of goods starts with raw material extraction followed by industrial conversion into products that are used and finally wasted. This linear system accelerates resource depletion and therefore hinders the development of sustainable societies. This is also valid for the use of water and the implied production of wastewater. The ongoing rapid urbanisation in many areas of the world including Europe has led to high increases in wastewater since the beginning of the 20th century. The initial goal of wastewater treatment was to protect surface water users from health risks due to pollution. Then, during the last decades the protection of the environment itself from nutrient pollution has been enforced by implementing stricter legal wastewater treatment plant (WWTP) effluent standards. The conventional activated sludge process is the currently most widely applied wastewater treatment technology in these plants. It succeeds in reaching legal standards for chemical oxygen demand (COD), nitrogen, and phosphorous effluent concentrations but in its currently applied form, it is considered unsustainable due to its low resource recovery potential and cost-effectiveness on the one hand and its high energy demand and environmental footprint on the other. To adapt wastewater treatment practices to urgent requirements for more sustainable urban environments, a paradigm shift has been proposed by academia since over a decade. It recognises the potential of wastewater as a resource and demands to perceive it as such instead of a waste stream.... @en

The objective of this paper is to compare, under Dutch market conditions, the energy consumption and net costs of membrane-based advanced treatment processes for three water reuse types (i.e. potable, industrial, agricultural reuse). The water source is municipal waste-water treatment plant effluent. Results indicate that the application of reverse osmosis is needed to reclaim high quality water for industrial and potable reuse but not for irrigation water which offers significant energy savings but may not lead automatically to lower net costs. While a reclamation process for industrial reuse is economically most promising, irrigation water reclamation processes are not cost effective due to low water prices. Moreover, process operational expenditures may exceed capital expenditures which is important for tender procedures. A significant cost factor is waste management that may exceed energy costs. Water recovery rates could be significantly enhanced through the integration of a softener/biostabilizer unit prior to reverse osmosis. Moreover, the energy consumption of wastewater reclamation processes could be supplied on-site with solar energy. The possibility of designing a ‘fit for multi-purpose’ reclamation process is discussed briefly. This comparative analysis allows for better informed decision making about which reuse type is preferably targeted in a municipal wastewater reuse project from a process design perspective.

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Municipal wastewater cannot any longer be perceived as a waste stream because it contains water, energy, fertilizer and other products that can be recovered with innovative technologies in so called ‘water resource factories’. Therefore a paradigm shift has been proclaimed to design water resource factories in the future that feed into a circular economy. The rapid development of new resource recovery technologies requires a solid analysis prior to their integration into treatment processes to understand more about their potential to contribute to more circular urban water management practices. Mass and energy balances are an excellent method to model resource recovery potentials of innovative processes at an early design stage because they allow quantifying recoverable resources as well as trade-offs between possible recovery technology choices. We modelled a real wastewater treatment plant which uses aerobic granular sludge treatment and is currently operated with no on-site resource recovery. Then, 5 different possible process designs that would recover chemical oxygen demand (COD) as energy and/or extracellular polymeric substances (EPS), and phosphorous (P) as struvite have been modelled. The integration of anaerobic digestion for subsequent electricity and heat generation from methane provides the possibility to recover on-site a rather small fraction of influent-COD as energy. But if this is combined with chemically enhanced primary treatment (CEPT), almost one third of the influent-COD may be recovered. Simultaneous energy and EPS recovery may lead to trade-offs as CEPT integration for maximum energy recovery may halve the EPS recovery potential but would increase the overall influent-COD recovery rate. Struvite fertilizer recovery integration may only recover a small fraction of influent-P and is therefore questionable when other P recovery options are possible that aim for higher recovery rates. The fertilizer recovery potential may be significantly decreased by EPS recovery since the latter contain P. This study helps to understand how aerobic granular sludge based treatment processes can be designed as water resource factories. Mass and energy balances can be conducted at a very early process design stage and results may be used to identify promising process designs for subsequent more in depth techno-economic or environmental impact assessments.@en

In recent decades, academia has elaborated a wide range of technological solutions to recover water, energy, fertiliser and other products from municipal wastewater treatment plants. Drivers for this work range from low resource recovery potential and cost effectiveness, to the high energy demands and large environmental footprints of current treatment-plant designs. However, only a few technologies have been implemented and a shift from wastewater treatment plants towards water resource facilities still seems far away. This critical review aims to inform decision-makers in water management utilities about the vast technical possibilities and market supply potentials, as well as the bottlenecks, related to the design or redesign of a municipal wastewater treatment process from a resource recovery perspective. Information and data have been extracted from literature to provide a holistic overview of this growing research field. First, reviewed data is used to calculate the potential of 11 resources recoverable from municipal wastewater treatment plants to supply national resource consumption. Depending on the resource, the supply potential may vary greatly. Second, resource recovery technologies investigated in academia are reviewed comprehensively and critically. The third section of the review identifies nine non-technical bottlenecks mentioned in literature that have to be overcome to successfully implement these technologies into wastewater treatment process designs. The bottlenecks are related to economics and value chain development, environment and health, and society and policy issues. Considering market potentials, technological innovations, and addressing potential bottlenecks early in the planning and process design phase, may facilitate the design and integration of water resource facilities and contribute to more circular urban water management practices.

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This paper guides decision making in more sustainable urban water management practices that feed into a circular economy by presenting a novel framework for conceptually designing and strategically planning wastewater treatment processes from a resource recovery perspective. Municipal wastewater cannot any longer be perceived as waste stream because a great variety of technologies are available to recover water, energy, fertilizer, and other valuable products from it. Despite the vast technological recovery possibilities, only a few processes have yet been implemented that deserve the name water resource factory instead of wastewater treatment plant. This transition relies on process designs that are not only technically feasible but also overcome various non-technical bottlenecks. A multidimensional and multidisciplinary approach is needed to design water resource factories (WRFs) in the future that are technically feasible, cost effective, show low environmental impacts, and successfully market recovered resources. To achieve that, the wastewater treatment plant (WWTP) design space needs to be opened up for a variety of expertise that complements the traditional wastewater engineering domain. Implementable WRF processes can only be designed if the current design perspective, which is dominated by the fulfilment of legal euent qualities and process costs, is extended to include resource recovery as an assessable design objective from an early stage on. Therefore, the framework combines insights and methodologies from different fields and disciplines beyond WWTP design like, e.g., circular economy, industrial process engineering, project management, value chain development, and environmental impact assessment. It supports the transfer of the end-of-waste concept into the wastewater sector as it structures possible resource recovery activities according to clear criteria. This makes recovered resources more likely to fulfil the conditions of the end-of-waste concept and allows the change in their definition from wastes to full-fledged products.

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