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Data belonging to results published in: Increased (Antibiotic-Resistant) Pathogen Indicator Organism Removal during (Hyper-)Thermophilic Anaerobic Digestion of Concentrated Black Water for Safe Nutrient Recovery, Sustainability 2020, 12(22), 9336, https://doi.org/10.3390/su12229336, Data belonging to results published in: Increased (Antibiotic-Resistant) Pathogen Indicator Organism Removal during (Hyper-)Thermophilic Anaerobic Digestion of Concentrated Black Water for Safe Nutrient Recovery, Sustainability 2020, 12(22), 9336, https://doi.org/10.3390/su12229336

Dataset containing continuous reactor data belonging to the following publication: Thermophilic (55 °C) and hyper-thermophilic (70 °C) anaerobic digestion as novel treatment technologies for concentrated black water, Bioresource Technology, 2021, 340, 125705, https://doi.org/10.1016/j.biortech.2021.125705, Dataset containing continuous reactor data belonging to the following publication: Thermophilic (55 °C) and hyper-thermophilic (70 °C) anaerobic digestion as novel treatment technologies for concentrated black water, Bioresource Technology, 2021, 340, 125705, https://doi.org/10.1016/j.biortech.2021.125705

This study aimed to assess the effect of carbohydrates on protein hydrolysis and potential implications for the design of anaerobic reactors for treatment of protein-rich wastewaters. Batch experiments were carried out with dissolved starch (Sta) and gelatine (Gel) at different chemical oxygen demand (COD) ratios ranging from 0 to 5.5 under methanogenic conditions for methane production and up to 3.8 under non-methanogenic conditions for volatile fatty acids (VFA), both at 35 °C. The Sta/Gel did not have a direct effect on the gelatine hydrolysis rate constants under methanogenic (0.51 ± 0.05 L g VSS-1 day-1) and non-methanogenic conditions (0.48 ± 0.05 L g VSS-1 day-1). However, under non-methanogenic conditions, gelatine hydrolysis was inhibited by 64% when a spectrum of VFA was added at a VFA/Gel (COD) ratio of 5.9. This was not caused by the ionic strength exerted by VFA but by the VFA itself. These results imply that methanogenesis dictates the reactor design for methane production but hydrolysis does for VFA production from wastewater proteins

The study has been carried out under the COST Action CA17133 Circular City (implementing nature-based solutions for creating a resourceful circular city, http://www.circular-city.eu, duration 22 October 2018–21 October 2022). COST Actions are funded within the EU Horizon 2020 Programme., Cities are producers of high quantities of secondary liquid and solid streams that are still poorly utilized within urban systems. In order to tackle this issue, there has been an ever-growing push for more efficient resource management and waste prevention in urban areas, following the concept of a circular economy. This review paper provides a characterization of urban solid and liquid resource flows (including water, nutrients, metals, potential energy, and organics), which pass through selected nature-based solutions (NBS) and supporting units (SU), expanding on that characterization through the study of existing cases. In particular, this paper presents the currently implemented NBS units for resource recovery, the applicable solid and liquid urban waste streams and the SU dedicated to increasing the quality and minimizing hazards of specific streams at the source level (e.g., concentrated fertilizers, disinfected recovered products). The recovery efficiency of systems, where NBS and SU are combined, operated at a micro- or meso-scale and applied at technology readiness levels higher than 5, is reviewed. The importance of collection and transport infrastructure, treatment and recovery technology, and (urban) agricultural or urban green reuse on the quantity and quality of input and output materials are discussed, also regarding the current main circularity and application challenges.

Thermophilic and hyper-thermophilic anaerobic digestion (AD) are promising techniques for the treatment of concentrated black water (toilet fraction of domestic wastewater collected by low flush volume toilets; BW) and recovery of nutrients. High temperatures are applied in this study to ensure pathogen removal and thus safe reuse of recovered nutrients. This technique is applicable when ultra-low flush-volume collection (e.g. vacuum toilets) is used to obtain a highly concentrated waste stream (15-20 g COD/L) suitable for high rate anaerobic treatment and efficient nutrient recovery. This study showed that thermophilic AD (55 °C) of concentrated BW could achieve the same methanisation and COD removal as mesophilic anaerobic treatment of BW (collected with conventional vacuum toilets) and kitchen waste (KW) while applying a higher loading rate (2.5-4.0 kgCOD/m3⋅day). With a retention time of 8.7 days, and loading rates exceeding 3 kgCOD/m3⋅day a COD removal of 70% and a methanisation of 62% (based on CODt) was achieved during thermophilic anaerobic treatment, despite the high temperature (55 °C) and possible increased ammonia toxicity. Hyper-thermophilic (70 °C) reached lower levels of methanisation (38%). A UASB treating (highly) concentrated BW can be started-up in 12 days. Furthermore, microbiological analysis showed that the high temperature combined with high ammonia concentrations resulted in increased abundance of species closely related to Thermacetogenium phaeum and Syntrophaceticus schinkii, two syntrophic acetate oxidizers, along with an increased abundance of hydrogenotrophic methanogens (eg. species closely related to Methanothermobacter tenebrarum). This indicates that a shift from acetoclastic methanogenesis to hydrogenotrophic methanogenesis combined with syntrophic acetate oxidation can be observed as a consequence of the thermophilic conditions and possibly the related increased ammonia toxicity.

Source separated toilet water is a valuable resource for energy and fertilizers as it has a high concentration of organics and nutrients, which can be reused in agriculture. Recovery of nutrients such as nitrogen, phosphorous, and potassium (NPK) decreases the dependency on energy-intensive processes or processes that rely on depleting natural resources. In new sanitation systems, concentrated black water (BW) is obtained by source-separated collection of toilet water. BW-derived products are often associated with safety issues, amongst which pathogens and antibiotic-resistant pathogens. This study presents results showing that thermophilic (55–60◦C) and hyperthermophilic (70◦C) anaerobic treatments had higher (antibiotic-resistant) culturable pathogen indicators removal than mesophilic anaerobic treatment. Hyperthermophilic and thermophilic anaerobic treatment successfully removed Escherichia coli and extended-spectrum β-lactamases producing E. coli from source-separated vacuum collected BW at retention times of 6–11 days and reached significantly higher removal rates than mesophilic (35◦C) anaerobic treatment (p < 0.05). The difference between thermophilic and hyperthermophilic treatment was insignificant, which justifies operation at 55◦C rather than 70◦C. This study is the first to quantify (antibiotic-resistant) E. coli in concentrated BW (10–40 gCOD/L) and to show that both thermophilic and hyperthermophilic anaerobic treatment can adequately remove these pathogen indicators.

Our modern cities are resource sinks designed on the current linear economic model which recovers very little of the original input. As the current model is not sustainable, a viable solution is to recover and reuse parts of the input. In this context, resource recovery using nature-based solutions (NBS) is gaining popularity worldwide. In this specific review, we focus on NBS as technologies that bring nature into cities and those that are derived from nature, using (micro)organisms as principal agents, provided they enable resource recovery. The findings presented in this work are based on an extensive literature review, as well as on original results of recent innovation projects across Europe. The case studies were collected by participants of the COST Action Circular City, which includes a portfolio of more than 92 projects. The present review article focuses on urban wastewater, industrial wastewater, municipal solid waste and gaseous effluents, the recoverable products (e.g., nutrients, nanoparticles, energy), as well as the implications of source-separation and circularity by design. The analysis also includes assessment of the maturity of different technologies (technology readiness level) and the barriers that need to be overcome to accelerate the transition to resilient, self-sustainable cities of the future.

Recovering nutrients from human excreta and wastewater has been receiving increasing attention as a means to supplement or replace synthetic fertilizer production. Apart from technologies for nutrient recovery at centralized wastewater treatment plants, numerous decentralized, source-separated sanitation systems, also known as new sanitation systems, have been developed to facilitate recovery. Decision-making for the planning and implementation of new sanitation systems would benefit from a spatially explicit inventory of nutrient hotspots in urban areas. To provide visual representations of nutrient loads, we developed a methodology that combines spatial-temporal modeling with geographic information system analysis, and used it for the city of Amsterdam. The methodology is new in the field of nutrient mapping, especially at the smallest geographical scale: building. Nitrogen, phosphorus, and potassium loads and hotspots are mapped at both building and neighborhood scale, drawing attention to the need for multiple scale analyses in decision-making. This study concludes with a discussion on the potential to further develop the method proposed to include more detailed and verified data and to identify nutrient hotspots that are promising as nutrient recovery sites with new sanitation systems.