Abstract: Nitrite oxidizing bacteria (NOB) and nitrous oxide (N2O) hinder the development of mainstream partial nitritation/anammox. To overcome these, endogenous free ammonia (FA) and free nitrous acid (FNA), which can be produced in the sidestream, were used for return-sludge treatment for two integrated-film activated sludge reactors containing biomass in flocs and on carriers. The repeated exposure of biomass from one reactor to FA shocks had a limited impact on NOB suppression but inhibited anammox bacteria (AnAOB). In the other reactor, repeated FNA shocks to the separated flocs failed to limit the system’s nitrate production since NOB activity was still high on the biofilms attached to the unexposed carriers. In contrast, the repeated FNA treatment of flocs and carriers favored aerobic ammonium-oxidizing bacteria (AerAOB) over NOB activity with AnAOB negligibly affected. It was further revealed that return-sludge treatment with higher FNA levels led to lower N2O emissions under similar effluent nitrite concentrations. On this basis, weekly 4 h FNA shocks of 2.0 mg of HNO2-N/L were identified as an optimal and realistic treatment, which not only enabled nitrogen removal efficiencies of ∼65% at nitrogen removal rates of ∼130 mg of N/L/d (20 °C) but also yielded the lowest cost and carbon footprint.

Abstract: Electroporation is a non-thermal electromagnetic phenomenon widely used in medical diseases treatment. Different mathematical models of electroporation have been proposed in literature to study pore evolution in biological membranes. This paper presents a nonlinear dispersive multiphysic model of electroporation in irregular shaped biological cells in which the spatial and temporal evolution of the pores size is taken into account. The model solves Maxwell and asymptotic Smoluchowski equations and it describes the dielectric dispersion of cell media using a Debye-based relationship. Furthermore, the irregular cell shape has been modeled using the Gielis superformula. Taking into account the cell in mitosis phase, the electroporation process has been studied comparing the numerical results pertaining the model with variable pore radius with those in which the pore radius is supposed constant. The numerical analysis has been performed exposing the biological cell to a rectangular electric pulse having duration of 10 μs. The obtained numerical results highlight considerable differences between the two different models underling the need to include into the numerical algorithm the differential equation modeling the spatial and time evolution of the pores size.

Abstract: Bimetallic plasmonic nanoparticles enable tuning of the optical response and chemical stability by variation of the composition. The present numerical simulation study compares Ag–Au alloy, Ag@Au core–shell, and Au@Ag core–shell bimetallic plasmonic nanoparticles of both spherical and anisotropic (nanotriangle and nanorods) shapes. By studying both spherical and anisotropic (with LSPR in the near-infrared region) shapes, cases with and without interband transitions of Au can be decoupled. Explicit comparisons are facilitated by numerical models supported by careful validation and examination of optical constants of Au–Ag alloys reported in the literature. Although both Au–Ag core–shell and alloy nanoparticles exhibit an intermediary optical response between that of pure Ag and Au nanoparticles, there are noticeable differences in the spectral characteristics. Also, the effect of the bimetallic constitution in anisotropic nanoparticles is starkly different from that in spherical nanoparticles due to the absence of Au interband transitions in the former case. In general, the improved chemical stability of Ag nanoparticles by incorporation of Au comes with a cost of reduction in plasmonic enhancement, also applicable to anisotropic nanoparticles with a weaker effect. A photothermal heat transfer study confirms that increased absorption by the incorporation of Au in spherical Ag nanoparticles also results in an increased steady-state temperature. On the other hand, anisotropic nanoparticles are inherently better absorbers and hence better photothermal sources, and their photothermal properties are apparently not strongly affected by the incorporation of one metal in the other. This study of the optical/spectral and photothermal characteristics of bimetallic Au–Ag alloy versus core–shell nanoparticles provides detailed physical insight for development of new taylor-made plasmonic nanostructures.

Abstract: Sustainable development is driving a rapid focus shift in the wastewater and organic waste treatment sectors, from a “removal and disposal” approach towards the recovery and reuse of water, energy and materials (e.g. carbon or nutrients). Purple phototrophic bacteria (PPB) are receiving increasing attention due to their capability of growing photoheterotrophically under anaerobic conditions. Using light as energy source, PPB can simultaneously assimilate carbon and nutrients at high efficiencies (with biomass yields close to unity (1 g CODbiomass·g CODremoved−1)), facilitating the maximum recovery of these resources as different value-added products. The effective use of infrared light enables selective PPB enrichment in non-sterile conditions, without competition with other phototrophs such as microalgae if ultraviolet-visible wavelengths are filtered. This review reunites results systematically gathered from over 177 scientific articles, aiming at producing generalized conclusions. The most critical aspects of PPB-based production and valorisation processes are addressed, including: (i) the identification of the main challenges and potentials of different growth strategies, (ii) a critical analysis of the production of value-added compounds, (iii) a comparison of the different value-added products, (iv) insights into the general challenges and opportunities and (v) recommendations for future research and development towards practical implementation. To date, most of the work has not been executed under real-life conditions, relevant for full-scale application. With the savings in wastewater discharge due to removal of organics, nitrogen and phosphorus as an important economic driver, priorities must go to using PPB-enriched cultures and real waste matrices. The costs associated with artificial illumination, followed by centrifugal harvesting/dewatering and drying, are estimated to be 1.9, 0.3–2.2 and 0.1–0.3 $·kgdry biomass−1. At present, these costs are likely to exceed revenues. Future research efforts must be carried out outdoors, using sunlight as energy source. The growth of bulk biomass on relatively clean wastewater streams (e.g. from food processing) and its utilization as a protein-rich feed (e.g. to replace fishmeal, 1.5–2.0 $·kg−1) appears as a promising valorisation route.

Abstract: Human activities related to urbanization and industrialization have established a vast territory of urban soil worldwide. On traditional soil maps, urban and industrial areas usually appear as blind spots as they were beyond the interest of national soil survey campaigns. Furthermore, these soil maps are likely already outdated with respect to urban soil due to rapid urban expansion in recent decades. This research aims to evaluate the use of land cover data to estimate the urban soil information gap considering the highly urbanized region of Flanders, Belgium, as a case study. The current extent and spatial distribution of anthropogenic urban soil (1) was estimated through reclassification of recently acquired (2012) exhaustive land cover data, discriminating three qualitative likelihood levels (high-intermediate-low) of anthropogenic influence by urbanization, and (2) compared with its occurrence as represented by the 'Technosols/Not Surveyed area' in the legacy soil map of Belgium, as this map unit best matches with the likelihood for anthropogenic urban soil at the time of the National Soil Survey conducted between end 1940s and mid 1970s. The proposed reclassification of the land cover map resulted in 16.3% and 16.7% of Flanders' total area that corresponds with a high and intermediate likelihood for anthropogenic urban soil, which highlights the underestimation of the anthropogenic urban soil extent as represented by the 'Technosol/Not Surveyed' unit in the legacy soil map (only 13.7%). Moreover, a more realistic spatial pattern of anthropogenic urban soil occurrence was obtained, providing an improved basis for urban soil spatial analysis studies. The produced anthropogenic urban soil likelihood map therefore presents a useful supporting tool for coordinating future soil surveys in urban environments.

Abstract: Aquafeeds contain protein ingredients such as fishmeal and soybean meal, yet their production puts pressure on the environment. Finding novel protein sources such as dried microbial biomass produced on recovered or renewable resources, so-called single-cell protein or microbial protein, can contribute to a more sustainable aquaculture industry. New microbial protein sources are emerging with photoheterotrophic grown purple non‑sulfur bacteria (PNSB) showing high potential, yet research of PNSB as added-value protein ingredient is limited. This research studied their use as a protein source for the white leg shrimp (Penaeus vannamei) and investigated the shrimp's tolerance against Vibrio and ammonia stress. A 28-day shrimp feeding trial was performed with a commercial formulation without PNSB as experimental control (diet i), two pure PNSB species, namely Rhodopseudomonas palustris (diets ii-iii), Rhodobacter capsulatus (diets iv-v) at two protein inclusion levels of 5 and 11 g PNSBprotein 100 g−1 feedprotein and a PNSB enriched culture at a protein inclusion level of 11 g PNSBprotein 100 g−1 feedprotein (diet vi). For the shrimp fed with Rb. capsulatus, 5–25% higher individual weights (p < .05) and better feed conversion ratios were observed relative to the commercial diet (1.3–1.4 vs. control 1.7 g feed g−1 biomass; p < .05). The diet containing Rps. palustris at 5 g PNSBprotein 100 g−1 feedprotein inclusion also showed higher individual weights (26%, p < .05) and a better feed conversion ratio compared to the commercial feed (1.3 vs. control 1.7 g feed g−1 biomass; p < .05). The challenge test subsequent to the feeding trial showed a higher tolerance against ammonia (3 mg N L−1) for shrimp fed with Rps. palustris (survival 63–75% vs. 8% commercial diet; p < .05). For a post-feeding challenge test with Vibrio parahaemolyticus TW01, mortality rates were equal among all treatments. Yet, in vitro tests in 96-Well plates and agar spot assays showed that the PNSB species (i) Rps. palustris, (ii) Rb. capsulatus, (iii) Rb. sphaeroides, (iv) Rhodospirillum rubrum and (v) Afifella marina suppressed the pathogens V. parahaemolyticus TW01 and V. campbellii LMG 21363. Overall, this study demonstrated the potential of PNSB as an added-value protein ingredient in shrimp nursery feed. This can contribute to a circular economy, as PNSB can be cultivated on recovered or renewable resources (e.g. wastewater).

Abstract: Pd nanometal particles encapsulated in macroporous Na-ZSM-5 with only Lewis acid sites have been successfully synthesized by a steam-thermal approach. The synergistic effect of Pd and Lewis acid sites have been investigated for significant enhancement of the catalytic selectivity towards furfural alcohol in furfural hydroconversion.

Abstract: Long-term human Space missions will rely on regenerative life support as resupply of water, oxygen and food comes with constraints. The International Space Station (ISS) relies on an evaporation/condensation system to recover 74–85% of the water in urine, yet suffers from repetitive scaling and biofouling while employing hazardous chemicals. In this study, an alternative non-sanitary five-stage treatment train for one “astronaut” was integrated through a sophisticated monitoring and control system. This so-called Water Treatment Unit Breadboard (WTUB) successfully treated urine (1.2-L-d−1) with crystallisation, COD-removal, ammonification, nitrification and electrodialysis, before it was mixed with shower water (3.4-L-d−1). Subsequently, ceramic nanofiltration and single-pass flat-sheet RO were used. A four-months proof-of-concept period yielded: (i) chemical water quality meeting the hygienic standards of the European Space Agency, (ii) a 87-±-5% permeate recovery with an estimated theoretical primary energy requirement of 0.2-kWhp-L−1, (iii) reduced scaling potential without anti-scalant addition and (iv) and a significant biological reduction in biofouling potential resulted in stable but biofouling-limited RO permeability of 0.5 L-m−2-h−1-bar−1. Estimated mass breakeven dates and a comparison with the ISS Water Recovery System for a hypothetical Mars transit mission show that WTUB is a promising biological membrane-based alternative to heat-based systems for manned Space missions.

Abstract: Marine recirculating aquaculture system (MRAS) is an effective technology that provides sustainable farming of food fish globally. However, dissolved organics material (chemical oxygen demand, COD) and especially ammonia are produced from uneaten feed and metabolic wastes of fish. To purify the MRAS water, this study adopted a sequencing biofilm batch reactor (SBBR) and comparatively investigated the performances of four different carriers on ammonia and COD removal. Results indicated that the NH4+-N removal rates were 0.045 +/- 0.05, 0.065 +/- 0.008, 0.089 +/- 0.005, and 0.093 +/- 0.003 kg/(m(3)center dot d), and the COD removal rates were 0.019 +/- 0.010, 0.213 +/- 0.010, 0.255 +/- 0.015, and 0.322 +/- 0.010 kg/(m(3)center dot d) in the SBBRs packed with porous plastic, bamboo ring, maifan stone, and ceramsite carriers, respectively. Among the four carriers, ceramsite exhibited the best performance for both NH4+-N (80%) and COD (33%) removal after the SBBR reached the steady-state operation conditions. For all carriers studied, the NH4+-N removal kinetics could be well simulated by the first-order model, and the NH4+-N and COD removal rates were logarithmically correlated with the carrier's specific surface area. Due to its high ammonia removal, stable performance and easy operation, the ceramsite-packed SBBR is feasible for MRAS water treatment.

Abstract: Cities with resilience to climate change appear to be a vision of the future, but are inevitable to ensure the quality of life for citizens and to avoid an increase in civilian mortality. Urban green infrastructure (UGI), with the focus on vertical green, poses a beneficial mitigation and adaptation strategy for challenges such as climate change through cooling effects on building and street level. This review article explores recent literature regarding this considerable topic and investigates how green walls can be applied to mitigate this problem. Summary tables (see additional information) and figures are presented that can be used by policy makers and researchers to make informed decisions when installing green walls in built-up environments. At last, knowledge gaps are uncovered that need further investigation to exploit the benefits at its best.

Abstract: Quantitative PCR (qPCR) is broadly used as the gold standard to quantify microbial community fractions in environmental microbiology and biotechnology. Benchmarking efforts to ensure the comparability of qPCR data for environmental bioprocesses are still scarce. Also, for partial nitritation/anammox (PN/A) systems systematic investigations are still missing, rendering meta-analysis of reported trends and generic insights potentially precarious. We report a baseline investigation of the variability of qPCR-based analyses for microbial communities applied to PN/A systems. Round-robin testing was performed for three PN/A biomass samples in six laboratories, using the respective in-house DNA extraction and qPCR protocols. The concentration of extracted DNA was significantly different between labs, ranged between 2.7 and 328 ng mg−1 wet biomass. The variability among the qPCR abundance data of different labs was very high (1−7 log fold) but differed for different target microbial guilds. DNA extraction caused maximum variation (3–7 log fold), followed by the primers (1–3 log fold). These insights will guide environmental scientists and engineers as well as treatment plant operators in the interpretation of qPCR data.

Abstract: Production of struvite (MgNH4PO4·6H2O) from waste streams is increasingly implemented to recover phosphorus (P), which is listed as a critical raw material in the European Union (EU). To facilitate EU-wide trade of P-containing secondary raw materials such as struvite, the EU issued a revised fertilizer regulation in 2019. A comprehensive overview of the supply of struvite and its quality is presently missing. This study aimed: i) to determine the current EU struvite production volumes, ii) to evaluate all legislated physicochemical characteristics and pathogen content of European struvite against newly set regulatory limits, and iii) to compare not-regulated struvite characteristics. It is estimated that in 2020, between 990 and 1250 ton P are recovered as struvite in the EU. Struvite from 24 European production plants, accounting for 30% of the 80 struvite installations worldwide was sampled. Three samples failed the physicochemical legal limits; one had a P content of <7% and three exceeded the organic carbon content of 3% dry weight (DW). Mineralogical analysis revealed that six samples had a struvite content of 80–90% DW, and 13 samples a content of >90% DW. All samples showed a heavy metal content below the legal limits. Microbiological analyses indicated that struvite may exceed certain legal limits. Differences in morphology and particle size distribution were observed for struvite sourced from digestate (rod shaped; transparent; 82 mass% < 1 mm), dewatering liquor (spherical; opaque; 65 mass% 1–2 mm) and effluent from upflow anaerobic sludge blanket reactor processing potato wastewater (spherical; opaque; 51 mass% < 1 mm and 34 mass% > 2 mm). A uniform soil-plant P-availability pattern of 3.5–6.5 mg P/L soil/d over a 28 days sampling period was observed. No differences for plant biomass yield were observed. In conclusion, the results highlight the suitability of most struvite to enter the EU fertilizer market.

Abstract: A novel type of activated carbon fiber filter was developed for indoor air purification. The filter is equipped with electrodes for thermo-electrical regeneration at the point of saturation. The electrodes are arranged in such a way that the filter forms a pleated structure with an electrode in the tip of each pleat. This allows for a uniform temperature distribution on the filter surface during the regeneration process and the pleated structure reduces the overall pressure drop across the filter. The latter was validated by Computational Fluid Dynamics, using Darcy-Forchheimer parameters derived in previous work. The CFD model was further used to perform a virtual sensitivity study in search for the optimal ACF filter design by varying the pleat length, pleat height and filter thickness. Finally, adsorption and desorption properties were investigated with acetaldehyde and toluene as model compounds. Freundlich and Langmuir adsorption parameters, derived in previous work were successfully validated with a Multiphysics model.