365 research outputs found

    ZeroWasteWater: short-cycling of wastewater resources for sustainable cities of the future

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    Sewage treatment relies mainly on conventional activated sludge (CAS) systems, reaching sufficiently low pollutant effluent levels. Yet, CAS has a low cost-effectiveness and recovery potential and a high electricity demand and environmental footprint. By 2050, globally we have to solve severe water and phosphorus shortages while significantly decreasing greenhouse gas emissions. In this review and opinion paper, the ZeroWasteWater concept is proposed as a sustainable centralised technology train to short-cycle water, energy and valuable materials from sewage, while adequately abating pathogens, heavy metals and trace organics. Electrical energy recovery from anaerobic digestion of the organics present in sewage and kitchen waste (KW) has a value of 4.0 per inhabitant equivalent (IE) per year. In addition to sewerage improvements and water conservation, prerequisites include an advanced physico-chemical and/or biological concentration step at the entry of the sewage treatment plant. In the side stream, the recovery of phosphorus and carbon-sequestrating biochar from the digested sludge and of nitrogen from the digestate has a value of 6.3IE-1 year-1. Alternatively, recovery of biogas and materials can occur directly on source-separated black water. In the main stream, partial nitritation and anammox oxidise residual nitrogen. Moreover, two serial heat pumps recover thermal energy, valued at 6.9IE-1 year-1, cooling the water by 5 degrees C, and membrane technologies recover potable water at 65IE-1 year-1. Interestingly, ZeroWasteWater is expected to be economically viable. Key steps are to incorporate water chain management into holistic urban planning and thus produce a cradle-to-cradle approach that society will find acceptable

    Increased salinity improves the thermotolerance of mesophilic nitrification

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    Nitrification is a well-studied and established process to treat ammonia in wastewater. Although thermophilic nitrification could avoid cooling costs for the treatment of warm wastewaters, applications above 40 A degrees C remain a significant challenge. This study tested the effect of salinity on the thermotolerance of mesophilic nitrifying sludge (34 A degrees C). In batch tests, 5 g NaCl L-1 increased the activity of aerobic ammonia-oxidizing bacteria (AerAOB) by 20-21 % at 40 and 45 A degrees C. For nitrite-oxidizing bacteria (NOB), the activity remained unaltered at 40 A degrees C, yet decreased by 83 % at 45 A degrees C. In a subsequent long-term continuous reactor test, temperature was increased from 34 to 40, 42.5, 45, 47.5 and 50 A degrees C. The AerAOB activity showed 65 and 37 % higher immediate resilience in the salt reactor (7.5 g NaCl L-1) for the first two temperature transitions and lost activity from 45 A degrees C onwards. NOB activity, in contrast to the batch tests, was 37 and 21 % more resilient in the salt reactor for the first two transitions, while no difference was observed for the third temperature transition. The control reactor lost NOB activity at 47.5 A degrees C, while the salt reactor only lost activity at 50 A degrees C. Overall, this study demonstrates salt amendment as a tool for a more efficient temperature transition for mesophilic sludge (34 A degrees C) and eventually higher nitrification temperatures

    Effects of salinity, pH and growth phase on the protein productivity by Dunaliella salina

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    BACKGROUND Microalgae have long been adopted for use as human food, animal feed and high‐value products. For carotenogenesis, Dunaliella salina is one of the most studied microalgae, yet its protein synthesis has been limitedly reported. In this study, D. salina was cultivated at different NaCl and pH levels to optimize its protein productivity. RESULTS The biomass protein content followed an increase–decrease pattern throughout the growth phases, with a maximum in the exponential phase (60–80% over ash‐free dry weight). Adversely, the biomass pigment contents were at relatively stable levels (around 0.5% carotenoids, 1.3% chlorophyll a and 0.5% chlorophyll b over ash‐free dry weight). Among the tested conditions (1–3 mol L−1 salinity, pH 7.5–9.5), the highest protein productivity (43.5 mg L−1 day−1) was achieved at 2 mol L−1 salinity and pH 7.5 during the exponential phase, which surpassed others by 16–97%. Additionally, table salts were tested to be equivalent and cost‐efficient salt sources for the growth medium. CONCLUSION This study highlighted the suitability of D. salina as a protein source, providing guidelines for 70% cheaper medium formulation in the lab and for maximum protein productivity at larger scale

    The nitrogen and phosphorus budget of Flanders: a tool for efficient waste management and nutrient recovery

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    The region of Flanders in Belgium is, due to its high population density, intensive industry and livestock production, a nutrient-rich region. This results in important anthropogenic emissions to the environment, but also a large potential for the recovery and reuse of nitrogen (N ) and phosphorus (P) from waste streams. In this study, a substance flow analysis study for N and P is presented, in which the anthropogenic fluxes, stocks and hot spots of these two nutrients are quantified throughout the Flemish economy and environment. The environmental impact of the different economic sectors is addressed through the determination of the N and P footprint. The importance of food production in the nutrient cycle is thereby demonstrated through the large contribution of agriculture to the nutrient footprint (49% of N and 36% of P). Further focus is placed on the nutrient use efficiencies across the different sectors of the food supply nexus to target key nutrient losses and inefficiencies. This leads to an overall fertilizer-to-consumer efficiency of 14% for N and P, with the main nutrient losses originating from livestock production and food processing. At the end of the production and consumption chain, important nutrient quantities are embedded in concentrated waste streams such as excess manure, food processing waste streams and activated sludge. This demonstrates the large potential for nutrient recovery as a tool to improve nutrient use efficiencies and reduce the dependency of inorganic fertilizers. Several nutrient recovery strategies, both physicochemical and microbial, were evaluated for their economic feasibility and their impact on the primary energy demand of the total food supply chain

    Media Optimization, Strain Compatibility, and Low-Shear Modeled Microgravity Exposure of Synthetic Microbial Communities for Urine Nitrification in Regenerative Life-Support Systems

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    Urine is a major waste product of human metabolism and contains essential macro- and micronutrients to produce edible microorganisms and crops. Its biological conversion into a stable form can be obtained through urea hydrolysis, subsequent nitrification, and organics removal, to recover a nitrate-enriched stream, free of oxygen demand. In this study, the utilization of a microbial community for urine nitrification was optimized with the focus for space application. To assess the role of selected parameters that can impact ureolysis in urine, the activity of six ureolytic heterotrophs (Acidovorax delafieldii, Comamonas testosteroni, Cupriavidus necator, Delftia acidovorans, Pseudomonas fluorescens, and Vibrio campbellii) was tested at different salinities, urea, and amino acid concentrations. The interaction of the ureolytic heterotrophs with a nitrifying consortium (Nitrosomonas europaea ATCC 19718 and Nitrobacter winogradskyi ATCC 25931) was also tested. Lastly, microgravity was simulated in a clinostat utilizing hardware for in-flight experiments with active microbial cultures. The results indicate salt inhibition of the ureolysis at 30 mS cm(-1), while amino acid nitrogen inhibits ureolysis in a strain-dependent manner. The combination of the nitrifiers with C. necator and V. campbellii resulted in a complete halt of the urea hydrolysis process, while in the case of A. delafieldii incomplete nitrification was observed, and nitrite was not oxidized further to nitrate. Nitrate production was confirmed in all the other communities; however, the other heterotrophic strains most likely induced oxygen competition in the test setup, and nitrite accumulation was observed. Samples exposed to low-shear modeled microgravity through clinorotation behaved similarly to the static controls. Overall, nitrate production from urea was successfully demonstrated with synthetic microbial communities under terrestrial and simulated space gravity conditions, corroborating the application of this process in space

    13C Incorporation as a tool to estimate biomass yields in thermophilic and mesophilic nitrifying communities

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    Current methods determining biomass yield require sophisticated sensors for in situ measurements or multiple steady-state reactor runs. Determining the yield of specific groups of organisms in mixed cultures in a fast and easy manner remains challenging. This study describes a fast method to estimate the maximum biomass yield (Y-max ), based on C-13 incorporation during activity measurements. It was applied to mixed cultures containing ammonia oxidizing bacteria (AOB) or archaea (AOA) and nitrite oxidizing bacteria (NOB), grown under mesophilic (15-28 degrees C) and thermophilic (50 degrees C) conditions. Using this method, no distinction could be made between AOB and AOA co-existing in a community. A slight overestimation of the nitrifier biomass due to C-13 redirection via SMP to heterotrophs could occur, meaning that this method determines the carbon fixation activity of the autotrophic microorganisms rather than the actual nitrifier biomass yield. Thermophilic AOA yields exceeded mesophilic AOB yields (0.22 vs. 0.06-0.11 g VSS g(-1) N), possibly linked to a more efficient pathway for CO(2 )incorporation. NOB thermophilically produced less biomass (0.025-0.028 vs. 0.048-0.051 g VSS g(-1) N), conceivably attributed to higher maintenance requirement, rendering less energy available for biomass synthesis. Interestingly, thermophilic nitrification yield was higher than its mesophilic counterpart, due to the dominance of AOA over AOB at higher temperatures. An instant temperature increase impacted the mesophilic AOB yield, corroborating the effect of maintenance requirement on production capacity. Model simulations of two realistic nitrification/denitrification plants were robust toward changing nitrifier yield in predicting effluent ammonium concentrations, whereas sludge composition was impacted. Summarized, a fast, precise and easily executable method was developed determining Y(max )of ammonia and nitrite oxidizers in mixed communities

    Microbial resource management of one-stage partial nitritation/anammox

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    About 30 full-scale partial nitritation/anammox plants are established, treating mostly sewage sludge reject water, landfill leachate or food processing digestate. Although two-stage and one-stage processes each have their advantages, the one-stage configuration is mostly applied, termed here as oxygen-limited autotrophic nitrification/denitrification (OLAND), and is the focus of this review. The OLAND application domain is gradually expanding, with technical-scale plants on source-separated domestic wastewater, pre-treated manure and sewage, and liquors from organic waste bioenergy plants. A microbial resource management (MRM) OLAND framework was elaborated, showing how the OLAND engineer/operator (1: input) can design/steer the microbial community (2: biocatalyst) to obtain optimal functionality (3: output). In the physicochemical toolbox (1), design guidelines are provided, as well as advantages of different reactor technologies. Particularly the desirable aeration regime, feeding regime and shear forces are not clear yet. The development of OLAND trickling filters, membrane bioreactors and systems with immobilized biomass is awaited. The biocatalyst box (2) considers Who: biodiversity and its dynamic patterns, What: physiology, and Where: architecture creating substrate gradients. Particularly community dynamics and extracellular polymeric substances (EPS) still require insights. Performant OLAND (3) comprises fast start-up (storage possibility; fast growth of anammox bacteria), process stability (endured biomass retention; stress resilience), reasonable overall costs, high nitrogen removal efficiency and a low environmental footprint. Three important OLAND challenges are elaborated in detailed frameworks, demonstrating how to maximize nitrogen removal efficiency, minimize NO and N2O emissions and obtain through OLAND a plant-wide net energy gain from sewage treatment
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