“Introducing bioflocculation boundaries in process control to enhance effluent quality of high‐rate contact‐stabilization systems”. Ngo KN, Tampon P, Van Winckel T, Massoudieh A, Sturm B, Bott C, Wett B, Murthy S, Vlaeminck SE, DeBarbadillo C, De Clippeleir H, Water environment research 94, e10772 (2022). http://doi.org/10.1002/WER.10772
Abstract: High-rate activated sludge (HRAS) systems suffer from high variability of effluent quality, clarifier performance, and carbon capture. This study proposed a novel control approach using bioflocculation boundaries for wasting control strategy to enhance effluent quality and stability while still meeting carbon capture goals. The bioflocculation boundaries were developed based on the oxygen uptake rate (OUR) ratio between contactor and stabilizer (feast/famine) in a high-rate contact stabilization (CS) system and this OUR ratio was used to manipulate the wasting setpoint. Increased oxidation of carbon or decreased wasting was applied when OUR ratio was <0.52 or >0.95 to overcome bioflocculation limitation and maintain effluent quality. When no bioflocculation limitations (OUR ratio within 0.52–0.95) were detected, carbon capture was maximized. The proposed control concept was shown for a fully automated OUR-based control system as well as for a simplified version based on direct waste flow control. For both cases, significant improvements in effluent suspended solids level and stability (<50-mg TSS/L), solids capture over the clarifier (>90%), and COD capture (median of 32%) were achieved. This study shows how one can overcome the process instability of current HRAS systems and provide a path to achieve more reliable outcomes.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 3.1
DOI: 10.1002/WER.10772
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“Enhancing bioflocculation in high-rate activated sludge improves effluent quality yet increases sensitivity to surface overflow rate”. Van Winckel T, Ngo N, Sturm B, Al-Omari A, Wett B, Bott C, Vlaeminck SE, De Clippeleir H, Chemosphere 308, 136294 (2022). http://doi.org/10.1016/J.CHEMOSPHERE.2022.136294
Abstract: High-rate activated sludge (HRAS) relies on good bioflocculation and subsequent solid-liquid separation to maximize the capture of organics. However, full-scale applications often suffer from poor and unpredictable effluent suspended solids (ESS). While the biological aspects of bioflocculation are thoroughly investigated, the effects of fines (settling velocity < 0.6 m3/m2/h), shear and surface overflow rate (SOR) are unclear. This work tackled the impact of fines, shear, and SOR on the ESS in absence of settleable influent solids. This was assessed on a full-scale HRAS step-feed (SF) and pilot-scale HRAS contact-stabilization (CS) configuration using batch settling tests, controlled clarifier experiments, and continuous operation of reactors. Fines contributed up to 25% of the ESS in the full-scale SF configuration. ESS decreased up to 30 mg TSS/L when bioflocculation was enhanced with the CS configuration. The feast-famine regime applied in CS promoted the production of high-quality extracellular polymeric substances (EPS). However, this resulted in a narrow and unfavorable settling velocity distribution, with 50% ± 5% of the sludge mass settling between 0.6 and 1.5 m3/m2/h, thus increasing sensitivity towards SOR changes. A low shear environment (20 s−1) before the clarifier for at least one min was enough to ensure the best possible settling velocity distribution, regardless of prior shear conditions. Overall, this paper provides a more complete view on the drivers of ESS in HRAS systems, creating the foundation for the design of effective HRAS clarifiers. Tangible recommendations are given on how to manage fines and establish the optimal settling velocity of the sludge.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 8.8
DOI: 10.1016/J.CHEMOSPHERE.2022.136294
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“Overcoming floc formation limitations in high-rate activated sludge systems”. Van Winckel T, Liu X, Vlaeminck SE, Takács I, Al-Omari A, Sturm B, Kjellerup BV, Murthy SN, De Clippeleir H, Chemosphere 215, 342 (2019). http://doi.org/10.1016/J.CHEMOSPHERE.2018.09.169
Abstract: High-rate activated sludge (HRAS) is an essential cornerstone of the pursuit towards energy positive sewage treatment through maximizing capture of organics. The capture efficiency heavily relies on the degree of solid separation achieved in the clarifiers. Limitations in the floc formation process commonly emerge in HRAS systems, with detrimental consequences for the capture of organics. This study pinpointed and overcame floc formation limitations present in full-scale HRAS reactors. Orthokinetic flocculation tests were performed with varying shear, sludge concentration, and coagulant or flocculant addition. These were analyzed with traditional and novel settling parameters and extracellular polymeric substances (EPS) measurements. HRAS was limited by insufficient collision efficiency and occurred because the solids retention time (SRT) was short and colloid loading was high. The limitation was predominantly caused by impaired flocculation rather than coagulation. In addition, the collision efficiency limitation was driven by EPS composition (low protein over polysaccharide ratio) instead of total EPS amount. Collision efficiency limitation was successfully overcome by bio-augmenting sludge from a biological nutrient removal reactor operating at long SRT which did not show any floc formation limitations. However, this action brought up a floc strength limitation. The latter was not correlated with EPS composition, but rather EPS amount and hindered settling parameters, which determined floc morphology. With this, an analysis toolkit was proposed that will enable design engineers and operators to tackle activated solid separation challenges found in HRAS systems and maximize the recovery potential of the process. (C) 2018 Elsevier Ltd. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.1016/J.CHEMOSPHERE.2018.09.169
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“The impact of local hydrodynamics on high-rate activated sludge flocculation in laboratory and full-scale reactors”. Balemans S, Vlaeminck SE, Torfs E, Hartog L, Zaharova L, Rehman U, Nopens I, Processes 8, 131 (2020). http://doi.org/10.3390/PR8020131
Abstract: High rate activated sludge (HRAS) processes have a high potential for carbon and energy recovery from sewage, yet they suffer frequently from poor settleability due to flocculation issues. The process of flocculation is generally optimized using jar tests. However, detailed jar hydrodynamics are often unknown, and average quantities are used, which can significantly differ from the local conditions. The presented work combined experimental and numerical data to investigate the impact of local hydrodynamics on HRAS flocculation for two different jar test configurations (i.e., radial vs. axial impellers at different impeller velocities) and compared the hydrodynamics in these jar tests to those in a representative section of a full scale reactor using computational fluid dynamics (CFD). The analysis showed that the flocculation performance was highly influenced by the impeller type and its speed. The axial impeller appeared to be more appropriate for floc formation over a range of impeller speeds as it produced a more homogeneous distribution of local velocity gradients compared to the radial impeller. In contrast, the radial impeller generated larger volumes (%) of high velocity gradients in which floc breakage may occur. Comparison to local velocity gradients in a full scale system showed that also here, high velocity gradients occurred in the region around the impeller, which might significantly hamper the HRAS flocculation process. As such, this study showed that a model based approach was necessary to translate lab scale results to full scale. These new insights can help improve future experimental setups and reactor design for improved HRAS flocculation.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.3390/PR8020131
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“Pinpointing wastewater and process parameters controlling the AOB to NOB activity ratio in sewage treatment plants”. Seuntjens D, Han M, Kerckhof F-M, Boon N, Al-Omari A, Takacs I, Meerburg F, De Mulder C, Wett B, Bott C, Murthy S, Carvajal Arroyo JM, De Clippeleir H, Vlaeminck SE, Water research 138, 37 (2018). http://doi.org/10.1016/J.WATRES.2017.11.044
Abstract: Even though nitrification/denitrification is a robust technology to remove nitrogen from sewage, economic incentives drive its future replacement by shortcut nitrogen removal processes. The latter necessitates high potential activity ratios of ammonia oxidizing to nitrite oxidizing bacteria (rAOB/rNOB). The goal of this study was to identify which wastewater and process parameters can govern this in reality. Two sewage treatment plants (STP) were chosen based on their inverse rAOB/rNOB values (at 20 °C): 0.6 for Blue Plains (BP, Washington DC, US) and 1.6 for Nieuwveer (NV, Breda, NL). Disproportional and dissimilar relationships between AOB or NOB relative abundances and respective activities pointed towards differences in community and growth/activity limiting parameters. The AOB communities showed to be particularly different. Temperature had no discriminatory effect on the nitrifiers' activities, with similar Arrhenius temperature dependences (ΘAOB = 1.10, ΘNOB = 1.061.07). To uncouple the temperature effect from potential limitations like inorganic carbon, phosphorus and nitrogen, an add-on mechanistic methodology based on kinetic modelling was developed. Results suggest that BP's AOB activity was limited by the concentration of inorganic carbon (not by residual N and P), while NOB experienced less limitation from this. For NV, the sludge-specific nitrogen loading rate seemed to be the most prevalent factor limiting AOB and NOB activities. Altogether, this study shows that bottom-up mechanistic modelling can identify parameters that influence the nitrification performance. Increasing inorganic carbon in BP could invert its rAOB/rNOB value, facilitating its transition to shortcut nitrogen removal.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.1016/J.WATRES.2017.11.044
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“Design and construction of an experimental setup to enhance mineral weathering through the activity of soil organisms”. Calogiuri T, Hagens M, Van Groenigen JW, Corbett T, Hartmann J, Hendriksen R, Janssens I, Janssens IA, Ledesma Dominguez G, Loescher G, Mortier S, Neubeck A, Niron H, Poetra RP, Rieder L, Struyf E, Van Tendeloo M, De Schepper T, Verdonck T, Vlaeminck SE, Vicca S, Vidal A, Journal of visualized experiments , e65563 (2023). http://doi.org/10.3791/65563
Abstract: Enhanced weathering (EW) is an emerging carbon dioxide (CO2) removal technology that can contribute to climate change mitigation. This technology relies on accelerating the natural process of mineral weathering in soils by manipulating the abiotic variables that govern this process, in particular mineral grain size and exposure to acids dissolved in water. EW mainly aims at reducing atmospheric CO2 concentrations by enhancing inorganic carbon sequestration. Until now, knowledge of EW has been mainly gained through experiments that focused on the abiotic variables known for stimulating mineral weathering, thereby neglecting the potential influence of biotic components. While bacteria, fungi, and earthworms are known to increase mineral weathering rates, the use of soil organisms in the context of EW remains underexplored. This protocol describes the design and construction of an experimental setup developed to enhance mineral weathering rates through soil organisms while concurrently controlling abiotic conditions. The setup is designed to maximize weathering rates while maintaining soil organisms' activity. It consists of a large number of columns filled with rock powder and organic material, located in a climate chamber and with water applied via a downflow irrigation system. Columns are placed above a fridge containing jerrycans to collect the leachate. Representative results demonstrate that this setup is suitable to ensure the activity of soil organisms and quantify their effect on inorganic carbon sequestration. Challenges remain in minimizing leachate losses, ensuring homogeneous ventilation through the climate chamber, and avoiding flooding of the columns. With this setup, an innovative and promising approach is proposed to enhance mineral weathering rates through the activity of soil biota and disentangle the effect of biotic and abiotic factors as drivers of EW.
Keywords: A1 Journal article; Engineering sciences. Technology; Internet Data Lab (IDLab); Applied mathematics; Sustainable Energy, Air and Water Technology (DuEL); Plant and Ecosystems (PLECO) – Ecology in a time of change
Impact Factor: 1.2
DOI: 10.3791/65563
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“Autotrophic nitrogen polishing of secondary effluents : Alkaline pH and residual nitrate control S0-driven denitratation for downstream anammox treatment”. Xie Y, Van Tendeloo M, Zhu W, Peng L, Vlaeminck SE, Journal of Water Process Engineering 56, 104402 (2023). http://doi.org/10.1016/J.JWPE.2023.104402
Abstract: Energy-lean nitrogen removal technologies, such as partial nitritation/anammox, often encounter effluent issues due to elevated nitrate and ammonium levels. This study proposed a novel autotrophic polishing strategy coupling sulfur-driven denitratation with anammox. To explore the denitratation potential in obtaining stable and sufficient nitrite accumulation, the effects of pH, residual nitrate level, and biomass-specific nitrate loading rate (BSNLR) were investigated in an S0-packed bed reactor at low hydraulic retention time (i.e., 0.2 h). Implementing pH and residual nitrate control strategies would be easier in practice than BSNLR control to polish secondary effluent. Alkaline pH values could realize successful nitrite accumulation without residual nitrate, and further intensify the accumulation under increased residual nitrate levels. The nitrate level was positively correlated with the nitrite accumulation efficiency. At pH 8.5 and nitrate concentration of 1.0 ± 0.8 mg N L−1, sulfur-driven denitratation could successfully maintain nitrite accumulation of 6.4 ± 1.0 mg NO2−-N L−1, ideally for the downstream anammox in case of residual ammonium levels of around 5 mg N L−1. Since Thiobacillus members play a key role in managing nitrite accumulation, their abundance should be guaranteed in the practical application.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 7
DOI: 10.1016/J.JWPE.2023.104402
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“Piloting carbon-lean nitrogen removal for energy-autonomous sewage treatment”. Van Tendeloo M, Bundervoet B, Carlier N, Van Beeck W, Mollen H, Lebeer S, Colsen J, Vlaeminck SE, Environmental Science-Water Research &, Technology 7, 2268 (2021). http://doi.org/10.1039/D1EW00525A
Abstract: Energy-autonomous sewage treatment can be achieved if nitrogen (N) removal does not rely on organic carbon (∼chemical oxygen demand, COD), so that a maximum of the COD can be redirected to energy recovery. Shortcut N removal technologies such as partial nitritation/anammox and nitritation/denitritation are therefore essential, enabling carbon- and energy-lean nitrogen removal. In this study, a novel three-reactor pilot design was tested and consisted of a denitrification, an intermittent aeration, and an anammox tank. A vibrating sieve was added for differential sludge retention time (SRT) control. The 13 m3 pilot was operated on pre-treated sewage (A-stage effluent) at 12–24 °C. Selective suppression of unwanted nitrite-oxidizing bacteria over aerobic ammonium-oxidizing bacteria was achieved with strict floccular SRT management combined with innovative aeration control, resulting in a minimal nitrate production ratio of 17 ± 10%. Additionally, anoxic ammonium-oxidizing bacteria (AnAOB) activity could be maintained in the reactor for at least 150 days because of long granular SRT management and the anammox tank. Consequently, the COD/N removal ratio of 2.3 ± 0.7 demonstrated shortcut N removal almost three times lower than the currently applied nitrification/denitrification technology. The effluent total N concentrations of 17 ± 3 mg TN per L (at 21 ± 1 °C) and 17 ± 6 mg TN per L (at 15 ± 1 °C) were however too high for application at the sewage treatment plant Nieuwveer (Breda, The Netherlands). Corresponding N removal efficiencies were 52 ± 12% and 37 ± 21%, respectively. Further development should focus on redirecting more nitrite to AnAOB in the B-stage, exploring effluent-polishing options, or cycling nitrate for increased A-stage denitrification.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 2.817
DOI: 10.1039/D1EW00525A
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“Proof of concept of high-rate decentralized pre-composting of kitchen waste : optimizing design and operation of a novel drum reactor”. Sakarika M, Spiller M, Baetens R, Donies G, Vanderstuyf J, Vinck K, Vrancken KC, Van Barel G, Du Bois E, Vlaeminck SE, Waste management 91, 20 (2019). http://doi.org/10.1016/J.WASMAN.2019.04.049
Abstract: Each ton of organic household waste that is collected, transported and composted incurs costs (€75/ton gate fee). Reducing the mass and volume of kitchen waste (
KW) at the point of collection can diminish transport requirements and associated costs, while also leading to an overall reduction in gate fees for final processing. To this end, the objective of this research was to deliver a proof of concept for the so-called “urban pre-composter”; a bioreactor for the decentralized, high-rate pre-treatment of KW, that aims at mass and volume reduction at the point of collection. Results show considerable reductions in mass (33%), volume (62%) and organic solids (32%) of real KW, while provision of structure material and separate collection of leachate was found to be unnecessary. The temperature profile, C/N ratio (12) and VS/TS ratio (0.69) indicated that a mature compost can be produced in 68 days (after pre-composting and main composting). An economic Monte Carlo simulation yielded that the urban pre-composter concept is not more expensive than the current approach, provided its cost per unit is €8,000–€14,500 over a 10-year period (OPEX and CAPEX, in 80% of the cases). The urban pre-composter is therefore a promising system for the efficient pre-treatment of organic household waste in an urban context.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL); Product development
DOI: 10.1016/J.WASMAN.2019.04.049
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“Evaluation of lignocellulosic wastewater valorization with the oleaginous yeasts R. kratochvilovae EXF7516 and C. oleaginosum ATCC 20509”. Broos W, Wittner N, Geerts J, Dries J, Vlaeminck SE, Gunde-Cimerman N, Richel A, Cornet I, Fermentation 8, 204 (2022). http://doi.org/10.3390/FERMENTATION8050204
Abstract: During the conversion of lignocellulose, phenolic wastewaters are generated. Therefore, researchers have investigated wastewater valorization processes in which these pollutants are converted to chemicals, i.e., lipids. However, wastewaters are lean feedstocks, so these valorization processes in research typically require the addition of large quantities of sugars and sterilization, which increase costs. This paper investigates a repeated batch fermentation strategy with Rhodotorula kratochvilovae EXF7516 and Cutaneotrichosporon oleaginosum ATCC 20509, without these requirements. The pollutant removal and its conversion to microbial oil were evaluated. Because of the presence of non-monomeric substrates, the ligninolytic enzyme activity was also investigated. The repeated batch fermentation strategy was successful, as more lipids accumulated every cycle, up to a total of 5.4 g/L (23% cell dry weight). In addition, the yeasts consumed up to 87% of monomeric substrates, i.e., sugars, aromatics, and organics acids, and up to 23% of non-monomeric substrates, i.e., partially degraded xylan, lignin, cellulose. Interestingly, lipid production was only observed during the harvest phase of each cycle, as the cells experienced stress, possibly due to oxygen limitation. This work presents the first results on the feasibility of valorizing non-sterilized lignocellulosic wastewater with R. kratochvilovae and C. oleaginosum using a cost-effective repeated batch strategy.
Keywords: A1 Journal article; Pharmacology. Therapy; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL); Biochemical Wastewater Valorization & Engineering (BioWaVE)
DOI: 10.3390/FERMENTATION8050204
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“Urine nitrification with a synthetic microbial community”. Christiaens MER, De Paepe J, Ilgrande C, De Vrieze J, Barys J, Teirlinck P, Meerbergen K, Lievens B, Boon N, Clauwaert P, Vlaeminck SE, Systematic and applied microbiology 42, Unsp 126021 (2019). http://doi.org/10.1016/J.SYAPM.2019.126021
Abstract: During long-term extra-terrestrial missions, food is limited and waste is generated. By recycling valuable nutrients from this waste via regenerative life support systems, food can be produced in space. Astronauts' urine can, for instance, be nitrified by micro-organisms into a liquid nitrate fertilizer for plant growth in space. Due to stringent conditions in space, microbial communities need to be be defined (gnotobiotic); therefore, synthetic rather than mixed microbial communities are preferred. For urine nitrification, synthetic communities face challenges, such as from salinity, ureolysis, and organics. In this study, a synthetic microbial community containing an AOB (Nitrosomonas europaea), NOB (Nitrobacter winogradskyi), and three ureolytic heterotrophs (Pseudomonas fluorescens, Acidovorax delafieldii, and Delftia acidovorans) was compiled and evaluated for these challenges. In reactor 1, salt adaptation of the ammonium-fed AOB and NOB co-culture was possible up to 45 mS cm(-1), which resembled undiluted nitrified urine, while maintaining a 44 +/- 10 mg NH4+-N L-1 d(-1) removal rate. In reactor 2, the nitrifiers and ureolytic heterotrophs were fed with urine and achieved a 15 +/- 6 mg NO3--N L-1 d(-1) production rate for 1% and 10% synthetic and fresh real urine, respectively. Batch activity tests with this community using fresh real urine even reached 29 +/- 3 mg N L-1 d(-1). Organics removal in the reactor (69 +/- 15%) should be optimized to generate a nitrate fertilizer for future space applications. (C) 2019 Elsevier GmbH. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.1016/J.SYAPM.2019.126021
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“A bioreactor and nutrient balancing approach for the conversion of solid organic fertilizers to liquid nitrate-rich fertilizers : mineralization and nitrification performance complemented with economic aspects”. Xie Y, Spiller M, Vlaeminck SE, The science of the total environment 806, 150415 (2022). http://doi.org/10.1016/J.SCITOTENV.2021.150415
Abstract: Due to the high water- and nutrient-use efficiency, hydroponic cultivation is increasingly vital in progressing to environment-friendly food production. To further alleviate the environmental impacts of synthetic fertilizer production, the use of recovered nutrients should be encouraged in horticulture and agriculture at large. Solid organic fertilizers can largely contribute to this, yet their physical and chemical nature impedes application in hydroponics. This study proposes a bioreactor for mineralization and nitrification followed by a supplementation step for limiting macronutrients to produce nitrate-based solutions from solid fertilizers, here based on a novel microbial fertilizer. Batch tests showed that aerobic conversions at 35 °C could realize a nitrate (NO₃−-N) production efficiency above 90% and a maximum rate of 59 mg N L−1 d−1. In the subsequent bioreactor test, nitrate production efficiencies were lower (44–51%), yet rates were higher (175–212 mg N L−1 d−1). Calcium and magnesium hydroxide were compared to control the bioreactor pH at 6.0 ± 0.2, while also providing macronutrients for plant production. A mass balance estimation to mimic the Hoagland nutrient solution showed that 92.7% of the NO₃−-N in the Ca(OH)₂ scenario could be organically sourced, while this was only 37.4% in the Mg(OH)₂ scenario. Besides, carbon dioxide (CO₂) generated in the bioreactor can be used for greenhouse carbon fertilization to save operational expenditure (OPEX). An estimation of the total OPEX showed that the production of a nutrient solution from solid organic fertilizers can be cost competitive compared to using commercially available liquid inorganic fertilizer solutions.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 9.8
DOI: 10.1016/J.SCITOTENV.2021.150415
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“Screen versus cyclone for improved capacity and robustness for sidestream and mainstream deammonification”. Van Winckel T, Vlaeminck SE, Al-Omari A, Bachmann B, Sturm B, Wett B, Takács I, Bott C, Murthy SN, De Clippeleir H, Environmental Science: Water Research &, Technology 5, 1769 (2019). http://doi.org/10.1039/C9EW00384C
Abstract: Deammonification systems are being implemented as cost- and resource-efficient nitrogen removal processes. However, their complexity is a major hurdle towards successful transposition from side- to mainstream application. Merely out-selecting nitrite oxidizing bacteria (NOB) or retaining anammox bacteria (AnAOB) does not guarantee efficient mainstream deammonification. This paper presents for the first time the interactions and synergies between kinetic selection, through management of residual substrates, and physical selection, through separation of solid retention times (SRTs). This allowed the formulation of tangible operational recommendations for successful deammonification. Activity measurements were used to establish retention efficiencies (η) for AnAOB for full-scale cyclones and rotating drum screens installed at a sidestream and mainstream deammonification reactor (Strass, Austria). In the sidestream reactor, using a screen (η = 91%) instead of a cyclone (η = 88%) may increase the capacity by up to 29%. For the mainstream reactor, higher AnAOB retention efficiencies achieved by the screen (η = 72%) compared to the cyclone (η = 42%) induced a prospective increase in capacity by 80–90%. In addition, the switch in combination with bioaugmentation from the sidestream made the process less dependent on nitrite availability, thus aiding in the outselection of NOB. This allowed for a more flexible (intermittent) aeration strategy and a reduced need for tight SRT control for NOB washout. A sensitivity analysis explored expected trends to provide possible operational windows for further calibration. In essence, characterization of the physical selectors at full scale allowed a deeper understanding of operational windows of the process and quantification of capacity, ultimately leading to a more space and energy conservation process.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.1039/C9EW00384C
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“13C incorporation as a tool to estimate biomass yields in thermophilic and mesophilic nitrifying communities”. Vandekerckhove TGL, Bodé, S, De Mulder C, Vlaeminck SE, Boon N, Frontiers in microbiology 10, 192 (2019). http://doi.org/10.3389/FMICB.2019.00192
Abstract: 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 (Ymax), based on 13C 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 (1528∘C) and thermophilic (50∘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 13C 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. 0.060.11 g VSS g-1 N), possibly linked to a more efficient pathway for CO2 incorporation. NOB thermophilically produced less biomass (0.0250.028 vs. 0.0480.051 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 Ymax of ammonia and nitrite oxidizers in mixed communities.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.3389/FMICB.2019.00192
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“Empowering a mesophilic inoculum for thermophilic nitrification : growth mode and temperature pattern as critical proliferation factors for archaeal ammonia oxidizers”. Courtens ENP, Vandekerckhove T, Prat D, Vilchez-Vargas R, Vital M, Pieper DH, Meerbergen K, Lievens B, Boon N, Vlaeminck SE, Water research 92, 94 (2016). http://doi.org/10.1016/J.WATRES.2016.01.022
Abstract: Cost-efficient biological treatment of warm nitrogenous wastewaters requires the development of thermophilic nitrogen removal processes. Only one thermophilic nitrifying bioreactor was described so far, achieving 200 mg N L-1 d-1 after more than 300 days of enrichment from compost samples. From the practical point of view in which existing plants would be upgraded, however, a more time-efficient development strategy based on mesophilic nitrifying sludge is preferred. This study evaluated the adaptive capacities of mesophilic nitrifying sludge for two linear temperature increase patterns (non-oscillating vs. oscillating), two different slopes (0.25 vs. 0.08 °C d-1) and two different reactor types (floc vs. biofilm growth). The oscillating temperature pattern (0.25 °C d-1) and the moving bed biofilm reactor (0.08 °C d-1) could not reach nitrification at temperatures higher than 46°C. However, nitrification rates up to 800 mg N L-1 d-1 and 150 mg N g-1 volatile suspended solids d-1 were achieved at a temperature as high as 49°C by imposing the slowest linear temperature increase to floccular sludge. Microbial community analysis revealed that this successful transition was related with a shift in ammonium oxidizing archaea dominating ammonia oxidizing bacteria, while for nitrite oxidation Nitrospira spp. was constantly more abundant than Nitrobacter spp.. This observation was accompanied with an increase in observed sludge yield and a shift in maximal optimum temperature, determined with ex-situ temperature sensitivity measurements, predicting an upcoming reactor failure at higher temperature. Overall, this study achieved nitrification at 49°C within 150 days by gradual adaptation of mesophilic sludge, and showed that ex-situ temperature sensitivity screening can be used to monitor and steer the transition process.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.1016/J.WATRES.2016.01.022
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“Harvesting time and biomass composition affect the economics of microalgae production”. Sui Y, Jiang Y, Moretti M, Vlaeminck SE, Journal Of Cleaner Production 259, 120782 (2020). http://doi.org/10.1016/J.JCLEPRO.2020.120782
Abstract: Cost simulations provide a strong tool to render the production of microalgae economically viable. This study evaluated the unexplored effect of harvesting time and the corresponding microalgal biomass composition on the overall production cost, under both continuous light and light/dark regime using techno-economic analysis (TEA). At the same time, the TEA gives evidence that a novel product “proteinaceous salt” from Dunaliella microalgae production is a promising high-value product for commercialization with profitability. The optimum production scenario is to employ natural light/dark regime and harvest microalgal biomass around late exponential phase, obtaining the minimum production cost of 11 €/kg and a profitable minimum selling price (MSP) of 14.4 €/kg for the “proteinaceous salt”. For further optimization of the production, increasing microalgal biomass concentration is the most effective way to reduce the total production cost and increase the profits of microalgae products.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL); Engineering Management (ENM)
Impact Factor: 11.1
Times cited: 5
DOI: 10.1016/J.JCLEPRO.2020.120782
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“Boosting aerobic microbial protein productivity and quality on brewery wastewater : impact of anaerobic acidification, high-rate process and biomass age”. Papini G, Muys M, Van Winckel T, Meerburg FA, Van Beeck W, Vermeir P, Vlaeminck SE, Bioresource technology 368, 128285 (2023). http://doi.org/10.1016/J.BIORTECH.2022.128285
Abstract: Consortia of aerobic heterotrophic bacteria (AHB) are appealing as sustainable alternative protein ingredient for aquaculture given their high nutritional qualities, and their production potential on feed-grade industrial wastewater. Today, the impacts of pre-treatment, bioprocess choice and key parameter settings on AHB productivity and nutritional properties are unknown. This study investigated for the first time AHB microbial protein production effects based on (i) raw vs anaerobically fermented brewery wastewater, (ii) high-rate activated sludge (HRAS) without vs with feast-famine conditions, and (iii) three short solid retention time (SRT): 0.25, 0.50 and 1.00 d. High biomass (4.4–8.0 g TSS/L/d) and protein productivities (1.9–3.2 g protein/L/d) were obtained while achieving COD removal efficiencies up to 98 % at SRT 0.50 d. The AHB essential amino acid (EAA) profiles were above rainbow trout requirements, excluding the S-containing EAA, highlighting the AHB biomass replacement potential for unsustainable fishmeal in salmonid diets.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 11.4
DOI: 10.1016/J.BIORTECH.2022.128285
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“Nitrous oxide emissions and carbon footprint of decentralized urine fertilizer production by nitrification and distillation”. Faust V, Gruber W, Ganigue R, Vlaeminck SE, Udert KM, ACS ES&T engineering 2, 1745 (2022). http://doi.org/10.1021/ACSESTENGG.2C00082
Abstract: Combining partial nitrification, granular activated carbon (GAC) filtration, and distillation is a well-studied approach to convert urine into a fertilizer. To evaluate the environmental sustainability of a technology, the operational carbon footprint and therefore nitrous oxide (N2O) emissions should be known, but N2O emissions from urine nitrification have not been assessed yet. Therefore, N2O emissions of a decentralized urine nitrification reactor were monitored for 1 month. During nitrification, 0.4-1.2% of the total nitrogen load was emitted as N2O-N with an average N2O emission factor (EFN2O) of 0.7%. Additional N2O was produced during anoxic storage between nitrification and GAC filtration with an estimated EFN2O of 0.8%, resulting in an EFN2O of 1.5% for the treatment chain. N2O emissions during nitrification can be mitigated by 60% by avoiding low dissolved oxygen or anoxic conditions and nitrite concentrations above 5 mg-N L-1. Minimizing the hydraulic retention time between nitrification and GAC filtration can reduce N2O formation during intermediate storage by 100%. Overall, the N2O emissions accounted for 45% of the operational carbon footprint of 14 kg-CO2,equiv kg-N-1 for urine fertilizer production. Using electricity from renewable sources and applying the proposed N2O mitigation strategies could potentially lower the carbon footprint by 85%.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.1021/ACSESTENGG.2C00082
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“Solubilization of struvite as a sustainable nutrient source for single cell protein production”. Muys M, Derese S, Verliefde A, Vlaeminck SE, Communications in agricultural and applied biological sciences 81, 179 (2016)
Abstract: By 2050, the world population will have considerably expanded and the life standard of many will increase, yielding a 50% higher demand in protein (FAO, 2011), and even increases of 82 and 102% for diary and meat products, respectively (Boland et al., 2013). To provide in this increasing demand we are highly dependent on our classical fertilizer to food chain which has a high environmental impact and lacks efficiency. Nutrient losses cause eutrophication and biodiversity loss and the input of resources is already beyond the boundaries of environmental sustainability (Steffen et al., 2015). Phosphate fertilizers are made from phosphate rock (apatite), of which the reserves are predicted to be depleted within 50 100 years if we continue business as usual (Cordell et al., 2009). Next to problems related to the unbalanced geopolitical distribution with dominance in China and Morocco, the decreasing quality of the remaining apatite will result in an increasing environmental impact of fertilizer production. Finally, our traditional food production model requires 30% of all ice-free land, 70% of all available freshwater and produces up to one third of the global greenhouse gas emission, of which 80 to 86% is linked to agricultural production (Vermeulen et al., 2012). To ensure food security, nutrient recovery from waste streams can provide an important strategy. In this context, struvite ( ) crystallisation may be applied to recover phosphorus, along with some nitrogen. Reusing these nutrients as agricultural fertilizer on the field will lead to considerable losses to the environment. In contrast, their use to cultivate micro-organisms, e.g. for single cell protein (SCP), offers to potential of a near perfect conversion efficiency (Moed et al., 2015). At this moment, microalgae represent the most developed type of SCP, and are a promising protein source due to their growth rate, high nutritional quality and extremely high nutrient usage efficiency (Becker, 2007). Reliable solubilisation data are essential to design a technological strategy for struvite dosage in bioreactors for SCP production. The effect on solubility and solubilisation rate of relevant physicochemical parameters was studied experimentally in aqueous solutions. Because pH and temperature greatly affect solubilisation kinetics they were set at a constant value of 7 and 20°C respectively. The effect of some parameters on struvite solubility was already studied (Bhuiyan et al., 2007; Ariyanto et al., 2014; Roncal-Herrero and Oelkers, 2011), but solubilisation rates were not yet considered and pH was not controlled at a constant value. The chemical parameters considered in this study include the concentration of different common ions ( and ), foreign ions ( and the chelating agent ethylenediaminetetraacetic acid, EDTA) present in micro-algal cultivation media as well as ionic strength (as set by NaCl). The main physical parameter included was contact surface, through variation in initial particle size and as well as in struvite dosage concentration.
Keywords: A2 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
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“Storage without nitrite or nitrate enables the long-term preservation of full-scale partial nitritation/anammox sludge”. Zhu W, Van Tendeloo M, Xie Y, Timmer MJ, Peng L, Vlaeminck SE, The science of the total environment 806, 151330 (2022). http://doi.org/10.1016/J.SCITOTENV.2021.151330
Abstract: Bioaugmentation with summer harvested sludge during winter could compensate for bacterial activity loss but requires that sludge activity can be restored after storage. This study assesses the effect of temperature and redox adjustment during the storage over 180 days of partial nitritation/anammox (PN/A) granular resp. floccular sludge from potato processing resp. sludge reject water treatment. Anoxic storage conditions (in the presence of nitrite or nitrate and the absence of oxygen) resulted in a loss of 80-100% of the anammox bacteria (AnAOB) activity capacity at 20 degrees C and 4 degrees C, while anaerobic conditions (without oxygen, nitrite, and nitrate) lost only 45-63%. Storage at 20 degrees C was more cost-effective compared to 4 degrees C, and this was confirmed in the sludge reactivation experiment (20 CC). Furthermore, AnAOB activity correlated negatively with the electrical conductivity level (R-2 > 0.85, p < 0.05), so strong salinity increases should be avoided. No significant differences were found in the activity capacity of aerobic ammonia-oxidizing bacteria (AerAOB) under different storage conditions (p > 0.1). The relative abundance of dominant AnAOB (Candidatus Brocadia) and AerAOB genera (Nitrosomonas) remained constant in both sludges. In conclusion, preserving PN/A biomass without cooling and nitrite or nitrate addition proved to be a cost-effective strategy. (C) 2021 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 9.8
DOI: 10.1016/J.SCITOTENV.2021.151330
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“Effects of salinity, pH and growth phase on the protein productivity by Dunaliella salina”. Sui Y, Vlaeminck SE, Journal of chemical technology and biotechnology 94, 1032 (2019). http://doi.org/10.1002/JCTB.5850
Abstract: 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 increasedecrease pattern throughout the growth phases, with a maximum in the exponential phase (6080% 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 (13 mol L−1 salinity, pH 7.59.5), 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 1697%. 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.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.1002/JCTB.5850
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“Sulfur-based denitrification treating regeneration water from ion exchange at high performance and low cost”. Vandekerckhove TGL, Kobayashi K, Janda J, Van Nevel S, Vlaeminck SE, Bioresource technology 257, 266 (2018). http://doi.org/10.1016/J.BIORTECH.2018.02.047
Abstract: Autotrophic denitrification with sulfur is an underexplored alternative to heterotrophic denitrification to remove nitrate from wastewater poor in organics. The application on ion exchange regeneration water (19.432.1 mS cm−1) is novel. Three fixed bed reactors were tested at 15 °C for >4 months, inoculated with activated sludge from sewage treatment. All were fast in start-up (<10 days) with high performance (94 ± 2% removal efficiency). pH control with NaOH rendered higher nitrate removal rates than limestone addition to the bed (211 ± 13 vs. 102 ± 13 mg N L−1 d−1), related to higher pH (6.64 vs. 6.24) and sulfur surface area. Bacterial communities were strongly enriched in Sulfurimonas (6367%) and Thiobacillus (2426%). In an economic comparison, sulfur-based denitrification (5.3 kg−1 N) was 15% cheaper than methanol-based denitrification (6.22 kg−1 N) and both treatments were opex dominated (85.9 vs. 86.5%). Overall, the technological and economic feasibility should boost further implementation of sulfurotrophic denitrification.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.1016/J.BIORTECH.2018.02.047
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“Purple bacteria as added-value protein ingredient in shrimp feed : Penaeus vannamei growth performance, and tolerance against Vibrio and ammonia stress”. Alloul A, Wille M, Lucenti P, Bossier P, Van Stappen G, Vlaeminck SE, Aquaculture 530, 735788 (2021). http://doi.org/10.1016/J.AQUACULTURE.2020.735788
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).
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 2.57
DOI: 10.1016/J.AQUACULTURE.2020.735788
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“Adaptation and characterization of thermophilic anammox in bioreactors”. Vandekerckhove TGL, Props R, Carvajal-Arroyo JM, Boon N, Vlaeminck SE, Water Research 172, 115462 (2020). http://doi.org/10.1016/J.WATRES.2019.115462
Abstract: Anammox, the oxidation of ammonium with nitrite, is a key microbial process in the nitrogen cycle. Under mesophilic conditions (below 40 °C), it is widely implemented to remove nitrogen from wastewaters lacking organic carbon. Despite evidence of the presence of anammox bacteria in high-temperature environments, reports on the cultivation of thermophilic anammox bacteria are limited to a short-term experiment of 2 weeks. This study showcases the adaptation of a mesophilic inoculum to thermophilic conditions, and its characterization. First, an attached growth technology was chosen to obtain the process. In an anoxic fixed-bed biofilm bioreactor (FBBR), a slow linear temperature increase from 38 to over 48 °C (0.05–0.07 °C d−1) was imposed to the community over 220 days, after which the reactor was operated at 48 °C for over 200 days. Maximum total nitrogen removal rates reached up to 0.62 g N L−1 d−1. Given this promising performance, a suspended growth system was tested. The obtained enrichment culture served as inoculum for membrane bioreactors (MBR) operated at 50 °C, reaching a maximum total nitrogen removal rate of 1.7 g N L−1 d−1 after 35 days. The biomass in the MBR had a maximum specific anammox activity of 1.1 ± 0.1 g NH4+-N g−1 VSS d−1, and the growth rate was estimated at 0.075–0.19 d−1. The thermophilic cultures displayed nitrogen stoichiometry ratios typical for mesophilic anammox: 0.93–1.42 g NO2--Nremoved g−1 NH4+-Nremoved and 0.16–0.35 g NO3--Nproduced g−1 NH4+-Nremoved. Amplicon and Sanger sequencing of the 16S rRNA genes revealed a disappearance of the original “Ca. Brocadia” and “Ca. Jettenia” taxa, yielding Planctomycetes members with only 94–95% similarity to “Ca. Brocadia anammoxidans” and “Ca. B. caroliniensis”, accounting for 45% of the bacterial FBBR community. The long-term operation of thermophilic anammox reactors and snapshot views on the nitrogen stoichiometry, kinetics and microbial community open up the development path of thermophilic partial nitritation/anammox. A first economic assessment highlighted that treatment of sludge reject water from thermophilic anaerobic digestion of sewage sludge may become attractive.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 12.8
Times cited: 5
DOI: 10.1016/J.WATRES.2019.115462
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“Fertilizer type influences dynamics of the microbial community structure in the rhizosphere of tomato and impact the nutrient turnover and plant performance”. Grunert O, Robles Aguilar AA, Hernandez-Sanabria E, Reheul D, Vlaeminck SE, Boon N, Jablonowski ND, Communications in agricultural and applied biological sciences 81, 67 (2016)
Abstract: Ammonia-oxidizing microorganisms (AOB and AOA) and nitrite oxidizing bacteria (NOB) are the most important organisms responsible for ammonia and nitrite oxidation in agricultural ecosystems and growing media. Ammonia and nitrite oxidation are critical steps in the soil nitrogen cycle and can be affected by the application of mineral fertilizers or organic fertilizers. The functionality of the microbial community has a major impact on the nutrient turnover and will finally influence plant performance. The microbial community associated with the growing medium and its functionality will also be influenced by the rhizosphere and the bulk soil. In our study, we used a tomato plant with a high root exudation capacity in order to stimulate microbial activity. We studied plant performance in rhizotrons (a phentotyping system for imaging roots), including an optical method (planar optodes) for non-invasive, quantitative and high-resolution imaging of pH dynamics in the rhizosphere and adjacent medium. The horticultural growing medium was supplemented with organic-derived nitrogen or ammonium derived from struvite. The possible differences in the root structure between treatments is compared with the total root length. Destructive growing medium sampling and high throughput sequencing analysis of the bacterial abundance of the communities present in the rhizosphere and the bulk soil is used to study the growing medium-associated microbial community structure and functionality, and this will be related to pH changes in the rhizosphere and the bulk soil. Our hypothesis is that the growing medium-associated microbial community structure changes depending on the nitrogen form provided and we expect a higher abundance of bacteria in the treatment with organic fertilizer and a higher abundance of AOB and NOB in the rhizosphere in comparison to the bulk soil.
Keywords: A2 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
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“Cocultivating aerobic heterotrophs and purple bacteria for microbial protein in sequential photo- and chemotrophic reactors”. Alloul A, Muys M, Hertoghs N, Kerckhof F-M, Vlaeminck SE, Bioresource Technology 319, 124192 (2021). http://doi.org/10.1016/J.BIORTECH.2020.124192
Abstract: Aerobic heterotrophic bacteria (AHB) and purple non-sulfur bacteria (PNSB) are typically explored as two separate types of microbial protein, yet their properties as respectively a bulk and added-value feed ingredient make them appealing for combined use. The feasibility of cocultivation in a sequential photo- and chemotrophic approach was investigated. First, mapping the chemotrophic growth kinetics for four Rhodobacter, Rhodopseudomonas and Rhodospirillum species on different carbon sources showed a preference for fructose (µmax 2.4–3.9 d−1 28 °C; protein 36–59%DW). Secondly, a continuous photobioreactor inoculated with Rhodobacter capsulatus (VFA as C-source) delivered the starter culture for an aerobic batch reactor (fructose as C-source). This two-stage system showed an improved nutritional quality compared to AHB production: higher protein content (45–71%DW), more attractive amino/fatty acid profile and contained up to 10% PNSB. The findings strengthen protein production with cocultures and might enable the implementation of the technology for resource recovery on streams such as wastewater.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 5.651
DOI: 10.1016/J.BIORTECH.2020.124192
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“Ammonia oxidation by novel “Candidatus Nitrosacidococcus urinae&rdquo, is sensitive to process disturbances at low pH and to iron limitation at neutral pH”. Faust V, van Alen TA, Op den Camp HJM, Vlaeminck SE, Ganigué, R, Boon N, Udert KM, Water Research X 17, 100157 (2022). http://doi.org/10.1016/J.WROA.2022.100157
Abstract: Acid-tolerant ammonia-oxidizing bacteria (AOB) can open the door to new applications, such as partial nitritation at low pH. However, they can also be problematic because chemical nitrite oxidation occurs at low pH, leading to the release of harmful nitrogen oxide gases. In this publication, the role of acid-tolerant AOB in urine treatment was explored. On the one hand, the technical feasibility of ammonia oxidation under acidic conditions for source-separated urine with total nitrogen concentrations up to 3.5 g-N L−1 was investigated. On the other hand, the abundance and growth of acid-tolerant AOB at more neutral pH was explored. Under acidic conditions (pH of 5), ammonia oxidation rates of 500 mg-N L−1 d−1 and 10 g-N g-VSS-1 d-1 were observed, despite high concentrations of 15 mg-N L−1 of the AOB-inhibiting compound nitrous acid and low concentration of 0.04 mg-N L−1 of the substrate ammonia. However, ammonia oxidation under acidic conditions was very sensitive to process disturbances. Even short periods of less than 12 h without oxygen or without influent resulted in a complete cessation of ammonia oxidation with a recovery time of up to two months, which is a problem for low maintenance applications such as decentralized treatment. Furthermore, undesirable nitrogen losses of about 10% were observed. Under acidic conditions, a novel AOB strain was enriched with a relative abundance of up to 80%, for which the name “Candidatus (Ca.) Nitrosacidococcus urinae” is proposed. While Nitrosacidococcus members were present only to a small extent (0.004%) in urine nitrification reactors operated at pH values between 5.8 and 7, acid-tolerant AOB were always enriched during long periods without influent, resulting in an uncontrolled drop in pH to as low as 2.5. Long-term experiments at different pH values showed that the activity of “Ca. Nitrosacidococcus urinae” decreased strongly at a pH of 7, where they were also outcompeted by the acid-sensitive AOB Nitrosomonas halophila. The experiment results showed that the decreased activity of “Ca. Nitrosacidococcus urinae” correlated with the limited availability of dissolved iron at neutral pH.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.1016/J.WROA.2022.100157
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“Synergistic exposure of return-sludge to anaerobic starvation, sulfide and free ammonia to suppress nitrite oxidizing bacteria”. Seuntjens D, Van Tendeloo M, Chatzigiannidou I, Carvajal-Arroyo JM, Vandendriessche S, Vlaeminck SE, Boon N, Environmental science and technology 52, 8725 (2018). http://doi.org/10.1021/ACS.EST.7B06591
Abstract: A key step toward energy-positive sewage treatment is the development of mainstream partial nitritation/anammox, a nitrogen removal technology where aerobic ammonium-oxidizing bacteria (AerAOB) are desired, while nitrite-oxidizing bacteria (NOB) are not. To suppress NOB, a novel return-sludge treatment was investigated. Single and combined effects of sulfide (0-600 mg S L-1), anaerobic starvation (0-8 days), and a free ammonia (FA) shock (30 mg FA-N L-1 for 1 h) were tested for immediate effects and long-term recovery. AerAOB and NOB were inhibited immediately and proportionally by sulfide, with AerAOB better coping with the inhibition, while the short FA shock and anaerobic starvation had minor effects. Combinatory effects inhibited AerAOB and NOB more strongly. A combined treatment of sulfide (150 mg S L-1), 2 days of anaerobic starvation, and FA shock (30 mg FA-N L-1) inhibited AerAOB 14% more strongly compared to sulfide addition alone, while the AerAOB/NOB activity ratio remained constant. Despite no positive change being observed in the immediate-stress response, AerAOB recovered much faster than NOB, with a nitrite accumulation ratio (effluent nitrite on nitrite + nitrate) peak of 50% after 12 days. Studying long-term recovery is therefore crucial for design of an optimal NOB-suppression treatment, while applying combined stressors regularly may lead toward practical implementation.
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.1021/ACS.EST.7B06591
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“Dried aerobic heterotrophic bacteria from treatment of food and beverage effluents: Screening of correlations between operation parameters and microbial protein quality”. Muys M, Papini G, Spiller M, Sakarika M, Schwaiger B, Lesueur C, Vermeir P, Vlaeminck SE, Bioresource Technology 307, 123242 (2020). http://doi.org/10.1016/J.BIORTECH.2020.123242
Keywords: A1 Journal article; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 11.4
Times cited: 1
DOI: 10.1016/J.BIORTECH.2020.123242
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“The age of wastewater mining : selection for sludge with a maximum capture potential for organics in a high-rate contact stabilization system”. Meerburg FA, Boon N, Van Winckel T, Pauwels K, Vlaeminck SE, , 3 p.
T2 (2015)
Keywords: P3 Proceeding; Engineering sciences. Technology; Sustainable Energy, Air and Water Technology (DuEL)
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