New insights in the metabolic behaviour of PAO under negligible poly-P reserves

[EN] In a previous study the authors confirmed the ability of PAOs to perform GAO metabolism in short-term experiments. However, what happens when PAOs are exposed to poly-P shortage for an extended period of time? The answer to this question was the aim of this work from a macroscopic and microscopic point of view. Therefore, the poly-P was removed from a PAO enriched SBR and maintained without poly-P during five solid retention time. The PAOs were found to quickly change their metabolism to a clear GAO performance and remained without GAO colonization for the entire experimental period, even though GAO was present (around 5%) at the beginning of the experiment. Unlike the results obtained in the short-term experiments, in this case PAO Type I performed the GAO metabolism at the end of the experimental period. (C) 2016 Elsevier B.V. All rights reserved.This research work has been supported by the Generalitat Valenciana (GVPRE/2008/044) and the Polytechnic University of Valencia (PAID-06-08-3227), which are gratefully acknowledged. Special acknowledgements to the Consejo Nacional de Ciencia y Tecnologia de Mexico (CONACYT) No. 207966.Acevedo Juárez, B.; Murgui Mezquita, M.; Borrás Falomir, L.; Barat, R. (2017). New insights in the metabolic behaviour of PAO under negligible poly-P reserves. Chemical Engineering Journal. 311:82-90. https://doi.org/10.1016/j.cej.2016.11.073S829031

Thermophilic anaerobic conversion of raw microalgae: Microbial community diversity in high solids retention systems

[EN] The potential of microbial communities for efficient anaerobic conversion of raw microalgae was evaluated in this work. A long-term operated thermophilic digester was fed with three different Organic Loading Rates (OLR) (0.2, 0.3 and 0.4¿g·L¿1·d¿1) reaching 32¿41% biodegradability values. The microbial community analysis revealed a remarkable presence of microorganisms that exhibit high hydrolytic capabilities such as Thermotogae (~44.5%), Firmicutes (~17.6%) and Dictyoglomi, Aminicenantes, Atribacteria and Planctomycetes (below ~5.5%) phyla. The suggested metabolic role of these phyla highlights the importance of protein hydrolysis and fermentation when only degrading microalgae. The ecological analysis of the reactor suggests the implication of the novel group EM3 in fermentation and beta-oxidation pathways during microalgae conversion into methane. Scenedesmus spp. substrate and free ammonia concentration strongly shaped thermophilic reactor microbial structure. Partial Least Square Discriminant Analysis (PLS-DA) remarked the resilient role of minor groups related to Thermogutta, Armatimonadetes and Ruminococcaceae against a potential inhibitor like free ammonia. Towards low-cost biogas production from microalgae, this study reveals valuable information about thermophilic microorganisms that can strongly disrupt microalgae and remain in high solids retention anaerobic digesters.This research work has been supported by the Spanish Ministry of Economy and Competitiveness (MINECO, Project CTM2011-28595-C02-02) jointly with the European Regional Development Fund (ERDF), which are gratefully acknowledged. The authors are thankful to Fernando Fdz-Polanco research team (University of Valladolid, Spain) for providing the thermophilic sludge from their pilot plant to inoculate the bioreactor and Llúcia Martínez and Giusseppe D'Aria from FISABIO sequencing service (Valencia, Spain) for their technical support during the Illumina sequencing design.Zamorano-López, N.; Greses-Huerta, S.; Aguado García, D.; Seco Torrecillas, A.; Borrás Falomir, L. (2019). Thermophilic anaerobic conversion of raw microalgae: Microbial community diversity in high solids retention systems. Algal Research. 41:1-9. https://doi.org/10.1016/j.algal.2019.101533S194

Acclimatised rumen culture for raw microalgae conversion into biogas: Linking microbial community structure and operational parameters in anaerobic membrane bioreactors (AnMBR)

[EN] Ruminal fluid was inoculated in an Anaerobic Membrane Reactor (AnMBR) to produce biogas from raw Scenedesmus. This work explores the microbial ecology of the system during stable operation at different solids retention times (SRT). The 16S rRNA amplicon analysis revealed that the acclimatised community was mainly composed of Anaerolineaceae, Spirochaetaceae, Lentimicrobiaceae and Cloacimonetes fermentative and hydrolytic members. During the highest biodegradability achieved in the AnMBR (62%) the dominant microorganisms were Fervidobacterium and Methanosaeta. Different microbial community clusters were observed at different SRT conditions. Interestingly, syntrophic bacteria Gelria and Smithella were enhanced after increasing 2-fold the organic loading rate, suggesting their importance in continuous systems producing biogas from raw microalgae.This research work has been supported by the Spanish Ministry of Economy and Competitiveness (MINECO, Projects CTM2011-28595-C02-01 and CTM2011-28595-C02-02), which is gratefully acknowledged. The Education, Investigation, Culture and sports Council from the Valencian Generality for the Post-Doctoral fellowship of the third co-author is also acknowledged (APOSTD/2016/104). The authors are thankful to Ion Pérez Baena from the Universitat Politècnica de Valencia, Institut de Ciència I Tecnología Animal for gently providing the ruminal fluid use in this work.Zamorano-López, N.; Borrás Falomir, L.; Giménez, JB.; Seco Torrecillas, A.; Aguado García, D. (2019). Acclimatised rumen culture for raw microalgae conversion into biogas: Linking microbial community structure and operational parameters in anaerobic membrane bioreactors (AnMBR). Bioresource Technology. 290:1-9. https://doi.org/10.1016/j.biortech.2019.121787S1929

Effect of long residence time and high temperature over anaerobic biodegradation of Scenedesmus microalgae grown in wastewater

[EN] Anaerobic digestion of indigenous Scenedesmus spp. microalgae was studied in continuous lab-scale anaerobic reactors at different temperatures (35 degrees C and 55 degrees C), and sludge retention time - SRT (50 and 70 days). Mesophilic digestion was performed in a continuous stirred-tank reactor (CSTR) and in an anaerobic membrane bioreactor (AnMBR). Mesophilic CSTR operated at 50 days SRT only achieved 11.9% of anaerobic biodegradability whereas in the AnMBR at 70 days SRT and 50 days HRT reached 39.5%, which is even higher than the biodegradability achieved in the thermophilic CSTR at 50 days SRT (30.4%). Microbial analysis revealed a high abundance of cellulose-degraders in both reactors, AnMBR (mainly composed of 9.4% Bacteroidetes, 10.1% Chloroflexi, 8.0% Firmicutes and 13.2% Thermotogae) and thermophilic CSTR (dominated by 23.8% Chloroflexi and 12.9% Firmicutes). However, higher microbial diversity was found in the AnMBR compared to the thermophilic CSTR which is related to the SRT. since high SRT promoted low growth-rate microorganisms, increasing the hydrolytic potential of the system. These results present the membrane technology as a promising approach to revalue microalgal biomass, suggesting that microalgae biodegradability and consequently the methane production could be improved operating at higher SRT. (C) 2018 Elsevier Ltd. All rights reserved.This research work has been supported by the Spanish Ministry of Economy and Competitiveness (MINECO, Project CTM2011-28595-C02-01/02) jointly with the European Regional Development Fund (ERDF), which are gratefully acknowledged. The authors are thankful to Fernando Fernandez-Polanco for providing the thermophilic sludge to inoculate the reactor.This research work has been financially supported by the Generalitat Valenciana (PROMETEO/2012/029 PROJECT), which is gratefully acknowledged.Greses-Huerta, S.; Zamorano -López, N.; Borrás Falomir, L.; Ferrer, J.; Seco Torrecillas, A.; Aguado García, D. (2018). Effect of long residence time and high temperature over anaerobic biodegradation of Scenedesmus microalgae grown in wastewater. Journal of Environmental Management. 218:425-434. https://doi.org/10.1016/j.jenvman.2018.04.086S42543421

A multivariate approach of changes in filamentous, nitrifying and protist communities and nitrogen removal efficiencies during ozone dosage in a full-scale wastewater treatment plant

[EN] The application of low ozone dosage to minimize the problems caused by filamentous foaming was evaluated in two bioreactors of an urban wastewater treatment plant. Filamentous and nitrifying bacteria, as well as protist and metazoa, were monitored throughout a one-year period by FISH and conventional microscopy to examine the effects of ozone application on these specific groups of microorganisms. Multivariate data analysis was used to determine if the ozone dosage was a key factor determining the low carbon and nitrogen removal efficiencies observed throughout the study period, as well as to evaluate its impact on the biological communities monitored. The results of this study suggested that ozonation did not significantly affect the COD removal efficiency, although it had a moderate effect on ammonia removal efficiency. Filamentous bacteria were the community most influenced by ozone (24.9% of the variance explained by ozone loading rate), whilst protist and metazoa were less affected (11.9% of the variance explained). Conversely, ozone loading rate was not a factor in determining the nitrifying bacterial community abundance and composition, although this environmental variable was correlated with ammonia removal efficiency. The results of this study suggest that different filamentous morphotypes were selectively affected by ozone. (C) 2019 Elsevier Ltd. All rights reserved.This work was supported by grant from the Entitat de Sanejament d Aigües (EPSAR). P. Barbarroja acknowledges support from MINECO grant PTA2014-09555-I.Barbarroja-Ortiz, P.; Zornoza-Zornoza, AM.; Aguado García, D.; Borrás Falomir, L.; Alonso Molina, JL. (2019). A multivariate approach of changes in filamentous, nitrifying and protist communities and nitrogen removal efficiencies during ozone dosage in a full-scale wastewater treatment plant. Environmental Pollution. 252-B:1500-1508. https://doi.org/10.1016/j.envpol.2019.06.068S15001508252-

Nitrite inhibition of microalgae induced by the competition between microalgae and nitrifying bacteria

Outdoor microalgae cultivation systems treating anaerobic membrane bioreactor (AnMBR) effluents usually present ammonium oxidising bacteria (AOB) competition with microalgae for ammonium uptake, which can cause nitrite accumulation. In literature, nitrite effects over microalgae have shown controversial results. The present study evaluates the nitrite inhibition role in a microalgae-nitrifying bacteria culture. For this purpose, pilot- and lab-scale assays were carried out. During the continuous outdoor operation of the membrane photobioreactor (MPBR) plant, biomass retention time (BRT) of 2 d favoured AOB activity, which caused nitrite accumulation. This nitrite was confirmed to inhibit microalgae performance. Specifically, continuous 5-d lab-scale assays showed a reduction in the nitrogen recovery efficiency by 32, 42 and 80% when nitrite concentration in the culture accounted for 5, 10 and 20 mg N·L−1, respectively. On the contrary, short 30-min exposure to nitrite showed no significant differences in the photosynthetic activity of microalgae under nitrite concentrations of 0, 5, 10 and 20 mg N·L−1. On the other hand, when the MPBR plant was operated at 2.5-d BRT, the nitrite concentration was reduced to negligible values due to increasing activity of microalgae and nitrite oxidising bacteria (NOB). This allowed obtaining maximum MPBR performance; i.e. nitrogen recovery rate (NRR) and biomass productivity of 19.7 ± 3.3 mg N·L−1·d−1 and 139 ± 35 mg VSS·L−1·d−1, respectively; while nitrification rate (NOxR) reached the lowest value (13.5 ± 3.4 mg N·L−1·d−1). Long BRT of 4.5 d favoured NOB growth, avoiding nitrite inhibition. However, it implied a decrease in microalgae growth and the accumulation of nitrate in the MPBR effluent. Hence, it seems that optimum BRT has to be within the range 2-4.5 d in order to favour microalgae growth with respect to AOB and NOB

Influence of Food Waste addition over microbial communities in an Anaerobic Membrane Bioreactor plant treating urban wastewater

[EN] Notorious changes in microbial communities were observed during and after the joint treatment of wastewater with Food Waste (FW) in an Anaerobic Membrane Bioreactor (AnMBR) plant. The microbial population was analysed by high-throughput sequencing of the 16S rRNA gene and dominance of Chloroflexi, Firmicutes, Synergistetes and Proteobacteria phyla was found. The relative abundance of these potential hydrolytic phyla increased as a higher fraction of FW was jointly treated. Moreover, whereas Specific Methanogenic Activity (SMA) rose from 10 to 51 mL CH4 g(-1) VS, Methanosarcinales order increased from 34.0% over 80.0% of total Archaea, being Methanosaeta the dominant genus. The effect of FW over AnMBR biomass was observed during the whole experience, as methane production rose from 49.2 to 144.5 L CH4 . kg(-1) influent COD. Furthermore, biomethanization potential was increased over 82% after the experience. AnMBR technology allows the established microbial community to remain in the bioreactor even after the addition of FW, improving the anaerobic digestion of urban wastewater. (C) 2018 Elsevier Ltd. All rights reserved.This research work has been financially supported by the Generalitat Valenciana (PROMETEO/2012/029 PROJECT), which is gratefully acknowledged.Zamorano -López, N.; Moñino Amoros, P.; Borrás Falomir, L.; Aguado García, D.; Barat, R.; Ferrer, J.; Seco Torrecillas, A. (2018). Influence of Food Waste addition over microbial communities in an Anaerobic Membrane Bioreactor plant treating urban wastewater. Journal of Environmental Management. 217:788-796. https://doi.org/10.1016/j.jenvman.2018.04.018S78879621

Improving membrane photobioreactor performance by reducing light path: operating conditions and key performance indicators

Microalgae cultivation has been receiving increasing interest in wastewater remediation due to their ability to assimilate nutrients present in wastewater streams. In this respect, cultivating microalgae in membrane photobioreactors (MPBRs) allows decoupling the solid retention time (SRT) from the hydraulic retention time (HRT), which enables to increase the nutrient load to the photobioreactors (PBRs) while avoiding the wash out of the microalgae biomass. The reduction of the PBR light path from 25 to 10 cm increased the nitrogen and phosphorus recovery rates, microalgae biomass productivity and photosynthetic efficiency by 150, 103, 194 and 67%, respectively. The areal biomass productivity (aBP) also increased when the light path was reduced, reflecting the better use of light in the 10-cm MPBR plant. The capital and operating operational expenditures (CAPEX and OPEX) of the 10-cm MPBR plant were also reduced by 27 and 49%, respectively. Discharge limits were met when the 10-cm MPBR plant was operated at SRTs of 3-4.5 d and HRTs of 1.25-1.5 d. At these SRT/HRT ranges, the process could be operated without a high fouling propensity with gross permeate flux (J20) of 15 LMH and specific gas demand (SGDp) between 16 and 20 Nm3air·m−3permeate, which highlights the potential of membrane filtration in MPBRs. When the continuous operation of the MPBR plant was evaluated, an optical density of 680 nm (OD680) and soluble chemical oxygen demand (sCOD) were found to be good indicators of microalgae cell and algal organic matter (AOM) concentrations, while dissolved oxygen appeared to be directly related to MPBR performance. Nitrite and nitrate (NOx) concentration and the soluble chemical oxygen demand:volatile suspended solids ratio (sCOD:VSS) were used as indicators of nitrifying bacteria activity and the stress on the culture, respectively. These parameters were inversely related to nitrogen recovery rates and biomass productivity and could thus help to prevent possible culture deterioration

Exploring the limits of anaerobic biodegradability of urban wastewater by AnMBR technology

[EN] Anaerobic membrane bioreactors (AnMBRs) can achieve maximum energy recovery from urban wastewater (UWW) by converting influent COD into methane. The aim of this study was to assess the anaerobic biodegradability limits of urban wastewater with AnMBR technology by studying the possible degradation of the organic matter considered as non-biodegradable as observed in aerobic membrane bioreactors operated at very high sludge retention times. For this, the results obtained in an AnMBR pilot plant operated at very high SRT (140 days) treating sulfate-rich urban wastewater were compared with those previously obtained with the system operating at lower SRT (29 to 70 days). At 140 days SRT the organic matter biodegraded by the AnMBR system accounted for 64.4% of the influent COD (45.9% was removed by sulfate reducing bacteria (SRB), and only 18.5% was converted into methane, highlighting the strong competition between SRB and methanogenic archaea (MA) when treating sulfate-rich wastewater). Almost half of the methane produced (46%) was dissolved in the permeate and most of it was recovered by a degassing membrane. The organic matter biodegraded by the AnMBR system was similar to the influent anaerobic biodegradability determined by wastewater characterization assays (68.5% of the influent COD), indicating that nearly all the influent's biodegradable organic matter had been removed. This percentage of degraded COD was similar to that obtained in previous studies working at 70 days SRT, showing that the limit of anaerobic biodegradability was already reached in this SRT. The organic matter considered as non-biodegradable according to wastewater characterization assays therefore was not seen to degrade in the AnMBR pilot plant, even at very high SRT. Once the biodegraded COD is close to the influent's anaerobic biodegradability, increasing the SRT is not justified as it only leads to higher operational costs for the same biogas production. These findings support the use of mathematical models for AnMBR design since they accurately represent the behaviour of these systems in a wide range of operating conditions.This research project was supported by the Spanish Ministry of Economy and Competitiveness (MINECO, Project CTM2014-54980-C2-2-R). The authors are also grateful for the support received from the Generalitat Valenciana via CPI-16-155 fellowships.Seco Torrecillas, A.; Mateo-Llosa, O.; Zamorano-López, N.; Sanchis-Perucho, P.; Serralta Sevilla, J.; Martí Ortega, N.; Borrás Falomir, L.... (2018). Exploring the limits of anaerobic biodegradability of urban wastewater by AnMBR technology. Environmental Science: Water Research & Technology. 4(11):1877-1887. https://doi.org/10.1039/c8ew00313kS18771887411Li, W.-W., & Yu, H.-Q. (2011). From wastewater to bioenergy and biochemicals via two-stage bioconversion processes: A future paradigm. Biotechnology Advances, 29(6), 972-982. doi:10.1016/j.biotechadv.2011.08.012Shin, C., & Bae, J. (2018). Current status of the pilot-scale anaerobic membrane bioreactor treatments of domestic wastewaters: A critical review. Bioresource Technology, 247, 1038-1046. doi:10.1016/j.biortech.2017.09.002EEA , Performance of water utilities beyond compliance (Technical report No. 5/2014) , Luxemburg , 2014Martin, I., Pidou, M., Soares, A., Judd, S., & Jefferson, B. (2011). Modelling the energy demands of aerobic and anaerobic membrane bioreactors for wastewater treatment. 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The Domain-specific Probe EUB338 is Insufficient for the Detection of all Bacteria: Development and Evaluation of a more Comprehensive Probe Set. Systematic and Applied Microbiology, 22(3), 434-444. doi:10.1016/s0723-2020(99)80053-8C. W. Gellings and K. E.Parmenter , Energy efficiency in fertilizer production and use. In Knowledge for Sustainable Development , Encyclopedia of Life Support Systems (EOLSS), Eolss Publisher , Oxford , 2004 , vol. II , pp. 419–450J. B. Giménez , Estudio del tratamiento anaerobio de aguas residuales urbanas en biorreactores de membrana (Doctoral Thesis) , Universitat de València , Valencia , 2014Giménez, J. B., Martí, N., Robles, A., Ferrer, J., & Seco, A. (2014). Anaerobic treatment of urban wastewater in membrane bioreactors: evaluation of seasonal temperature variations. Water Science and Technology, 69(7), 1581-1588. doi:10.2166/wst.2014.069Robles, A., Ruano, M. V., Ribes, J., & Ferrer, J. (2012). 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Correlation analysis between nitrifying bacteria abundance and operational and physico-chemical parameters associated with nitrification biological process in activated sludge systems

[ES] Los estudios integrados que relacionan la abundancia de bacterias nitrificantes con las variables fisicoquímicas y operacionales en estaciones depuradoras de aguas residuales a escala real son escasos. El conocimiento de estas relaciones bajo una perspectiva integrada permite aportar valiosa información para la optimización del proceso de nitrificación. El presente estudio fue realizado en una estación depuradora de agua residual (EDAR) con sistema AO y eliminación biológica de nitrógeno mediante aireación intermitente. El objetivo principal fue establecer la asociación entre la abundancia de bacterias nitrificantes y los parámetros operacionales, fisicoquímicos y rendimientos de eliminación del nitrógeno, utilizando para ello un análisis de correlación bivariante. Los resultados obtenidos han permitido establecer una metodología adecuada para la cuantificación de bacterias nitrificantes y definir los parámetros asociados con su abundancia (como la carga másica, la DQO soluble y el tiempo de retención hidráulico) y, por tanto, de interés para la monitorización del proceso.[EN] Integrated studies relating nitrifying bacteria abundance to physicochemical and operational variables in wastewater treatment plants are scarce. The knowledge of these relationships under an integrated perspective can provide valuable information to optimize the nitrification process. The present study was carried out in a wastewater treatment plant (WWTP) with AO and biological nitrogen removal system via intermittent aeration. The aim of this study was to establish the relationships between nitrifying bacteria abundance, and operational and physico-chemical parameters, as well as nitrogen removal performance, using bivariate correlation analysis. The results obtained allowed to establish an appropriate methodology for the quantification of nitrifying bacteria and define parameters associated with its abundance, and therefore of interest for process monitoring, such as the food to microorganism (F/M) ratio, soluble COD and hydraulic retention time.Este estudio forma parte del proyecto de investigación 'Estudio integrado del proceso de fangos activos' financiado por la Entidad Pública de Saneamiento de Aguas Residuales de la Comunidad Valenciana (EPSAR). Agradecer la colaboración de la empresa AVSA-EGEVASA y del Subprograma MICINN PTA-2011.Zornoza-Zornoza, AM.; Avendaño-Villafranca, LM.; Borrás Falomir, L.; Aguado García, D.; Alonso Molina, JL. (2014). Análisis de las correlaciones entre la abundancia de bacterias nitrificantes y los parámetros operacionales y fisicoquímicos relacionados con el proceso biológico de nitrificación en fangos activos. Tecnoaqua. 5:2-12. http://hdl.handle.net/10251/98062S212