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The use of mixed microbial cultures (MMC) and organic wastes and wastewaters as feed sources is considered an appealing approach to reduce the current polyhydroxyalkanoates (PHAs) production costs. However, this method entails an additional hurdle to the PHAs downstream processing (recovery and purification). In the current work, the effect of a sodium hypochlorite (NaClO) pre-treatment coupled with dimethyl carbonate (DMC) or chloroform (CF) as extraction solvents on the PHAs recovery efficiency (RE) from MMC was evaluated. MMC were harvested from a sequencing batch reactor (SBR) fed with a synthetic prefermented olive mill wastewaster. Two different carbon-sources (acetic acid and acetic/propionic acids) were employed during the batch accumulation of polyhydroxybutyrate (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) from MMC. Obtained PHAs were characterized by 1H and 13C nuclear magnetic resonance, gel-permeation chromatography, differential scanning calorimetry, and thermal gravimetric analysis. The results showed that when a NaClO pre-treatment is not added, the use of DMC allows to obtain higher RE of both biopolymers (PHB and PHBV), in comparison with CF. In contrast, the use of CF as extraction solvent required a pre-treatment step to improve the PHB and PHBV recovery. In all cases, RE values were higher for PHBV than for PHB.

Altres ajuts: acords transformatius de la UAB Mainstream partial nitritation/anammox (PN/AMX) has attracted large attention in the last decade. Two-stage configurations have been pointed out as an appealing technology for the application of the PN/AMX process at mainstream conditions. However, the process requires of an efficiency improvement by designing a new technology to remove the nitrate produced by anammox bacteria. A new reactor configuration was developed by coupling anammox to heterotrophic denitrification in a single reactor unit while avoiding competition between both processes. The addition of acetate as an external C-source allowed the removal of nitrate by heterotrophic microorganisms without hampering the anammox process by maintaining high nitrogen removal rates (0.16 ± 0.03 g N L-1 d-1) and nitrogen removal efficiencies (91 ± 8 %) (on average from acetate addition periods). Further, a proper organic load management showed to be effective to face the drawbacks derived from previous mainstream treatment stages (i.e. undesired nitrate production), without compromising effluent COD concentrations. By withdrawing samples along the sludge bed, nitrogen compounds and COD concentrations were determined at different reactor heights. This set of experimental data demonstrated that the combination of anammox and heterotrophic denitrification in a single reactor unit was possible as anammox activity dominated within bottom sludge bed sections, while heterotrophic denitrification occurred within middle and upper sludge sections. Microbial diversity results of 16S rRNA gene-targeted sequencing analyses confirmed that anammox and heterotrophic denitrifiers communities occupied two differentiated sludge bed sections along the reactor being dominated by Candidatus Brocadia (30 %) and Thauera (33 to 46 %), respectively. When heterotrophic denitrification occurred, the average N2O emissions with COD addition was ca. 50 % lower than that in periods without COD addition.

Altres ajuts: acords transformatius de la UAB Volatile fatty acids (VFAs) are a group of carboxylic acids considered as building block chemicals. Nowadays, commercial production of VFAs is performed using fossil fuel sources. As an alternative, acidogenic fermentation of wastes by mixed microbial cultures (MMC) is starting to be considered as a potential bioproduction process that would replace conventional production processes and contribute to the circular economy. Nevertheless, more research is needed to control the VFA production yields and to precisely drive the fermentation process to the production of a certain VFA or a mixture of VFAs, either by modifying the operational parameters or by appropriately tunning the substrate composition. Following this gap, this review starts screening the metabolic routes that yield VFAs by anaerobic fermentation. Subsequently, the effect of different operational parameters on VFA production yield and VFA composition distribution is extensively discussed depending on the organic composition of the waste in terms of proteins, carbohydrates and lipids. To the best of our knowledge, previous review articles analyzed the impact of these parameters for different types of wastes, but without specifically considering their organic composition in terms of proteins, carbohydrates and lipids. Afterwards, energy-based metabolic models are presented as the one of the best modelling approaches to predict VFA composition. Then, polyhydroxyalkanoates (PHAs) production by MMC is described since it is one of the most promising applications of waste derived VFAs. Finally, we highlight the research gaps that should be further investigated to develop a large scale VFA bioprocess based on MMC platform from waste streams.

The increasing amount of source separated organic fraction of municipal solid wastes (OFMSW) treated by anaerobic digestion for energy recovery requires the implementation of cost-efficient processes for the treatment of the produced digestate, especially in terms of nitrogen removal. The autotrophic nitrogen removal process, based on the coupling of two biological processes, partial nitritation (PN) and anammox (A), appears as a suitable solution due to important savings in operational costs compared to conventional treatment processes. However, its application could be hampered by the high salinity and inhibitory potential of this kind of digestate. In this contribution, two lab-scale granular sludge reactors performing the PN and anammox processes, respectively, were used to treat (opportunely diluted) real OFMSW digestate originating from full-scale biogas plants with the aim of assessing their treatment feasibility in a two-stage PN/A configuration. The PN process was implemented in an air-lift granular sludge reactor and was able to treat a nitrogen loading rate of about 1 g N L−1 d−1 at 30 ± 0.5 °C; moreover, its effluent was suitable for the subsequent anammox treatment, with an appropriate effluent NO2−/NH4+ ratio and marginal inhibiting effects. In the anammox granular sludge reactor, the anammox activity was affected by high salinity levels, nonetheless a stable reactor performance at a nitrogen removing rate of 0.83 ± 0.20 and 0.31 ± 0.04 g N L−1 d−1 at 35 ± 0.5 °C, were achieved when treating 50% and 30% diluted real wastewaters at a conductivity in the reactor of 9.1 and 11.2 mS cm−1, respectively.

Unidad de excelencia María de Maeztu CEX2019-000940-M Altres ajuts: acords transformatius de la UAB A paradigm shift is needed in wastewater treatment plants (WWTPs) to progress from traditional pollutant removal to resource recovery. However, whether this transformation produces overall environmental benefits will depend on the efficient and sustainable use of resources by emerging technologies. Given that many of these technologies are still being tested at the pilot scale, there is a lack of environmental assessments quantifying their impacts and benefits. In particular, an integrated approach to energy and nutrient recovery can elucidate the potential configurations for WWTPs. In this study, we conduct a life cycle assessment (LCA) of emergent wastewater treatment technologies aimed at increasing resource circularity in WWTPs. We focus on increasing energy self-sufficiency through biogas upgrades and a more radical circular approach aimed at nutrient recovery. Based on a case-study WWTP, we compare its current configuration with (1) implementing autotrophic nitrogen removal in the mainstream and deriving most of the organic matter for biogas production, which increases the quality and quantity of biogas available for energy production; (2) implementing struvite recovery through enhanced biological phosphorus removal (EBPR) as a radical approach to phosphorus management, offering an alternative to mineral fertilizer; and (3) a combination of both approaches. The results show that incremental changes in biogas production are insufficient for compensating for the environmental investment in infrastructure, although autotrophic nitrogen removal is beneficial for increasing the quality of the effluent. Combined phosphorus and energy recovery reduce the environmental impacts from the avoided use of fertilizers and phosphorus and the nitrogen release into water bodies. An integrated approach to resource management in WWTPs is thus desirable and creates new opportunities toward the implementation of circular strategies with low environmental impact in cities.

El presente artículo propone la aplicación del enfoque decolonial al estudio de las fiestas populares latinoamericanas. Para ello, recorre las distintas perspectivas que analizan la relación entre las tradiciones locales y el proyecto moderno-colonial que se inicia con la invasión europea del continente y continúa vigente en la actualidad con el fenómeno denominado globalización. A lo largo de ese tiempo se han producido distintos procesos de resistencia, acomodación e hibridación generados por la tensión entre las dinámicas globales y las prácticas e imaginarios de los grupos colonizados; al respecto, la perspectiva decolonial nos ofrece algunas herramientas analíticas novedosas para observar estos fenómenos, las cuales intentamos emplear en un estudio de caso, el Tinkunaco riojano en la Argentina.

Acidogenic fermentation of wastes produces volatile fatty acid (VFA)-rich streams that can be used as low-cost carbon sources for polyhydroxyalkanoate (PHA) production. In this study, an inoculum collected from an anaerobic reactor of a municipal WWTP was conditioned to suppress methanogenic activity. The heat-shock conditioning method of the inoculum proved to be more efficient than acid and alkaline conditioning methods for methanogen inhibition. Then, the pre-conditioned inoculum was used to determine the acidogenic potential of different wastes: three waste activated sludge (WAS) samples generated at different sludge retention times (SRTs, 2, 7 and 14 days), olive mill wastewater (OMW), glycerol, apple pomace (AP) and winterization oil cake (WOC). Batch tests were performed in quintuplicate at 37°C and pH 7. A higher degree of acidification was observed for high-rate activated sludge (2 days of SRT) (69%), followed by olive mill wastewater (OMW) (43%), while the lowest was for glycerol (16%). The results for the winterization oil cake (WOC) samples interestingly elucidated a high content of propionic acid with a high odd-to-even ratio (0.86) after fermentation. Feeding the VFA profile obtained from WOC into a PHA production system led to a significant production of 0.64 g PHA g− 1 C with 30% polyhydrobutyrate (PHB) to 69% polyhydroxyvalerate (PHV) as monomeric units of HB-co-HV, decoupling the need for a related carbon source for co-polymer production.

This study was supported by the AGAUR and ACC1Ó through the ANFIBIO project (2010VALOR0096). J. Pérez acknowledges the mobility fellowship (PRX12/00418, Ministerio de Educación, Cultura y Deporte, through the Programa Nacional de Movilidad de Recursos Humanos del Plan Nacional de I + D + I 2008-2011) provided by the Spanish Government. Partial nitritation for a low-strength wastewater at low temperature was stably achieved in an aerobic granular reactor. A bench-scale granular sludge bioreactor was operated in continuous mode treating an influent of 70 mg N-NH₄⁺ L⁻¹ to mimic pretreated municipal nitrogenous wastewater and the temperature was progressively decreased from 30 to 12.5ºC. A suitable effluent nitrite to ammonium concentrations ratio to a subsequent anammox reactor was maintained stable during 300 days at 12.5ºC. The average applied nitrogen loading rate at 12.5 ºC was 0.7 ± 0.3 g N L⁻¹ d⁻¹, with an effluent nitrate concentration of only 2.5 ± 0.7 mg N--NO₃ L⁻¹. The biomass fraction of nitrite-oxidizing bacteria (NOB) in the granular sludge decreased from 19% to only 1% in 6 months of reactor operation at 12.5ºC. Nitrobacter spp. where found as the dominant NOB population, whereas Nitrospira spp. were not detected. Simulations indicated that: (i) NOB would only be effectively repressed when their oxygen half-saturation coefficient was higher than that of ammonia-oxidizing bacteria; and (ii) a lower specific growth rate of NOB was maintained at any point in the biofilm (even at 12.5ºC) due to the bulk ammonium concentration imposed through the control strategy.

To explore the changes in the microbial community structure during the recovery process of an anammox reactor after a temperature shock, the 454-pyrosequencing technique was used. The temperature shock reduced the nitrogen removal rate up to 92% compared to that just before the temperature shock, and it took 70 days to recover a similar nitrogen removal rate to that before the temperature shock (ca. 0.30 g N L−1 d−1). Pyrosequencing results indicated that microbial diversity in the reactor decreased as the reactor progressively recovered from the temperature shock. Anammox bacteria were accounted as 6%, 35% and 46% of total sequence reads in samples taken 13, 45 and 166 days after the temperature shock. These results were in agreement with N-removal performance results and anammox activity measured in the reactor during the recovery process. An anammox specific primer was used to precisely determine the anammox species in the biomass samples.

The aim of the present study was to evaluate the capability of an up-flow anammox sludge bed reactor (13 L) of dampening a 10 °C temperature drop at mainstream conditions while operating at constant nitrogen loading rates (0.11 ± 0.01 g N L−1 d−1). The up-flow anammox sludge bed reactor was fed with an aerobically pre-treated mainstream wastewater. The reactor temperature was controlled as to mimic a (realistic) summer-to-winter transition from 20 to 10 °C plus a three months period at 10 °C. During the 350 days of operation, the average nitrogen removal rate remained high (0.10 ± 0.01 g N L−1 d−1), indicating that the 10 °C drop did not affect the overall efficiency of the reactor. This can be explained as anammox activity differed among the different sludge bed sections. At 20 °C, anammox activity was mainly located at the bottom of the sludge bed. At 10 °C, the anammox activity decrease of the bottom sludge bed was compensated by an activity increase within the upper sludge bed sections. The contribution of heterotrophic denitrifying activity to the total nitrogen removal rate was assessed to be 3-to-5 times lower than that of anammox, even at 10 °C. Microbial community of 16S rRNA gene-targeted sequencing analyses resulted in the identification of an uncharacterized Planctomycetes in high numbers. This study demonstrated that the low temperatures should not be an obstacle for the feasibility of anammox bacteria in the main water line of an urban wastewater treatment plant.

A sequencing batch reactor (SBR) was inoculated with p -nitrophenol-degrading activated sludge to biodegrade a mixture of monosubstituted phenols: p -nitrophenol (PNP), PNP and o -cresol; and PNP, o -cresol and o -chlorophenol. Settling times were progressively decreased to promote biomass granulation. PNP was completely biodegraded. The PNP and o -cresol mixture was also biodegraded although some transitory accumulation of intermediates occurred (mainly hydroquinone and catechol). o -Chlorophenol was not biodegraded and resulted in inhibition of o -cresol and PNP biodegradation and complete failure of the SBR within a few days. The biomass had very good settling properties when a settling time of 1 min was applied: sludge volume index (SVI 5 ) below 50 mL g −1 , SVI 5 /SVI 30 ratio of 1 and average particle size of 200 μm.

Financial support was provided by the Spanish Ministerio de Medio Ambiente y Medio Rural y Marino (Project Exp. 007/RN08/03.1). Altres ajuts: MAPAMA/007/RN08/03.1 Growth in production and use of nanoparticles (NPs) will result increased concentrations of these in industrial and urban wastewaters and, consequently, in wastewater-treatment facilities. The effect of this increase on the performance of the wastewater-treatment process has not been studied systematically and including all the microbial communities involved in wastewater treatment. The present work investigates, by using respiration tests and biogas-production analysis, the inhibitory effect of four different commonly used metal oxide (CeO₂ and TiO₂) and zero-valent metal (Ag and Au) nanoparticles on the activity of the most important microbial communities present in a modern wastewater-treatment plant. Specifically, the actions of ordinary heterotrophic organisms, ammonia oxidizing bacteria, and thermophilic and mesophilic anaerobic bacteria were tested in the presence and absence of the nanoparticles. In general, CeO₂ nanoparticles caused the greatest inhibition in biogas production (nearly 100%) and a strong inhibitory action of other biomasses; Ag nanoparticles caused an intermediate inhibition in biogas production (within 33-50%) and a slight inhibition in the action of other biomasses, and Au and TiO₂ nanoparticles caused only slight or no inhibition for all tested biomasses.

Long-term operation (390 days) of a continuous airlift reactor with aerobic granular biomass was successfully applied to treat a highly complex wastewater composed of: ammonium (1000 mg N L−1), o-cresol (100 mg L−1), phenol (100 mg L−1), quinoline (50 mg L−1) and salts (16 g salts L−1). High nitrogen loading rate (1.1 g N L−1 d−1) and organic loading rate of 0.7 (g COD L−1 d−1) were achieved for the simultaneous nitritation and complete biodegradation of the aromatic compounds. The successful operation of the granular airlift reactor can be related to (i) the growth of specialized microorganisms in the aerobic granules and (ii) the continuous feeding regime. Aerobic granules were maintained stable in spite of the high salinity conditions. Dissolved oxygen (DO) concentration and DO/ammonium concentrations ratio were the key parameters to select a suitable effluent for anammox or heterotrophic denitrification via nitrite. Besides, nitrous oxide emissions were related to the DO concentration in the reactor.

Altres ajuts: acords transformatius de la UAB Altres ajuts: LIFE14/ENV/ES/000633 The use of high-rate activated sludge (HRAS) reactors for the removal of COD in urban wastewater treatment plants (WWTPs) has been investigated because its potential contribution to energy generating WWTPs. A one-year operation period of a pilot plant treating the effluent of the primary settler of a full-scale WWTP was analyzed. The HRAS pilot plant operated without iron salts addition at temperatures between 12 and 28 ºC at an average organic loading rate 2.8 ± 0.5 kg COD m-3 d-1 and with an average inflow COD concentration of 330 ± 86 mg O2 L-1. The influence of sludge retention time (SRT) on COD recovery and biomethane potential of the produced sludge was investigated and compared to the full scale WWTP performance. The highest observed sludge yield coefficient and biomethane potential of the sludge were achieved at SRT of 0.6 days. The weak point of the HRAS performance at STR of 0.6 days is the high loss of organic matter in the effluent due to the limited efficiency of the solids separation in the secondary settler. At higher SRT (in the range 1.0-2.1 days), the secondary settler efficiency and the COD recovery are higher than those achieved at SRT of 0.6 days but part of the inlet ammonium can be nitrified in the HRAS system at temperatures above 20 ºC. A detailed energy balance indicated that two-thirds reduction of aeration requirements and one-third increase of biogas production could be achieved in a plant configuration in which HRAS is coupled to autotrophic biological nitrogen removal (BNR) compared to the heterotrophic BNR configuration, yielding a net energy production of ca. 0.1 kWh m-3 of treated water.

Polyhydroxyalkanoates (PHAs) are biopolyesters accumulated as carbon and energy storage materials under unbalanced growth conditions by various microorganisms. They are one of the most promising potential substitutes for conventional non-biodegradable plastics due to their similar physicochemical properties, but most important, its biodegradability. Production cost of PHAs is still a great barrier to extend its application at industrial scale. In order to reduce that cost, research is focusing on the use of several wastes as feedstock (such as agro-industrial and municipal organic waste and wastewater) in a platform based on mixed microbial cultures. This review provides a critical illustration of the state of the art of the most likely-to-be-scale-up PHA production processes using mixed microbial cultures platform and waste streams as feedstock, with a particular focus on both, upstream and downstream processes. Current pilot scale studies, future prospects, challenges and developments in the field are also highlighted.

Altres ajuts: Clara Reino acknowledges the Xunta de Galicia (Spain) and the CRETUS Institute of Santiago de Compostela for her postdoctoral fellowship (ED481B-2019-008) One of the main challenges for the full-scale implementation of the autotrophic biological nitrogen removal process is to achieve a stable long-term partial nitritation under the mainstream conditions of urban wastewater treatment plants. Here, the performance of partial nitritation process under mainstream conditions was investigated based on the change of the nitrifying community developed. A lab-scale airlift reactor was operated for 430 days with a granular sludge highly enriched in ammonia oxidizing bacteria (AOB) performing partial nitritation treating a mainstream-mimicked synthetic influent. The changes in solid retention time (SRT), dissolved oxygen (DO) concentration and temperature strongly affected to the microbial community developed, especially to the dynamics of the nitrite oxidizing bacteria (NOB) population, which triggered to instabilities in the partial nitritation process. The extremely high values of SRT applied (SRT = ∞) and long-term exposure to low temperature (10 °C) promoted the growth of NOB Nitrotoga genus and development of nitratation activity; and the subsequent variability in temperature (between 10 and 30 °C) and in DO concentration (between 0.4 ± 0.1 and 1.4 ± 0.3 mg O2 L−1) influenced the competitiveness between nitrifiers and the growth of species previously undetected in the culture, as Nitrospira genus. Anaerobic ammonia oxidizing bacteria were also identified during cultivation and assisted to the repression of the NOB activity at 25-15 °C. The results of the present study uphold that understanding the niche differentiation and competitiveness of NOB will be key to develop strategies for NOB repression in order to make possible full-scale implementation of partial nitritation process at mainstream conditions.

In the race to achieve a sustainable urban wastewater treatment plant, not only the energy requirements have to be considered but also the environmental impact of the facility. Thus, nitrous oxide (N2O) emissions are a key-factor to pay attention to, since they can dominate the total greenhouse gases emissions from biological wastewater treatment. In this study, N2O production factors were calculated during the operation of a granular sludge airlift reactor performing partial nitritation treating a low-strength synthetic influent, and furthermore, the effect of temperature on N2O production was assessed. Average gas emission relative to conversion of ammonium was 1.5 ± 0.3% and 3.7 ± 0.5% while the effluent contained 0.5 ± 0.1% and 0.7 ± 0.1% (% N-oxidized) at 10 and 20 °C, respectively. Hence, temperature increase resulted in higher N2O production. The reasons why high temperature favoured N2O production remained unclear, but different theoretical hypotheses were suggested.

Polyhydroxyalkanoates (PHA) are biopolymers that can be an alternative against conventional plastics. The study reported herein evaluated the enrichment of a mixed microbial culture (MMC) operated under feast/famine regime and different pHs in a sequencing batch reactor (SBR) using acetate as sole carbon source to produce polyhydroxyalkanoates (PHAs). The enrichment step was evaluated at controlled pH of 7.5 and also without pH control (averaged value of 9.0). The acetate uptake rate (− q S ) of both enrichments at the end of the experimental period exhibited similar behaviour being about 0.18 Cmol Ac Cmol X − 1 h − 1 and 0.19 Cmol Ac Cmol X − 1 h − 1 for SBR-A and SBR-B, respectively. However, the PHA-storing capacity of the biomass enriched without pH control was better, exhibiting a maximum PHA content of 36% (gPHA g − 1 VSS) with a PHA production rate (q PHA ) of 0.16 Cmol PHA Cmol X − 1 h − 1 . Batch experiments were performed to evaluate PHA-storing capacity of the enriched culture at different pHs and nutrients concentrations. In the pH experiments (without nutrient limitation), it was found that in the absence of controlled pH, the enriched biomass exhibited a PHA content of 44% gPHA g − 1 VSS with − q S and PHA to substrate yield (Y PHA/Ac ) of 0.57 Cmol Ac Cmol X − 1 h − 1 and 0.33 Cmol PHA Cmol Ac − 1 , respectively. Regarding the experiments at variable nutrients concentration (pH ranging 8.8 to 9.2), the results indicate that the PHA content in the enriched biomass is significantly higher being around 51% gPHA g − 1 VSS under nitrogen limitation. This work demonstrated the feasibility of the enrichment of a MMC with PHA storage ability without pH control. Results also suggest that better PHAs contents and substrate uptake rates are obtained without controlling the pH in the accumulation step. Finally, this work also highlights the importance of understanding the role of nutrients concentration during the accumulation step.

En las últimas décadas se ha construido una nueva imagen del mundo rural pampeano que ha complejizado el análisis con nuevos temas, métodos y fuentes. En estos estudios si bien los pulperos y pulperías están presentes siempre figuran de manera lateral o complementaria. En este trabajo me propuse profundizar el estudio de pulperos y pulperías rurales una vez reconocida su influencia en materia económica, política y social tanto en la campaña en su conjunto como hacia el interior de los pueblos. El tema elegido entonces responde a la necesidad de un estudio exclusivo y exhaustivo sobre un grupo que entendemos ha cumplido una función muy relevante como elemento central en la expansión, ocupación y estructuración de la sociedad rural bonaerense al igual que lo fueron las estancias, los fuertes y las parroquias. La expansión y consolidación de la campaña bonaerense ha sido acompañada por el despliegue comercial en las últimas décadas del siglo XVIII. Podemos hablar de un fenómeno de retroalimentación entre comerciantes y explotaciones ganaderas protagonizado con frecuencia por las mismas personas. En este sentido las pulperías contribuyeron a la formación de pueblos, la ocupación de nuevas tierras y el desarrollo de relaciones pacíficas con los pueblos originarios, aunque a veces fueron agentes disruptores. Nos queda claro que las pulperías eran engranajes importantes dentro de la economía local y ubicaban a sus propietarios por encima de la mayoría de los productores. Sin embargo muchos pulperos también eran productores o viceversa y esa diversificación les permitía disminuir los riesgos y las posibilidades de "naufragio". Creemos haber matizado y en algunos casos rechazado algunas de las imágenes literarias que en general configuraron una visión muy negativa de los pulperos y sus negocios. El pulpero no era muy distinto a su clientela y formaba parte de las costumbres predominantes de la campaña más allá de tener, en muchos casos, una posición económica más holgada. En este sentido, muchos pulperos fueron vecinos referentes en sus pueblos cumpliendo distintas funciones más allá de la fundamental que era el abastecimiento de bienes básicos, ocuparon cargos en el andamiaje institucional y se erigieron en la "voz del pueblo". La posición privilegiada de algunos pulperos les permitía evadir el peso de la justicia y cuando ocupaban cargos sacar provecho de ellos. Esto refuerza la idea de connivencia entre comercializadores locales y el aparato institucional local en torno al usufructo del tráfico de cueros que cada vez se hacía más rentable., Facultad de Humanidades y Ciencias de la Educación

Aquest article pertany al grup de recerca GENOCOV. https://ddd.uab.cat/collection/genocov Heterotrophic denitrification of nitrite (denitritation) with phenol as the only organic carbon source was successful achieved in an Upflow Sludge Blanket (USB) reactor with granular biomass. High nitrite removal (over 95%) and complete biodegradation of phenol were obtained at low COD/N ratio (2.5 ± 0.1) and at high nitrogen and organic loading rates (0.6 ± 0.1 g N L⁻¹ d⁻¹ and 1.6 ± 0.3 g COD L⁻¹ d⁻¹ at 30 C, respectively). The granulation remained stable throughout the operational period with an average granule size of 0.80 ± 0.08 mm and 95% of the biomass with a diameter higher than 0.2 mm. The denitrifying granular biomass was also able to use nitrate as electron acceptor after one year consuming exclusively nitrite. However, the granular biomass was not able to use o-cresol as electron donor although phenol and nitrite degradations were not affected by the presence of o-cresol and the granules remained stable. Most of the genera identified in the granules after one year operation of the anoxic USB reactor were denitrifying bacteria able to use nitrite and nitrate as electron acceptors and aromatic compounds as electron donors. The results presented in this study open the possibility of designing a new process for the treatment of complex wastewaters contaminated with aromatic compounds.

A new type of structural extracellular polymers (EPS) was extracted from aerobic granular sludge dominated by ammonium‐oxidizing bacteria. It was analyzed by Raman and FTIR spectroscopy to characterize specific amino acids and protein secondary structure, and by SDS‐PAGE with different stains to identify different glycoconjugates. Its intrinsic fluorescence was captured to visualize the location of the extracted EPS in the nitrifying granules, and its hydrogel‐forming property was studied by rheometry. The extracted EPS is abundant with cross ß‐sheet secondary structure, contains glycosylated proteins/polypeptides, and rich in tryptophan. It forms hydrogel with high mechanical strength. The extraction and discovery of glycosylated proteins and/or amyloids further shows that conventionally used extraction and characterization techniques are not adequate for the study of structural extracellular polymers in biofilms and/or granular sludge. Confirming amyloids secondary structure in such a complex sample is challengeable due to the possibility of amyloids glycosylation and self‐assembly. A new definition of extracellular polymers components which includes glycosylated proteins and a better approach to studying them is required to stimulate biofilm research.

The effect of salinity over granular biomass treating a mixture of aromatic compounds (phenol, o-cresol and p-nitrophenol) was evaluated in a continuous airlift reactor. To mimic an industrial wastewater, increasing concentrations (from 2.0 to 29.0 g salts L(-1)) of a mixture of salts (MgSO4, NaCl, KCl, CaCl2 and NaHCO3) were introduced in the influent. The gradual salinity increase led to a good acclimation of the biomass obtaining complete biodegradation of the aromatic compounds and no accumulation of metabolic intermediates. However, a deterioration of the morphology of aerobic granules with a complete loss of granulation after 125 days was produced at 29.0 g salts L(-1). At that moment, anaerobic granules were added to promote granulation and after 50 days new aerobic granules were formed. These new aerobic granules remained stable for more than 100 days at the highest salinity condition with 100% removal of the mixture of aromatic compounds.

The short-term effect of several aromatic compounds ( o -cresol, p -nitrophenol, o -chlorophenol and quinoline) was evaluated over granular anammox sludge cultivated over 2 years in a Sequencing Batch Reactor (SBR). The anammox granular sludge had an average size of 1.0 ± 0.2 mm and was enriched in Brocadia sp. Specific Anammox Activity (SAA) batch tests with this granular biomass were carried out in the presence of o -cresol, p -nitrophenol, o -chlorophenol, quinoline and their mixtures. The anammox biomass was never exposed to the tested aromatic compounds, prior to the SAA tests. The concentration and the mixture of aromatic compounds had a strong effect over the loss of the anammox activity. The higher the concentrations of the aromatic compounds, the higher the reduction of the SAA. Quinoline and p -nitrophenol have a lower negative effect compared to o -cresol and o -chlorophenol. The Luong inhibition model seems to adjust better the inhibition of anammox biomass by the tested aromatic compounds. Depending on the aromatic compound, toxic or inhibitory effect was measured. o -Cresol and o -chlorophenol caused a toxic effect whereas p -nitrophenol and quinoline produced an inhibitory effect. In general, synergistic effects were observed when mixtures of aromatic compounds were studied.

The efforts for implementing the anammox process at mainstream conditions with high nitrogen removal rates have gained much attention in the race for achieving an energy-positive urban wastewater treatment plant. Here, the successful and stable long-term operation of an Upflow Anammox Sludge Bed (UAnSB) reactor treating a low-strength synthetic influent amended with ammonium and nitrite for 420 days, and a nitrite-amended pre-treated real urban wastewater for 110 days at temperatures as low as 11 °C is presented. The short and long-term effects of temperature on anammox activity were assessed when the synthetic influent was treated, and the UAnSB reactor was demonstrated to be a robust reactor to confront low temperatures, typically found at mainstream conditions. In fact, a nitrogen loading rate as high as 1.8 ± 0.1 g N L−1 d−1 with 82 ± 4% of nitrogen removal was achieved at 11 °C treating the low-strength synthetic influent. Furthermore, the effect of treating a nitrite-amended pre-treated real urban wastewater at 11 °C at long-term in the UAnSB reactor was evaluated, and a stable operation was achieved with a high average nitrogen removal rate (1.2 ± 0.5 g N L−1 d−1). The relative abundance of anammox bacteria was maintained higher than 70% according to fluorescence in situ hybridization during the whole operation, being Candidatus Brocadia anammoxidans the predominant microbial species. The presence of heterotrophs in the sludge bed was surmised through heterotrophic batch tests, but anammox activity was demonstrated to be higher than heterotrophic activity, even when the synthetic influent was replaced by the nitrite-amended pre-treated real wastewater. The feasibility of operating an enriched anammox reactor at high nitrogen removal rate at long-term at mainstream conditions was demonstrated in this study.

In the race to achieve a sustainable urban wastewater treatment plant, not only the energy requirements have to be considered but also the environmental impact of the facility. Thus, nitrous oxide (N

Aquest article pertany al grup de recerca GENOCOV https://ddd.uab.cat/collection/genocov Two-stage systems have been proposed to overcome the drawbacks associated to the implementation of the autotrophic biological nitrogen removal process in the mainstream of urban wastewater treatment plants. In this study, an upflow anammox sludge blanket (UAnSB) reactor was successfully operated for 325 days treating a low-strength synthetic influent mimicking mainstream conditions. A nitrogen loading rate of up to 1.8 ± 0.2 g N L⁻¹ d⁻¹ was achieved at 26 ºC and the nitrogen removal rate obtained (1.7 ± 0.1 g N L⁻¹ d⁻¹) resulted considerably higher than most of the previously reported values for systems treating low-strength wastewater at similar temperatures. Fluorescence in situ hybridization analysis showed a high enrichment in the anammox specie Candidatus Brocadia anammoxidans during the whole operation. The evolution of the granule diameter was followed throughout the operation of the UAnSB reactor and a direct correlation of the average granule diameter with the liquid upflow velocity (Vup) was established, being the higher the Vup, the bigger the granules. A stable granule diameter of 790 ± 40 μm was achieved by maintaining a Vup of 1.0 ± 0.1 m h⁻¹. The low VupS applied avoid the use of effluent recirculation which would present a huge inconvenient to implement UAnSB reactors at real scale, however these low VupS led to external mass transfer problems in the reactor. In spite of the mass transfer limitations, not only a high specific anammox activity (0.26 ± 0.02 g N g⁻¹ VS d⁻¹) was achieved in the UASB reactor but also a high nitrogen removal (80 ± 3%).

A ratio control strategy has been used to demonstrate the feasibility of this automatic control procedure for the achievement of stable full and partial nitritation. The control strategy assured constant ratio between the dissolved oxygen (DO) and the total ammonia nitrogen (TAN) concentrations in the bulk liquid of aerobic granular sludge reactors operating in continuous mode. Three different set-ups with different reactor capacities were used (3, 110, and 150 L). High strength synthetic wastewaters and reject water were tested with similar performance. Achieved nitrogen loading rates ranged between 0.4 and 6.1 kgN·m−3·d−1, at temperatures between 20°C and 30°C. Granular sludge and nitritation were stable in the long term continuous operation of the reactors. Suitable stable effluent for Anammox has been obtained using the desired TAN setpoint (i.e. 50% of influent ammonium oxidation). An existing biofilm model developed incorporating the implemented control loops and validated in a previous publication was used to investigate the effects of the ammonium concentration of the influent and the biofilm density on the achievement of full nitritation. The model demonstrated how sludge recirculation events led to a stable and significant increase of the biomass concentration in the reactor, which in turn resulted in the achievement of high nitrogen loading rates, due to the action of the control strategy. The model predicted an enhancement of stable full nitritation at higher ammonium concentrations in the influent. Poor influence of the biofilm density in the achievement of full nitritation was predicted with the model.

A granular airlift reactor enriched in ammonia oxidizing bacteria (AOB) was operated at 10 °C performing stable partial nitritation in the long-term. The reactor treated a synthetic low-strength influent during 250 days with an average nitrogen loading rate of 0.63 ± 0.06 g N L(-1) d(-1). Nitrate production was barely detected, being the average concentration in the effluent of 0.6 ± 0.3 mg N-NO3 L(-1). Furthermore, a suitable effluent for a subsequent reactor performing the anammox process was achieved. A maximum specific growth rate as high as 0.63 ± 0.05 d(-1) was determined by performing kinetic experiments with the granular sludge in a chemostat and fitting the results to the Monod model. Pyrosequencing analysis showed a high enrichment in AOB (41 and 65% of the population were identified as Nitrosomonas genus on day 98 and 233, respectively) and an effective repression of nitrite oxidizing bacteria in the long-term. Pyrosequencing analysis also identified the coexistence of nitrifying bacteria and heterotrophic psychrotolerant microorganisms in the granular sludge. Some psychrotolerant microorganisms are producers of cryoprotective extracellular polymeric substances that could explain the better survival of the whole consortia at cold temperatures.

Continuous feeding operation of an airlift reactor and its inoculation with mature aerobic granules allowed the successful treatment of a mixture of aromatic compounds (p-nitrophenol, o-cresol and phenol). Complete biodegradation of p-nitrophenol, o-cresol, phenol and their metabolic intermediates was achieved at an organic loading rate of 0.61 g COD L(-1)d(-1). Stable granulation was obtained throughout the long-term operation (400 days) achieving an average granule size of 2.0 ± 1 mm and a sludge volumetric index of 26 ± 1 mL g(-1) TSS. The identified genera in the aerobic granular biomass were heterotrophic bacteria able to consume aromatic compounds. Therefore, the continuous feeding regimen and the exposure of aerobic granules to a mixture of aromatic compounds make possible to obtain good granulation and high removal efficiency.

Bioaugmentation with an enriched microbial population was applied in an aerobic sequencing batch reactor (SBR) receiving transient or continuous shock loads of p-nitrophenol (PNP). The effect of the amount of biomass added for bioaugmentation was assessed by using two different dosages (2% or 5% w/w of the total biomass in the seeded SBR). In both cases, total PNP removal was achieved during the transient PNP shock load occurring after bioaugmentation. However, after a long PNP starvation period the only experiment still showing total PNP removal during a second PNP shock load was the one where a dosage of 5% w/w was applied. The results suggested that the dosage is a key factor for the implementation of a successful bioaugmentation strategy. In addition, the performance of a bioaugmented SBR receiving a continuous PNP shock load was enhanced when compared to a non-bioaugmented SBR.

Carlos Mayo initiative has been instrumental in exploring the often complex world of retail business through the study of the pulperías in Buenos Aires with novel sources. However, there is little reference to other actors within the retail business in the nineteenth century embody multiple expressions displacing end pulperías in outlying areas of the city and end well with the dominance they had had since the founding of the city

Aerobic granular sludge is presented as an alternative technology to conventional activated sludge processes for the treatment of low-strength wastewaters. Results obtained with granular aerobic reactors at laboratory scale are promising but, there are few studies carried out at pilot scale. Therefore, more information about the stability of granules and their performance at larger scale is needed to establish if aerobic granulation could be a feasible treatment. With this aim, a 100 L granular sequencing batch reactor (GSBR) operating at high loading rate and treating low-strength wastewater for simultaneous carbon, nitrogen and phosphorus removal was operated for 11 months. Mature granules prevailed in the GSBR during a period of 5 months (from days 150 to 330), with a SVI 30 of 13 ± 6 mL g −1 TSS, a granule density around 114 ± 5 g TSS L −1 and an average particle size of 2.4 mm. The biological nitrogen removal with mature granules was mainly performed via nitrite, probably due to the large granule size achieved. Nitrification efficiency was higher than 75% and occurred simultaneously with denitrification during the aerobic phase of the GSBR. A progressive accumulation of P-salts (probably apatite), was found from days 150 to 300, which could enhance the destabilization of granules at the end of the experimental period.

The use of different carbon sources (ethanol, acid-fermented primary sludge centrate, acid-fermented secondary sludge centrate, glycerol and landfill leachate) in heterotrophic denitrification from nitrite (denitritation) was studied in a sequencing batch reactor, operated without pH control. Complete denitritation of a high-strength nitrite wastewater was achieved using these organic carbon sources with the exception of fermented secondary sludge centrate. Loading rates around 0.2 g N L −1 d −1 were obtained for glycerol, landfill leachate and ethanol after a short start-up period of 20 days. The maximum specific nitrite removal rate of 0.25 g N g −1 VSS d −1 was achieved for glycerol, while values between 0.13 and 0.17 g N g −1 VSS d −1 were obtained using ethanol, landfill leachate and fermented primary sludge centrate. The COD/N ratio consumed varied between 3.0 for ethanol and 8.8 for landfill leachate. The denitritation rates and the required COD/N ratio for each carbon source are reported for the first time – they can be used for the scale-up of the denitritation process.

The operation of a sequencing batch reactor (SBR) with aerobic granular biomass was successfully simulated using a one-dimensional biofilm model. The biological processes considered were described based on the activated sludge model (ASM) platform with two main modifications: (i) simultaneous growth and storage of organic substrates by heterotrophic bacteria; and (ii) inclusion of nitrite as intermediate compound in the nitrification and denitrification processes. Three different operational conditions were evaluated, characterized by different chemical oxygen demand to nitrogen (COD/N) ratios in the influent of: 0, 1.25 and 5.5 kg kg−1, representing a purely autotrophic media and two heterotrophic media, respectively. An accurate description of the experimental concentrations of COD, ammonium, nitrite, nitrate, dissolved oxygen (DO) and alkalinity along the cycles was obtained. Total solids concentration inside the reactor (5.0, 2.0 and 1.0 kg VSS m−3 for (COD/N) ratio of 5.5, 1.25 and 0 kg kg−1, respectively) and biofilm density ( 23 kg m granule − 3 ) were correctly described with the model. To obtain an accurate description of both solids concentration and biofilm density different densities were defined for the particulate compounds and a porosity profile along the granule was imposed. Oxygen penetration depths obtained with the model were 0.35 × 10−3, 0.30 × 10−3 and 0.12 × 10−3 m for (COD/N) ratio of 5.5, 1.25 and 0 kg kg−1, respectively. The values were in agreement with those used in the description of the porosity profiles.

The biological treatment of a high-strength p-nitrophenol (PNP) wastewater in an aerobic Sequencing Batch Reactor (SBR) has been studied. A specific operational strategy was applied with the main aim of developing a K-strategist PNP-degrading activated sludge. The enrichment of a K-strategist microbial population was performed using a non-acclimated biomass coming from a municipal WWTP as inoculum, and following a feeding strategy in which the PNP-degrading biomass was under endogenous conditions during more than 50% of the aerobic reaction phase. Hundred per cent of PNP removal was achieved in the whole operating period with a maximum specific PNP loading rate of 0.26 g PNP g(-1)VSS d(-1). A kinetic characterization of the obtained PNP-degrading population was carried out using respirometry assays in specifically designed batch tests. With the experimental data obtained a kinetic model including substrate inhibition has been used to describe the time-course of the PNP concentration and specific oxygen uptake rate (SOUR), simultaneously. The kinetic parameters obtained through optimization, validated with an additional respirometric test, were k(max)=1.02 mg PNP mg(-1) COD d(-1), K(s)=1.6 mg PNP L(-1) and K(i)=54 mg PNP L(-1). The values obtained for the K(s) and k(max) are lower than those reported in the literature for mixed populations, meaning that the biomass is a K-strategist type, and therefore demonstrating the success of the operational strategy imposed to obtain such a K-strategist population. Moreover, our measured K(i) value is higher than those reported by most of the bibliographic references; therefore the acclimated activated sludge used in this work was evidently more adapted to PNP inhibition than the other reported cultures.

Calibration of kinetic models of wet air oxidation (WAO) is usually performed through minimisation algorithms with respect to total organic carbon (TOC) experimental data. However, the reliability of the estimated value of the kinetic parameters is frequently not reported. Moreover, the influence of data quantity/quality in the kinetic parameters identifiability is not properly assessed. The objective of this study is to compare the calibration goodness of a proposed kinetic model when using one set of data (total effluent TOC [TOCeff]) or two sets of independent experimental measurements (total effluent TOC [TOCeff] and residual TOC of target pollutant [TOC[A]]). The systematic comparison was made using identifiability analysis with contour plots of both objective functions and the confidence intervals were calculated through the Fisher information matrix (FIM). The experimental data used in this study comes from a previous one, where WAO was investigated as a suitable precursor for the biological treatment of industrial wastewater containing high concentrations of o-cresol or 2-chlorophenol [M.E. Suarez-Ojeda, J. Carrera, I.S. Metcalfe, J. Font, Wet air oxidation (WAO) as a precursor to biological treatment of substituted phenols: refractory nature of the WAO intermediates, Chem. Eng. J. 144 (2008) 205–212.]. The results show that the model correctly fitted the experimental [TOCeff] in all cases with less than 6% as averaged relative deviation, either using one set of data ([TOCeff]) or two sets of independent experimental measures ([TOCeff] and [TOC[A]]) in the objective function. However, when using only [TOCeff], the model was not capable of fitting the proportion between [TOC[A]] and intermediates TOC. The obtained EACT for the calibration made with [TOCeff] and [TOC[A]] were 71 ± 20 kJ mol−1 (R2 = 0.92) and 47 ± 9 kJ mol−1 (R2 = 0.96) for o-cresol and 2-chlorophenol, respectively. However, when using just [TOCeff], the obtained EACT values were not in the range of the values reported in the literature and had smaller regression coefficients. Moreover, the calibration with just [TOCeff] presented a high correlation between the obtained rate constants, whereas the calibration with [TOCeff] and [TOC[A]] was statistically more reliable. As example, the D-criterion values are three to six times larger for the calibration made with ([TOCeff] and [TOC[A]] than for the calibration made only with [TOCeff], in the framework of OED/PE criteria, this is related to minimisation of the geometric mean of the identification errors.

Wet air oxidation (WAO) was investigated as a suitable precursor for the biological treatment of industrial wastewaters that contained high concentrations of phenol, o-cresol or 2-chlorophenol. Two hours WAO semi-batch experiments were conducted at 2 and 9 bar of oxygen partial pressure ( P O 2 ) and at 215, 240 and 265 °C with total organic carbon (TOC) abatement up to 86%. The influence of hydroxyl-, methyl- and chloride ring substitution on the oxidation mechanism of aromatic compounds was established. Also, the readily biodegradable COD fraction (%CODRB) of the WAO effluents was found by respirometric techniques. The maximum %CODRB was 24% for phenol WAO at 265 °C and 9 bar of P O 2 , 10% for o-cresol WAO at 265 °C and 9 bar of P O 2 and 19% for 2-chlorophenol WAO at 215 °C and 2 bar of P O 2 . These results allow comparison of whether or not the WAO effluents were suitable for a conventional activated sludge plant with non-acclimated biomass. Also, the results were compared to those obtained from a previous study for the same model compounds but using catalytic WAO (CWAO) with activated carbon (AC) as a catalyst [1]. This comparison allows us to establish whether or not the WAO effluents were less biodegradable or had more refractory intermediates than CWAO effluents.

The influence of temperature (140 and 160 ◦ C) and oxygen partial pressure (2 and 9 bar) on the continuous catalytic wet air oxidation (CWAO) over activated carbon (AC) has been investigated for the removal of phenol, o-cresol and 2-chlorophenol in aqueous solutions. Seventy-twohour tests were performed in a fixed bed reactor in trickle flow regime. A commercial AC was employed as catalyst. The pollutant elimination effectiveness, the distribution of major reaction products and the AC behaviour were studied for each compound. Also, respirometric screening tests were completed to the effluents before and after each CWAO experiment to assess the biodegradability enhancement. The results show that pollutant disappearance, chemical oxygen demand (COD) removal, total organic carbon (TOC) abatement and biodegradability enhancement (fraction of COD readily biodegradable, %CODRB) were very sensitive to temperature but rather independent of the oxygen partial pressure (PO2 ). On the contrary, AC catalyst preservation was strongly influenced by both temperature and pressure. For instance, for phenol CWAO at 2 bar of PO2 ,a s temperature increased from 140 to 160 ◦ C, phenol conversion increased from 45% to 78%, COD removal from 33% to 65%, TOC abatement from 21% to 62% and %CODRB from 4% to 36%. Similar behaviour was found for the other model compounds tested, although the level of refractoriness was rather different. © 2007 Elsevier B.V. All rights reserved.

The aim of this work is to study the viability of the H2O2 Promoted Catalytic Wet Air Oxidation (PP-CWAO) process, using activated carbon (AC) as catalyst, to increase the biodegradability of phenolic aqueous solutions. Seventy-two hours experiments were performed in a trickle bed reactor at 140 8C and 2 bar of oxygen partial pressure. Feed concentrations, in terms of theoretical chemical oxygen demand (ThCOD), were 11.8 g COD l � 1 for phenol, 12.6 g COD l � 1 for o-cresol and 8.0 g COD l � 1 for p-nitrophenol. Air was used as main oxidant and 20% of the stoichiometric amount of H2O2needed for pollutant complete mineralisation was added as oxidation promoter. Adding H2O2to the CWAO process not only increases pollutant removal but also leads to higher mineralisation of the remaining oxidation products. For instance, removal of phenol, o-cresol and p-nitrophenol increase from 45, 33 and 15% in the CWAO process to 64, 64 and 49% in the PP-CWAO process. In addition, the PP-CWAO process leads to better biodegradability enhancements, when compared to CWAO, as demonstrated by the respirometric tests. However, it is still necessary to improve the oxidation step in order to assure more biodegradable effluents that could be combined with a subsequent biological wastewater plant. # 2007 Elsevier B.V. All rights reserved.

This study examines the feasibility of coupling a Catalytic Wet Air Oxidation (CWAO), with activated carbon (AC) as catalyst, and an aerobic biological treatment to treat a high-strength o-cresol wastewater. Two goals are pursued: (a) To determine the effect of the main AC/CWAO intermediates on the activated sludge of a municipal WasteWater Treatment Plant (WWTP) and (b) To demonstrate the feasibility of coupling the AC/CWAO effluent as a part of the influent of a municipal WWTP. In a previous study, a high-strength o-cresol wastewater was treated by AC/CWAO aiming to establish the distribution of intermediates and the biodegradability enhancement. In this work, the biodegradability, toxicity and inhibition of the most relevant intermediates detected in the AC/CWAO effluent were determined by respirometry. Also, the results of a pilot scale municipal WWTP study for an integrated AC/CWAO-aerobic biological treatment of this effluent are presented. The biodegradation parameters (i.e. maximum oxygen uptake rate and oxygen consumption) of main AC/CWAO intermediates allowed the classification of the intermediates into readily biodegradable, inert or toxic/ inhibitory compounds. This detailed study, allowed to understand the biodegradability enhancement exhibited by an AC/CWAO effluent and to achieve a successful strategy for coupling the AC/CWAO step with an aerobic biological treatment for a high-strength o-cresol wastewater. Using 30%, as COD, of AC/CWAO effluent in the inlet to the pilot scale WWTP, the integrated AC/CWAO-biological treatment achieved a 98% of total COD removal and, particularly, a 91% of AC/CWAO effluent COD removal without any undesirable effect on the biomass. � 2006 Elsevier Ltd. All rights reserved.