RESUMEN

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.

RESUMEN

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.

Asunto(s)

Eliminación de Residuos Líquidos , Aguas Residuales , Biocombustibles , Fertilizantes , Nitrógeno , Fósforo/química , Estruvita , Eliminación de Residuos Líquidos/métodos

RESUMEN

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.

Asunto(s)

Polihidroxialcanoatos , Biopolímeros , Carbono , Industrias , Aguas Residuales

RESUMEN

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 ±â€¯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 ±â€¯0.20 and 0.31 ±â€¯0.04 g N L-1 d-1 at 35 ±â€¯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.

Asunto(s)

Aguas del Alcantarillado , Residuos Sólidos , Anaerobiosis , Reactores Biológicos , Nitrógeno , Eliminación de Residuos Líquidos , Aguas Residuales

RESUMEN

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.

Asunto(s)

Compuestos de Amonio/metabolismo , Proteínas Amiloidogénicas/metabolismo , Bacterias/metabolismo , Polímeros/metabolismo , Aguas del Alcantarillado/microbiología , Aerobiosis , Proteínas Amiloidogénicas/química , Bacterias/genética , Bacterias/aislamiento & purificación , Glicosilación , Oxidación-Reducción , Polímeros/química , Conformación Proteica en Lámina beta , Aguas del Alcantarillado/química , Espectroscopía Infrarroja por Transformada de Fourier

RESUMEN

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.

Asunto(s)

Compuestos de Amonio/metabolismo , Reactores Biológicos/microbiología , Nitritos/metabolismo , Nitrógeno/aislamiento & purificación , Administración de Residuos , Anaerobiosis , Bacterias , Estudios de Factibilidad , Hibridación Fluorescente in Situ , Oxidación-Reducción , Aguas del Alcantarillado/microbiología , Temperatura , Aguas Residuales

RESUMEN

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.

Asunto(s)

Nitrificación , Óxido Nitroso/síntesis química , Aguas del Alcantarillado/química , Temperatura , Aguas Residuales/química , Compuestos de Amonio/análisis , Compuestos de Amonio/síntesis química , Reactores Biológicos , Óxido Nitroso/análisis

RESUMEN

An aerobic granular bioreactor was operated for over 4months, treating a synthetic wastewater with a high ammonium content (100mgNL-1). The inoculum was collected from a bioreactor performing simultaneous partial nitrification and aromatic compounds biodegradation. From day-56 onwards, 2-fluorophenol (2-FP) (12.4mgL-1) was added to the feeding wastewater and the system was bioaugmented with a 2-FP degrading bacteria (Rhodococcus sp. FP1). By the end of operation, complete 2-FP biodegradation and partial nitrification were simultaneously achieved. Aerobic granules remained stable over time. During the 2-FP loading, a shift in the community structure occurred, coinciding with the improvement of 2-FP degradation. DGGE analysis did not allow to infer on the bioaugmented strain presence but pyrosequencing analysis detected Rhodococcus genus by the end of operation. Together with other potential phenolic-degraders within granules, these microorganisms were probably responsible for 2-FP degradation.

Asunto(s)

Reactores Biológicos , Nitrificación , Fenoles , Biodegradación Ambiental , Biomasa

RESUMEN

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 (-qS) of both enrichments at the end of the experimental period exhibited similar behaviour being about 0.18CmolAcCmolX-1h-1 and 0.19CmolAcCmolX-1h-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% (gPHAg-1 VSS) with a PHA production rate (qPHA) of 0.16CmolPHACmolX-1h-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% gPHAg-1 VSS with -qS and PHA to substrate yield (YPHA/Ac) of 0.57CmolAcCmolX-1h-1 and 0.33CmolPHACmolAc-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% gPHAg-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.

Asunto(s)

Reactores Biológicos/microbiología , Polihidroxialcanoatos/metabolismo , Concentración de Iones de Hidrógeno , Consorcios Microbianos , Nitrógeno/análisis , Fósforo/análisis , Eliminación de Residuos Líquidos

RESUMEN

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.

Asunto(s)

Reactores Biológicos/microbiología , Aguas Residuales/microbiología , Nitritos , Nitrógeno , Aguas del Alcantarillado/microbiología , Eliminación de Residuos Líquidos

RESUMEN

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.

Asunto(s)

Hidrocarburos Aromáticos/química , Residuos Industriales/análisis , Eliminación de Residuos Líquidos/métodos , Aguas Residuales/química , Contaminantes Químicos del Agua/química , Aerobiosis , Bacterias/metabolismo , Análisis de la Demanda Biológica de Oxígeno , Biomasa , Reactores Biológicos , Tamaño de la Partícula , Microbiología del Agua

RESUMEN

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.

Asunto(s)

Bacterias , Biodegradación Ambiental , Reactores Biológicos/microbiología , Sales (Química) , Aguas Residuales/química , Aerobiosis , Bacterias/efectos de los fármacos , Bacterias/metabolismo , Fenoles/análisis , Fenoles/metabolismo , Salinidad , Sales (Química)/química , Sales (Química)/farmacología , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/metabolismo

RESUMEN

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 12.5 °C. A suitable effluent nitrite to ammonium concentrations ratio to a subsequent anammox reactor was maintained stable during 300 days at 12.5 °C. The average applied nitrogen loading rate at 12.5 °C 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 12.5 °C. 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 12.5 °C) due to the bulk ammonium concentration imposed through the control strategy.

Asunto(s)

Reactores Biológicos/microbiología , Nitratos/análisis , Nitritos/análisis , Aguas Residuales/química , Aguas Residuales/microbiología , Aerobiosis , Compuestos de Amonio/análisis , Compuestos de Amonio/metabolismo , Anaerobiosis , Bacterias/genética , Bacterias/crecimiento & desarrollo , Bacterias/metabolismo , Biopelículas , Hibridación Fluorescente in Situ , Microscopía Confocal , Modelos Teóricos , Nitratos/metabolismo , Nitrificación , Nitritos/metabolismo , Nitrobacter/genética , Nitrobacter/metabolismo , Nitrobacter/fisiología , Nitrógeno/análisis , Nitrógeno/metabolismo , Oxidación-Reducción , Oxígeno/metabolismo , Reproducibilidad de los Resultados , Aguas del Alcantarillado/química , Aguas del Alcantarillado/microbiología , Temperatura , Factores de Tiempo , Eliminación de Residuos Líquidos/métodos

RESUMEN

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.

Asunto(s)

Amoníaco/metabolismo , Bacterias/crecimiento & desarrollo , Reactores Biológicos/microbiología , Análisis de Secuencia de ADN/instrumentación , Análisis de Secuencia de ADN/métodos , Temperatura , Compuestos de Amonio/metabolismo , Anaerobiosis , Biodegradación Ambiental , Biodiversidad , Biomasa , Nitratos/metabolismo , Nitritos/metabolismo , Nitrógeno/aislamiento & purificación , Oxidación-Reducción , Factores de Tiempo

RESUMEN

Industrial wastewater treatment plants must operate properly during the transient-state conditions often found in the industrial production. This study presents the performance of simultaneous partial nitritation and o-cresol biodegradation in a continuous aerobic granular reactor under sequentially alternating pollutant (SAP) scenarios. Three SAP scenarios were imposed during the operation of the granular reactor. In each one, a secondary recalcitrant compound (either p-nitrophenol (PNP), phenol or 2-chlorophenol (2CP)) were added for a short period of time to the regular influent containing only ammonium and o-cresol. Partial nitritation and o-cresol biodegradation were not inhibited by the presence of PNP or phenol and both compounds were fully biodegraded. On the contrary, the presence of 2CP strongly inhibited both processes within 2days. However, the reactor was recovered in a few days. These findings demonstrate that treatment of complex industrial wastewaters with variable influent composition is feasible in a continuous aerobic granular reactor.

Asunto(s)

Reactores Biológicos , Fenoles/química , Contaminantes Químicos del Agua/química , Fenoles/metabolismo , Aguas del Alcantarillado , Contaminantes Químicos del Agua/metabolismo

RESUMEN

Nitrous oxide (N2O) and methane emissions were monitored in a continuous granular airlift nitritation reactor from ammonium-rich wastewater (reject wastewater). N2O emissions were found to be dependent on dissolved oxygen (DO) concentration in the range of 1-4.5 mg O2/L, increasing within this range when reducing the DO values. At higher DO concentrations, N2O emissions remained constant at 2.2% of the N oxidized to nitrite, suggesting two different mechanisms behind N2O production, one dependent and one independent of DO concentration. Changes on ammonium, nitrite, free ammonia and free nitrous acid concentrations did not have an effect on N2O emissions within the concentration range tested. When operating the reactor in a sequencing batch mode under high DO concentration (>5 mg O2/L), N2O emissions increased one order of magnitude reaching values of 19.3 ± 7.5% of the N oxidized. Moreover, CH4 emissions detected were due to the stripping of the soluble CH4 that remained dissolved in the reject wastewater after anaerobic digestion. Finally, an economical and carbon footprint assessment of a theoretical scaled up of the pilot plant was conducted.

Asunto(s)

Contaminantes Atmosféricos/análisis , Reactores Biológicos , Nitrificación , Óxido Nitroso/análisis , Aguas Residuales/química , Purificación del Agua/métodos , Contaminantes Atmosféricos/economía , Contaminación del Aire/economía , Contaminación del Aire/prevención & control , Compuestos de Amonio/análisis , Biodegradación Ambiental , Carbono/análisis , Metano/análisis , Nitritos/análisis , Nitrógeno/análisis , Oxígeno/análisis , Proyectos Piloto , Purificación del Agua/economía

RESUMEN

Several chemical industries produce wastewaters containing both, ammonium and phenolic compounds. As an alternative to treat this kind of complex industrial wastewaters, this study presents the simultaneous partial nitritation and o-cresol biodegradation in a continuous airlift reactor using aerobic granular biomass. An aerobic granular sludge was developed in the airlift reactor for treating a high-strength ammonium wastewater containing 950 ± 25 mg N-NH4(+) L(-1). Then, the airlift reactor was bioaugmented with a p-nitrophenol-degrading activated sludge and o-cresol was added progressively to the ammonium feed to achieve 100 mg L(-1). The results showed that stable partial nitritation and full biodegradation of o-cresol were simultaneously maintained obtaining a suitable effluent for a subsequent anammox reactor. Moreover, two o-cresol shock-load events with concentrations of 300 and 1000 mg L(-1) were applied to assess the capabilities of the system. Despite these shock load events, the partial nitritation process was kept stable and o-cresol was totally biodegraded. Fluorescence in situ hybridization technique was used to identify the heterotrophic bacteria related to o-cresol biodegradation and the ammonia oxidising bacteria along the granules.

Asunto(s)

Biomasa , Reactores Biológicos , Cresoles/aislamiento & purificación , Aerobiosis , Hibridación Fluorescente in Situ

RESUMEN

The chemical and petrochemical industries produce wastewaters containing ammonium and phenolic compounds. Biological treatment of these wastewaters could be problematic due to the possible inhibitory effects exerted by phenolic compounds. The feasibility of performing simultaneous nitritation and p-nitrophenol (PNP) biodegradation using a continuous aerobic granular reactor was evaluated. A nitrifying granular sludge was bioaugmented with a PNP-degrading floccular sludge, while PNP was progressively added to the feed containing a high ammonium concentration. Nitritation was sustained throughout the operational period with ca. 85% of ammonium oxidation and less than 0.3% of nitrate in the effluent. PNP biodegradation was unstable and the oxygen limiting condition was found to be the main explanation for this unsteadiness. An increase in dissolved oxygen concentration from 2.0 to 4.5 mg O2 L(-1) significantly enhanced PNP removal, achieving total elimination. Acinetobacter genus and ammonia-oxidising bacteria were the predominant bacteria species in the granular biomass.

Asunto(s)

Biomasa , Reactores Biológicos/microbiología , Nitrificación , Nitrofenoles/aislamiento & purificación , Aguas del Alcantarillado/microbiología , Aerobiosis , Compuestos de Amonio/aislamiento & purificación , Bacterias/metabolismo , Biodegradación Ambiental , Biopolímeros/análisis , Oxidación-Reducción , Volatilización , Aguas Residuales/microbiología

RESUMEN

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 (SVI5) below 50 mL g(-1), SVI5/SVI30 ratio of 1 and average particle size of 200 µm.

Asunto(s)

Reactores Biológicos , Clorofenoles/química , Cresoles/química , Nitrofenoles/química , Acinetobacter/metabolismo , Aerobiosis , Arthrobacter/metabolismo , Técnicas de Cultivo Celular por Lotes , Biodegradación Ambiental , Biomasa , Catecoles/química , Hidroquinonas/química , Hibridación Fluorescente in Situ , Pseudomonas/metabolismo , Aguas del Alcantarillado/microbiología , Temperatura , Factores de Tiempo