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1.
Waste Manag ; 105: 482-491, 2020 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-32143144

RESUMEN

Rapeseed meal (RSM) is a candidate for biopolymer production due to its abundance, low cost and potential integration with other rapeseed-derived products. However, existing studies pursuing such schemes are limited. The feasibility of different strategies for RSM valorization via protein extraction and polyhydroxyalkanoate production were evaluated. Nitrogen-limited RSM media was produced from hydrolysis of residues which had undergone extensive protein extraction using sodium hydroxide. A study of oxygen-limited fermentation was also performed on hydrolysate of untreated RSM via batch feeding. The typical strategy of using a high carbon-to-nitrogen ratio may not be the most suitable route for polyhydroxyalkanoate (PHA) production using nitrogen-rich biomass as a feedstock. Central composite design-based experiments show that due to mass transfer limitations protein extraction at 1-L scale could only achieve yields around 50% and 69%, at room temperature and 60 °C, respectively. Protein extraction yields reduced with successive extractions, meaning that whilst the RSM hydrolysate is viable for growth, designing a valorization scheme which has the fermentation step dictated by the protein extraction may not be practical/economical. A better route which utilizes oxygen-limitation to initially induce stationary phase was identified, giving accumulation of polyhydroxyalkanoate once the oxygen levels began to recover; 8.93% and 1.75% PHA accumulation in fed-batch cultures of synthetic and RSM media, respectively. The findings demonstrate that decoupling of protein extraction performance from PHA synthesis is feasible. This study provides important insight into the degrees of freedom available in the design of a holistic valorization scheme of rapeseed meal, and high protein lignocellulosic biomass in general.


Asunto(s)
Brassica napus , Polihidroxialcanoatos , Pseudomonas putida , Biomasa , Reactores Biológicos , Fermentación , Nitrógeno , Oxígeno
2.
World J Microbiol Biotechnol ; 36(3): 46, 2020 Mar 05.
Artículo en Inglés | MEDLINE | ID: mdl-32140791

RESUMEN

Azotobacter vinelandii is a microorganism with biotechnological potential because its ability to produce alginate and polyhydroxybutyrate. Large-scale biotechnological processes are oriented to sustainable production by using biomass hydrolysates that are mainly composed by glucose and xylose. In the present study, it was observed that A. vinelandii was unable to consume xylose as the sole carbon source and that glucose assimilation in the presence of xylose was negatively affected. Adaptive Laboratory Evolution (ALE) was used as a metabolic engineering tool in A. vinelandii, to improve both carbohydrate assimilation. As a result of ALE process, the CT387 strain was obtained. The evolved strain (CT387) grown in shaken flask cultivations with xylose (8 g L-1) and glucose (2 g L-1), showed an increase of its specific growth rate (µ), as well as of its glucose and xylose uptake rates of 2, 6.45 and 3.57-fold, respectively, as compared with the parental strain. At bioreactor level, the µ, the glucose consumption rate and the relative expression of gluP that codes for the glucose permease in the evolved strain were also higher than in the native strain (1.53, 1.29 and 18-fold, respectively). Therefore, in the present study, we demonstrated the potential of ALE as a metabolic engineering tool for improving glucose and xylose consumption in A. vinelandii.


Asunto(s)
Azotobacter vinelandii/metabolismo , Glucosa/metabolismo , Ingeniería Metabólica/métodos , Xilosa/metabolismo , Azotobacter vinelandii/genética , Azotobacter vinelandii/crecimiento & desarrollo , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Biomasa , Reactores Biológicos , Medios de Cultivo/química , Fermentación , Regulación Bacteriana de la Expresión Génica , ARN Bacteriano/genética , ARN Bacteriano/aislamiento & purificación
3.
J Environ Manage ; 261: 109665, 2020 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-32148247

RESUMEN

Biotechnology has proven effective in removing a wide variety of VOCs. In this study, the effects of pH (from 3 to 7), operating temperature (20-30 °C), empty bed residence time (EBRT, 10-40 s) and transient inlet concentration (400-4000 mg m-3) on the removal performance of an airlift packing bioreactor (ALPR) was investigated. The removal efficiency (RE) and stability of the ALPR was evaluated and compared with the conventional airlift bioreactor (ALR). The results showed that under the influence of single factor variation, the ALPR showed significant higher RE and better stability than the ALR in removing dichloromethane (DCM) and toluene. Besides, a factorial design was used to analyses the interaction of multiple factors and their influence on the removal of DCM and toluene in the ALPR and ALR. It shows that pH value has the most significant influence, and plays a crucial role in maintaining high RE of DCM and toluene in both of the ALPR and ALR. Temperature has a great effect on the removal of toluene. EBRT has certain effect on the removal of DCM in the ALPR. The transient concentration of a single substrate has a significant negative effect on the RE of this substrate, while it does not significantly affect the removal of another substrate in the ALPR. However, the steep increase of DCM concentration has an adverse effect on the RE of high concentration toluene in the ALR. The overall RE and degradation capacity of both toluene and DCM by the ALPR are much higher than that of the conventional ALR.


Asunto(s)
Cloruro de Metileno , Tolueno , Biodegradación Ambiental , Reactores Biológicos
4.
J Environ Manage ; 261: 110241, 2020 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-32148310

RESUMEN

A novel Anoxic-Aerobic Process (AnAP) that eliminated the anaerobic process was optimized and operated for the simultaneous remediation of phosphate, nitrate, and chemical oxygen demand (COD) from industrial effluents. Two sequential batch reactors (SBR) with AnAP were established for the treatment of effluent from two industries; phosphate fertilizer (AnASBR_PPL) and dairy industry (AnASBR_DW). The adaptability of the bacterial consortium in the SBRs, dominated by denitrifying phosphate accumulating organisms (DNPAOs), facilitates the stable performance of AnAP for simultaneous nutrient and COD removal. Up to 90% and ~80% of COD removal were achieved in AnASBR_PPL and AnASBR_DW, respectively. Nearly complete denitrification was observed along with phosphate removal accounted for ~90% in both the reactors. Granulation of sludge has been widely reported in aerobic reactors; however, interestingly, in this study, partial granulation of the sludge was observed in both the AnASBRs which facilitated the microorganisms to uptake a minimal amount of phosphate and nitrate even under the aerobic condition. The underlying mechanism of DNPAOs and other associated microbes in the consortium were investigated for microbial diversity by 16S rDNA based targeted amplicon sequencing using the Illumina platform and imputed metagenomic analysis. The dominance of Betaproteobacteria, Alphaproteobacteria, Gammaproteobacteria, and Bacteroidia was observed in AnASBRs. At steady-state operation, the identity of the core community members remained largly stable, but their relative abundances changed considerably in both the reactors as a function of varying industrial effluent. However, population of few strains such as Lactobacteriales, Enterobacteriales changed drastically with respect to the influent, as these strains were predominat in AnASBR_DW but not present in AnASBR_PPL. The dominant strains were the vital contributor to the gene pool encoding for denitrification, dephosphatation, TCA cycle, glycolysis, EPS production, and polyhydroxyalkanoate (PHA) storage, etc. Few less abundant but persistent species were also detected as contributors to these functional groups. It unveiled the TCA cycle remains preferable over conventional glycolysis in both the SBR irrespective of carbon source. The new AnASBR was proved to be an efficient alternative system that is energy efficient with higher ease of operation for the treatment of different industrial effluents without fail.


Asunto(s)
Betaproteobacteria , Reactores Biológicos , Análisis de la Demanda Biológica de Oxígeno , Desnitrificación , Nitrógeno , Aguas del Alcantarillado , Eliminación de Residuos Líquidos
5.
Bioresour Technol ; 304: 122959, 2020 May.
Artículo en Inglés | MEDLINE | ID: mdl-32135472

RESUMEN

Bioelectrochemical systems like microbial fuel cells (MFCs) are quaint systems known to metamorphose the chemical energy of organic matter into electrical energy using catalytic activity of microorganisms. A novel continuous Auto Circulating Bio-Electrochemical Reactor (AutoCirBER) was developed to fulfil the gap of 'simple, inexpensive and compact design' that can continuously treat larger amount of organic wastewater at shorter residence time and without consuming external energy for liquid mixing. AutoCirBER eliminated the need for external agitation for liquid-mixing and therefore, energy requirements. AutoCirBER was operated in continuous-mode and hydraulic retention time was optimized. The reactor underwent performance check-up viz. COD removal, net power output, columbic efficiency, sludge generation and an attributional life cycle assessment (LCA) was also conducted. AutoCirBER was sustainable to run in continuous-mode and showed more than 90.4% of COD removal, and 59.55 W.h net annual energy recovery. Experimental LCA of AutoCirBER also displays its environmental feasibility in longer run.


Asunto(s)
Fuentes de Energía Bioeléctrica , Aguas Residuales , Reactores Biológicos , Electricidad , Aguas del Alcantarillado , Eliminación de Residuos Líquidos
6.
Chemosphere ; 244: 125513, 2020 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-32050330

RESUMEN

To achieve efficient biological nutrients removal at low temperature, a modified sequencing batch reactor (SBR) was developed at 10 °C by extending sludge retention time (SRT), shortening aerobic stage and compensating anoxic stage. The average removal rates of ammonium (NH4+-N), total nitrogen (TN) and total phosphorus (TP) were 98.82%, 94.12% and 96.04%, respectively. Variation of carbon source in a typical cycle demonstrated the maximum synthesis of poly-ß-hydroxybutyrate (PHB) (60 mg/L) occurred after feast period. Furthermore, the TP in sludge reached 50.4 mg/g mixed liquor suspended solids (MLSS) (78.4% was inorganic phosphorus and 21.6% was organic phosphorus) after 120 days of operation, indicating an excellent P-accumulating capacity was achieved in this system. Ammonia oxidizing bacteria (AOB) activity inhibition test verified both AOB and ammonia oxidizing archaea (AOA) were involved in ammonia-oxidizing process and the latter accounted for 17%-19%. Metagenomic-based taxonomy revealed the dominant genera were Candidatus Accumulibacter (12.18%), Dechloromonas (7.54%), Haliangium (6.69%) and Candidatus Contendobacter (3.40%). As described from the denitrifying genes perspective, with the exception of nitrite reduction (performed by denitrifiers), denitrifying phosphorus-accumulating organisms (DPAOs) played a leading role in denitrification pathway, showing that poly-ß-hydroxyalkanoates (PHA)-driven nutrients removal was the dominate process.


Asunto(s)
Reactores Biológicos/microbiología , Eliminación de Residuos Líquidos/métodos , Amoníaco/metabolismo , Compuestos de Amonio , Betaproteobacteria/metabolismo , Carbono/metabolismo , Frío , Desnitrificación , Hidroxibutiratos , Metagenoma , Microbiota , Nitritos/metabolismo , Nitrógeno/análisis , Nitrógeno/metabolismo , Fósforo/análisis , Fósforo/metabolismo , Poliésteres , Aguas del Alcantarillado/química , Temperatura Ambiental , Contaminantes del Agua/análisis , Contaminantes del Agua/metabolismo
7.
Chemosphere ; 244: 125529, 2020 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-32050333

RESUMEN

Fluidized bed bioreactors can overcome the limitations of packed bed bioreactors such as clogging, which has been observed in the industrial application for decades. The key to establish a gaseous fluidized bed bioreactor for treatment of volatile organic compounds is to achieve microbial growth on a light packing material. In this study, Two fungal species and two bacterial species were isolated to build a fungal fluidized-bed reactor (FFBR). A light packing material with wheat bran coated on expended polystyrene was used. The FFBR was operated for 65 days for gaseous ethanol removal and obtained elimination capacities of 500-1800 g∙m-3∙h-1 and removal efficiencies of 20-50%. The pressure drops was well controlled with values around 400 Pa∙m-1. Stress tolerant genera including Aureobasidium, Stenotrophomonas and Brevundimonas were dominant. Meyerozyma, whose species were present in an initial inoculated isolate, was detected among the dominant species with 28.70% relative abundance; they were reported to degrade complicated compounds under similarly stressful environments.


Asunto(s)
Reactores Biológicos/microbiología , Etanol/metabolismo , Hongos , Gases
8.
Chemosphere ; 244: 125544, 2020 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-32050341

RESUMEN

Bacterial mercury oxidation coupled to denitrification offers great potential for simultaneous removal of elemental mercury (Hg0) and nitric oxide (NO) in a denitrifying membrane biofilm reactor (MBfR). Four potentially contributory mechanisms tested separately, namely, membrane gas separation, medium absorption, biosorption and biotransformation, which contributed 4.9%/7.2%, 8.1%/8.9%, 38.8%/9.5% and 48.2%/84.9% of overall Hg0/NO removal in MBfR. Herein, Hg0 bio-oxidation, oxidative Hg0 biosorption and denitrification played leading roles in simultaneous removal of Hg0 and NO. Living microbes performed simultaneous Hg0 bio-oxidation and denitrification, in which Hg0 as electron donor was biologically oxidized to oxidized mercury (Hg2+), while NO as the terminal electron acceptor was denitrified to N2. The Hg2+ further complexed with humic acids in extracellular polymeric substances via functional groups (-SH, -OH, -NH- and -COO-) and formed humic acids bound mercury (HA-Hg). Non-living microbial matrix performed oxidative Hg0 biosorption, in which Hg0 may be physically adsorbed by cellular matrix, then non-metabolically oxidized to Hg2+ via oxidative complexation with -SH in humic acids and finally cleavage of S-H bond and surface charge transfer led to formation of HA-Hg. Therefore, bioconversion of Hg0 to HA-Hg by Hg0 bio-oxidation and oxidative Hg0 biosorption coupled with NO denitrification to N2 dynamically cooperated to accomplish simultaneous removal of Hg0 and NO in MBfR.


Asunto(s)
Reactores Biológicos/microbiología , Mercurio/metabolismo , Óxido Nítrico/metabolismo , Eliminación de Residuos Líquidos/métodos , Contaminantes Químicos del Agua/metabolismo , Bacterias , Biopelículas , Desnitrificación , Sustancias Húmicas , Membranas , Mercurio/análisis , Oxidación-Reducción
9.
Chemosphere ; 244: 125570, 2020 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-32050348

RESUMEN

In this paper, the enhancement of sodium glutamate (SG) on activity of anaerobic ammonia oxidizing (anammox) bacteria was investigated by batch tests. The results illustrated that SG played an important role in enhancing anammox bacterial activity when the SG dosage ranged from 0.50 to 1.25 mM, and the optimal SG concentration was 1.00 mM. The performance of anammox was the best and the total nitrogen removal rate (TNRR) was 138.2 mg N g-1·VSS·d-1 when the concentration of SG was 1.00 mM. The results of EPS and anammox bacterial biomass measurement indicated that protein (PN), polysaccharide (PS), total EPS and the bacterial abundance reached the maximum of 1.00 mM SG addition. Compared to the control tests, the EPS content and bacterial abundance increased by 38.2% and 75.8%, respectively. In addition, the cloning results showed that the community structure of anammox bacteria evolved in species level of Candidatus Brocadia genus under the condition of SG enhancement.


Asunto(s)
Bacterias/metabolismo , Glutamato de Sodio/metabolismo , Anaerobiosis , Biomasa , Reactores Biológicos/microbiología , Nitrógeno/metabolismo , Oxidación-Reducción
10.
Ultrasonics ; 103: 106086, 2020 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-32070827

RESUMEN

Ultrasonic bioreactors have been used for in vitro experimentation to study cellular responses to low-intensity pulsed ultrasound. The presence of an air interface in these bioreactors contributes to variability in the acoustic pressure field, reducing experimental reproducibility. A multiphysics finite element model was developed to simulate the acoustic field in an in-dish ultrasonic bioreactor, where the transducer is immersed in culture medium above the dish surface, and the effects of replacing air below the dish in the bioreactor with a water layer bounded by an acoustic absorbent layer were evaluated. Frequency domain simulations showed that the spatially-averaged pressure at the dish surface alternated between a minimum and maximum level as the distance between the dish and transducer increased. The ratio of the maximum to minimum level was 6.5-fold when the air interface was present, and this ratio dropped to 1.8-fold with replacement of the air interface. However, radial pressure variability was present with or without the air interface in the bioreactor model. Time-dependent simulations showed that the increase in acoustic pressure to a maximum level after US signal activation and the pressure drop after signal cessation were faster when the water-coupled non-reflective layer was used to replace the air layer below the dish, generating a pressure pattern that more closely followed the applied pulsed ultrasound signal due to reduced wave reflection and interference. Overall, this work showed that having water rather than air in contact with the lower dish surface when paired with an acoustic absorbent layer resulted in a less variable pressure field, providing an improved bioreactor design for in vitro experiments.


Asunto(s)
Acústica , Reactores Biológicos , Análisis de Elementos Finitos , Fenómenos Biofísicos , Medios de Cultivo , Diseño de Equipo , Presión , Programas Informáticos , Propiedades de Superficie , Transductores , Ultrasonido , Agua
11.
Sci Total Environ ; 711: 135087, 2020 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-32000338

RESUMEN

Oxygen has not been purposely introduced to the autotrophic denitrification systems and simultaneous nitrification/autotrophic denitrification (SNAD) has not been proposed. In this study, oxygen was introduced into a micro-electrolysis-enhanced Fe0-supported autotrophic denitrification (mFe0AD) system. The nitrogen removal performance was investigated and the application potential of iron-scraps-supported simultaneous nitrification/mFe0AD was evaluated. The results showed that Fe0AD was surprisingly enhanced by oxygen together with nitrification at average dissolved oxygen (DO) of 0.08-1.56 mg/L. The ammonia oxidizing bacterial, nitrite oxidizing bacteria, facultative autotrophic denitrificans, and iron compounds transformation bacteria were markedly enriched. Average denitrification rate shifted from 0.116 to 0.340 kg N/(m3·d) with increase of average total nitrogen removal efficiency from 31.4% to 90.5%. Oxygen could enhance the biological conversion and storage of iron compounds, which was capable of reducing the coating of Fe0 surface.The accelerating of oxygen on  Fe0 passivation appeared when increasing the average DO from 1.56 to 2.17 mg/L. Therefore, the SNAD was recommended to be operated at the DO range of 0.08-1.56 mg/L. ME significantly enhanced Fe0AD, and the utilization of iron-scraps reduced its cost. The denitrification rate is comparable with methanol supported heterotrophic denitrification with 58.9% reduction on the cost. The iron-scraps supported SNAD is competitive in both denitrification rate and costs in the ammonia contaminated low-carbon water treatment.


Asunto(s)
Desnitrificación , Nitrificación , Reactores Biológicos , Electrólisis , Hierro , Nitrógeno , Oxígeno
12.
Water Res ; 174: 115599, 2020 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-32086134

RESUMEN

The optimal automatic start-up of anaerobic digesters has remained an elusive problem over the years to be solved at the lowest possible costs, including that of process monitoring. In this work, a non-linear model predictive control (NMPC) system was developed, under two proposed configurations, for the optimal start-up of anaerobic digesters treating soluble non-recalcitrant substrates. The minimum set of low cost practical control variables (CVs) selected for process start-up include (i) the effluent quality as acetate COD, (ii) the level of aceticlastic methanogenic biomass in the reactor, and (iii) the methane production rate (only for one of the NMPC configurations). The manipulated variables (MVs) consist of the volumetric inflow rates of the organic substrate, dilution water, and of a possible concentrated alkali addition. To be able to apply the above selected CVs (technically and economically feasible to measure/estimate), a simplified tailored AD model was specifically designed as the prediction model, integral part of the NMPC system. The NMPC system developed was evaluated for a case scenario consisting of the automatic start-up of a high rate AD reactor treating a readily biodegradable carbohydrate based substrate. The AD plant was virtually represented by the complex Anaerobic Digestion Model No. 1. Compared to other manual start-up strategies, the two configurations of the NMPC developed appeared to reach the target methane production rate faster (39 and 18 days for the NMPC versus 70-75 days for the manual strategies) together with an overall superior CV set-point tracking error performance. Interestingly, the two configurations of the NMPC developed appear to propose two very different, almost opposite, start-up feeding strategies to both eventually start-up the reactor successfully with no process destabilizations throughout. A number of practical scenarios were also considered to evaluate the NMPC configurations for robustness and any possible improvements. These tests indicate that the NMPC objective function formulation is a key factor of the success and robustness exhibited during start-up.


Asunto(s)
Reactores Biológicos , Euryarchaeota , Anaerobiosis , Bacterias Anaerobias , Biomasa , Metano
13.
Waste Manag ; 105: 279-288, 2020 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-32092533

RESUMEN

Co-digestion of blackwater (BW) and organic kitchen waste (KW) is a promising and effective resource-recovery based approach for municipal waste and wastewater treatment. In this study, anaerobic co-digestion treatments of BW and KW using anaerobic sequencing batch reactors under mesophilic and thermophilic conditions were compared. Our results showed that although higher sludge specific methanogenesis activities were observed in the thermophilic reactor, mesophilic treatment achieved significantly higher treatment capacity and methane production. It was concluded that thermophilic conditions introduced H2 inhibition and reduced activities of syntrophic acetogenic bacteria and syntrophic acetate oxidizing bacteria in the reactor. Further investigation on microbial communities showed significantly different microbial communities between reactors, where Thermotogaceae and Methanothermobacter were the most prevalent bacteria and archaea in the thermophilic reactor, and Cloacamonaceae and Methanosarcina were the most prevalent ones in the mesophilic reactor.


Asunto(s)
Reactores Biológicos , Metano , Anaerobiosis , Archaea , Aguas del Alcantarillado
14.
Water Res ; 174: 115595, 2020 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-32097807

RESUMEN

Nitrate removal efficiency of aerobic methane oxidation coupled with denitrification (AME-D) process was elevated by enhancing the methanol-linked synergy in a membrane biofilm reactor (MBfR) under a low O2:CH4 ratio. After 140 days' enrichment, the nitrate removal rate increased significantly from 3 to 4 mg-N L-1 d-1 to 22.09 ± 1.21 mg-N L-1 d-1 and the indicator, mol CH4 consumed/mol reduced NO3--N (C/N ratio), decreased to 1.79 which was very close to the theoretical minimum value (1.27-1.39). The increased nitrate removal efficiency was largely related to the enhanced relationship between aerobic methanotrophs and methanol-utilizing denitrifiers. Type I methanotrophs and some denitrifiers, especially those potential methanol-utilizing denitrifiers from Methylobacillus, Methylotenera, Methylophilus and Methyloversatilis, were abundant in the MBfR sludge. Aerobic methanotrophs and potential methanol-utilizing denitrifiers were closely associated in many globular aggregates (5-10 µm diameter) in the MBfR sludge, which may have promoted the denitrifiers to capture methanol released by methanotrophs efficiently. If we assume methanol is the only cross-feeding intermediate in the MBfR, about 38-60% of the CH4 supplied would be converted to methanol and secreted rather than continuing to be oxidized. At least 63% of this secreted methanol should be utilized for denitrification instead of being oxidized by oxygen in the MBfR. These findings suggest that the nitrate removal efficiency of the AME-D process could be significantly improved.


Asunto(s)
Reactores Biológicos , Metanol , Biopelículas , Desnitrificación , Metano , Nitratos , Oxidación-Reducción
15.
Water Res ; 174: 115632, 2020 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-32105998

RESUMEN

The granulation of anaerobic ammonium oxidation (Anammox) biomass plays a key role in high rate performance of upflow-type Anammox reactors. However, the formation of cavitation inside granules may result in sludge flotation problem, which negatively affects the operation stability. For quantitative evaluation of the Anammox granules flotation in upflow reactors, an integrated mathematical model was formulated based on the principles that the limitation of substrate diffusion would result in bacterial starvation, lysis and subsequently aiding the formation of cavitation in the inner zone of granules. The proposed model is used to investigate the possible mechanism of cavitation formation and granules flotation. The combined modelling and experimental results showed that the model predictions matched well with the actual floating behavior of granules (R2 = 0.83 for settled sludge and 0.76 for floating sludge). Based on the model results, the granule flotation could be divided into three zones namely (i) no-flotation zone (no flotation occurrence), (ii) transition zone (flotation with a part of granules), and (iii) flotation zone (inevitable flotation occurrence). The floating behavior of granules was mainly influenced by granule diameter (2.5-4.5 mm) and substrate concentration (NO2-N, 50-250 mg/L) in the transition zone. The optimum granule diameter to avoid flotation but with excellent settling performance was identified around 2.5 mm. Additionally, the granule size is more sensitivity to flotation than substrate concentration. Hence, controlling the size of granules is more important to alleviate granule flotation in Anammox reactors' operation.


Asunto(s)
Reactores Biológicos , Aguas del Alcantarillado , Anaerobiosis , Bacterias , Modelos Teóricos , Nitrógeno , Oxidación-Reducción
16.
Water Res ; 174: 115633, 2020 May 01.
Artículo en Inglés | MEDLINE | ID: mdl-32109752

RESUMEN

This study combined at pilot scale the recovery of cellulosic primary sludge from the sieving of municipal wastewater followed by the production of bio-based VFAs through acidogenic fermentation. The sieving of municipal wastewater was accomplished by a rotating belt filter which allowed the removal of around 50% of suspended solids when operated at solids loading rates higher than 30-35 kgTSS/m2 h. The solids recovered by sieving contained around 40% of cellulose, which is a suitable raw material for the production of bio-based VFAs. Initially, fermentation batch tests of cellulosic primary sludge were carried out adjusting the initial pH of the sludge at values of 8, 9, 10 and 11, in order to evaluate the best production yields of bio-based VFAs and their composition. The highest VFAs yield achieved was 521 mgCODVFA/gVS occurring when pH was adjusted at 9, while propionic acid reached 51% of the total VFAs. Then, the optimal conditions were applied at long term in a sequencing batch fermentation reactor where the highest potential productivity of bio-based VFAs (2.57 kg COD/m3 d) was obtained by adjusting the pH feeding at 9 and operating with an hydraulic retention time of 6 days under mesophilic conditions. The cost-benefit analyses for the implementation of cellulosic primary sludge recovery was carried out consideringthe anaerobic digestion as reference scenario. The economical assessment showed that the production of bio-based VFAs from cellulosic primary sludge as carbon source and/or as chemical precursors give higher net benefits instead of the only biogas production.


Asunto(s)
Reactores Biológicos , Aguas Residuales , Ácidos Grasos Volátiles , Fermentación , Aguas del Alcantarillado
17.
Sci Total Environ ; 713: 136698, 2020 Apr 15.
Artículo en Inglés | MEDLINE | ID: mdl-32019036

RESUMEN

Bio-electrochemical denitrification (BED) is a promising organic carbon-free nitrate remediation technology. However, the relationship between engineering conditions, biofilm community composition, and resultant functions in BED remains under-explored. This study used deep sequencing and variation partitioning analysis to investigate the compositional shifts in biofilm communities under varied poised potentials in the batch mode, and correlated these shifts to reactor-level functional differences. Interestingly, the results suggest that the proliferation of a key species, Thiobacillus denitrificans, and community diversity (the Shannon index), were almost equally important in explaining the reactor-to-reactor functional variability (e.g. variability in denitrification rates was 51% and 38% attributable to key species and community diversity respectively, with a 30% overlap), but neither was heavily impacted by the poised potential. The findings suggest that while enriching the key species may be critical in improving the functional efficiency of BED, poised potentials may not be an effective strategy to achieve the desired level of enrichment in substrate-limited real-world conditions.


Asunto(s)
Desnitrificación , Biopelículas , Reactores Biológicos , Nitratos , Thiobacillus
18.
Sci Total Environ ; 713: 136739, 2020 Apr 15.
Artículo en Inglés | MEDLINE | ID: mdl-32019052

RESUMEN

Nitrate-dependent anaerobic methane oxidation (N-DAMO), a bioprocess that couples the oxidation of green gas and the removal of nitrogen oxides in a microbial group, has gained much attention as a potential economical method of biological removal of nitrates and methane from wastewater. Low-temperature (20 °C) operation of N-DAMO would be beneficial to utilize the methane dissolved in the effluent and thus decrease the cost of maintaining the bioreactor temperature in wastewater treatment. Here, the long-term (>350 days) operational activities of N-DAMO were evaluated to assess the performance of N-DAMO from stepwise cooling (30-20 °C) to ambient temperatures (13-38 °C). Under stepwise cooling conditions, the activity of the N-DAMO community was first inhibited and then rapidly adjusted. Notably, a similar N-DAMO activity was observed at 30 °C and 20 °C. Under ambient temperature conditions, the highest nitrate removal rate observed at the beginning of the test was 7.14 mg-N/L/d, which was 5.3 times higher than that recorded at the end of the test. This indicates that the long-term temperature fluctuation irreversibly inhibited N-DAMO activity. 16S rRNA gene sequencing analyses found that the functional archaea were ANME-2D, which has been deemed as the dominant culture in the N-DAMO process. The abundance of ANME-2D on the last day at stepwise cooling temperature conditions was much higher than on day 0, but disappeared after a long period of operation at ambient temperature. It was assumed that N-DAMO would stabilize at stepwise cooling temperature conditions, but not at ambient temperature. Our findings could offer a promising technology for anaerobic wastewater treatment plants (WWTPs) in temperate and warm climate zones.


Asunto(s)
Metano/química , Anaerobiosis , Reactores Biológicos , Desnitrificación , Nitritos , Oxidación-Reducción , ARN Ribosómico 16S , Temperatura Ambiental
19.
Water Res ; 172: 115531, 2020 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-32004912

RESUMEN

Seawater can be introduced or intrude in sewer systems and can thereby negatively influence biological wastewater treatment processes. Here we studied the impact of artificial seawater on the enhanced biological phosphate removal (EBPR) process performance by aerobic granular sludge (AGS) with synthetic wastewater. Process performance, granule stability and characteristics as well as microbial community of a seawater-adapted AGS system were observed. In seawater conditions strong and stable granules formed with an SVI5 of 20 mL/g and a lower abrasion coefficient than freshwater-adapted granules. Complete anaerobic uptake of acetate, anaerobic phosphate release of 59.5 ± 4.0 mg/L PO43--P (0.35 mg P/mg HAc), and an aerobic P-uptake rate of 3.1 ± 0.2 mg P/g VSS/h were achieved. The dominant phosphate accumulating organisms (PAO) were the same as for freshwater-based aerobic granular sludge systems with a very high enrichment of Ca. Accumulibacter phosphatis clade I, and complete absence of glycogen accumulating organisms. The effect of osmotic downshocks was tested by replacing influent seawater-based medium by demineralized water-based medium. A temporary decrease of the salinity in the reactor led to a decreased phosphate removal activity, while it also induced a rapid release of COD by the sludge, up to 45.5 ± 1.7 mg COD/g VSS. This is most likely attributed to the release of osmolytes by the cells. Recovery of activity was immediately after restoring the seawater feeding. This work shows that functioning of aerobic granular sludge in seawater conditions is as stable as in freshwater conditions, while past research has shown a negative effect on operation of AGS processes with NaCl-based wastewater at the same salinity as seawater.


Asunto(s)
Fósforo , Aguas del Alcantarillado , Reactores Biológicos , Agua de Mar , Aguas Residuales
20.
Water Res ; 172: 115528, 2020 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-32004914

RESUMEN

The study demonstrated a novel anammox-like process to remove high-concentration ammonium using nitrate as terminal electron acceptor under Fe(III)/Fe(II) cycle. Compared with NO2- in common anammox, NO3- used here is more available in practice, suitable for in-situ removal of high-concentration NH4+ in a single anaerobic system. The NOx- and Fe(II) produced from Feammox [Fe(III) reduction coupled to anaerobic ammonium oxidation] subsequently react together via NOx--dependent Fe(II) oxidation to regenerate Fe(III) that potentially stimulates next round of Feammox. However, these processes couldn't be lasting due to inadequate Fe(III) regeneration because NOx- is non-dominant product during Feammox. In this study NO3- was added to supplement the insufficient NOx- to enhance Fe(III) regeneration and remove nitrogen successively. Results showed that periodically adding nitrate caused oscillations between Fe(III) and Fe(II) in the sludge, implying Fe(III) regeneration and consumption. Consequently, nitrogen removal of the digester with an initial total nitrogen of 1036.7 mg/L reached 90.1% after 98-day operation, much higher than that of control (41.6%) without NO3- addition. Adding NO3- in the digester to trigger Fe(III)/Fe(II) cycle for removing ammonium is just equivalent to an anammox-like process using NO3- as terminal electron acceptor to oxidize NH4+.


Asunto(s)
Compuestos de Amonio , Anaerobiosis , Reactores Biológicos , Electrones , Compuestos Férricos , Compuestos Ferrosos , Nitratos , Nitrógeno , Oxidación-Reducción
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