Kinetic and stoichiometric characterization of anoxic sulfide oxidation by SO-NR mixed cultures from anoxic biotrickling filters.

Monitoring the biological activity in biotrickling filters is difficult since it implies estimating biomass concentration and its growth yield, which can hardly be measured in immobilized biomass systems. In this study, the characterization of a sulfide-oxidizing nitrate-reducing biomass obtained from an anoxic biotrickling filter was performed through the application of respirometric and titrimetric techniques. Previously, the biomass was maintained in a continuous stirred tank reactor under steady-state conditions resulting in a growth yield of 0.328 ± 0.045 g VSS/g S. To properly assess biological activity in respirometric tests, abiotic assays were conducted to characterize the stripping of CO2 and sulfide. The global mass transfer coefficient for both processes was estimated. Subsequently, different respirometric tests were performed: (1) to solve the stoichiometry related to the autotrophic denitrification of sulfide using either nitrate or nitrite as electron acceptors, (2) to evaluate the inhibition caused by nitrite and sulfide on sulfide oxidation, and (3) to propose, calibrate, and validate a kinetic model considering both electron acceptors in the overall anoxic biodesulfurization process. The kinetic model considered a Haldane-type equation to describe sulfide and nitrite inhibitions, a non-competitive inhibition to reflect the effect of sulfide on the elemental sulfur oxidation besides single-step denitrification since no nitrite was produced during the biological assays.

A Novel Hybrid Membrane Process Coupled with Freeze Concentration for Phosphorus Recovery from Cheese Whey.

The ever-increasing demand for phosphorus fertilisers for securing global food production, coupled with finite phosphate rock reserves, is one of the emerging problems in the world. Indeed, phosphate rock is listed as an EU critical raw material, triggering attention to find an alternative source to substitute the use of this limited resource. Cheese whey, characterized by a high content of organic matter and phosphorus, represents a promising feedstock for phosphorus recovery and recycling. An innovative application of a membrane system coupled with freeze concentration was assessed to recover phosphorus from cheese whey. The performances of a microfiltration membrane (0.2 µm) and an ultrafiltration (200 kDa) membrane were evaluated and optimized under different transmembrane pressures and crossflow velocities. Once the optimal operating conditions were determined, a pre-treatment including lactic acid acidification and centrifugation was applied to increase the permeate recovery. Finally, the efficiency of progressive freeze concentration for the treatment of the permeate obtained from the optimum conditions (UF 200 kDa with TMP of 3 bar, CFV of 1 m/s and lactic acid acidification) was evaluated at specific operating conditions (-5 °C and 600 rpm of stirring speed). Finally, 70% of phosphorus could be recovered from cheese whey using the coupled technology of the membrane system and freeze concentration. A phosphorus-rich product was obtained with high agronomic value, which constitutes a further step towards establishing a broader circular economy framework.

Application of Vibrating Reverse Osmosis Technology for Nutrient Recovery from Pig Slurry in a Circular Economy Model.

The rapid growth of the livestock sector in some areas of Europe has caused an imbalance between the generation of livestock manure and the availability of agricultural soil for its direct application as a fertilizer. Since the transport of pig slurry to other areas with nutrient-deficient soils is costly from an economic point of view due to its high water content, the application of new technologies for the concentration of this waste is considered key for reducing management costs. Consequently, the main objective of this study was to demonstrate the potential of vibratory shear enhanced processing (VSEP) operated with reverse osmosis membranes to recover nutrients from the liquid fractions of pig slurry (LF-pig slurry) and digestate (LF-digestate) and obtain concentrated fertilizing products. Use of the VSEP unit permitted reductions in the water contents of the LF-pig slurry and LF-digestate, around 77% and 67%, respectively. Both VSEP concentrates were characterized by their significant nutrient contents and showed a nitrogen fertilizer replacement value similar to that of mineral fertilizer as demonstrated in a barley crop pot-test, although the salinity of the digestate concentrate was identified as a key limitation, negatively impacting the agronomic yield of the test crop.

Microbial Diversity Dynamics in a Methanogenic-Sulfidogenic UASB Reactor.

In this study, the long-term performance and microbial dynamics of an Upflow Anaerobic Sludge Blanket (UASB) reactor targeting sulfate reduction in a SOx emissions treatment system were assessed using crude glycerol as organic carbon source and electron donor under constant S and C loading rates. The reactor was inoculated with granular sludge obtained from a pulp and paper industry and fed at a constant inlet sulfate concentration of 250 mg S-SO42-L-1 and a constant C/S ratio of 1.5 ± 0.3 g Cg-1 S for over 500 days. Apart from the regular analysis of chemical species, Illumina analyses of the 16S rRNA gene were used to study the dynamics of the bacterial community along with the whole operation. The reactor was sampled along the operation to monitor its diversity and the changes in targeted species to gain insight into the performance of the sulfidogenic UASB. Moreover, studies on the stratification of the sludge bed were performed by sampling at different reactor heights. Shifts in the UASB performance correlated well with the main shifts in microbial communities of interest. A progressive loss of the methanogenic capacity towards a fully sulfidogenic UASB was explained by a progressive wash-out of methanogenic Archaea, which were outcompeted by sulfate-reducing bacteria. Desulfovibrio was found as the main sulfate-reducing genus in the reactor along time. A progressive reduction in the sulfidogenic capacity of the UASB was found in the long run due to the accumulation of a slime-like substance in the UASB.

Optimization of SO2 and NOx sequential wet absorption in a two-stage bioscrubber for elemental sulphur valorisation.

Flue gases contain SO2 and NOx that can be treated together for elemental sulphur recovery in bioscrubbers, a technology that couples physical-chemical and biological processes for gaseous emissions treatment in a more economic manner than classical absorption. Sequential wet absorption of SO2 and NOx from flue gas is thoroughly studied in this work in a two-stage bioscrubber towards elemental sulphur valorisation pursuing reuse of biological process effluents as absorbents. The optimal operating conditions required for SO2 and NOx absorption in two consecutive spray absorbers were defined using NaOH-based absorbents. Overall, removal efficiencies of 98.9% and 55.9% for SO2 and NOx abatement were obtained in two in-series scrubbers operated under a gas contact time of 1 and 100 s, and a liquid-to-gas ratio of 7.5 and 15 L m-3, respectively. Higher NOx removal efficiency to clean gas emission was obtained by oxidants dosing in the absorber for NOx absorption. High NaHCO3 concentration in a two-stage bioscrubber effluent was exploited as alkaline absorbent for flue gas treatment. The performance of scrubbers using an absorbent mimicking a reused effluent exhibited the same removal efficiencies than those observed using NaOH solutions. In addition, the reuse of bioprocess effluent reduced reagents' consumption by a 63.7%. Thus, the two-stage bioscrubber proposed herein offers an environmentally friendly and economic alternative for flue gas treatment.

Respirometric characterization of aerobic sulfide, thiosulfate and elemental sulfur oxidation by S-oxidizing biomass.

Respirometry was used to reveal the mechanisms involved in aerobic biological sulfide oxidation and to characterize the kinetics and stoichiometry of a microbial culture obtained from a desulfurizing biotrickling filter. Physical-chemical processes such as stripping and chemical oxidation of hydrogen sulfide were characterized since they contributed significantly to the conversions observed in respirometric tests. Mass transfer coefficient for hydrogen sulfide and the kinetic parameters for chemical oxidation of sulfide with oxygen were estimated. The stoichiometry of the process was determined and the different steps in the sulfide oxidation process were identified. The conversion scheme proposed includes intermediate production of elemental sulfur and thiosulfate and the subsequent oxidation of both compounds to sulfate. A kinetic model describing each of the reactions observed during sulfide oxidation was calibrated and validated. The product selectivity was found to be independent of the dissolved oxygen to hydrogen sulfide concentration ratio in the medium at sulfide concentrations ranging from 3 to 30 mg S L(-1). Sulfide was preferentially consumed (SOURmax = 49.2 mg DO g(-1) VSS min(-1)) and oxidized to elemental sulfur at dissolved oxygen concentrations above 0.8 mg DO L(-1). Substrate inhibition of sulfide oxidation was observed (K(i,S(2-))= 42.4 mg S L(-1)). Intracellular sulfur accumulation also affected negatively the sulfide oxidation rate. The maximum fraction of elemental sulfur accumulated inside cells was estimated (25.6% w/w) and a shrinking particle equation was included in the kinetic model to describe elemental sulfur oxidation. The microbial diversity obtained through pyrosequencing analysis revealed that Thiothrix sp. was the main species present in the culture (>95%).

[Management of the most frequent functional gastrointestinal dis orders in healthy infants]. / Manejo de los trastornos funcionales digestivos más frecuentes en lactantes sanos.

Healthy infants during the first year of life often have multiple functional gastrointestinal symptoms such as colic, regurgitation and constipation. The usual fuzziness and/or crying at this stage of life is interpreted as digestive discomfort or pain, and the corresponding concerns result in unsuitable behaviors as overeating, interruption of breastfeeding, multiple changes of formulas, innumerable queries and unnecessary medications. The aim of this paper is to update knowledge on the pathophysiology of the most common functional gastrointestinal dis orders, in order to avoid over diagnosis and select the most appropriate therapeutic approach and convenient nutritional interventions.

Examining thiosulfate-driven autotrophic denitrification through respirometry.

Anoxic respirometry was applied to characterize a sulfide-oxidizing nitrate-reducing (SO-NR) culture obtained from an anoxic biogas desulfurizing biotrickling filter treating high loads of H2S. Immobilized biomass extracted from the biotrickling filter was grown in a suspended culture with thiosulfate as electron donor to obtain the biomass growth yield and the S2O3(2)(-)/NO3(-) consumed ratio. Afterward, respirometry was applied to describe thiosulfate oxidation under anoxic conditions. A pure culture of Thiobacillus denitrificans was also used as a control culture in order to validate the procedure proposed in this work to characterize the SO-NR biomass. Respirometric profiles obtained with this microbial culture showed that nitrite was formed as intermediate during nitrate reduction and revealed that no competitive inhibition appeared when both electron acceptors were present in the medium. Although final bioreaction products depended on the initial S2O3(2)(-)/NO3(-) ratio, such ratio did not affect thiosulfate oxidation or denitrification rates. Moreover, respirometric profiles showed that the specific nitrite uptake rate depended on the biomass characteristics being that of a SO-NR mixed culture (39.8mgNg(-1) VSSh(-1)) higher than that obtained from a pure culture of T. denitrificans (19.7mgNg(-1) VSSh(-1)). For the first time, the stoichiometry of the two-step denitrification mechanism with thiosulfate oxidation and biomass growth associated was solved for both reactions.

Cross effect of temperature, pH and free ammonia on autotrophic denitrification process with sulphide as electron donor.

Autotrophic denitrification is a suitable technology to simultaneously remove oxidised nitrogen compounds and reduced sulphur compounds yielding nitrogen gas, sulphur and sulphate as the main products. In this work, several batch tests were conducted to investigate the cross effect of temperature, pH and free ammonia on the autotrophic denitrification. Denitrification efficiencies above 95% were achieved at 35°C and pH 7.5-8.0 with maximum specific autotrophic denitrifying activities up to 188mgN2g(-1)VSSd(-1). Free ammonia did not show any effect on denitrification at concentrations up to 53mg NH3-NL(-1). Different sulphide concentrations were also tested with stoichiometric nitrite and nitrate concentrations. Sulphide inhibited denitrification at concentrations higher than 200mgS(2-)L(-1). A 50% inhibition was also found at nitrite concentrations above 48mg NO2(-)-NL(-1). The maximum specific activity decreased until a value of 25mgN2g(-1) VSSd(-1) at 232mg NO2(-)-NL(-1). The Haldane model was used to describe denitrification inhibition caused by nitrite. Kinetic parameters determined from the fitting of experimental data were rmax=176mgN2g(-1)VSSd(-1), Ks=10.7mg NO2(-)-NL(-1) and Ki=34.7mg NO2(-)-NL(-1). The obtained model allowed optimising an autotrophic denitrification process by avoiding situations of inhibition and thus obtaining higher denitrification efficiencies.

Aerobic desulfurization of biogas by acidic biotrickling filtration in a randomly packed reactor.

Biotrickling filters for biogas desulfurization still must prove their stability and robustness in the long run under extreme conditions. Long-term desulfurization of high loads of H2S under acidic pH was studied in a lab-scale aerobic biotrickling filter packed with metallic Pall rings. Reference operating conditions at steady-state corresponded to an empty bed residence time (EBRT) of 130s, H2S loading rate of 52gS-H2Sm(-3)h(-1) and pH 2.50-2.75. The EBRT reduction showed that the critical EBRT was 75s and the maximum EC 100gS-H2Sm(-3)h(-1). Stepwise increases of the inlet H2S concentration up to 10,000 ppmv lead to a maximum EC of 220gS-H2Sm(-3)h(-1). The H2S removal profile along the filter bed indicated that the first third of the filter bed was responsible for 70-80% of the total H2S removal. The oxidation rate of solid sulfur accumulated inside the bioreactor during periodical H2S starvation episodes was verified under acidic operating conditions. The performance under acidic pH was comparable to that under neutral pH in terms of H2S removal capacity. However, bioleaching of the metallic packing used as support and chemical precipitation of sulfide/sulfur salts occurred.

Prevalence of celiac disease: multicentric trial among pediatric population from five urban districts in Argentina.

INTRODUCTION: No published material on the prevalence of celiac disease (CD) in the pediatric population of Argentina has been found up to date. Objective. To estimate the prevalence of CD in a pediatric population (hospital-based sample) from 5 urban districts of Argentina. METHODS: In a cross-sectional descriptive study, we analyzed serum samples from 2219 children, aged 3-16 years old, which had been requested for pre-surgical tests and for physical aptitude certificates for sports in the province of Buenos Aires, and cities of Buenos Aires, Córdoba, Santa Fe and Salta. Children with a previous and accurate diagnosis of CD were also included. IgA class tissue transglutaminase antibodies were determined using serum samples, and those samples which turned out positive were also tested for IgA class endomysium antibodies. A small intestine biopsy was proposed for those who had a positive serology. RESULTS: Between May 2008 and August 2009, 29 positive serologies were found. A total of 22 duodenum biopsies were performed, and 21 turned out compatible with CD. Out of 2219 children, 7 had a previous diagnosis. A prevalence of 1.26% (1:79 children), with female gender predominance (p < 0.023) was found. Ninety percent of the celiac children were over 6 years old (p < 0.021). Silent celiac disease predominated but there was a 33% of symptomatic cases. CONCLUSIONS: The results of the trial show a higher prevalence of CD than expected. The finding of symptomatic patients (33%) suggests the undertaking of different activities to spread the knowledge on this disease and promote the indication for serology test, to avoid complications by means of an early diagnosis.

Prevalence of celiac disease: multicentric trial among pediatric population from five urban districts in Argentina / Prevalencia de enfermedad celíaca: estudio multicéntrico en población pediátrica de cinco distritos urbanos de la Argentina

Introduction. No published material on the preva lence of celiac disease (CD) in the pediatric population of Argentina has been found up to date. Objective. To estimate the prevalence of CD in a pediatric population (hospital-based sample) from 5 urban districts of Argentina. Methods. In a cross-sectional descriptive study, we analyzed serum samples from 2219 children, aged 3-16 years old, which had been requested for pre-surgical tests and for physical aptitude certifcates for sports in the province of Buenos Aires, and cities of Buenos Aires, Córdoba, Santa Fe and Salta. Children with a previous and accurate diagnosis of CD were also included. IgA class tissue transglu taminase antibodies were determined using serum samples, and those samples which turned out positive were also tested for IgA class endomysium an tibodies. A small intestine biopsy was proposed for those who had a positive serology. Results. Between May 2008 and August 2009, 29 positive serologies were found. A total of 22 duo denum biopsies were performed, and 21 turned out compatible with CD. Out of 2219 children, 7 had a previous diagnosis. A prevalence of 1.26% (1:79 children), with female gender predominance (p < 0.023) was found. Ninety percent of the celiac children were over 6 years old (p < 0.021). Silent celiac disease predominated but there was a 33% of symptomatic cases. Conclusions. The results of the trial show a higher prevalence of CD than expected. The finding of symptomatic patients (33%) suggests the undertak ing of different activities to spread the knowledge on this disease and promote the indication for serology test, to avoid complications by means of an early diagnosis.

Introducción. Hasta la fecha del estudio no se hallaron estudios poblacionales publicados sobre prevalencia de enfermedad celíaca en la población pediátrica argentina. Objetivo. Estimar la prevalencia de la enfermedad celíaca en población pediátrica a partir de una muestra de base hospitalaria de cinco distritos urbanos. Método. Diseño descriptivo de corte transversal. Bajo consentimiento informado, participaron 2219 niños, de 3 a 16 años, que realizaban estudios de laboratorio para exámenes prequirúrgicos o certificados de aptitud física deportiva del Conurbano bonaerense, y ciudades de Buenos Aires, Santa Fe, Córdoba y Salta. Se incluyeron niños con diagnóstico previo y certero de enfermedad celíaca dentro de esa población. Se determinaron anticuerpos antitransglutaminasa y, en las muestras positivas, anticuerpo antiendomisio. Se propuso biopsia de intestino delgado a quienes presentaron ambas serologías positivas. Resultados: 29 serologías fueron positivas. Se realizaron 22 biopsias de duodeno, 21 fueron compatibles con enfermedad celíaca y 7 presentaron diagnóstico previo. La prevalencia fue de 1,26% (1:79) IC 95% 0,84-1,81, con predominio del sexo femenino (p <0,039). El 90% de los niños celíacos hallados fueron mayores de 6 años. Las formas clínicas silentes predominaron, pero hubo un 33% de casos sintomáticos. Conclusión. Los resultados en la población estudiada muestran una prevalencia mayor que la esperada. El hallazgo de formas sintomáticas (33%) sugiere emprender acciones de difusión del conocimiento de la enfermedad y ampliar la indicación de serología para obtener diagnóstico precoz.

Prevalencia de enfermedad celíaca: estudio multicéntrico en población pediátrica en cinco distritos urbanos de Argentina / Prevalence of celiac disease: multicentric trial among pediatric population in five urban districts of Argentina

INTRODUCCIÓN: Hasta la fecha del estudio no se hallaron estudios poblacionales publicados sobre prevalencia de EC en población pediátrica argentina. OBJETIVO: estimar la prevalencia de la EC en población pediátrica de cinco distritos urbanos. MÉTODOS: diseño descriptivo de corte transversal. Se invitó a participar a 2.230 niños, de 3 a 16 años, que realizaban estudios de laboratorio para exámenes prequirúrgicos o certificados de aptitud física deportiva. Se determinaron Anticuerpos Antitransglutaminasa, y en las muestras positivas Anticuerpo Antiendomisio. Se propuso biopsia de intestino delgado a quienes presentaron ambas serologías positivas. Se incluyeron niños con diagnóstico previo de EC que cumplían los criterios de inclusión. La prevalencia se expresó mediante el porcentajey su IC exacto. Las comparaciones entre grupos se efectuaron mediante la prueba exacta de Fisher. RESULTADOS: se testearon los sueros de 2.219 niños, 29 serologías fueron positivas. Se realizaron 22 biopsias de duodeno, 21 fueron compatibles con EC y 7 presentaron diagnóstico previo. La prevalencia fue de 1,26% (1:79)IC 95% 0,84-1.81, con predominio del sexo femenino (p<0,039) e importantes diferencias regionales. El 90% de los niños celíacos hallados fueron > 6 años. Las formas clínicas silentes predominaron pero hubo un 33% de casos sintomáticos. CONCLUSIÓN: los resultados en la población estudiada muestran una prevalencia mayor que estudios previos en adultos. El hallazgo de formas sintomáticas (33%) sugiere emprender acciones de difusión del conocimientode la enfermedad y ampliar la indicación de serología para obtener diagnóstico precoz.

INTRODUCTION: up the date of this study, published material about the prevalence of CD in pediatric population in Argentina has not been found. OBJECTIVE: to estimate CD prevalencein a pediatric population of 5 urban districts. METHODS: descriptive and cross sectional cut design. Were invited 2.230 children, between 3 and 16 years, which had been requested forpre-surgical studies and physical aptitude certificates for sports. IgA class tissue transglutaminase antibodies were determined and to positive samples IgA class endomysium antibodies. A small intestine biopsy was proposed for those who had both positive serology. Children with a previous diagnosis of CD who met the inclusion criteria were included. The prevalence was expressed by means of the percentage and its exact confidence interval and the comparisons between groups were performed using Fisher´s exact test. RESULTS: 2.219 children´s sera were studied. 29 were positive serologies. 22 duodenum biopsies were performed, 21 turned out compatible with CD. 7 children presented a previous diagnosis. A prevalence of 1.26% (1:79) CI 95% (0,84-1,81) was found, with female sex predominance ( p<0.039) and important regional differences as well. Ninety percent of the celiac children found were> 6 years Silent clinical manifestations predominated but there were 33% of symptomatic cases. CONCLUSIONS: the results in the study population showed a higher prevalence than previous studies in adults. The finding of symptomatic manifestations (33%)suggests actions to spread the knowledge of this disease promotingthe indication of serology for early diagnosis.

Enfermedad celíaca asociada con diabetes mellitus insulinodependiente / Coeliac disease associated with insulin dependent diabetes mellitus

Con el propósito de establecer la prevalencia de enfermedad celíaca (EC) asintomática u oligosintomática en niños que padecían diabetes mellitus insulinodependiente (DMID) efectuamos un rastreo en una de sus visitas de rutina durante el año 1991. Material y métodos: La detección de EC se realizó mediante la determinación de anticuerpos antigliadina clase IgA (AGA) por inmunoenzimoanálisis (ELISA). A los niños con AGA superior al valor de corte (25 U) se les realizó biopsia peroral de intestino delgado considerándose compatible con EC la presencia de atrofia vellositaria subtotal o total (atrofia grados III-IV). Resultados: Trece pacientes (30,2 por ciento) mostraron AGA elevados y cuatro, biopsias positivas. Considerando la existencia de dos pacientes con diagnóstico previo de EC, la prevalencia obtenida fue de 13,9 por ciento. Conclusiones: Este estudio confirma la asociación frecuente de enfermedad celíaca y diabetes insulinodependiente, obteniéndose una prevalencia de 13,9 por ciento

Perinonitis bacteriana espontánea asociada a hepatitis fulminante / Spontaneous bacterialperitonitis associated with fulminant hepatitis

Se presenta una niña de 8 años de edad, con un cuadro de hepatitis fulminante y peritonitis bacteriana espontánea (PBE) por E. coli. Su evolución fue desfavorable, falleciendo a los 22 días de internación. Se realizó necropsia parcial, la cual confirmó el diagnóstico. Se comenta la excepcional asociación de peritonitis primaria a enfermedad hepática aguda