Ibuprofen removal by a microfiltration membrane bioreactor during the startup phase.

The behavior of ibuprofen (IBU) during the startup phase of a microfiltration membrane bioreactor (MBR) was determined. A full-scale experimental installation treating real urban wastewater was used for the study. The MBR was composed of an anoxic and an aerobic bioreactors working in pre-denitrification configuration, followed of a membrane reactor. A full mass balance was carried out to estimate the contribution of biotransformation and sorption to biomass to the overall removal of the IBU. During the startup phase of the MBR system there were significant oscillations of the operational variables, mainly of the sludge retention time (SRT); nevertheless, the capacity of the system for IBU removal was very high, with yields of over 94%, despite reaching minimum SRT values of 4.15 d. The main IBU removal occurs in the aerobic reactor, both in the liquid phase and the one associated with the sludge, while in the anoxic bioreactor the removal was scarce, although a certain transfer of IBU from the liquid phase to the sludge took place under anoxic conditions. Despite the high IBU removal yields during startup, the SRT was the most influential variable in IBU removal, an effect observed in all bioreactors, particularly in the anoxic one.

Behaviour of biopolymeric substances in the activated sludge of an MBR system working with high hydraulic retention time.

This study was undertaken to analyse the activated sludge of a membrane bioreactor (MBR), the behaviour of extracellular polymeric substances (EPS) and soluble microbial products (SMP) as well as their biopolymers composition, in the activated sludge of a membrane bioreactor (MBR) and their influence on membrane fouling were analysed. For the experiment an experimental fullscale MBR working with real urban wastewater at high hydraulic retention time with a variable sludge-retention time (SRT) was used. The MBR system worked in denitrification/nitrification conformation at a constant flow rate (Q = 0.45 m3/h) with a recirculation flow rate of 4Q. The concentrations of SMP in the activated sludge were lower than the concentrations of EPS over the entire study, with humic substances being the main components of the two biopolymers. SMP and, more specifically, SMP carbohydrates, were the most influential biopolymers in membrane fouling, while for EPS and their components, no relation was found with fouling. The SRT and temperature were the operational variables that most influenced the SMP and EPS concentration, causing the increase of SRT and temperature a lower concentration in both biopolymers, although the effect was not the same for all the components, particularly for the EPS carbohydrates, which increased with longer SRTs. Both operational variables were also the ones most influential on the concentration of organic matter of the effluent, due to their effect on the SMP. The volatile suspended solid/total suspended solid (VSS/TSS) ratio in the activated sludge can be applied as a good indicator of the risk of membrane fouling by biopolymers in MBR systems.

Integrated in-line coagulation-aerated ultrafiltration for drinking-water production: A case study from laboratory to pilot plant.

A pilot-scale study was made for drinking-water production from low-quality influents with in-line coagulation as pre-treatment of aerated ultrafiltration. Optimum flocculation parameters were previously determined in the laboratory, searching for large and strong flocs that could resist aeration without increasing the membrane fouling. Nevertheless, the comparison of the jar tests and the pilot-scale results showed that the former could help pre-dimensioning the flocculation facilities but could not precisely reproduce the behavior of the flocs in the membrane tank. The optimum coagulant dosage enabled the highest dissolved organic carbon (DOC) removal without affecting membrane fouling. Additionally, as opposed to the jar-test results, long retention times led to the lowest fouling rates while the velocity gradient affected neither the effluent quality nor the membrane fouling. These findings suggested that the influence of the flocculation parameters was masked by aeration inside the membrane tank but, even so, 43% and 82% DOC and UVA254 removals, respectively, were reached. Furthermore, the growth of the total membrane resistance with time was logarithmic instead of linear, confirming the suitability of the pre-treatment for low-quality influents.

Comparison of five wastewater COD fractionation methods for dynamic simulation of MBR systems.

Five different wastewater COD fractionation methods were employed for simulating an experimental MBR wastewater treatment plant using WEST. The predictions of dynamic simulations using as input the data obtained according to each influent characterization methodology were compared with the results of the experimental system and differences between experimental and predicted values were analyzed in order to select the fractionation method which provides the best fitting and minimizes errors. Three of these methods were based on the determination of the biodegradable fractions using respirometric assays of real wastewater filtered through 0.45- and 0.22-µm pore size filters or adding a previous flocculation step before filtration. Moreover, a method based on physicochemical analyses and another one based on theoretical coefficients were also compared. Simulated system performance and effluent quality greatly depended upon the influent characterization and the proper model calibration. Thus the importance of selecting a suitable fractionation methodology is high, especially in MBR systems working at specific operational conditions that may alter COD fractions. In this study, MLSS in the bioreactors and sludge supernatant COD concentrations were better predicted when the influent characterization was based on respirometric methods. Both the method based on theoretical coefficients and the physicochemical method underestimated the particulate inert fraction and therefore, also the MLSS concentrations. Moreover, these results showed that for a correct effluent COD prediction in MBR systems, it is necessary to take into account that the membrane retained part of the soluble inert fraction.

Removal of low concentrations of phenanthrene, fluoranthene and pyrene from urban wastewater by membrane bioreactors technology.

The fate and removal of phenanthrene (Phen), fluoranthene (F) and pyrene (Py) in urban wastewater treatment by membrane bioreactor (MBR) with low influent polycyclic aromatic hydrocarbons (PAHs) concentration were studied. A full experimental ultrafiltration MBR with a pre-denitrification configuration and capacity to treat 20 m(3)/d was employed. The system was operated with real urban wastewater, to which a concentration of PAHs was added. A constant purge was achieved in order to obtain 12 d of sludge retention time and the hydraulic retention time was 34 h. Concentration of PAHs was determined by Gas Chromatography and Mass Spectrometry with Twister, and mass balance on the MBR system were calculated. Data were supplemented by respirometric analyses, isolation of PAHs degrading microorganisms and bench-scale experiments. All effluent samples presented concentrations of PAHs, with removal levels of 91% and 92% for F and Py respectively, while for Phen performance did not surpass 82%. In spite of the high hydrophobicity of the tested compounds, their accumulation in the biomass was scarce and the sludge presented a low PAH concentration. The experiments reveal that PAHs removal is mainly due to air stripping, with biodegradation and adsorption making an insignificant contribution.

Modification of Alvarado score with pain semiology for the diagnosis of acute appendicitis.

BACKGROUND: Acute appendicitis is the most frequent surgical pathology in the emergency services. It affects approximately 9% of the population. Its differential diagnosis is extremely difficult especially in the elderly, children and women of childbearing age. The Alvarado score (AS) is a useful tool for suspected diagnosis of appendicitis. Our experience suggests the possibility of improving the diagnostic performance of this scale by including pain semiology. OBJECTIVE: To compare the diagnostic utility of AS with and without including pain semiology used in the general surgery service of the high specialty naval hospital, as well as to identify fewer useful variables for the diagnosis. METHOD: The files of all the patients operated for the suspicion of acute appendicitis from March 2015 to March of the year 2017 were reviewed. The included patients have complete file and histopathological report. For each patient, diagnosis of appendicitis was established with the application of the AS and another, adding the pain semiology, and the result was contrasted with the histopathological diagnosis. The parameters of diagnostic utility were estimated, based on the cut points determined by the logistic regression model and the ROC curves. RESULTS: AS modified with pain semiology showed greater diagnostic utility than the original scale. Six variables were also identified with a satisfactory performance. CONCLUSION: Pain semiology can improve the diagnostic utility of the current AS.

ANTECEDENTES: La apendicitis aguda es la patología quirúrgica más frecuente en los servicios de urgencias. Afecta ­aproximadamente al 9% de la población. Su diagnóstico diferencial es en extremo difícil, en especial en ancianos, niños y mujeres en edad fértil. La escala de Alvarado (EA) es una herramienta útil para la sospecha diagnóstica de apendicitis. Nuestra experiencia sugiere la posibilidad de mejorar el desempeño diagnóstico de esta escala al incluir la semiología del dolor. OBJETIVO: Comparar la utilidad diagnóstica de la EA con y sin incluir semiología del dolor utilizada en el Servicio de Cirugía General del Hospital General Naval de Alta Especialidad, así como identificar el menor número de variables útiles para el diagnóstico. MÉTODO: Fueron revisados los expedientes de todos los pacientes operados por sospecha de apendicitis aguda de marzo de 2015 a marzo de 2017. Los pacientes incluidos cuentan con expediente completo y reporte histopatológico. Para cada paciente se establecieron el diagnóstico de apendicitis con la aplicación de la EA y agregando la semiología del dolor, y se contrastó el resultado con el diagnóstico histopatológico. Se estimaron los parámetros de utilidad diagnóstica de acuerdo con los puntos de corte determinados por el modelo de regresión logística y las curvas ROC. RESULTADOS: La EA modificada con semiología del dolor mostró una mayor utilidad diagnóstica que la escala original. Se identificaron, además, seis variables con un rendimiento satisfactorio. CONCLUSIÓN: La semiología del dolor puede mejorar la utilidad diagnóstica de la actual EA.

Laparoscopic Spigelian hernia repair with intraperitoneal onlay composite mesh and articulated fixing system. Two cases report.

INTRODUCTION: Spiegel hernia is an infrequent type of abdominal wall defect. Traditionally, it was repaired with an open technique, currently we have multiple laparoscopic techniques with the use of prosthetic material. CLINICAL CASE: We present two cases of Spiegel hernia, one patient scheduled electively and one patient of urgency due to incarcerated hernia, both diagnosed pre-surgically with abdominal tomography. DISCUSSION: Both patients were successfully operated laparoscopically with intraperitoneal onlay mesh technique using composite mesh and articulated fixation system. CONCLUSION: This technique is shown as a recommended option due to its technical facility, good results, both for elective surgeries and emergency surgeries.

INTRODUCCIÓN: La hernia de Spiegel es un tipo infrecuente de defecto de la pared abdominal. Tradicionalmente se realizaba su reparación con técnica abierta, pero en la actualidad contamos con múltiples técnicas laparoscópicas con uso de material protésico. CASO CLÍNICO: Presentamos dos casos de hernia de Spiegel, un paciente programado de manera electiva y otro de urgencia por hernia incarcerada, ambos diagnosticados de manera prequirúrgica con tomografía abdominal. DISCUSIÓN: Los dos pacientes fueron intervenidos de manera exitosa por vía laparoscópica con técnica de malla intraperitoneal utilizando malla compuesta y sistema de fijación articulado. CONCLUSIONES: Esta técnica se muestra como una opción recomendable por su facilidad de realización y buenos resultados, tanto para cirugías electivas como para cirugías de urgencia.

[Perforación de colon sigmoides secundaria a endometriosis. Reporte de un caso]. / Perforation of the sigmoid colon secondary to endometriosis. Case report.

ANTECEDENTES: La endometriosis es la presencia de glándulas endometriales o estroma viable fuera de la cavidad uterina, que afecta aproximadamente al 2-10% de las mujeres en edad reproductiva1. Es común la afección de estructuras pélvicas, incluyendo el intestino. La perforación del colon por endometriosis es muy rara y representa una urgencia quirúrgica. CASO CLÍNICO: Mujer de 28 años con cuadro de dolor abdominal en fosa iliaca derecha y hueco pélvico, fiebre y náuseas. Se realiza laparotomía exploradora con hallazgo de perforación de colon sigmoides, que requiere resección de la lesión y colostomía terminal, encontrando como diagnóstico definitivo endometriosis. CONCLUSIÓN: La perforación de intestino o de colon es una complicación poco frecuente, pero de gravedad, que debemos tener siempre presente como sospecha ante un cuadro de abdomen agudo en una paciente en edad fértil y con antecedentes de haber presentado sintomatología gastrointestinal intermitente. BACKGROUND: Endometriosis is the presence of endometrial glands or viable stroma outside the uterine cavity, which affects approximately 2-10% of women of reproductive age 1. Pelvic structures, including the bowel, are commonly affected. Perforation of the colon by endometriosis is very rare and represents a surgical emergency. CLINICAL CASE: A 28-year-old female patient with abdominal pain in the right iliac fossa and pelvic cavity, fever and nausea, exploratory laparotomy is performed with the discovery of sigmoid perforation of the colon, requiring resection of the lesion and terminal colostomy, finding as definitive diagnosis endometriosis. CONCLUSION: Bowel or colon perforation is a rare but serious complication, which should always be kept in mind as a suspicion of acute abdomen in a female patient of reproductive age and with a history of intermittent gastrointestinal symptoms.

Dual-stage peat beds in small community wastewater treatment.

In this study, the quality of water treated by two dual-stage peat bed systems was compared with a single-stage system, and a costs analysis was performed. The experiment was carried out on a pilot scale using pre-treated urban wastewater. The pilot setup consisted of a single-stage system with a hydraulic loading of 0.6 m(3)/m(2)d, and two dual-stage systems. The first of these worked with hydraulic loadings of 1.2 and 0.6 m(3)/m(2)d for the initial and second stages respectively. For the second dual-stage system hydraulic loadings were 1.8 and 0.9 m(3)/m(2)d. In comparison with the single-stage system, the dual-stage systems produced effluents with a substantial improvement in physicochemical quality (suspended solids, COD and BOD) and microbiological quality (faecal and total coliforms). Quality parameters were similar to a conventional system, meeting the legislative standards of European Union Directive 271/91 for wastewater treatment. Total costs of the peat-bed systems showed a reciprocal X-model regression depending on the average daily volume of urban wastewater to be treated, with a tendency towards convergence of costs between the single and dual-stage systems. The main problem with the dual-stage systems is the greater surface area required for their installation, which can be estimated by linear regression depending on the average volume of water to be treated per day.