Plant-wide modelling in wastewater treatment: showcasing experiences using the Biological Nutrient Removal Model.

Plant-wide modelling can be considered an appropriate approach to represent the current complexity in water resource recovery facilities, reproducing all known phenomena in the different process units. Nonetheless, novel processes and new treatment schemes are still being developed and need to be fully incorporated in these models. This work presents a short chronological overview of some of the most relevant plant-wide models for wastewater treatment, as well as the authors' experience in plant-wide modelling using the general model BNRM (Biological Nutrient Removal Model), illustrating the key role of general models (also known as supermodels) in the field of wastewater treatment, both for engineering and research.

Ecografía Doppler renal con medición de índices de resistencia vs. gammagrafía renal con 99mTc-DTPA para el diagnóstico de estenosis ureteropiélica en niños / Renal Doppler ultrasound resistive index vs. renal scintigraphy with 99mTc-DTPA as diagnostic test for ureteropelvic junction obstruction in children

Objetivo: Se llevó a cabo un estudio de corte transversal con el objetivo de evaluar la utilidad de la ecografía Doppler con índice de resistencia (IR) en comparación con la gammagrafía renal con 99mTc-DTPA en niños con estenosis ureteropiélica unilateral. Métodos: El estudio incluyó niños menores de 15 años con diagnóstico de estenosis ureteropiélica unilateral, riñón contralateral sano con o sin antecedente de plastia ureteropiélica. Los pacientes seleccionados se derivaron al Departamento de Medicina Nuclear para llevar a cabo la gammagrafía renal y días más tarde se derivaron al Departamento de Radiología para la realización de la ecografía Doppler renal con IR. Resultados: Un total de 21 pacientes fueron incluidos en el estudio, 15 hombres y 6 mujeres, que representan el 71,4% y el 28,6%, respectivamente. La edad promedio fue de 5,3 años. Solo 3 tuvieron un antecedente de plastia ureteropiélica en el riñón afectado. La gammagrafía renal informó datos de obstrucción unilateral en 18 pacientes, incluidos los 3 pacientes con cirugía previa. La tasa promedio de filtración glomerular (TFG) en general obtenida con la gammagrafía fue de 100,28 ml/min. El promedio de TFG fue de 43,03 ml/min en los riñones afectados y de 57,24 ml/min en los riñones sanos (p < 0,001). La ecografía Doppler con IR reportó ectasia en el 100% de los riñones afectados y en un riñón contralateral normal. El IR promedio fue de 0,69 mm/s en los riñones afectados y de 0,50 mm/s en los riñones sanos (p < 0,001). Conclusiones: Con los resultados obtenidos, podemos sugerir que la ecografía Doppler renal con medición del IR puede ser una herramienta alternativa a la gammagrafía renal con 99mTc-DTPA en algunos casos

Objective: A cross-sectional study was carried out with the objective of evaluating the usefulness of Doppler ultrasound with resistive index (RI) measure compared with renal scintigraphy with 99mTc-DTPA in children with unilateral ureteropelvic junction obstruction. Methods: The study included children under 15 years with a diagnosis of unilateral ureteropelvic junction obstruction, healthy contralateral kidney with or without an antecedent of ureteropyeloplasty. The selected patients were sent to the Nuclear Medicine Department to carry out a renal scintigraphy with 99mTc-DTPA and days later were sent to the Radiology Department for the performance of Renal Doppler Ultrasound with RI. Results: A total of 21 patients were included in the study, 15 males and 6 females, representing 71.4% and 28.6%, respectively. Mean age was 5.3 years. Only 3 had an antecedent of ureteropyeloplasty in the affected kidney. The scintigraphy reported data of unilateral obstruction in 18 patients, including the 3 patients with previous surgery. The average glomerular filtration rate (GFR) obtained with the scintigraphy was 100.28 ml/min. The average GFR in affected kidneys was 43.03 ml/min and 57.24 ml/min in healthy kidneys (p < .001). Doppler ultrasound with RI reported ectasia in 100% of the affected kidneys and one normal contralateral kidney. The average RI in affected kidneys was 0.69 mm/s and 0.50 mm/s in healthy kidneys (p < .001). Conclusions: With the results obtained, we can suggest that ultrasound Doppler with measurement of RI can be an alternative tool to renal scintigraphy with 99mTc-DTPA in some cases

Renal Doppler ultrasound resistive index vs. renal scintigraphy with 99mTc-DTPA as diagnostic test for ureteropelvic junction obstruction in children. / Ecografía Doppler renal con medición de índices de resistencia vs. gammagrafía renal con 99mTc-DTPA para el diagnóstico de estenosis ureteropiélica en niños.

OBJECTIVE: A cross-sectional study was carried out with the objective of evaluating the usefulness of Doppler ultrasound with resistive index (RI) measure compared with renal scintigraphy with 99mTc-DTPA in children with unilateral ureteropelvic junction obstruction. METHODS: The study included children under 15 years with a diagnosis of unilateral ureteropelvic junction obstruction, healthy contralateral kidney with or without an antecedent of ureteropyeloplasty. The selected patients were sent to the Nuclear Medicine Department to carry out a renal scintigraphy with 99mTc-DTPA and days later were sent to the Radiology Department for the performance of Renal Doppler Ultrasound with RI. RESULTS: A total of 21 patients were included in the study, 15 males and 6 females, representing 71.4% and 28.6%, respectively. Mean age was 5.3 years. Only 3 had an antecedent of ureteropyeloplasty in the affected kidney. The scintigraphy reported data of unilateral obstruction in 18 patients, including the 3 patients with previous surgery. The average glomerular filtration rate (GFR) obtained with the scintigraphy was 100.28ml/min. The average GFR in affected kidneys was 43.03ml/min and 57.24ml/min in healthy kidneys (p<.001). Doppler ultrasound with RI reported ectasia in 100% of the affected kidneys and one normal contralateral kidney. The average RI in affected kidneys was 0.69mm/s and 0.50mm/s in healthy kidneys (p<.001). CONCLUSIONS: With the results obtained, we can suggest that ultrasound Doppler with measurement of RI can be an alternative tool to renal scintigraphy with 99mTc-DTPA in some cases.

Stochastic self-tuning hybrid algorithm for reaction-diffusion systems.

Many biochemical phenomena involve reactants with vastly different concentrations, some of which are amenable to continuum-level descriptions, while the others are not. We present a hybrid self-tuning algorithm to model such systems. The method combines microscopic (Brownian) dynamics for diffusion with mesoscopic (Gillespie-type) methods for reactions and remains efficient in a wide range of regimes and scenarios with large variations of concentrations. Its accuracy, robustness, and versatility are balanced by redefining propensities and optimizing the mesh size and time step. We use a bimolecular reaction to demonstrate the potential of our method in a broad spectrum of scenarios: from almost completely reaction-dominated systems to cases where reactions rarely occur or take place very slowly. The simulation results show that the number of particles present in the system does not degrade the performance of our method. This makes it an accurate and computationally efficient tool to model complex multireaction systems.

Resource recovery from sulphate-rich sewage through an innovative anaerobic-based water resource recovery facility (WRRF).

This research work proposes an innovative water resource recovery facility (WRRF) for the recovery of energy, nutrients and reclaimed water from sewage, which represents a promising approach towards enhanced circular economy scenarios. To this aim, anaerobic technology, microalgae cultivation, and membrane technology were combined in a dedicated platform. The proposed platform produces a high-quality solid- and coliform-free effluent that can be directly discharged to receiving water bodies identified as sensitive areas. Specifically, the content of organic matter, nitrogen and phosphorus in the effluent was 45 mg COD·L-1, 14.9 mg N·L-1 and 0.5 mg P·L-1, respectively. Harvested solar energy and carbon dioxide biofixation in the form of microalgae biomass allowed remarkable methane yields (399 STP L CH4·kg-1 CODinf) to be achieved, equivalent to theoretical electricity productions of around 0.52 kWh per m3 of wastewater entering the WRRF. Furthermore, 26.6% of total nitrogen influent load was recovered as ammonium sulphate, while nitrogen and phosphorus were recovered in the biosolids produced (650 ± 77 mg N·L-1 and 121.0 ± 7.2 mg P·L-1).

Effect of temperature on ammonium removal in Scenedesmus sp.

The effect of temperature on microalgal ammonium uptake was investigated by carrying out four batch experiments in which a mixed culture of microalgae, composed mainly of Scenedesmus sp., was cultivated under different temperatures within the usual temperature working range in Mediterranean climate (15-34 °C). Ammonium removal rates increased with temperature up to 26 °C and stabilized thereafter. Ratkowsky and Cardinal temperatures models successfully reproduced the experimental data. Optimum (31.3 °C), minimum (8.8 °C) and maximum (46.1 °C) temperatures for ammonium removal by Scenedesmus sp. under the studied conditions were obtained as model parameters. These temperature-related parameters constitute very useful information for designing and operating wastewater treatment systems using these microalgae.

Effect of intracellular P content on phosphate removal in Scenedesmus sp. Experimental study and kinetic expression.

The present work determines the effect of phosphorus content on phosphate uptake rate in a mixed culture of Chlorophyceae in which the genus Scenedesmus dominates. Phosphate uptake rate was determined in eighteen laboratory batch experiments, with samples taken from a progressively more P-starved culture in which a minimum P content of 0.11% (w/w) was achieved. The results obtained showed that the higher the internal biomass P content, the lower the phosphate removal rate. The highest specific phosphate removal rate was 6.5mgPO4-PgTSS(-1)h(-1). Microalgae with a P content around 1% (w/w) attained 10% of this highest removal rate, whereas those with a P content of 0.6% (w/w) presented 50% of the maximum removal rate. Different kinetic expressions were used to reproduce the experimental data. Best simulation results for the phosphate uptake process were obtained combining Steele equation and Hill function to represent the effect of light and intracellular phosphorus content, respectively.

Microalgae cultivation in wastewater: nutrient removal from anaerobic membrane bioreactor effluent.

This study investigated the removal of nitrogen and phosphorus from the effluent of a submerged anaerobic membrane bioreactor (SAnMBR) by means of a lab-scale photobioreactor in which algae biomass was cultured in a semi-continuous mode for a period of 42 days. Solids retention time was 2 days and a stable pH value in the system was maintained by adding CO(2). Nitrogen and phosphorus concentrations in the SAnMBR effluent fluctuated according to the operating performance of the bioreactor and the properties of its actual wastewater load. Despite these variations, the anaerobic effluent proved to be a suitable growth medium for microalgae (mean biomass productivity was 234 mg l(-1)d(-1)), achieving a nutrient removal efficiency of 67.2% for ammonium (NH(4)(+)-N) and 97.8% for phosphate (PO(4)(-3)-P). When conditions were optimum, excellent water quality with very low ammonium and phosphate concentrations was obtained.

An improved topical formulation for urea.

The solubility of urea in different polar solvents was studied by means of determination of their dielectric constants. The most appropriate solvents turned out to be water and a water/propylene glycol (1:1 in volume) mixture. The best solvents were then used in the study of different semisolid vehicles for topical use (cetylic excipient, Beeler's base and Carbopol gel), which show different physicochemical characteristics. The final formulation contained a 40% (w/w) concentration in urea, since this value is most often used in Dermatology and, at the same time, it is the most problematic from a technological point of view. The stability of the different preparations was investigated by conductimetric and rheological determinations. The results are discussed in terms of both the solubility and stability of the active principles and the organoleptic and rheological characteristics of the final preparations.