Analysis of clogging in constructed wetlands using magnetic resonance

In this work we demonstrate the potential of permanent magnet based magnetic resonance sensors to monitor and assess the extent of pore clogging in water filtration systems. The performance of the sensor was tested on artificially clogged gravel substrates and on gravel bed samples from constructed wetlands used to treat wastewater. Data indicate that the spin lattice relaxation time is linearly related to the hydraulic conductivity in such systems. In addition, within biologically active filters we demonstrate the ability to determine the relative ratio of biomass to abiotic solids, a measurement which is not possible using alternative techniques

Efficacy and safety of preoperative preparation with Lugol''s iodine solution in euthyroid patients with Graves’ disease (LIGRADIS Trial): Study protocol for a multicenter randomized trial

Background: Currently, both the American Thyroid Association and the European Thyroid Association recommend preoperative preparation with Lugol''s Solution (LS) for patients undergoing thyroidectomy for Graves’ Disease (GD), but their recommendations are based on low-quality evidence. The LIGRADIS trial aims to provide evidence either to support or refute the systematic use of LS in euthyroid patients undergoing thyroidectomy for GD. Methods: A multicenter randomized controlled trial will be performed. Patients =18 years of age, diagnosed with GD, treated with antithyroid drugs, euthyroid and proposed for total thyroidectomy will be eligible for inclusion. Exclusion criteria will be prior thyroid or parathyroid surgery, hyperparathyroidism that requires associated parathyroidectomy, thyroid cancer that requires adding a lymph node dissection, iodine allergy, consumption of lithium or amiodarone, medically unfit patients (ASA-IV), breastfeeding women, preoperative vocal cord palsy and planned endoscopic, video-assisted or remote access surgery. Between January 2020 and January 2022, 270 patients will be randomized for either receiving or not preoperative preparation with LS. Researchers will be blinded to treatment assignment. The primary outcome will be the rate of postoperative complications: hypoparathyroidism, recurrent laryngeal nerve injury, hematoma, surgical site infection or death. Secondary outcomes will be intraoperative events (Thyroidectomy Difficulty Scale score, blood loss, recurrent laryngeal nerve neuromonitoring signal loss), operative time, postoperative length of stay, hospital readmissions, permanent complications and adverse events associated to LS. Conclusions: There is no conclusive evidence supporting the benefits of preoperative treatment with LS in this setting. This trial aims to provide new insights into future Clinical Practice Guidelines recommendations. Trial registration: ClinicalTrials.gov identifier: NCT03980132. © 202

Wetlands for wastewater treatment and subsequent recycling of treated effluent : a review

Due to water scarcity challenges around the world, it is essential to think about non-conventional water resources to address the increased demand in clean freshwater. Environmental and public health problems may result from insufficient provision of sanitation and wastewater disposal facilities. Because of this, wastewater treatment and recycling methods will be vital to provide sufficient freshwater in the coming decades, since water resources are limited and more than 70% of water are consumed for irrigation purposes. Therefore, the application of treated wastewater for agricultural irrigation has much potential, especially when incorporating the reuse of nutrients like nitrogen and phosphorous, which are essential for plant production. Among the current treatment technologies applied in urban wastewater reuse for irrigation, wetlands were concluded to be the one of the most suitable ones in terms of pollutant removal and have advantages due to both low maintenance costs and required energy. Wetland behavior and efficiency concerning wastewater treatment is mainly linked to macrophyte composition, substrate, hydrology, surface loading rate, influent feeding mode, microorganism availability, and temperature. Constructed wetlands are very effective in removing organics and suspended solids, whereas the removal of nitrogen is relatively low, but could be improved by using a combination of various types of constructed wetlands meeting the irrigation reuse standards. The removal of phosphorus is usually low, unless special media with high sorption capacity are used. Pathogen removal from wetland effluent to meet irrigation reuse standards is a challenge unless supplementary lagoons or hybrid wetland systems are used

Impact of prior physico-chemical treatment on the clogging process of subsurface flow constructed wetlands: model-based evaluation

The objective of this study was to check the effect of the use of a physico-chemical treatment on the clogging process of horizontal subsurface flow constructed wetlands by means of dynamic modelling. The hydraulic submodel was based on series as well as parallel branched complete stirred tanks of equal volume. The model was validated with data obtained from 2 identical experimental wetlands, which had a surface area of 0.54 m(2) and a water depth of 0.30 m, and that were monitored over a period of 5 months. One of the wetlands was fed with settled urban wastewater, whereas the other with the same wastewater, but previously treated with a physico-chemical treatment. In the model, pore volume reduction depends on the growth of bacteria and on solids retained. The effluent concentrations of COD and ammonium in both experimental wetlands were very similar in all the conditions tested, and therefore the physico-chemical treatment did not improve the removal efficiency. The model indicated that after 120 days of operation in some regions of the wetland fed with settled wastewater the porosity decreased in a 17%, whereas in the other wetlands it only decreased as much as 6%. The use of a prior physico-chemical treatment is a good alternative for avoiding an anticipated clogging of subsurface flow constructed wetlands

Study ofbrídge foundation with GPR

Ground penetrating radar is usually employed for non-destructive evaluations and maintenance of roads and bridges. This report describe the study of an emlbankmet where a bridge will be built due to the construction of a new road. The geology In this place, where the foundations of the bridge will be emplaced, are formed by hint sands layers between conglomerates ones. Flowing water eroses the sand causing holes and possible landslides, which could be damaging for the bridge. The study of the embakment with aground penetrating radar allows to know the thickness o f the sand layers and the posible holes placed into them. An antenna with center frecuency 100 MHz was used attending the characteristics o f the emplacement. The radar data shows among some other things, the different reflectors due to the conglomerate, the sand layers and their thicknesses. The presence and the emplacement of several holes in the layers are also observed. These results show where the foundations must be properly placed. A comparison with a geological profile was perfomed to assure the result

Jet-grouting determination in a subway metropolitan tunnel by using ground penetrating radar analysis

Several kilometers o f tunnel have been excavated to extend a metropolitan underground system. In some places, where the subsurface is mainly composed by gravel and sands, water can easly penetrate causing problems to the tunnel and the stations. In order to avoid such problems, a jet-grouting injection was carried out. To check the continuity of the jet-grouting a Ground Penetrating Radar analysis was applied. The radar used is a SIR 10 of Geophysical Survey Systems Inc., with a center frecuency antenna of 100 Mz, prepared for urban jobs. A good determination of the variantion of the thickness of the jet-grouting layer was obtained, although several difficulties, specially the irregular topography, were to be solved. Three boreholes to determine the quality and thickness of the jet-grouting in three different places provided the right calibration of the involved radargrams. During the processing of the data, several filters had to be applied to discriminate the radar signals from noise, coming mainly from the electrical system of the tunne

Georadar applications on concrete reinforced walls into a nuclear power plant

Accurate identification of frames into concrete reinforced walls in a nuclear power plant was required because of maintenance labours. Several cuts in the concrete, including the frame, were planned. The cutting lines were designed to avoid as much as possible the frame bars. To perfom this work the ground penetrating radar has been used. The use of ground prenetrating radar techniques allow to determine the vertical and horizontal position of the frame bars. GPR detects also other reflectors in to the walls. The ele ctric propertie s contrast betw een the concrete and th e steel o f the frame gives reflections clearly detected in the records. This near surface study requires to use high resolution antennas with a very high center frecuency. The measurement precision required In the work was obtained using a special marker to carry the antenna, specially design for this job. The marker allows to know the position of the antenna on the wall with a precission of centimeters. The measurements were acquired from one antenna with a center frecuency of 1000 MHz, with a SIR 10 system of Geophysical Survey Sistems Inc.. An experimental test made in a scale model help to the interpretation of the records.. A later and careful treatment in laboratory, using all the records obtained in the nuclear power plant, applying vertical lowpass and highpass filters and horizontal lowpass filter was perfomed, to place correctly the bars into the concret

GPR measurements to study an abandoned salt mine for tourlstlcal purposes

The opening of abandoned salt mines whit the idea of prepare cultural routes requires the use of hard machinery in abandoned places. The erosion caused by salt disolutions damage the mine structure, being dangerous for restoration and visiting purposes. Planed jobs were the opening of a new gallery to prepare a round route and restoring the part of the salt mine that will be open to the public. Ground penetrating measurements have been used, first to locate the position and depth of underground scour holes and subsurface voids in the ground and in the solid salt mountain, and second, to study the vault and gables end in the salt mine galleries. Three antennas were used in his job, with WO MHz, 300 MHz and 500 MHz center frecuencies.. Radar data has locate holes in the first meters under the floor of the mine galleries and into the contact between the salt mountain and the cover materials. The analisys of the anomalies also shows scour holes in to the slag heap caused by the flowing water which eroses the soft materials. These areas are not safety places for mining jobs. This work try to provide safety measurements to the salt mine workers and try to assists to the tourist mine maintenance plannin