Uncertainty with varying subsurface permeabilities reduced using coupled Random Field and extended Theory of Porous Media contaminant transport models

To maximize the usefulness of groundwater flow models for the protection of aquifers and abstraction wells, it is necessary to identify and decrease the uncertainty associated with the major parameters such as permeability. To do this, there is a need to develop set of estimates representing subsurface heterogeneity or representative soil permeability estimates. Here, we use a coupled Random Field and extended Theory of Porous Media (eTPM) simulation to develop a robust model with a good predictive ability that reduces uncertainty. The coupled model is then validated with a physical sandbox experiment. Uncertainty is reduced by using 500 realisations of the permeability parameter using the eTPM approach. A multi-layer contaminant transport scenario with varying permeabilities, similar to what could be expected with shallow alluvial sediments, is simulated. The results show that the contaminant arrival time could be strongly affected by random field realizations of permeability compared with a modelled homogenous permeability parameter. The breakthrough time for heterogeneous permeabilities is shorter than the homogeneous condition. Using the 75% confidence interval (CI), the average contaminant concentration shows 4.4% variation from the average values of the considered area and 8.9% variation in the case of a 95% confidence interval.European Union’s Horizon 2020 Programm

Subcritical water treatment of landfill leachate: Application of response surface methodology

WOS: 000343614400002PubMed: 25151110Context: Leachate is the liquid formed when waste breaks down in the landfill and water filters through that waste. This liquid is highly toxic and can pollute the land, ground water and water ways. It is mandatory for landfills to protect against leachate in most countries worldwide. Controlling the pollutant loading, means reducing its quantity by containing or treating the waste to comply with certain discharge characteristics which are compatible with the receptor medium. Objective: This paper describes the reduction of the organic load of a mature landfill leachate using a novel experimental set-up that employs hydrogen peroxide under subcritical conditions and aims to establish this method as an effective alternative to currently used options. Response surface methodology was applied to optimize the treatment process and determine which of the following there parameters - temperature, residence time and hydrogen peroxide concentration - played the most important role. Method: The method employed is based on the use of laboratory-scale, stainless steel reactors, filled with the leachate and appropriate quantities of hydrogen peroxide. Under subcritical conditions (temperature in the range of 100-374 degrees C and enough pressure to maintain the liquid state of water), hydrogen peroxide produces hydroxyl radicals which are highly reactive and oxidize the organic molecules of the leachate. Results: The highest COD decrease of 85% was experimentally observed at 300 degrees C, 500 mM H2O2 and 180 min residence time. It was determined that the combination of oxidant concentration and temperature is the rate-determining factor, whereas residence time has a lesser effect on the process. Conclusions: A simple, quick, effective and environmentally-friendly method for the treatment of the organic load of landfill leachate was developed and optimized at laboratory scale. (C) 2014 Elsevier Ltd. All rights reserved

TECTONIC REGIME OF THE SUBURBAN (SOUTHERN) AREA OF CHANIA CITY IN CRETE ISLAND BY USING GEOPHYSICAL METHODS

H μέθοδος παροδικών ηλεκτρομαγνητικών κυμάτων (ΤΕΜ), εφαρμόζεται ευρέως τα τελευταία χρόνια, με ιδιαίτερη έμφαση στις υδρογεωφυσικές και γεωτεκτονικές εφαρμογές. Το σύστημα ΤΕΜ-Fast 48HPC χρησιμοποιήθηκε για τη συλλογή των δεδομένων κατά την καλοκαιρινή περίοδο του 2015. Ο κύριος σκοπός αυτής της εργασίας ήταν ο προσδιορισμός των γεωτεκτονικών χαρακτηριστικών της περιοχής μελέτης. Πριν τις γεωφυσικές μετρήσεις διενεργήθηκε λεπτομερής γεωλογική έρευνα και συλλέχθηκαν όλα τα διαθέσιμα στοιχεία. Όλα τα δεδομένα ενοποιήθηκαν ώστε να προκύψει ένα αξιόπιστο γεωτεκτονικό μοντέλο της υπό έρευνα περιοχής. Το προτεινόμενο σύστημα ρηγμάτων επιβεβαιώνει και συμπληρώνει ανεξάρτητες γεωφυσικές μελέτες για την τεκτονική της περιοχής. Η παρούσα εργασία αποδεικνύει την εφαρμοσιμότητα και αποτελεσματικότητα της προτεινόμενης μεθοδολογίας για την αναγνώριση γεωτεκτονικών δομών σε σύνθετες γεωλογικά περιοχές έρευνας.The transient electromagnetic method (TEM) has gained increasing popularity over the last years especially in hydrogeophysical and geotectonic applications. TEM-Fast 48HPC was used for collecting the sounding data during summer 2015. The main purpose of this work was the definition of the geotectonic characteristics at the Southern area of the city of Chania by means of TEM-Fast sounding survey which was carried out in the summer of 2015. Detailed geological survey was applied prior the geophysical measurements and all the available borehole logs were collected. All data were integrated to provide a reliable geotectonic model of the area under investigation. Joint faults systems were detected which are in agreement with previous geophysical and tectonic studies in the area. This work shows clearly the applicability and efficiency of the TEM in studying complex geotectonic environment

Uncertainty with Varying Subsurface Permeabilities Reduced Using Coupled Random Field and Extended Theory of Porous Media Contaminant Transport Models

To maximize the usefulness of groundwater flow models for the protection of aquifers and abstraction wells, it is necessary to identify and decrease the uncertainty associated with the major parameters such as permeability. To do this, there is a need to develop set of estimates representing subsurface heterogeneity or representative soil permeability estimates. Here, we use a coupled Random Field and extended Theory of Porous Media (eTPM) simulation to develop a robust model with a good predictive ability that reduces uncertainty. The coupled model is then validated with a physical sandbox experiment. Uncertainty is reduced by using 500 realisations of the permeability parameter using the eTPM approach. A multi-layer contaminant transport scenario with varying permeabilities, similar to what could be expected with shallow alluvial sediments, is simulated. The results show that the contaminant arrival time could be strongly affected by random field realizations of permeability compared with a modelled homogenous permeability parameter. The breakthrough time for heterogeneous permeabilities is shorter than the homogeneous condition. Using the 75% confidence interval (CI), the average contaminant concentration shows 4.4% variation from the average values of the considered area and 8.9% variation in the case of a 95% confidence interval