A cargo de: Jaume Puigagut (GEMMA - Group of Environmental Engineering and Microbiology, UPC)
Fecha:jueves 11 de octubre en el Aula Cihs
Lugar: UPC- DEPARTAMENTO DE INGENIERIA CIVIL Y AMBIENTAL
Bioelectrochemical systems (Microbial fuel cells - MFCs) implemented in constructed wetlands (CW-MFCs), albeit a relatively new technology which is still under study, have shown to improve the treatment efficiency of domestic wastewater. So far the vast majority of CW-MFC systems investigated are designed as lab-scale systems working under rather unrealistic hydraulic conditions (up-flow, batch feeding) using synthetic wastewater. The main objective of this work was to quantify CW-MFCs performance operated under different conditions in a more realistic setup using meso-scale systems with horizontal flow fed with real domestic wastewater. The potential use of MFC electric signal as overall hetrotrophic bacterial activity indicator was also assessed. Operational conditions tested were organic loading rate (4.9±1.6, 6.7±1.4 and 13.6±3.2 g COD/m2.day) and hydraulic regime (continuous vs intermittent feeding) as well as different electrical connections; : CW control (conventional CW without electrodes), open-circuit CW-MFC (unpolarized – external circuit between anode and cathode is not connected) and closed- circuit CW-MFC (polarized – external circuit is connected).
For the purpose of this work, eight meso-scale horizontal subsurface flow CWs were operated for about four months. Each wetland consisted of a PVC reservoir of 0.193 m2 filled up with 4/8 mm granitic riverine gravel (wetted depth 25 cm). All wetlands had intermediate sampling points for gravel and interstitial liquid sampling. The CW- MFCs were designed as three MFC electrodes in series along the flow path of the wetland. The a anodes consisted of gravel with an incorporated current collector (stainless steel mesh) and the cathode consisted of a graphite felt layer. The eElectrodes of closed-circuit CW-MFC systems were connected externally over a 220 Ω resistance.
Results showed no significant differences between tested organic loading rates, hydraulic regimes or electrical connections regarding the treatment of domestic wastewater. However, on average, systems operated in closed-circuit CW-MFC mode under continuous flow outperformed the other experimental conditions, with open-circuit MFC and CW control being the worst performin experimental conditions. Closed-circuit CW-MFC compared to conventional CW control systems showed around 6% and 19% higher COD and ammonium removal, respectively. Correspondingly, overall bacteria activity, as measured by the fluorescein diacetate (FDA) technique, was higher (between 4% and to 30%) in closed- circuit systems when compared to CW control systems. Finally, in spite of hight results variability, MFC electric signal correlated well with overall heterotrophic bacterial activity (r2= 0.95), which evidences the potential use of MFC electric signal as a continuous indirect tool for bacterial activity monitoring.
A cargo de: Claus Haslauer (University of Tübingen)
Fecha: jueves 4 de octubre a las 12:15h
Lugar: UPC - Departamento de Ing. Civil y Ambiental
We need to assess change in human and natural systems quantitatively. Hydrology provides suitable assessment tools for planning, design, and societal issues. The basis for these informed decisions is data. Quantitative information about the subsurface is sparse. Given the
available data (e.g., measurements of hydraulic conductivity), we should tease out as much information as possible. I demonstrate copula-based methodology to describe and model non-linear spatial dependence in hydraulic conductivity data-sets. Subsequently, the effects of this non-linear spatial dependence structure on dependent processes (e.g., solute transport behaviour) are analysed. The characteristics of data are manifold: both direct and indirect measurements are useful data. Certain kinds of data (e.g., land cover,
snow equivalents) can be measured accurately with high spatial coverage.On the other hand, direct measurements are sparse. Thus, we need techniques to combine different kinds of information (censored,categorical, real-valued) as we need to estimate at unsampled times and locations. In the second part of this presentation, I will show an example where the goal is to predict groundwater quality parameters at
regional scale in the federal state of Baden-Württemberg, Germany.
For this purpose I am employing a stochastic copula-based model that is capable to mimic the following properties that were encountered in the data: the statistical distribution of the measurements, a varying degree of dependence in different quantiles, censored measurements (e.g., measurements below detection limit), the composition of categorical additional information in the neighbourhood (exhaustive secondary
information), and the spatial dependence of a dependent secondary variable, possibly measured with a different observation network
(non-exhaustive secondary data).
A cargo de : Cristina Valhondo
Fecha: Jueves 20 de Septiembre a las 12:15h
Lugar: Departamento de Ingeniería Civil y Ambiental, Modulo D2-Aula CIHS, Planta Baja.
The reuse of impaired waters has become a required component of water resources management due to the increasing demand of quality water, especially in arid and semiarid regions. Therefore, the development of sustainable, high-efficiency, low cost technologies for water treatment is urgent.
Artificial recharge of aquifers with impaired water is a low-energy and low-cost water recycling technology which allows to improve the recharge water quality and to increase groundwater resources. One of the major concerns with artificial recharge using impaired water is the potential contamination of the underlying aquifer with pathogens and inorganic and organic chemicals present in the infiltrating water.
The aim of this study is to test and improve reactive barriers to prevent leaching of pathogens, inorganic nutrients, and emerging organic compounds to underlying aquifers during artificial recharge of aquifers through infiltration basin.
A cargo de: Lazaro Perez (IDAEA-CSIC)
Fecha: Jueves 13 de septiembre a las 12:15 h
Lugar: Departamento de Ingeniería Civil y Ambienta, Modulo D2-Aula CIHS, Planta Baja
Mixing processes control chemical transformations such as precipitation/dissolution or degradation reactions that are fast compared to mass transfer processes. Chemical
reactions are intrinsically local phenomena, while many applications require predictions at large scales. Physical and chemical heterogeneities are found at all scales and are
at the root of complex spatial concentration distributions, segregation of reactants and phenomena related to the notion of incomplete mixing.
In order to assess the impact of medium and flow heterogeneity at pore-scale on mixingcontrolled reactions, we study the bimolecular irreversible chemical reaction A + B !
C. We consider the reactive displacement of B by a continuous injection of A in a 2-dimensional porous medium characterized by a random distribution of grain size and
position. We use a reactive random walk particle tracking (RWPT) method to simulate the reactive transport problem. This approach is fully equivalent to the advection-diffusionreaction-
equation. We observe three different regimes for the evolution of the product mass mC(t). In the first regime the reaction is controlled by diffusion, in the intermediate regime
it is dominated by advective heterogeneity and characterized by incomplete mixing, in the third, asymptotic regime, mass production is controlled by hydrodynamic dispersion. We
quantify the full evolution of the product mass through the dispersive lamella model (Perez et al., 2018), based on an effective dispersion coefficient, which captures the features of
stretching, compression and coalescence of the mixing front. The effective model predicts accurately the total mass of C. The developed methodology is applied to the pore-scale
experiments reported by Jim´enez-Mart´ınez et al. (2015).