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Papers by Kyriakos Kandris

Chloroethenes, and particularly the most chlorinated perchloroethene (PCE) and trichloroethene (T... more Chloroethenes, and particularly the most chlorinated perchloroethene (PCE) and trichloroethene (TCE), are among the most prevalent groundwater contaminants. In contaminated subsurface environments, PCE and TCE are often accompanied by dichloroethenes (DCEs) and the monochlorinated vinyl chloride (VC), which are produced by the microbially-mediated degradation of PCE and TCE.Anaerobic reductive dechlorination (referred to simply as dechlorination in the context of the thesis) has emerged as the most efficient biodegradation pathway of chloroethenes. Dechlorination is a stepwise microbial respiratory process, during which chloroethenes serve as electron acceptors and H2 serves as the electron donor. Ultimately, the environmentally benign ethene (ETH) is produced.Dechlorination depends upon, besides H2 availability, the presence of specific microbes (namely dechlorinators), often naturally-occurring, that mediate each step of the reaction and gain energy to support their maintenance an...

Geotechnical and Geological Engineering, 2011

This paper gathered available flow and transport solutions and used them for two composite liners... more This paper gathered available flow and transport solutions and used them for two composite liners, consisting of geomembrane (GM) overlying either a compacted clay liner (CCL) or a geosynthetic clay liner (GCL). Its aim is to provide a guiding framework for the possible choices of (a) approaches to bottom liner design, (b) respective analytical solutions to flow and transport equations, as well as (c) parameters required for each type of solution. On the basis of the obtained results, the following recommendations are made. When the goal of analysis is to determine material equivalency, leachate flow rate is an adequate key parameter for GM-CCL composite liners. For GM-GCL composite liners, it is necessary to compute contaminant concentration or mass flux, considering (a) transport through defects for inorganic contaminants and (b) diffusion and the contribution of any available attenuation layer for organic contaminants. When the goal of analysis is to assess impact to groundwater, it is advised to calculate both discharge rate and contaminant mass flux regardless of liner type. The critical parameter for the transport calculations is the retardation factor of the contaminant, for the case of CCLs, while the results for GCLs are much less sensitive to this parameter.

&lt;p&gt;Coastal resources are productive drivers of the so-called blue economy, ... more &lt;p&gt;Coastal resources are productive drivers of the so-called blue economy, impacting rapidly growing industries, as the Seawater desalination. Yet, the efficiency of desalination operations is at stake as a result of an imminent operational threat at a global scale, i.e., the proliferation of microscopic algae in seawater. Algal blooms are associated with operational difficulties in the desalination industry, i.e., clogging and bio-fouling, which increase the costs of chemicals, energy and maintenance.&lt;/p&gt;&lt;p&gt;To alleviate the impact of algal blooms, desalination could be supported by innovative tools that foretell the onset and evolution of bloom events. However, the desalination sector lacks near-real time decision-support tools. This work aims to address this gap. To this end, an operational forecasting service was developed, deployed and tested in a seawater desalination plant,&amp;#160; located at the Saronic Gulf (Greece).&lt;/p&gt;&lt;p&gt;The operational forecasting service comprises three components: (a) a hydrodynamic component, (b) a water quality component, and (c) an early warning system for algal bloom events.&lt;/p&gt;&lt;p&gt;The hydrodynamic model predicts the hydrodynamic regime in the Gulf, including vertical mixing, circulation patterns, temperature and salinity profiles. The hydrodynamic model accounts for the heat exchange between the water body and the atmosphere, the salinity, wind and wave action. Both the hydrodynamic and the wave component have been calibrated and validated using satellite-derived and reanalysis data for the first and in situ data for the latter. Specifically, on the validation of the hydrodynamic component, comparisons with satellite-derived water temperatures proved the model&amp;#8217;s ability to accurately predict water temperature profiles in the domain, with MAE=1.11oC and MAPE=4% at the validation period from 01/07/2018 to 30-11-2018. To further improve the predictive capacity of the forecast model, the service assimilates satellite-derived sea surface temperature (obtained by Landsat-8 imagery) using the Ensemble Kalman Filtering method.&lt;/p&gt;&lt;p&gt;The prediction of algal-related water quality attributes (i.e., chlorophyll-a) is based on a data-driven approach. An ensemble learning method (i.e., a random forest) was trained to map hydrodynamic data (temperature, mixed layer thickness), biogeochemical data (inorganic nutrients) and meteorological data (air temperature, wind speed, solar radiation) to chlorophyll-a concentrations at the area of interest. The random-forest-based model produced accurate predictions in hindcast (the mean absolute percentage error was 14% for the held-out data), allowing for its further deployment in an operational setting.&lt;/p&gt;&lt;p&gt;Ultimately, forecasted hydrodynamic and water quality attributes of the coastal zone are integrated into an early warning system that generates and disseminates readily interpretable warning information to enable operators threatened by a probable shift in the regime of the coastal environment to act promptly and appropriately to reduce the vulnerability of those due to be impacted.&lt;/p&gt;&lt;p&gt;In conclusion, this work delivers an operational platform that predicts accurately algal-related parameters in coastal waters. Following its deployment and testing in hindcast, the service line will be tested and validated in operational conditions, aiming to assess the limitations in its forecasting abilities.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Acknowledgements:&lt;/strong&gt; This work is supported by a grant from Iceland, Liechtenstein and Norway through the EEA Financial Mechanism 2014-2021, within the framework of the Programme &amp;#8220;Business Innovation Greece&amp;#8221;.&amp;#160;&lt;/p&gt;

Harmful algae blooms outbreaks in freshwater reservoirs used for drinking water production can ha... more Harmful algae blooms outbreaks in freshwater reservoirs used for drinking water production can have negative effects in human health and ecological status as well as serious economic costs. Furthermore increased amounts of suspended solids and turbidity may interfere with water treatment operations, resulting in increased treatment costs for drinking water facilities. Short term water quantity and quality forecasts for reservoirs intended for potable use, may increase the responsiveness level of water managers against possible changes and thus enable proactive informed decision making on an operational level. A fully operational service line for generating real-time water quality forecasts in reservoirs has been developed, by integrating satellite technology and in-situ monitoring data with state of the art hydrologic and water quality modelling using advanced ICT tools. The service is provided through a web based platform which has been designed in order to facilitate increased int...

The application of earth observation (EO) data to retrieve water quality for inland water bodies ... more The application of earth observation (EO) data to retrieve water quality for inland water bodies has attracted severe attention over the last years. Thereby, water quality products derived from EO data include significant ecological parameters such as turbidity, suspended matter, chlorophyll concentrations, or water temperature. This work investigates how EO-derived water quality data can be combined with data assimilation (DA) techniques to improve model-based predictions of (a) temperature variations, (b) outbreaks of chlorophyll-a concentrations, or (c) events of increased turbidity in surface water reservoirs. Specifically, EO-derived water temperature, chlorophyll-a and inorganic suspended matter were assimilated in coupled hydrodynamic and water quality models using two alternative DA schemes: a simple direct insertion (DI) scheme and the Ensemble Kalman Filter (EnKF) scheme. The two candidate DA techniques were benchmarked against a DA-free simulation in two case studies for ...

Journal of Contaminant Hydrology

Proceedings of IV International Conference on Geo-Engineering Education, 2016

Bulletin of environmental contamination and toxicology, 2015

This work puts forth a heuristic approach for investigating compromises between quality of fit an... more This work puts forth a heuristic approach for investigating compromises between quality of fit and parameter reliability for the Monod-type kinetics employed to model microbial reductive dechlorination of trichloroethene. The methodology is demonstrated with three models of increasing fidelity and complexity. Model parameters were estimated with a stochastic global optimization algorithm, using scarce and inherently noisy experimental data from a mixed anaerobic microbial culture, which dechlorinated trichloroethene to ethene completely. Parameter reliability of each model was assessed using a Monte Carlo technique. Finally, an alternate quantity of applied interest was evaluated in order to assist with model discrimination. Results from the application of our approach suggest that the modeler should examine the implementation of conceptually simple models, even if they are a crude abstraction of reality, as they can be computationally less demanding and adequately accurate when mod...

International Journal of Engineering Pedagogy (iJEP)

This paper offers detailed examples of how research-based learning princi-ples can be translated ... more This paper offers detailed examples of how research-based learning princi-ples can be translated into the instructional decisions involved in designing an engineering course. The redesign of the specific course on environmental geotechnics was prompted by transforming a lecture-based course to an online version. The implemented changes are compatible with research find-ings on learning, which are distilled in the literature in the form of the learn-ing principles reviewed herein. For presentation purposes, the changes are grouped in two main categories: logistical changes, i.e. modifications mainly imposed by the constraints of online study, and pedagogical changes, i.e. changes not related to the learning medium. Examples of implemented modi-fications are given in the body of the paper and in the Supplement. In most cases, the initial motivation for a change was not to achieve compatibility with results of research on learning. Rather, the intended overarching aim was to make trans...

Geotechnical and Geological Engineering, 2011

Journal of Contaminant Hydrology

Proceedings of IV International Conference on Geo-Engineering Education, 2016

Bulletin of environmental contamination and toxicology, 2015

International Journal of Engineering Pedagogy (iJEP)