publications

2021

1. Water Res.

   A framework for model-based assessment of resilience in water resource recovery facilities against power outage

   Pau Juan-García, Leiv Rieger, Geoff Darch, and 2 more authors

   Water Research, 2021

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   Current practice to enhance resilience in Water Resource Recovery Facilities (WRRFs) is to ensure redundancy or back-up for most critical equipment (e.g. pumps or blowers). Model-based assessment allows evaluation of different strategies for quantitatively and efficiently enhancing resilience and justifying the allocation of resources. The goal of this study is to provide guidance for the development of tailored deterministic models of full-scale WRRFs. A framework for model-based resilience assessment is proposed that provides guidance on data collection, model selection, model calibration and scenario analysis. The framework is embedded into the Good Modeling Practice (GMP) Unified Protocol, providing a new application for resilience assessment and an initial set of stressors for WRRFs. The usefulness of the framework is illustrated through a resilience assessment of the WRRF of Girona against power outage. Results show that, for the Girona facility, limited energy back-up can cause non-compliance of WRRF discharge limits in the case of a blower power shut-down of 6 h, and around 12 h when the blower shut-down is also combined with a shut-down of the recirculation pumps. The best option to enhance resilience would be increasing the power back-up by 218%, which allows the plant to run with recirculation pumps and blowers at minimum capacity. In such a case, resilience can be further enhanced by manipulating the air supply valves to optimise the air distribution, to balance oxygen needs in each reactor with the overall system pressure. We conclude that, with industry consensus on what is considered an acceptable level of resilience, a framework for resilience assessment would be a useful tool to enhance the resilience of our current water infrastructure. Further research is needed to establish if the permit structure should accommodate levels sof functionality to account for stress events.

   @article{JUANGARCIA2021117459,
     title = {A framework for model-based assessment of resilience in water resource recovery facilities against power outage},
     journal = {Water Research},
     volume = {202},
     pages = {117459},
     year = {2021},
     issn = {0043-1354},
     doi = {https://doi.org/10.1016/j.watres.2021.117459},
     url = {https://www.sciencedirect.com/science/article/pii/S0043135421006576},
     author = {Juan-García, Pau and Rieger, Leiv and Darch, Geoff and Schraa, Oliver and Corominas, Lluís},
     keywords = {WRRF resilience, Modelling, Stressor, Dynamic airflow model, Quantitative assessment, Uncertainty},
   }

2019

1. Thesis UdG

   Resilience of water resource recovery facilities: a framework for quantitative model-based assessment

   Pau Juan-García

   Feb 2019

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   The water sector is entering a period of uncertainty, as stressors such as climate change pose unknown risks to its infrastructure. Utilities need to build resilience to handle unpredictable changes, but the field of resilience in water management is still at its infancy. This thesis will first examine the state of the art of resilience implementation in water resource recovery facilities (WRRF) and identify challenges to its implementation. Secondly, a framework to measure resilience using modelling techniques is proposed. Thirdly, a WRRF model is calibrated and validated at full scale using state of the art dynamic aeration modelling, to be used to validate the framework with two stressors: stormwater and power outage

   @thesis{THESISPAUJUAN2019,
     title = {Resilience of water resource recovery facilities: a framework for quantitative model-based assessment},
     journal = {TDX (Tesis Doctorals en Xarxa)},
     year = {2019},
     month = feb,
     doi = {http://www.tdx.cat/handle/10803/667738},
     author = {Juan-García, Pau},
     keywords = {WRRF resilience, Modelling, Stressor, Dynamic airflow model, Quantitative assessment, Uncertainty},
     publisher = {Universitat de Girona},
   }

2018

1. Water Sci.

   Dynamic air supply models add realism to the evaluation of control strategies in water resource recovery facilities

   Pau Juan-García, Mehlika A. Kiser, Oliver Schraa, and 2 more authors

   Water Science and Technology, Aug 2018

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   This paper introduces the application of a fully dynamic air distribution model integrated with a biokinetic process model and a detailed process control model. By using a fully dynamic air distribution model, it is possible to understand the relationships between aeration equipment, control algorithms, process performance, and energy consumption, thus leading to a significantly more realistic prediction of water resource recovery facility (WRRF) performance. Consequently, this leads to an improved design of aeration control strategies and equipment. A model-based audit has been performed for the Girona WRRF with the goal of providing a more objective evaluation of energy reduction strategies. Currently, the Girona plant uses dissolved oxygen control and has been manually optimised for energy consumption. Results from a detailed integrated model show that the implementation of an ammonia-based aeration controller, a redistribution of the diffusers, and the installation of a smaller blower lead to energy savings between 12 and 21\%, depending on wastewater temperature. The model supported the development of control strategies that counter the effects of current equipment limitations, such as tapered diffuser distribution, or over-sized blowers. The latter causes an intermittent aeration pattern with blowers switching on and off, increasing wear of the equipment.

   @article{10.2166/wst.2018.356,
     author = {Juan-García, Pau and Kiser, Mehlika A. and Schraa, Oliver and Rieger, Leiv and Corominas, Lluís},
     journal = {Water Science and Technology},
     volume = {78},
     number = {5},
     pages = {1104-1114},
     year = {2018},
     month = aug,
     issn = {0273-1223},
     doi = {10.2166/wst.2018.356},
     url = {https://doi.org/10.2166/wst.2018.356},
   }

2. Water Sci.

   The future of WRRF modelling – outlook and challenges

   Pusker Regmi, Heather Stewart, Youri Amerlinck, and 21 more authors

   Water Science and Technology, Dec 2018

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   The wastewater industry is currently facing dramatic changes, shifting away from energy-intensive wastewater treatment towards low-energy, sustainable technologies capable of achieving energy positive operation and resource recovery. The latter will shift the focus of the wastewater industry to how one could manage and extract resources from the wastewater, as opposed to the conventional paradigm of treatment. Debatable questions arise: can the more complex models be calibrated, or will additional unknowns be introduced? After almost 30 years using well-known International Water Association (IWA) models, should the community move to other components, processes, or model structures like ‘black box’ models, computational fluid dynamics techniques, etc.? Can new data sources – e.g. on-line sensor data, chemical and molecular analyses, new analytical techniques, off-gas analysis – keep up with the increasing process complexity? Are different methods for data management, data reconciliation, and fault detection mature enough for coping with such a large amount of information? Are the available calibration techniques able to cope with such complex models? This paper describes the thoughts and opinions collected during the closing session of the 6th IWA/WEF Water Resource Recovery Modelling Seminar 2018. It presents a concerted and collective effort by individuals from many different sectors of the wastewater industry to offer past and present insights, as well as an outlook into the future of wastewater modelling.

   @article{10.2166/wst.2018.498,
     author = {Regmi, Pusker and Stewart, Heather and Amerlinck, Youri and Arnell, Magnus and García, Pau Juan and Johnson, Bruce and Maere, Thomas and Miletić, Ivan and Miller, Mark and Rieger, Leiv and Samstag, Randal and Santoro, Domenico and Schraa, Oliver and Snowling, Spencer and Takács, Imre and Torfs, Elena and van Loosdrecht, Mark C. M. and Vanrolleghem, Peter A. and Villez, Kris and Volcke, Eveline I. P. and Weijers, Stefan and Grau, Paloma and Jimenez, José and Rosso, Diego},
     title = {{The future of WRRF modelling – outlook and challenges}},
     journal = {Water Science and Technology},
     volume = {79},
     number = {1},
     pages = {3-14},
     year = {2018},
     month = dec,
     issn = {0273-1223},
     doi = {10.2166/wst.2018.498},
     url = {https://doi.org/10.2166/wst.2018.498},
   }

2017

1. Water Res.

   Resilience theory incorporated into urban wastewater systems management. State of the art

   P. Juan-García, D. Butler, J. Comas, and 4 more authors

   Water Research, Dec 2017

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   Government bodies, utilities, practitioners, and researchers have growing interest in the incorporation of resilience into wastewater management. Since resilience is a multidisciplinary term, it is important to review what has been achieved in the wastewater sector, and describe the future research directions for the forthcoming years. This work presents a critical review of studies that deal with resilience in the wastewater treatment sector, with a special focus on understanding how they addressed the key elements for assessing resilience, such as stressors, system properties, metrics and interventions to increase resilience. The results showed that only 17 peer-reviewed papers and 6 relevant reports, a small subset of the work in wastewater research, directly addressed resilience. The lack of consensus in the definition of resilience, and the elements of a resilience assessment, is hindering the implementation of resilience in wastewater management. To date, no framework for resilience assessment is complete, comprehensive or directly applicable to practitioners; current examples are lacking key elements (e.g. a comprehensive study of stressors, properties and metrics, examples of cases study, ability to benchmark interventions or connectivity with broader frameworks). Furthermore, resilience is seen as an additional cost or extra effort, instead of a means to overcome project uncertainty that could unlock new opportunities for investment.

   @article{JUANGARCIA2017149,
     title = {Resilience theory incorporated into urban wastewater systems management. State of the art},
     journal = {Water Research},
     volume = {115},
     pages = {149-161},
     year = {2017},
     issn = {0043-1354},
     doi = {https://doi.org/10.1016/j.watres.2017.02.047},
     url = {https://www.sciencedirect.com/science/article/pii/S0043135417301392},
     author = {Juan-García, P. and Butler, D. and Comas, J. and Darch, G. and Sweetapple, C. and Thornton, A. and Corominas, Ll},
     keywords = {Management, Resilience, Sewer systems, Wastewater, WRRF},
   }