Doctoral defense in Environmental Engineering - Selina Hube

Doctoral candidate: Selina Hube

Dissertation title: Gravity-driven Membrane Filtration of Municipal Wastewater: Process Optimization and Life Cycle Assessment

Opponents:  Dr. John Chew, Professor, Department of Chemical Engineering, Bath University, United Kingdom
Dr. Alberto Tiraferri, Associate Professor, Department of Environmental, Land and Infrastructure Engineering, Politecnico di Torino, Italy.

Advisor: Dr.Bing Wu, Professor at the Faculty of Civil and Environmental Engineering, University of Iceland

Doctoral committee: Dr. Sigurður Brynjólfsson, Professor, Faculty of Industrial Engineering, Mechanical Engineering and Computer Science, University of Iceland
Dr. Michael Burkhardt, Professor, Institute of Environmental and Process Engineering, Eastern Switzerland University of Applied Sciences, Switzerland.

Chair of Ceremony: Dr. Guðmundur Freyr Úlfarsson, Professor and Head of Faculty of Civil and Environmental Engineering, University of Iceland

Abstract

Towards fulfilling increasingly stricter wastewater discharge standards, there is a need for developing reliable decentralized wastewater treatment processes. The goal of this research was to optimize gravity-driven membrane (GDM) filtration and assess its technical, environmental, and economical feasibility for decentralized wastewater treatment under cold climate. The GDM systems treated primary municipal wastewater at different temperatures (22°C and 8°C), with different membrane configurations (side-stream organic membrane and submerged ceramic membrane), and different periodic cleaning strategies. The results highlighted that (1) the treated water quality in the GDM systems met EU discharge standards, regardless of temperature and membrane configurations; (2) In the GDM systems, the dominant fouling mechanism shifted with filtration time and cake fouling was predominant after flux stabilization (1.6-4.3 L/m2h); (3) Compared to periodic backwash, two-phase flow cleaning, and chemical-enhanced physical cleaning, periodic ultrasonication improved water productivity more efficiently through creating a porous cake nature by cake expansion and detachment of particulate foulants and soluble organics from the membrane; (4) The presence of microplastics in the feed water led to a reduced water productivity and more accumulation of heavy metals in the GDM system. The cake layer morphology was strongly associated with microplastic sizes and amounts. A comparative LCA revealed that the GDM system could achieve ~90% lower global warming and ~40% higher eutrophication potential than conventional septic tank, or septic tank + constructed wetlands. Finally, the cost analysis showed that the wastewater treatment cost of GDM (with recycled materials-based ceramic membranes) was ~0.213 EUR/m3, which was comparable to those of conventional treatment processes.

About the doctoral candidate

Selina Hube completed her BS degree in Environmental Engineering at the Technical University of Braunschweig in Germany in 2018. After graduation she moved to Iceland to pursue her MS in Environmental Engineering (environmental quality and water resource engineering) at the University of Iceland in cooperation with the Nanyang Technological University in Singapore. She started her doctoral study at the University of Iceland in 2020.