Gravity-Driven Membrane (GDM) filtration has recently gained interest as a potential decentralized system for the treatment of rainwater, greywater, and wastewater and as pre-treatment for Seawater Reverse Osmosis. As low energy and chemical-free process, GDM displays lower environmental impact compared to conventional membrane processes. The GDM performance (i.e., permeate flux and water quality) is directly linked to the biofilm layer on the membrane surface. This dissertation increases the understanding of the relations between membrane biofilm and GDM performance, applying in-situ observations and biofilm characterization under different GDM operating conditions for: (i) decentralized wastewater treatment (DWWT) and (ii) pre-treatment of seawater desalination.
For DWWT, the effect of periodic biofilm control strategies was investigated, manipulating the level of biofilm thickness and density with enhanced permeate flux (chapter 2). Subsequently, the permeate flux was linked to a wide range of wastewater qualities, with understandings on the associated structural properties of biofilm (i.e. thickness, roughness, density) and its hydraulic resistance (chapter 3). For pre-treatment of seawater desalination, the biofilm properties formed in high feed salinity treatment (i.e., raw seawater), were characterized and linked to biofilm response under mechanical loading (chapter 4). In chapter 5, the beneficial effect of the biofilm on the produced water quality was assessed, tailoring the membrane biofilm by operational parameters (Hydraulic Retention Time) to increase effluent quality (removal of Assimilable Organic Carbon).
This work highlights that microbial biofilm can be manipulated by selecting GDM design and operational parameters to benefit the treatment performance.
Luigi Ranieri holds a Bachelor of Science degree in Civil Engineering and a Master of Science in Environmental Engineering from the University of Salerno, Italy.
During his master’s degree, Luigi joined the King Abdullah University of Science and Technology (KAUST) as a visiting student to investigate sustainable membrane processes for decentralized wastewater treatment.
Following his master's degree, Luigi joined as a Ph.D. candidate in the Environmental Science and Engineering program with Prof. Vrouwenvelder. His research efforts focus on addressing the role of biofilm in a Gravity-Driven Membrane (GDM) filtration system.
During his time at KAUST, Luigi has actively participated in events organized by the Water Desalination and Reuse Center (WDRC), including KAUST Research Open Week and the UN2023 Gamechanger Challenge.