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

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


Title: Gravity-driven Membrane Filtration of Municipal Wastewater: Process Optimization and Life Cycle Assessment
Author: Hube, Selina
Advisor: Bing Wu
Date: 2023
Language: English
University/Institute: Háskóli Íslands
University of Iceland
School: Verkfræði- og náttúruvísindasvið (HÍ)
School of Engineering and Natural Sciences (UI)
Department: Umhverfis- og byggingarverkfræðideild (HÍ)
Faculty of Civil and Environmental Engineering (UI)
ISBN: 978-9935-9742-0-4
Subject: Doktorsritgerðir; Frárennsli; Fráveitukerfi
URI: https://hdl.handle.net/20.500.11815/4558

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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.
 
Til að uppfylla sífellt strangari losunarstaðla frárennslis er þörf á að þróa áreiðanleg dreifð hreinsunarferli frárennslis. Markmið þessarar rannsóknar var að besta þyngdardrifna himnu (GDM) síun og meta tæknilega, umhverfislega og hagkvæma möguleika hennar fyrir dreifða skólphreinsun í köldu loftslagi. GDM kerfin meðhöndluðu skólp frá sveitarfélögum við mismunandi hitastig (22°C og 8°C), mismunandi himnustillingar (lífræn himna hliðarstraums og keramikhimna á kafi) og mismunandi reglubundnar hreinsunaraðferðir. Niðurstöðurnar sýndu að (1) meðhöndluð vatnsgæði í GDM kerfunum uppfylltu losunarstaðla ESB, óháð hitastigi og himnustillingum; (2) Í GDM kerfunum hliðraðist ríkjandi gangverk óhreininda með síunartímanum og óhreinindalag varð ríkjandi þegar flæðið hafði náð jafnvægi (1.6-4.3 L/m2 klst); (3) Tveggja fasa skolun, efnahreinsun og hátíðnihreinsun bættu hreinsunina samanborðið við reglubundna skolun með því að þenja óhreinindalagið og losa um agnir og uppleyst lífræn efni úr himnunni; (4) Tilvist örplasts í vatninu leiddi til minni framleiðni vatns og meiri uppsöfnunar þungmálma í GDM kerfinu. Formgerð óhreinindalaga var mjög tengd stærð og magni örplasts. Til samanbrðar leiddi LCA greining í ljós að GDM kerfið gæti minnkað áhrif á hlýnun jarðar um ~90% jarðar og ~40% meiri ofauðgun en hefðbundin rotþró, eða rotþró + tilbúið votlendi. Að lokum sýndi kostnaðargreiningin að kostnaður við skólphreinsun með GDM (með keramikhimnum sem byggir á endurunnum efnum) var ~0.213 EUR/m3 , sem var sambærilegt við hefðbundna hreinsunarferla.
 

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