Membrane bioreactor process for removing biodegradable organic matter from water |
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Authors: | Williams Mark D Pirbazari Massoud |
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Affiliation: | Department of Civil and Environmental Engineering, University of Southern California, 3620 S. Vermont Avenue, Kaprielian Hall (KAP) 260, Los Angeles, CA 90089-2531, USA. |
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Abstract: | This research investigated a membrane bioreactor (MBR) process for removing biodegradable organic matter (BOM) and trihalomethane (THM) precursors from pre-ozonated water. Bench-scale and mini-pilot-scale MBR experiments were conducted using powdered activated carbon (PAC) and acclimated biomass. Dissolved organic carbon (DOC) was removed through a combination of adsorption and biodegradation mechanisms, and the initial DOC removals depended on carbon dose, while steady-state removals were in the 20-60 percent range under various operating conditions. Both assimilable organic carbon (AOC) and total aldehydes were mostly removed to near detection limits and were not affected by PAC dosage. The AOC(NOX) removals were significantly higher than AOC(P17) or total AOC removals probably because the MBR microbial consortium was closer in characteristics to Aquaspirillum NOX than to Pseudomonas fluorescens (P17). The DOC was used instead of biodegradable organic carbon (BDOC) as a parameter for evaluating disinfection byproduct formation and bacterial regrowth potentials because BDOC assays did not yield consistent and conclusive results due to analytical difficulties. The removals of THM precursors were high when PAC was added; however, steady-state removals were a function of operating conditions and PAC dosage. Addition of PAC enhanced DOC removals and membrane permeate fluxes. Furthermore, pre-ozonation reduced membrane fouling and enhanced membrane permeate flux. |
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Keywords: | AOC assimilable organic carbon measured using a mixture of both Pseudomonas fluorescens P17 and Aquaspirillum NOX at the same time AOCNOX assimilable organic carbon measured using Aquaspirillum NOX only AOCP17 assimilable organic carbon measured using Pseudomonas fluorescens P17 only BDOC biodegradable dissolved organic carbon BOC biodegradable organic carbon BOM biodegradable organic matter DBP disinfection byproduct DBPFP disinfection byproduct formation potential D-DBP disinfection-disinfection byproduct DOC dissolved organic carbon DOM dissolved organic matter EBCT empty bed contact time GC/ECD gas chromatography/electron capture detection HAA haloacetic acid HAAFP haloacetic acid formation potential HRT hydraulic retention time HPC heterotrophic plate count MBR membrane bioreactor MCL maximum contaminant level NOM natural organic matter PAC powdered activated carbon THM trihalomethane THMFP trihalomethane formation potential TMP trans-membrane pressure TOC total organic carbon SRT solids retention time USEPA United States Environmental Protection Agency |
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