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UBC Theses and Dissertations

The design and testing of a short HRT attached growth pre-fermenter system: SCVFA production by two media types and two feed sources Dumitrescu, Alex


A pilot-scale, short Hydraulic Retention Time (HRT), fixed film fermenter system was constructed to test for Short Chain Volatile Fatty Acids (SCVFA) production performance at various retention times. The performance of two media types, Ringlace® and Kaldnes media, was monitored at intervals of 20min, 40min and 60min provided by three 20min hydraulic retention time (HRT) reactors in each media series. The UBC waste water pilot plant was used as the waste source for all experiments. Two fermentation runs were completed; the first using primary effluent as feed and the second using screened raw wastewater. The sampling and processing scheme addressed temporal variations in the following parameters: SCVFA concentration, total organic carbon (TOC), total chemical oxygen demand (tCOD), soluble chemical oxygen demand (sCOD) and suspended solids analysis. Turbidity analysis was attempted but was not continued for the duration of the research. Metabolic fingerprinting, using the BIOLOG plate assay, provided a snapshot of the biofilm's grouped microbial metabolic activities present at the time of sampling. SCVFA production in the BF-system was near zero in the reactors containing no media during both the primary effluent and raw wastewater runs. Significant levels of SCVFA's were produced by short HRT attached growth fermenters using both primary effluent and raw wastewater as feed. Both sets of media reactors tested produced more SCVFA's than the control reactors. TOC and sCOD analyses, which measure dissolved organics in the waste stream, indicated a net solubilization of filterable solids in both media series fed raw wastewater. Kaldnes media was deemed not suitable as a short HRT pre-fermentation media in the current BF-system configuration, due to an inability to handle the solids loading of the waste stream. Suspended solids analysis supported the choice of appropriate media for future research by demonstrating the tendency of Kaldnes media to become clogged with solids. Ringlace® media has proven itself as a suitable short HRT pre-fermentation media by resisting plugging under the solids loading conditions tested. Results of the two fermentation runs indicate that, a 60min HRT fermenter system fed raw domestic wastewater, is capable of producing significantly more SCVFA's than a system fed primary effluent, (11.2mg/l and 5.6mg/l, respectively).

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