Liquid phase optimisation in a horizontal flow biofilm reactor (HFBR) technology for the removal of methane at low temperatures.
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Kennelly, Colm, Gerrity, Seán, Collins, Gavin, & Clifford, Eoghan. (2013). Liquid phase optimisation in a horizontal flow biofilm reactor (HFBR) technology for the removal of methane at low temperatures. Paper presented at the 5th IWA Odour and Air Emissions Conference jointly held with 10th Conference on Biofiltration for Air Pollution Control, San Francisco, California, USA, 04-07 March.
In this study, methods of improving the methane oxidation performance of a biofilm technology, the horizontal flow biofilm reactor (HFBR), operated at low temperatures were investigated. Three pilot scale HFBRs were commissioned to treat an air mixture containing methane (CH4) gas and were operated over 3 phases (Phases 1, 2 & 3) lasting 310 days in total. The reactors, loaded with 13.2 g CH4/m3 reactor volume/hr during each phase, were operated at an average temperature of 10oC throughout. In Phase 1, nutrients were added to the biofilm via a liquid nutrient feed (LNF) comprising water and nutrient mineral salts. Removals averaged 4.1, 3.1 and 2.7 g CH4/m3 /hr for HFBRs 1, 2 and 3 respectively. In Phase 2 silicone oil was added to the LNF of all three HFBRs to enhance mass transfer of methane to the liquid phase and thus improve treatment performance. Following this removal rates for Phase 2 averaged 5.6, 5.5 and 4.0 g CH4/m3/hr for HFBRs 1, 2 and 3 respectively. In Phase 3 a non ionic surfactant (Brij 35) was added to the LNF and silicone oil liquid phase of HFBRs 1 and 2. The operating conditions of HFBR 3 were not changed and it was used as a control. Various concentrations were trialled, with 1.0 g Brij 35/L proving most successful. Removal rates increased to 8.6 g CH4/m3/hr and 8.4 g CH4/m3/hr for HFBRs 1 and 2 respectively under these conditions, representing increases of 54% and 53% for HFBRs 1 and 2 respectively. These results indicate the potential of liquid phase optimisation as an efficient solution to improving the performance of biological reactors treating CH4 emissions and overcome traditional constraints posed by mass transfer limitations.