Liquid phase optimisation in a horizontal flow biofilm reactor (HFBR) technology for the removal of methane at low temperatures

Abstract

Methane (CH4) is a potent greenhouse gas often emitted in low concentrations from waste sector activities. Biological oxidation techniques have the potential to offer effective methods for the remediation of such emissions. In this study, methods of improving the CH4 oxidation performance of a horizontal flow biofilm reactor (HFBR) technology, operated at low temperatures, were investigated.Three pilot scale HFBRs were operated over three phases (Phases 1, 2 & 3) lasting 310 days in total. The reactors were loaded with 13.2 g CH4/m 3 /hr during each phase and operated at an average temperature of 10 o C.In Phase 1, nutrients were added to the biofilm via a liquid nutrient feed (LNF) comprising water and nutrient mineral salts. Average removals were 4.2, 3.1 and 2.3 g CH4/m 3 /hr for HFBRs 1, 2 and 3 respectively. Commented [NU1]:In response to Reviewer #1 comment; "Authors must start the abstract with the motivational statement related to the background of study" Commented [NU2]:In response to Reviewer #2 comment; "Standardize the format of units for performance variables (methane load, methane removal, etc.) through the document included the abstract" units have been standardised as g XX/m 3 /hr In Phase 2 silicone oil was added to the LNF of all three HFBRs. Average removals increased, when compared to Phase 1, by 31%, 79% and 78% 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. A concentration of 1.0 g Brij 35/L proved most effective in improving reactor performance; with removal rates increasing by 105% and 171% for HFBRs 1 and 2 respectively when compared to Phase 1.These results indicate the potential of liquid phase optimisation for improving mass transfer rates and removal performances in biological reactors treating CH4.

Hydrogen sulfide oxidation in novel Horizontal-Flow Biofilm Reactors dominated by an Acidithiobacillus and a Thiobacillus species

“…Removal rates for biofilm-based reactors of between 5 and 169 g H2S m -3 [reactor volume] h -1 at residence times of less than 1 min have been reported [1,2,11,12,13,14,15]. Horizontal-Flow Biofilm Reactor (HFBR) technology has previously been used to treat methane-contaminated airstreams [16,17] and were also shown to be capable of H2S removal in a short proof of concept trial [18]. This study investigated H2S removal in HFBRs in more detail than previously reported.…”

Capture of Methane by Fungi: Evidence from Laboratory-Scale Biofilter and Chromatographic Isotherm Studies

“…The short residence times sufficient for capturing and oxidizing soluble odors (i.e., NH 3 , H 2 S) ) are too short for capturing hydrophobic CH 4 (Melse and Van der Werf, 2005;Nikiema and Heitz, 2009). As large-volume biofilters are not cost-effective for use on farms (Melse and Van der Werf, 2005;Montes et al, 2013;Streese and Stegmann, 2005), or the use of specialized liquid phase sorbents (Estrada et al, 2014;Kennelly et al, 2014;Ramirez et al, 2012), other CH 4 capture improvements must be developed.…”

Innovative approaches for enhancing the cost-efficiency of biological methane abatement

“…ECs of 45 g m −3 h −1 at EBRTs of 4 min, while a BTF operated under identical conditions without silicone oil reached a maximum EC of 35 g m −3 h −1 [52,54,55]. Thus, the addition of the NAP consistently supported a remarkable improvement in BTF performance compared to conventional aqueous phase systems.…”

“…Different NAPs have been tested to enhance CH 4 mass transfer, although silicone oil (with an affinity for CH 4 15 times higher than water) was the most popular transfer vector [14,48,51,52]. The performance of two-phase partitioning bioreactors (TPPB) has been repeatedly evaluated using diluted CH 4 emissions, although the results seem to be configuration specific [14,44,46,49,53].…”

“…However, Rocha-Rios et al (2011) did not observe a significant improvement in the performance of a two-phase partitioning airlift bioreactor constructed with 10% (v/v) of silicone oil under a CH 4 IL of 170 g m −3 h −1 and an internal gas recirculation of 1-2 m air 3 m reactor -3 min -1 , mainly due to the poor dispersion of silicone oil [56] (table 2). Although, TPPBs have achieved promising results for the treatment of hydrophobic volatile organic compounds, controversial results in terms of CH 4 biodegradation enhancement have been repeatedly reported [48,52,54,55]. In this context, the enrichment of hydrophobic methanotrophs capable of growing immerse inside the NAP, where much higher concentrations of methane are available for the growth of methanotrophs, could support a direct pollutant uptake and improve both, the overall CH 4 mass transfer capacity and the robustness of the bioreactor [41,53] (Figure 1.6).…”