Thermophilic anaerobic digestion of methanol in UASB reactor

Bonilla-Salinas

Biotech & Bioengineering

et al. 2008

Anaerobic methanethiol (MT) degradation by mesophilic (30 degrees C) alkaliphilic (pH 10) communities was studied in a lab-scale Upflow Anaerobic Sludge Bed (UASB) reactor inoculated with a mixture of sediments from the Wadden Sea (The Netherlands), Soap Lake (Central Washington), and Russian soda lakes. MT degradation started after 32 days of incubation. During the first 252 days, complete degradation was achieved till a volumetric loading rate of 7.5 mmol MT/L/day, and sulfide, methane, and carbon dioxide were the main reaction products. Temporary inhibition of MT degradation occurred after MT peak loads and in the presence of dimethyl disulfide (DMDS), which is the autooxidation product of MT. From day 252 onwards, methanol was dosed to the reactor as co-substrate at a loading rate of 3-6 mmol/L/day to stimulate growth of methylotrophic methanogens. Methanol was completely degraded and also a complete MT degradation was achieved till a volumetric loading rate of 13 mmol MT/L/day (0.77 mmol MT/gVSS/day). However, from day 354 till the end of the experimental run (day 365), acetate was formed and MT was not completely degraded anymore, indicating that methanol-degrading homoacetogenic bacteria had partially outcompeted the methanogenic MT-degrading archea. The archeal community in the reactor sludge was analyzed by DGGE and sequencing of 16S rRNA genes. The methanogenic archea responsible for the degradation of MT in the reactor were related to Methanolobus oregonensis. A pure culture, named strain SODA, was obtained by serial dilutions in medium containing both trimethyl amine and dimethyl sulfide (DMS). Strain SODA degraded MT, DMS, trimethyl amine, and methanol. Flow sheet simulations revealed that for sufficient MT removal from liquefied petroleum gas, the extraction and biological degradation process should be operated above pH 9.

Section: Continuous Uasb Reactormentioning

confidence: 99%

Anaerobic methanethiol degradation and methanogenic community analysis in an alkaline (pH 10) biological process for liquefied petroleum gas desulfurization

Bonilla-Salinas

Biotech & Bioengineering

et al. 2008

“…It contained the following macronutrients (in mg/L): NaCl (280,00), NH 4 Cl (480), K 2 HPO 4 (200), MgCl 2 Á6H 2 O (160), KCl (770), CaCl 2 Á2H 2 O (160) and yeast extract (100). Micronutrients (1 mL/L) were added according to Paulo et al (2001).…”

Section: Continuous Uasb Reactor Experimentsmentioning

confidence: 99%

“…Sulfide (Trüper and Schlegel, 1964) and polysulfide (Kleinjan et al, 2005) were measured photometrically. Biogas composition (CH 4 , CO 2 , N 2 , and H 2 S) was analyzed on a Packard Becker gas chromatograph, model 433 (Delft, The Netherlands) according to Paulo et al (2001).…”

Section: Analytical Techniquesmentioning

confidence: 99%

Anaerobic methanethiol degradation in upflow anaerobic sludge bed reactors at high salinity (≥0.5 M Na⁺)

Biotech & Bioengineering

Lens

et al. 2007

The feasibility of anaerobic methanethiol (MT) degradation at elevated sodium concentrations was investigated in a mesophilic (30 degrees C) lab-scale upflow anaerobic sludge bed (UASB) reactor, inoculated with estuarine sediment originating from the Wadden Sea (The Netherlands). MT was almost completely degraded (>95%) to sulfide, methane and carbon dioxide at volumetric loading rates up to 37 mmol MT x L(-1) x day(-1), 0.5 M sodium (NaCl or NaHCO(3)) and between pH 7.3 and 8.4. Batch experiments revealed that inhibition of MT degradation started at sodium (both NaCl and NaHCO(3)) concentrations exceeding 0.8 M. Sulfide inhibited MT degradation already around 3 mM (pH 8.3).

“…Trace elements were added from a stock solution (1 ml/liter) according to the method of Paulo et al (19). An influent containing 2 to 6 mM MT was composed by mixing the MT stock solution with the nutrient solution near the inlet of the reactor.…”

Section: Methodsmentioning

confidence: 99%

Degradation of Methanethiol by Methylotrophic Methanogenic Archaea in a Lab-Scale Upflow Anaerobic Sludge Blanket Reactor

Lomans

et al. 2006

Appl Environ Microbiol

In a lab-scale upflow anaerobic sludge blanket reactor inoculated with granular sludge from a full-scale wastewater treatment plant treating paper mill wastewater, methanethiol (MT) was degraded at 30°C to H 2 S, CO 2 , and CH 4 . At a hydraulic retention time of 9 h, a maximum influent concentration of 6 mM MT was applied, corresponding to a volumetric loading rate of 16.5 mmol liter ؊1 day ؊1 . The archaeal community within the reactor was characterized by anaerobic culturing and denaturing gradient gel electrophoresis analysis, cloning, and sequencing of 16S rRNA genes and quantitative PCR. Initially, MT-fermenting methanogenic archaea related to members of the genus Methanolobus were enriched in the reactor. Later, they were outcompeted by Methanomethylovorans hollandica, which was detected in aggregates but not inside the granules that originated from the inoculum, the microbial composition of which remained fairly unchanged. Possibly other species within the Methanosarcinacaea also contributed to the fermentation of MT, but they were not enriched by serial dilution in liquid media. The archaeal community within the granules, which was dominated by Methanobacterium beijingense, did not change substantially during the reactor operation. Some of the species related to Methanomethylovorans hollandica were enriched by serial dilutions, but their growth rates were very low. Interestingly, the enrichments could be sustained only in the presence of MT and did not utilize any of the other typical substrates for methylotrophic methanogens, such as methanol, methyl amine, or dimethylsulfide.Organosulfur compounds present in petroleum and other fossil fuels are receiving considerable attention because of their potential direct and indirect negative effects on the environment. Thiols and H 2 S, the major (organo)sulfur compounds in liquefied petroleum gas (LPG), are extracted using alkaline solutions. Currently, thiol-containing LPG (mainly methanethiol [MT]) is treated by the Merox process, in which H 2 S and thiols are extracted from the LPG separately. The thiols are then catalytically oxidized to water-insoluble disulfide oil (33).Alternatively, H 2 S and thiols can be extracted simultaneously from LPG, which results in a solvent stream loaded with H 2 S, MT, and at least 1 M of Na ϩ . The thiols present in the solvent are converted in an anaerobic bioreactor to H 2 S, CO 2 , and CH 4 (26). In a second reactor, H 2 S is biologically oxidized to elemental sulfur, a process that has been studied in detail (7,8) and is already being applied. After separation of the elemental sulfur, the solvent is reused for the extraction process.Under anaerobic conditions, MT is fermented by methanogens, but oxidation by sulfate reducers has also been reported (15,30). Kiene et al. showed that sulfate reducers compete with methanogens for MT and dimethylsulfide (DMS), but only at concentrations below 10 M (10). Theoretically, conversion of MT to acetate or to H 2 , CO 2 , and H 2 S, as described for methanol (20,21), is also possibl...