Kinetics of toluene and sulfur compounds removal by means of an integrated process involving the coupling of absorption and biodegradation

Abstract

International audienceBACKGROUND: Scrubbing using an organic solution instead of an aqueous solution could be a useful way to improve the removal of hydrophobic compounds. Absorption of toluene, dimethyldisulfide (DMDS) and dimethylsulfide (DMS) in an organic solution (di-2-ethylhexyladipate--DEHA), followed by biodegradation by activated sludge was considered, with particular attention to kinetic aspects. DEHA was selected for its relevance in terms of absorption capacity and absorption velocity of the selected volatile organic compounds (VOCs). After the biodegradation step and owing to its cost, recycling of the VOC-free solvent should be considered. RESULTS: Enhancement of VOC mass transfer from the organic to the aqueous phase due to bacterial activity was highlighted and the main driving force was found to be biosurfactant production rather than biodegradation reaction. However, the mass transfer rate between the two phases was shown to be lower than VOC biodegradation rate; hence, significant biodegradation of DMDS and toluene was recorded in a few days during batch experiments, 0.10 and 0.09 mmol respectively. Toluene showed higher biodegradation rates (about 0.05 and 0.10 mg h−1 for DMDS and toluene), leading to higher growth rates. Contrarily, owing to its high volatility, important DMS losses were observed. CONCLUSION: The relevance of the proposed integrated process was shown for hydrophobic VOC removal, at least for toluene and DMDS. Unfortunately, the absorbent phase was also degraded, proved by detection of by-products during analyses of the aqueous phase headspace. The comparison of DEHA with other solvents or solid polymers available for multiphase bioreactor applications may be a reliable option to continue this work

A novel mathematical approach for the understanding and optimization of two-phase partitioning bioreactors devoted to air pollution control

“…This result highlights the relevance of the NAP selection in order to implement TPPBs with a NAP highly affine for the target VOC. Thus, VOC-NAP pairs yielding is one of the most critical parameters in TPPB design [13,36,48,49]. The model also showed a high sensitivity towards a decrease in…”

Absorption and biodegradation of toluene: Optimization of its initial concentration and the biodegradable non-aqueous phase liquid volume fraction

“…The value (H') obtained for pure DEHP was 0.99 Pa.m 3 .mole -1 . As a comparison, the value of the toluene partition coefficient in silicone oil (PDMS, 5 cP viscosity) and hexadecane given in the literature were 1.6 and 2.50 Pa.m 3 .mole -1 , respectively (Vuong et al, 2009;Darracq et al, 2010). Several volume ratios of DEHP in water were tested (5%, 2%, 0.5% and 0.1%).…”

“…However, NAPL can be attacked by microorganisms: for example (Darracq et al, 2009) found that DEHA was assimilated by activated sludge. Possible NAPL assimilation is especially undesired owing to their significant cost and hence their recycling is important in view of their reuse in a TPPB (Cesário et al, 1998;Darracq et al, 2010). Muñoz et al, (2007) considered that it is difficult to predict the stability of a given NAPL in the presence of microorganisms on long term, owing to a possible emergence of microorganisms able to degrade the NAPL.…”

Activated Sludge and Other Suspended Culture Processes

“…The reducing load test was able to show the relationship between a declining free nitrous acid (FNA) concentration and the decreasing nitrite production. Darracq et al (2010) by Hafez et al (2010). It was found that the process achieved significant biomass yield reduction due to anoxic consumption of organic matter.…”