Removal of high concentrations of hydrogen sulfide using a biofilter packed with expanded schist under extreme acidic conditions was performed. The impact of various parameters such as H2S concentration, pH changes and sulfate accumulation on the performances of the process was evaluated. Elimination efficiency decreased when the pH was lower than 1 and the sulfate accumulation was more than 12 mg S-SO4(2-)/g dry media, due to a continuous overloading by high H2S concentrations. The influence of these parameters on the degradation of H2S was clearly underlined, showing the need for their control, performed through an increase of watering flow rate. A maximum elimination capacity (ECmax) of 24.7 g m(-3) h(-1) was recorded. As a result, expanded schist represents an interesting packing material to remove high H2S concentration up to 360 ppmv with low pressure drops. In addition, experimental data were fitted using both Michaelis-Menten and Haldane models, showing that the Haldane model described more accurately experimental data since the inhibitory effect of H2S was taken into account.

h i g h l i g h t sThe treatment of sulfur odorous compounds in mixture, H 2 S, DMDS and EtSH by biofiltration was examined. Removal efficiencies of biofilters packed with pine bark and composted wood mulch were compared. The degradation of the three compounds decreased as follows: H 2 S > DMDS > EtSH. Contrarily to EtSH and DMDS, H 2 S removal was not affected by the lack of nutrients in the biofilter. pH decrease caused by H 2 SO 4 accumulation impacted EtSH and DMDS degradation contrarily to H 2 S removal. a b s t r a c tThe treatment of sulfur odorous compounds in mixture, hydrogen sulfide (H 2 S), dimethyl disulfide (DMDS) and ethanethiol (EtSH), by biofiltration was examined. A significant effort was focused on the impact of nutrients supply, without forgetting the effect of other parameters such as the pH, on the process performances. Removal efficiencies of three biofilters packed with pine bark and composted wood mulch and sprinkled by different nutritive solutions were compared.Owing to the biodegradability of H 2 S, its removal was not affected by the lack of nutrients in the biofilter. However, for EtSH and DMDS, considered as more recalcitrant, the influence of nutrients on biodegradation was clearly observed; it was enhanced when the supplementation in the watering solution was increased. Furthermore, EtSH removal yield increased from 80% in the absence of supplementation to an almost total removal in the presence of nutrients in the watering solution. The degradation of the three compounds decreased as follows: H 2 S > DMDS > EtSH. The impact of the pH of the packing materials was also underlined. The decrease in pH caused by the accumulation of sulfuric acid in the packing material, the most abundant product of the biological oxidation of sulfur compounds, led to a reduction of the elimination efficiencies of EtSH and DMDS; while the microorganisms involved in H 2 S degradation appeared active in a large pH range, from less than 3 to close to 9.

a b s t r a c tThe treatment of hydrogen sulfide using a biofilter packed with expanded schist and topped with a layer of a synthetic nutritional material (UP20) was examined at a constant H 2 S concentration (100 ppmv). The impact of the empty bed residence time (EBRT) on process performances was clearly underlined by varying the polluted air flow from 4 to 20 m 3 h −1 corresponding to a variation in the EBRT from 63 to 13 s. Complete H 2 S degradation was observed when the EBRT was higher than 51 s. Experimental data collected at various EBRTs (13-63 s) were fitted using the Ottengraf model equations. The ␣ lump parameter value was found to be 26.4 g 1/2 m −3/2 h −1 . This single parameter, which enables the performance of the biofilter as a whole to be characterized whatever its composition (mixture or layers of different packing materials) and whatever the EBRT, is a powerful tool to compare packing materials and to design such bioreactors. The ␣ lump value characterizing the performances of expanded schist coupled with a thin layer of UP20 was higher than the ␣ lump values obtained for other packing materials (natural or synthetic) reported in previous studies.

Please cite this article as: M. Ben Jaber, A. Couvert, A. Amrane, P.L. Cloirec, E. Dumont, Removal of hydrogen sulfide in air using cellular concrete waste: biotic and abiotic filtrations, Chemical Engineering Journal (2017), doi: http://dx.doi.org/10. 1016/j.cej.2017.03.014 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractThe objective of this study was to investigate the removal of hydrogen sulfide (H 2 S) present in air using cellular concrete waste as the packing material. Air filtration was performed under biotic and abiotic conditions. Experiments were carried out in a laboratory-scale PVC column (internal diameter of 300 mm) filled with a volume of 70 L of cellular concrete (1 m height).The polluted air flow was generated at 4 m 3 h -1 corresponding to an Empty Bed Residence Time (EBRT) of 63 s. In dry conditions without biomass (abiotic conditions), cellular concrete can be an effective medium for the treatment of H 2 S in air. For an H 2 S concentration of 100 ppmv, the removal efficiency was around 70 % (Elimination Capacity (EC) of 5.6 g m -3 h -1 ). This finding can be explained by the physicochemical reactions that can take place between H 2 S and the cellular concrete components (mainly CaO, CaCO 3 and Fe 2 O 3 ).However, interactions between cellular concrete and H 2 S are not yet fully understood. Used as a packing material for H 2 S biofiltration (biotic conditions), cellular concrete waste efficiently 2 treated (Removal Efficiency = 100 %) high concentrations of H 2 S (up to 133 ppmv corresponding to an EC of up to 10.5 g m -3 h -1 ). Physicochemical and biological mechanisms explaining H 2 S removal seem to occur simultaneously in the biofilter. At an EBRT of 63 s, the maximal elimination capacity (EC max ) was 17.8 g m -3 h -1 . A packed bed of cellular concrete also presents a satisfactory mechanical behavior with low pressure drops.

International audienceThe biofiltration of hydrogen sulfide present in a biogas mimic under anoxic conditions was performed using expanded schist and cellular concrete waste as packing materials. The impact of various parameters, such as H2S concentrations, Empty Bed Residence Time (EBRT) and molar ratio N/S, on the performances of biofilters was evaluated. At an EBRT of 300 s, expanded schist efficiently treated H2S concentrations up to 1100 ppmv (maximum elimination capacity ECmax = 30.3 g m-3 h-1). At an EBRT of 240 s, cellular concrete waste was an effective material for the treatment of concentrations of H2S up to 900 ppmv (ECmax = 25.2 g m-3 h-1). Whatever the molar ratio N/S selected, sulfate and elemental sulfur were produced in the biofilters. Both materials presented a satisfactory mechanical behavior with low pressure drops. Therefore, this study showed that biofilters could be used to treat moderate concentrations of H2S in biogas under anoxic conditions