Dimethyl Sulfide Removal Research Articles

Performance and microbial analysis of defined and non‐defined inocula for the removal of dimethyl sulfide in a biotrickling filter

The performance and microbial communities of three differently inoculated biotrickling filters removing dimethyl sulfide (DMS) were compared. The biotrickling filters were inoculated with Thiobacillus thioparus TK-m (THIO), sludge (HANDS) and sludge + T. thioparus TK-m + Hyphomicrobium VS (HANDS++), respectively. The criteria investigated were length of the start-up period, the maximum elimination capacity, and the effects of intermittent loading rates, low pH, peak loading and very low loading rate on the DMS removal efficiency. The HANDS++ reactor exhibited the best performance considering all treatments. HANDS performed almost equally well as HANDS++, except during the determination of the EC(max), while THIO was generally the least efficient. During stable DMS loading at concentrations of 20 ppmv or lower, all reactors exhibited similar and high removal efficiencies (>99%). Denaturing gradient gel electrophoresis (DGGE) analysis showed the establishment of T. thioparus in the biofilm of all reactors, but not of Hyphomicrobium VS. Quantitative monitoring of the introduced bacterial strains was performed with a newly developed real-time PCR protocol. Initially, the inoculated strains were exclusively found in the reactors in which they were added. Afterwards, however, both strains developed in the biofilm of all three reactors, although T. thioparus attained higher cell densities than Hyphomicrobium. The presence of T. thioparus in THIO was related with the DMS loading rates that were applied, in the sense that intermittent DMS loading and very low DMS loading rates (0.5 ppmv) induced a decrease in gene copy numbers. Real-time PCR and DGGE both gave consistent results regarding the presence of Hyphomicrobium VS and Thiobacillus thioparus TK-m in the reactors. Only real-time PCR could be used to detect bacteria comprising of less than 1.4% of the total bacterial community ( approximately 10(5) copies ring(-1)).

Methanol and Dimethyl Sulfide Removal by Pulsed Corona Part I: Experiment

Methanol and dimethyl sulfide are volatile organic compound (VOC) air pollutants that are subject of severe environmental regulations due to their toxicity, environmental persistence and odor. Traditional technologies are often inefficient for their removal, especially in the case of the dilute industrial streams. Non-thermal plasma methods, typically characterized by high removal efficiency, energy yields and good economy, offer possible alternative solutions. The present research employs pulsed corona discharge known for its high selectivity and low energy costs of emission control. This paper provides experimental (Part I) and in a later issue numerical (Part II) data on removal of methanol and dimethyl sulfide from dry and humid air streams. The removal efficiency and the specific energy input are evaluated along with the energy costs required for the removal process. Particular attention is given to the formation of unwanted byproducts such as NO x , CO, and SO2.

Photodegradation of Dimethyl Sulfide (DMS) in Natural Waters: Laboratory Assessment of the Nitrate-Photolysis-Induced DMS Oxidation

The interaction of sunlight and dissolved chromophoric matter produces reactive chemical species that are significant in the removal of dimethyl sulfide (DMS) in the surface ocean. Using artificial solar radiation, we examined the role of several inorganic components of seawater on the kinetics of NO3- -photolysis-induced DMS removal in aqueous solution. This study strongly suggests that NO3- photolysis products react significantly with DMS in aqueous solution possibly via an electrophilic attack on the electron-rich sulfur atom. This supports previous field observations that indicate that NO3- photolysis has a substantial control on DMS photochemistry in nutrient-rich waters. A key finding of this research is that the oxidation rate of DMS induced by NO3- photolysis is dramatically enhanced in the presence of bromide ion. Moreover, our results suggest that bicarbonate/carbonate ions are involved in free radical production/scavenging processes important for DMS photochemistry. These reactions are pH dependent. We propose that DMS removal by some selective free radicals derived from bromide and bicarbonate/carbonate ion oxidation is a potentially important and previously unrecognized pathway for DMS photodegradation in marine waters.

Dimethylsulfide and Dimethylsulfoniopropionate Production in the Antarctic Pelagic Food Web

Dimethylsulfide (DMS) is the most abundant form of volatile sulfurs in the ocean. Many biogeochemical studies have been conducted in the past several decades to unveil the processes driving the production, transformation and removal of DMS. They have shown that the Southern Ocean is an area with one of the highest levels of DMS concentrations during the austral summer in the global oceans. It has recently been observed that Antarctic krill, Euphausia superba, produces DMS and dissolved dimethyl-sulfoniopropionate (DMSP) in its gazing process. Copepods also produce DMS, and the potential production rates of DMS in the Southern Ocean by krill and copepods are estimated to be as much as <TEX>$21{\mu}mol\;m^{-2}d^{-1}$</TEX> and <TEX>$0.6{\mu}mol\;m^{-2}d^{-1}$</TEX>, respectively. These production rates of zooplankton and the presence of phytoplanktot which have high DMSP contents in their cells, might facilitate in situ DMS production in the Southern Ocean.

Titanium dioxide mediated heterogeneous photocatalytic degradation of gaseous dimethyl sulfide: Parameter study and reaction pathways

This paper deals with the photocatalytic degradation of gaseous dimethyl sulfide (DMS) in a wide range of inlet concentrations (3ppmv<[DMS]in<545ppmv), gas residence times (5s<τ<55s) and relative humidities (3%<RH<75%), using TiO2 Degussa P25 as a photocatalyst in a flat-plate photoreactor. DMS removal efficiencies increased with lower [DMS]in and higher τ, while the optimum RH was 22%. Although DMS removal efficiencies higher than 90% (peaks over 97%) could be obtained for at least 180min at τ=55s, RH<53% and [DMS]in<10ppmv, prolonged irradiation and/or increased [DMS]in resulted into catalyst deactivation due to accumulation of reaction products on the TiO2 surface. During photocatalytic DMS degradation at [DMS]in≥100ppmv, dimethyl disulfide, carbon dioxide and sulfur dioxide were detected as gas-phase reaction products, while solid–liquid extraction revealed dimethyl sulfoxide, dimethyl sulfon, methane sulfonic acid and sulfate as reaction products adsorbed on the exposed catalyst. Consequently, detailed photocatalytic DMS degradation pathways were proposed, starting with TiO2(h+) or OH mediated DMS oxidation and followed by CS bond cleavage, S-oxidation and C-oxidation. Carbon and sulfur mass balances were closed for 90–105% and 98–110%, respectively. [DMS]in did not have an important effect on product distribution, but interesting trends in DMS degradation products were observed as a function of RH.

Operational and microbiological aspects of a bioaugmented two‐stage biotrickling filter removing hydrogen sulfide and dimethyl sulfide

A two-stage biotrickling filter was developed for removing dimethyl sulfide (DMS) and hydrogen sulfide (H2S). The first biotrickling filter (ABF) was inoculated with Acidithiobacillus thiooxidans and operated without pH control, while the second biotrickling filter (HBF) was inoculated with Hyphomicrobium VS and operated at neutral pH. High DMS elimination capacities were observed in the HBF (8.2 g DMS m(-3) h(-1) at 90% removal efficiency) after 2 days. Maximal observed elimination capacities were 83 g H2S m(-3) h(-1) (100% removal efficiency) and 58 g DMS m(-3) h(-1) (88% removal efficiency) for the ABF and the HBF, respectively. The influence of a decreasing empty bed residence time (120 down to 30 sec) and the robustness of the HBF towards changing operational parameters (low pH, starvation, and DMS and H2S peak loadings) were investigated. Suboptimal operational conditions rapidly resulted in lower DMS removal efficiencies, but recovery of the HBF was mostly obtained within a few days. The H2S removal efficiency in the ABF, however, was not influenced by varying operational conditions. In both reactors, microbial community dynamics of the biofilm and the suspended bacteria were investigated, using denaturing gradient gel electrophoresis (DGGE). After a period of gradual change, a stable microbial community was observed in the HBF after 60 days, although Hyphomicrobium VS was not the dominant microorganism. In contrast, the ABF biofilm community was stable from the first day and only a limited bacterial diversity was observed. The planktonic microbial community in the HBF was very different from that in the biofilm.

Adsorptive removal of dimethylsulfide and t-butylmercaptan from pipeline natural gas fuel on Ag zeolites under ambient conditions

Desulfurization of pipeline natural gas fuel at ambient conditions before introduction to reforming processes is strongly needed for stationary applications of fuel cells. Adsorptive removal of dimethlysulfide (DMS) and t-butylmercaptan (TBM) from pipeline natural gas was efficiently carried out by using silver exchanged Y zeolites (AgNa-Y) in the presence of water at room temperature and normal pressure. The capacity and adsorptivity for DMS and TBM on AgNa-Y were improved by an increase in silver content of AgNa-Y. Adsorption runs for DMS and TBM were carried out separately to compare their adsorptivity on AgNa-Y. The sulfur adsorption capacity for DMS on Ag(18)Na-Y (1.9mmolg−1) was much higher than that for TBM (0.6mmolg−1). The clear color change of AgNa-Y during the period of adsorption run provides information regarding the formation of silver sulfide species on AgNa-Y. The used AgNa-Y was regenerated easily by heat treatment in air at 500°C.

Biogenic sulfur distribution and cycling in the surface microlayer and subsurface water of Funka Bay and its adjacent area

A total of 27 sea surface microlayer and corresponding subsurface samples collected from Funka Bay, Japan and its adjacent area (western North Pacific) in March 2001 were analyzed for dimethylsulfide (DMS), dimethylsulfoniopropionate, dissolved (DMSPd), particulate (DMSPp), and chlorophyll a. The sea surface microlayer samples generally showed marked differences from bulk water with respect to concentrations of DMS, DMSPd, DMSPp and chlorophyll a. DMS generally exhibited a small extent of enrichment in the microlayer, with enrichment factors (EF) ranging from 0.70 to 2.62 with an average of 1.18. The concentrations of DMSPd and DMSPp in the microlayer were remarkably higher than those in the subsurface water. This may be attributed to higher chlorophyll a level and greater biological activity found in the microlayer. The mean EFs for DMSPd and DMSPp were 2.41 and 2.12, respectively. Interestingly, we observed higher production rates and consumption rates of DMS in the surface microlayer relative to the subsurface water. Moreover, the production rates of DMS were significantly correlated with DMSPd concentrations. However, no relationship appeared between the production rate of DMS and chlorophyll a levels in seawater, suggesting that the DMS production in seawater was largely controlled by DMSPd availability rather than algal biomass. Although it is generally believed that biological production and consumption represent the principal mechanisms controlling the concentration of DMS in the oceanic surface mixed layer and its emission to the atmosphere, biological processes were demonstrated to be unimportant in controlling the source and sink of DMS within the microlayer. Thus atmospheric ventilation would become a predominant mechanism in the removal of DMS in the surface microlayer.

A membrane bioreactor for the removal of dimethyl sulphide and toluene from waste air

In biotrickling filters, mass transfer of hydrophobic compounds is the limiting factor. Biofilters are static systems, and so control and regulation of operational parameters such as pH and nutrient supply can be a problem. In membrane bioreactors, these drawbacks can be avoided. The hydrophobic membrane separates the waste air from the aqueous phase, thus avoiding mass-transfer limitation, while pH and nutrient supply can be directly controlled. In this contribution, an overview will be given of results obtained during a four-year project. First, the physical chemical characteristics (solubility, permeability, diffusivity) and microbial adhesion of different membranes were tested. This led to the selection of a composite membrane consisting of a porous polyvinylidenefluoride (PVDF) support layer coated with a thin (1 or 2.5 microm) dense polydimethylsiloxane (PDMS) top layer. This membrane was mounted into a module provided with four parallel rectangular channels for gas flow (in contact with the porous layer) and nutrient solution (in contact with the dense layer) respectively. After inoculation, a biofilm developed on the dense layer. Experiments were performed with dimethyl sulphide and toluene as target VOCs. Operational characteristics such as elimination capacity as a function of the volumetric load and residence time, effect of nutrient supply, long-term performance) were determined. Mass transfer was studied by measuring concentration profiles along the channels of the module in different conditions.

Dimethyl sulfide removal from synthetic waste gas using a flat poly(dimethylsiloxane)-coated composite membrane bioreactor.

The reduction of volatile organic sulfur emissions should be completely as they cause odor nuisance, even when they are emitted in very small amounts. In general, biofilters are applied for odor reduction, but their operational control is limited. A new biotechnique for the treatment of complex emissions is the use of membranes integrated within bioreactors (MBRs). In this study, the reactor performance of MBRs for removal of dimethyl sulfide (DMS) as a model compound is presented. Composite membranes with a poly(dimethylsiloxane) (PDMS)-coating layer were used. The MBRs were inoculated with the sulfur-degrading culture Hyphomicrobium VS or a suspension of Hyphomicrobium VS, ammonium-oxidizing bacteria (AOB), and nitrite-oxidizing bacteria (NOB) to colonize the PDMS-coating layer. Although inoculation with AOB and NOB might give rise to competition for space on the membrane, their presence in the MBRs appeared to be positive as they co-oxidize DMS. Dimethyl sulfide elimination depended on the inoculum type, DMS inlet concentration, gas residence time, and membrane polymer. For equal loading rates, the elimination capacity (EC) increased at larger gas residence times and inlet concentrations. The maximum EC obtained with the MBRs was 4.8 kg of DMS x m(-3) x d(-1). This value is higher than any reported figure for biofilters and biotrickling filters.

Removal of dimethyl sulfide from waste air in a membrane bioreactor

Long-term experiments with a membrane bioreactor to remove dimethyl sulfide (Me 2S) from waste air are reported for the first time. The membrane bioreactor contained a polydimethylsiloxane/Zirfon® composite membrane and was inoculated with Hyphomicrobium VS, a methylotrophic micro-organism. The optimal conditions of pH (6–7) and sulfate contents (< 8 g SO 4 2−-S.L −1) for maximum Me 2S-degradation were determined in batch studies and applied during membrane biofiltration. Dimethyl sulfide conversion depended both on gas residence time and inlet concentration. The removal efficiency of air contaminated with 38 mg Me 2S.m −3 was found to be 99% at 24 s, 90% at 12 s and 85% at 8 s gas residence time. At a gas residence time of 24 s, removal efficiencies of 99%, 93% and maximum 87% were observed for Me 2S concentrations of 33 mg.m −3 116 mg.m −3 and 375 mg.m −3, respectively. The maximum elimination capacity was 4.82 kg Me 2S.m r −3.d −1 (efficiency of 74%) which is higher than ever obtained with the conventional biofilters and biotrickling filters.

Control of Dimethyl Sulfide Emissions Using Biofiltration

Laboratory scale experiments were conducted to evaluate the performance of a biofilter for eliminating dimethyl sulfide(DMS). A commercial compost/pine bark nugget mixture served as the biofilter material for the experiments. The gas flow rate and DMS concentration entering the filter were varied to study their effect on the biofilter efficiency. The operating parameters, such as the residence time, inlet concentration, pH, water content, and temperature, were all monitored throughout the filter operation. The kinetic dependence of the DMS removal along the column length was also studied to obtain a quantitative description of the DMS elimination. High DMS removal efficiencies(>95％) were obtained using the compost filter material seeded with activated sludge. DMS pollutant loading rates of up to 5.2 and 5.5 g-DMS/m/hr were effectively handled by the upflow and downflow biofilter columns, respectively. The macrokinetics of the DMS removal were found to be fractional-order diffusion-limited over the 9 to 25 ppm range of inlet concentrations tested. The upflow column had an average macrokinetic coefficient(Kf/) of 0.0789 0.0178 ppm//sec, while the downflow column had an average coefficient of 0.0935 0.0200 ppm//sec. Shorter residence times resulted in a lower mass transfer of the pollutant from the gas phase to the aqueous liquid phase, thereby decreasing the efficiency.

Transformation of dimethylsulphoniopropionate to dimethyl sulphide during summer in the North Sea with an examination of key processes via a modelling approach

Abstract This study describes the routes and rates of transformation of dimethylsulphoniopropionate (DMSP) to dimethyl sulphide (DMS) in a phytoplankton bloom in the northern North Sea (59°N 2°E). A region on the edge of the high reflectance waters that characterised the bloom was labelled with SF6-tracer and tracked for 6 days. Within the framework of this Lagrangian experiment, it was possible to compile a comprehensive budget of the transformation of DMSP to DMS in the surface mixed layer of 15–30 m depth and a subsurface layer that extended to ⩾40 m. As a basis to the synthesis of the DMS(P) biogeochemistry, an attempt was made to accurately constrain DMS emissions from the Lagrangian water mass. Included in the study is a comparison of estimates of the transfer velocity and DMS sea to air flux derived from two well established and two recently introduced parameterisations. The two recent approaches encouragingly gave similar rates of total DMS sea to air flux of 1.60 mg S m−2 over the 6-day experimental period, and this value was intermediate to values derived from the two more routinely used approaches. The DMS sea to air flux was equivalent in terms of sulphur, to 10% of the DMS production and 1.3% of the particulate DMSP (DMSPp) production in the surface layer over the 6 days. Bacterial consumption accounted for the majority of DMS removal in both surface (62–82%) and subsurface layers (average 98%) and DMS concentrations decreased over the 6 days, despite increasing DMS production. Microzooplankton were the main agents of the transformation of DMSPp to the dissolved phase but little DMS appeared to be produced directly by the grazers. Instead, bacteria rapidly turned over the dissolved DMSP (DMSPd) made available by the grazers. An upper limit of 17% of the DMSPd consumed by bacteria in the surface layer was cleaved to DMS over the 6 days. Lower transformation efficiencies of ∼6% were estimated for the subsurface layer. An ecosystem model incorporating DMS(P) biogeochemistry was developed on the basis of the empirical data. Simple sensitivity analyses were employed to demonstrate the importance of both microzooplankton and bacterial metabolism in controlling the yield of DMS from DMSP production and hence, the DMS sea to air flux. Greater yields of DMS are likely to occur when DMSPp is transformed directly to DMS, in this case due to grazing, than when transformed to DMSPd and subsequently cleaved to DMS by bacterial activity. The point of DMS production in the DMSPp to DMS transformation pathway is likely to alter in relation to phytoplankton bloom progression and with season. The complex interaction amongst heterotrophic processes that control DMS concentrations suggests that attempts to predict global DMS flux may need to couple comprehensive ecosystem models of the type used in this study, to general circulation models.

Distribution and cycling of dimethylsulfide in surface microlayer and subsurface seawater

Abstract Laboratory experiments, along with in situ investigation in Funka Bay, Japan, were conducted to determine the enrichment factor (EF) of dimethylsulfide (DMS) in the sea surface microlayer, as well as its the production and consumption rates. The EF of DMS in the microlayer was largely affected by various factors including sampling methods, sampling thickness, temperature, salinity, and DMS concentration in bulk water. In all cases but the sealed system, a part of DMS in the microlayer was always unavoidably lost during sampling. High temperature, great wind speed, and slow sampling would increase the extent of loss of DMS due to volatilization. In the field, the screen-collected samples usually exhibited greater microlayer enrichment for DMS than the plate-collected samples, showing that the screen sampler might be more effective for collecting the in situ microlayer DMS. The production and consumption rates of DMS in the surface microlayer were higher than those in the bulk water and these two rates were significantly correlated with the microlayer DMS concentrations. Moreover, the EF of DMS appeared to be related to the microlayer production rate of DMS, providing evidence supporting the observed DMS enrichment in the microlayer. The DMS production and consumption rates were not directly related to its concentrations in the bulk water, suggesting that the processes of production and consumption of DMS were very complex. In the surface microlayer, the biological turnover time of DMS varied from 0.4 to 1.9 days, with an average of 0.9 days, which was about 540-fold greater than the mean DMS sea–air turnover time (2.4 min). Thus, the biological process occurring within the microlayer can be neglected when we consider the sea–air exchange of DMS. Considering the microlayer production rate of DMS (an average of 9.7 nM day−1) to be too small to counteract the sea-to-air removal of DMS, the main source of DMS in the microlayer appears to be through vertical transport by turbulent diffusion from the underlying water.

Removal of dimethyl sulfide and t-butylmercaptan from city gas by adsorption on zeolites

The removal of dimethyl sulfide (DMS) and t-butylmercaptan (TBM) from city gas by use of zeolites was studied. Na-Y, Na-X, and Ca-X showed high removal ratios of the sulfur compounds at 1 h after the start of the adsorption run in city gas flow, though DMS broke through rapidly for a few hours. On the other hand, H-β and USY showed continuously high removal ratios for 9 h, and trace amounts of H 2S were detected in the effluent gas. The adsorption mechanisms on Na-Y and H-β were studied by adsorption in the absence of hydrocarbons, IR spectroscopy, and temperature programmed desorption (TPD). The desorbed peaks of DMS and TBM during TPD of binary components on Na-Y were located over the same temperature ranges as the peak during TPD of DMS and that of TBM, respectively, which findings suggested that the adsorption states at binary adsorption were similar to those at single component adsorption. The main adsorption site was presumably Na +. On H-β, TBM reacted to H 2S on Brönsted acidic sites. On the adsorption run in the absence of hydrocarbons, the removal ratio of TBM was enhanced on H-β in the presence of DMS. During TPD of binary components on H-β, a peak of m/ e=41 at 120°C grew, which findings indicated that the polymerization of isobutene-like compounds produced from TBM was depressed by co-existent DMS.

Impact of solar radiation on the biological removal of dimethylsulfoniopropionate and dimethylsulfide in marine surface waters

The effect of natural surface solar radiation on the biological removal of dimethylsulfo- niopropionate (DMSP) and dimethylsulfide (DMS) was determined and compared to the photochem- ical removal of DMSP and DMS. Natural bacterial assemblages (0.8 µm filtered seawater) from the northern Adriatic Sea and the coastal North Sea were exposed to surface solar radiation and incu- bated in the dark; the DMSP and DMS concentrations were measured concurrently. Photochemical removal rates were determined in 0.2 µm filtered seawater. Biological removal of DMSP in the light was 62 ± 14% lower than the biological removal rate obtained in the dark. High spatial and temporal variability in the biological removal rates was observed for the dark treatments, as well as for its sen- sivity to solar radiation, with rates for light treatments varying from 29 to 81% of those in the dark. The DMSP concentration above which no further increase of the biological DMSP removal rate was observed was substantially lower in the light treatments (~30 nM) than in the dark treatments (>80 nM). UV-B radiation only accounted for a minor inhibitory effect (~15% of total inhibition), whereas UV-A and PAR (photosynthetically active radiation) both contributed ~42% of total inhibi- tion. Biological DMS removal under solar radiation was only ~40 ± 14% of the biological DMS removal in the dark. Under surface solar radiation, photochemical removal was always higher than the dark biological removal. Our results indicate therefore, that the DMSP and DMS dynamics in the oceanic surface waters are severely influenced by solar radiation due to the partial inhibition of the microbial consortia responsible for DMSP and DMS turnover.

Biogeochemical Variation in Dimethylsulfide, Phytoplankton Pigments and Heterotrophic Bacterial Production in the Subarctic North Pacific during Summer

Dimethylsulfide (DMS), chlorophyll a (Chl-a), accessory pigments (fucoxanthin, peridinin and 19′-hexanoyloxyfucoxanthin), and bacterial production (BP) were measured in the surface layer (0–100 m) of the subarctic North Pacific, including the Bering Sea, during summer (14 July–5 September, 1997). In surface sewater, the concentrations of DMS and Chl-a varied widely from 1.3 to 13.2 nM (5.1 ± 3.0 nM, mean ± S.D., n = 48) and from 0.1 to 2.4 µg L−1 (0.6 ± 0.6 µg L−1, n = 24), respectively. In the subarctic North Pacific, DMS to Chl-a ratios (DMS/Chl-a) were higher on the eastern side than the western side (p < 0.0001). Below the euphotic zone, DMS/Chl-a ratios were law and the correlation between DMS and Chl-a was relatively strong (r2 = 0.700, n = 27, p < 0.0001). In the euphotic zone, DMS/Chl-a ratios were higher and the correlation between DMS and Chl-a was weak (r2 = 0.128, n = 50, p = 0.01). The wide variation in DMS/Chl-a ratios would be at least partially explained by the geographic variation in the taxonomic composition of phytoplankton, because of the negative correlation between DMS/Chl-a and fucoxanthin-to-Chl-a ratios (Fuc/Chl-a) (r2 = 0.476, n = 26, p = 0.0001). Furthermore, there was a positive correlation between DMS and BP (r2 = 0.380, n = 19, p = 0.005). This suggests that BP did not represent DMS and dimethylsulfoniopropionate (DMSP) removal by bacterial consumption but rather DMSP degradation to DMS by bacterial enzyme.

Removal of Dimethyl Sulphide from Off-Gas Mixtures Containing Hydrogen Sulphide and Methanethiol by a Biotrickling Filter

Long-term laboratory-scale experiments with a biotrickling filter were conducted to study a process capable of removing mixtures of odorous reduced sulphur compounds from off-gases. The biotrickling filter was inoculated with a consortium of microorganisms enriched from the sludge water of a Finnish refinery. Its liquid phase contained from 4 to 6 microorganisms at a density of 9×105−3×108 cells ml−1. Two of the strains were isolated in pure cultures. The gas volumetric load was 53-178 m3 m−3 h−1 and the superficial liquid flow rate was between 25-87 l m−2 d−1. The sulphate toxicity level in the liquid phase was observed to be 15-20 g l−1. The efficiency of dimethyl sulphide (Me2S) removal with a concentration of 77 (±13) mg m−3 Me2S-S was found to be 78 (±9) % when the concentration of methanethiol-sulphur (MeSH-S) in the gas mixture was below 21 mg m−3 (removal efficiency over 97 %) and that of hydrogen sulphide-sulphur (H2S-S) below 200 mg m−3 (removal efficiency over 99 %). The maximum Me2S-S removal capacity of the gas mixture was 959 g m−3 d−1 (removal efficiency 79 %), which is higher than any previously reported figure. Saddle-shaped ceramics and plastic grits were also tested as potential packing materials. The biofilm in a biotrickling filter filled with plastics was not so resistant towards changes in pH or liquid circulation rate than that of one filter filled with ceramics.

Removal of organo-sulphur odour compounds by Thiobacillusnovellus SRM, sulphur-oxidizing microorganisms

The microorganism was isolated from sewage and characterized as Thiobacillus novellus SRM. The optimal pH and temperature for cell growth were pH 7.0 and 30°C, respectively. The content of G and C of the DNA was 67.2%. The unsaturated fat consisted of octadenoicacid plus cyclopropane of C 19(C 18:1+19cyc) and the saturated fat of 3-hydroxydodecanoic acid (3-OH C 10:0). Thiobacillus novellus SRM oxidized S 2O 3 −2 to S 4O 6 −2 and S 4O 6 −2 to SO 4 −2. Thiobacillus novellus SRM removed 200 ppm H 2S in 1.8 h, the 50 ppm of methyl mercaptan (MM) in 2.6 h, 30 ppm of dimethyl sulphide (DMS) in 7.0 h, and 30 ppm of dimethyl disuphide (DMDS) in 6.0 h. The optimal pH for the removal of DMS was pH 7.0 and the optimal temperature was 30°C. 10 g immobilized Thiobacillus novellus SRM removed 98% of 30 ppm DMDS and 50% of 40 ppm DMDS. When the DMDS concentration increased to 40 ppm, the removal efficiency decreased to less than 50%. The removal efficiency by immobilized Thiobacillus novellus SRM was H 2S>MM>DMDS>DMS. 100% of H 2S and MM, and 87% of DMDS were removed in 15 days. The removal efficiency of DMS was less than that of DMDS.

Photolysis of dimethylsulfide in the northern Adriatic Sea: Dependence on substrate concentration, irradiance and DOC concentration

Abstract The influence of dimethylsulfide (DMS) and DOC concentrations and varying irradiance levels on the photolysis of DMS was evaluated. Laboratory experiments were conducted with 0.2 μm filtered aged seawater from the northern Adriatic Sea and artificial radiation. Photolysis of DMS followed pseudo first-order kinetics with the photolysis rate constant k directly dependent on irradiance intensity. Photolysis rates of DMS were also directly dependent on DOC concentration. In field experiments using natural solar radiation, DMS (5 nM initial conc.) was removed from freshly collected 0.2 μm filtered seawater at rates of 0.6±0.1 nmol l−1 h−1, equivalent to k=0.12±0.02 h−1. Based on these photolysis rates and using in situ profiles of downwelling irradiance, DMS and DOC concentrations, we calculated a water-column-integrated DMS removal rate due to photolysis of 165±20 μmol m−2 d−1. Averaged over the entire water column, the photochemical turnover time of DMS was 3.1±0.5 days. Most (88%) of the DMS was photolyzed in the top 10 m of the water column. Comparison of our data with photochemical and biological turnover rates published elsewhere indicates that photolysis may be an important sink of DMS in shallow coastal waters.