Removal of hydrogen sulfide by immobilized Thiobacillus thioparus in a biotrickling filter packed with polyurethane foam

A simple medium modification for isolation, growth and enumeration of Acidithiobacillus thiooxidans (syn. Thiobacillus thiooxidans) from water samples

High concentrations of H(2)S in groundwater are commonly removed using Biological Trickling Filter (BTF) that contains high numbers of biofilm immobilized sulfur oxidizing bacteria (mainly Thiobacillus thiooxidans). BTF performance requires continuous monitoring of these bacteria at several sampling points. The Most Probable Number (MPN) technique is at the moment the method of choice to enumerate viable T. thiooxidan cells under the above conditions. However, this method is extremely time-consuming (7-10days) and not always suitable for environmental monitoring. In the present study, Thiobacillus agar recommended for isolation and cultivation of Thiobacillus species by Spread plate method was modified by addition of bromocresol green (BCG) in order obtain a clear-cut resolution of the growing colonies resulting in similar or higher numbers compared to other methods. Visual emergence of bacterial colonies on the 3rd and 4th days, from the initial plating, was associated with sulfuric acid production, resulting in an unambiguous color change from blue to yellow, around each colony. This study revealed that BCG modified Thiobacillus agar is substantially time saving and much easier to infer compared to MPN technique.

Kinetic evaluation of removal of odorous contaminants in a three-stage biological air filter

Biofiltration is a cost-effective technology for removing air contaminants from animal facilities. Kinetic analysis can be helpful in understanding and designing the process but has not been performed on full-scale filters treating complex mixtures. In this study, kinetics was investigated in a full-scale biological filter treating air pollutants from a pig facility. Due to the high air flow rates used in the filter, both a plug flow model and a model based on complete mixing were tested with respect to kinetic order and Michaelis-Menten kinetics. Application of these models only gave poor to moderate agreement with air filter removal data. Two alternative kinetic models (Stover-Kincannon model and Grau second-order model) adopted from wastewater biofiltration process analysis were introduced to analyze contaminant removal in the biological air filter. Data analysis demonstrated the applicability of these two models with a high degree of precision on contaminant removal in the biological air filter. Whereas the Stover-Kincannon model demonstrated that pollutant removal rates were related to the mass loading rates, the Grau second-order kinetic model indicated that the removal efficiencies were dependent on air loading rates. Therefore, the kinetic data can be used for comparing biofilter performances and for design purposes.

Kinetics of the bio-oxidation of volatile reduced sulphur compounds in a biotrickling filter

Mixtures of volatile reduced sulphur compounds (VRSCs) like hydrogen sulphide (H(2)S), methylmercaptan (MM), dimethyl sulphide (DMS) and dimethyl disulphide (DMDS) are found in gaseous emissions of several industrial activities creating nuisance in the surroundings. Hydrogen sulphide (H(2)S) decreases the removal efficiency of volatile reduced sulphur compounds (VRSCs) in biofilters but the kinetics of this effect is still unknown. Kinetic expressions that represent the rate of bio-oxidation of H(2)S, MM, DMS and DMDS are proposed. In order to observe and quantify this effect, equimolar mixtures of MM, DMS and DMDS were fed into a biotrickling filter inoculated with Thiobacillus thioparus at different H(2)S loads. Experimental results shown a good agreement with the simulations generated by the model considering the kinetic equations proposed. The estimated kinetic constants show that H(2)S and MM have a significant inhibitory effect on the bio-oxidation of DMS and DMDS, having the H(2)S the higher effect.

Biomass accumulation modelling in a highly loaded biotrickling filter for hydrogen sulphide removal

A pilot scale test on a biotrickling filter packed with polyurethane foam cubes was carried out for 110 d at high volumetric mass load (up to 280 g m(bed)(-3) h(-1)) with the aim of studying the accumulation of solids in the treatment of H(2)S. Removal rate up to 245 g m(bed)(-3) h(-1) was obtained; however, an accumulation of gypsum, elemental sulphur and, above all, inert biomass was identified as the cause of an increased pressure drop over the long term. A mathematical model was applied and calibrated with the experimental results to describe the accumulation of biomass. The model was capable of describing the accumulation of solids and, corresponding to a solids retention time of 50 d, the observed yield resulted in 0.07 g of solids produced g(-1) H(2)S removed. Respirometric tests showed that heterotrophic activity is inhibited at low pH (pH < 2.3), and the contribution to biomass removal through decay was negligible.

Microbial removal of NOX at high temperature by a novel aerobic strain Chelatococcus daeguensis TAD1 in a biotrickling filter

The removal of NO(X) at high temperature by Chelatococcus daeguensis TAD1 in a biotrickling filter was studied. Media components of the recycling liquid were screened using Plackett-Burman design and then were optimized using response surface methodology, which enhanced the efficiency of nitrate removal by TAD1. The optimal medium was used to perform long-term experiments of NO(X) removal in a biotrickling filter under high concentrations of O(2) and NO in simulated flue gas. Results showed that the biotrickling filter was able to consistently remove 80.2-92.3% NO(X) when the inlet NO concentration was 600ppm under the conditions of oxygen concentration ranging between 2% and 20% and empty bed residence time (EBRT) being 112.5s. Analyses by polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE) indicated that TAD1 was always predominant in the biofilm under a flue gas environment. Overall, the present study demonstrated that utilizing a biotrickling filter inoculated with the aerobic denitrifier TAD1 to remove NO(X) at high temperature was practically feasible.

Effect of VOCs and methane in the biological oxidation of the ferrous ion by an acidophilic consortium

During the elimination of H2S from biogas in an aqueous ferric sulphate solution, volatile organic compounds (VOCs) and methane are absorbed and may have an effect on the subsequent biological regeneration of ferric ion. This study was conducted to investigate the effect of maximum concentrations of methane and some VOCs found in biogas on the ferrous oxidation of an acidophilic microbial consortium (FO consortium). The presence and impact of heterotrophic microorganisms on the activity of the acidophilic consortium was also evaluated. No effect on the ferrous oxidation rate was found with gas concentrations of 1500 mg toluene m(-3), 1400 mg 2-butanol m(-3) or 1250 mg 1,2-dichloroethane m(-3), nor with methane at gas concentrations ranging from 15-25% (v/v). A tenfold increase in VOCs concentrations totally inhibited the microbial activity of the FO consortium and the heterotrophs. The presence of a heterotrophic fungus may promote the autotrophic growth of the FO consortium.

Hydrogen sulfide and odor removal by field-scale biotrickling filters: influence of seasonal variations of load and temperature

Two biotrickling filters were set up at two wastewater treatment plants (WWTP) in The Netherlands to investigate their effectiveness for treatment of odorous waste gases from different sources. One biotrickling filter was installed at Nieuwe Waterweg WWTP in Hook of Holland to study the hydrogen sulfide removal from headworks waste air. The other reactor was installed at Harnaschpolder WWTP (treating wastewater of the city of The Hague) to remove mercaptans and other organic compounds (odor) coming from the emissions of the anaerobic tanks of the biological nutrient removal (BNR) activated sludge. The performance of both units showed a stable and highly efficient operation under seasonal variations of load and temperature over nearly one year of monitoring. The Nieuwe Waterweg unit achieved removals of up to 99%, corresponding to a maximum daily average elimination capacity (EC) of 55.8 g H(2)S/m(3)/h at an empty bed residence time (EBRT) as short as 8.5 s. Odor reduction at the Harnaschpolder unit was 95% at an EBRT of 18.9 s, with average outlet concentration lower than the objective value which was established as 1000 European Odor Units (OU(E)/m(3)).

Strategies for pH control in a biofilter packed with sugarcane bagasse for hydrogen sulfide removal

The biological removal of hydrogen sulfide at low concentration (<120 ppmv) was studied in a laboratory-scale biofilter packed with sugarcane bagasse and inoculated with a sulfur-oxidizing bacterial consortium isolated from activated sludge from a wastewater treatment plant (WWTP). Inlet loads from 1.31 to 20.2 g Sm(-3) h(-1) were supplied to the biofilter, and empty bed residence times (EBRTs) of 30, 20 and 10 s were tested. In all cases, the removal efficiency was greater than 99%. Two methods for the pH control were tested: increasing the phosphate buffer capacity of the mineral medium (method I), and a new method, which involves the addition of solid CaCO(3) to the bagasse at the upper inlet of the biofilter (method II). For method I, pH increased gradually along the bed (from the bottom to the top), from a constant value of 3.0 to 7.0. For method II, pH was constant (2.4 ± 0.8) along the bed, and then a steep increase of pH was observed at the top to 7.1. We suggest the use of CaCO(3) instead of phosphate buffer because the former is less expensive, it is a simple method and the results obtained with the two methods are similar.

Parameters affecting HS emissions removal and re-circulating water quality in a pilot-scale sequential biological treatment system at a wastewater lift station in Brownsville, Texas, USA

In this study, a pilot-scale sequential biological treatment system combining a biotrickling filter and biofilter was used to optimize the removal of variable emission H(2)S loadings ranging from 30 to 120 g m(-3) h(-1)at a wastewater lift station in Brownsville, Texas USA. The biotrickling filter recycle water pH remained between 2.0 to 3.0 during the four months of unit operation and the overall removal efficiency for H(2)S was >99%. The biotrickling filter removal efficiency was 70 ± 8%, with an elimination capacity of 10 to 80 g m(-3) h(-1) while the biofilter elimination capacity ranged from 10 to 40 g m(-3) h(-1). The sequential treatment system was operated initially at an Empty Bed Residence Time (EBRT) of 120 s (50 s for the biotrickling filter and 70 s for biofilter) for two months and then at an EBRT of 60 s (25 s for biotrickling filter and 35s for biofilter) for the remainder of the operating period; remarkably, there was only a slight decrease in removal efficiency at 60 s EBRT. In order to qualitatively evaluate the changes in recycle water quality in the system on the performance of the unit in precipitating sulfur species, the equilibrium chemical model, Visual MINTEQ was employed. The model predicted speciation results based on the feed water quality and sulfur loadings, and also forecast some iron-sulfur complexes which have potential to form some complex precipitates. This research demonstrated that low pH re-circulating water quality in the biological treatment of H(2)S was possible without compromising the high removal efficiency, and that an improved understanding of the recycle water chemistry of the trickling unit of a sequential treatment system could be useful in the overall optimization of the process.

Styrene removal from polluted air in one and two-liquid phase biotrickling filter: steady and transient-state performance and pressure drop control

A Sporothrix variecibatus-inoculated biotrickling filter (BTF) was examined for styrene removal, without and with the addition of silicone oil, at different empty bed residence times. The highest elimination capacities (ECs) were 172.8 (without silicone oil) and 670 g m(-3)h(-1) (with silicone oil), respectively, corresponding to a 4-fold improvement in presence of oil. The addition of silicone oil formed a well-coalesced emulsion of fungi and silicone oil, resulting in filter-bed clogging. Clogging prevention strategies adopted were; (i) lowering the volume ratio of silicone oil from 10% to 2% (v/v), and (ii) periodic increase in trickling rate of the medium from 50 to 190 mL min(-1). During shock-load experiments, the BTF with silicone oil (2% v/v) could withstand high styrene loads, of up to 1900 g m(-3)h(-1), when compared to the BTF without silicone oil (400 g m(-3)h(-1)).

Biofiltration of reduced sulphur compounds and community analysis of sulphur-oxidizing bacteria

The present work aims to use a two-stage biotrickling filters for simultaneous treatment of hydrogen sulphide (H(2)S), methyl mercaptan (MM), dimethyl sulphide (DMS) and dimethyl disulphide (DMDS). The first biofilter was inoculated with Acidithiobacillus thiooxidans (BAT) and the second one with Thiobacillus thioparus (BTT). For separate feeds of reduced sulphur compounds (RSC), the elimination capacity (EC) order was DMDS>DMS>MM. The EC values were 9.8 g(MM-S)/m(3)/h (BTT; 78% removal efficiency (RE); empty bed residence time (EBRT) 58 s), 36 g(DMDS-S)/m(3)/h (BTT; 94.4% RE; EBRT 76 s) and 57.5 g(H2S-S)/m(3)/h (BAT; 92% RE; EBRT 59 s). For the simultaneous removal of RSC in BTT, an increase in the H(2)S concentration from 23 to 293 ppmv (EBRT of 59 s) inhibited the RE of DMS (97-84% RE), DMDS (86-76% RE) and MM (83-67% RE). In the two-stage biofiltration, the RE did not decrease on increasing the H(2)S concentration from 75 to 432 ppmv.

Co-treatment of single, binary and ternary mixture gas of ethanethiol, dimethyl disulfide and thioanisole in a biotrickling filter seeded with Lysinibacillus sphaericus RG-1

The work reports the aerobic co-treatment characteristics of single, binary and ternary mixture gas of ethanethiol, dimethyl disulfide (DMDS) and thioanisole in a biotrickling filter seeded with Lysinibacillus sphaericus RG-1. 100% removal efficiency (RE) was achieved for sole ethanethiol, DMDS and thioanisole at inlet concentration below 1.05, 0.81 and 0.33 mg/L, respectively, at empty bed resident time 110 s. In addition, 100% RE was also obtained with binary ethanethiol and DMDS (1:1) and ternary ethanethiol, DMDS and thioanisole (3:2:1). Michaelis-Menten equation was modified to incorporate the plug flow behavior of the bioreactor. The maximum removal rate (V(max)) was calculated as 56.18, 57.14 and 22.78 g/m(3)/h for sole ethanethiol, DMDS and thioanisole, respectively, while the V(max) was 41.84 and 14.56 g/m(3)/h for DMDS and thioanisole in binary and ternary systems, respectively. Overall, these suggest that not only sole but also binary and ternary mixture can be efficiently removed in this system.

Effect of oxygen dosing point and mixing on the microaerobic removal of hydrogen sulphide in sludge digesters

Limited oxygen supply to anaerobic sludge digesters to remove hydrogen sulphide from biogas was studied. Micro-oxygenation showed competitive performance to reduce considerably the additional equipment necessary to perform biogas desulphurization. Two pilot-plant digesters with an HRT of ∼ 20 d were micro-oxygenated at a rate of 0.25 NL per L of feed sludge with a removal efficiency higher than 98%. The way of mixing (sludge or biogas recirculation) and the point of oxygen supply (headspace or liquid phase) played an important role on hydrogen sulphide oxidation. While micro-oxygenation with sludge recirculation removed only hydrogen sulphide from the biogas, dissolved sulphide was removed if micro-oxygenation was performed with biogas recirculation. Dosage in the headspace resulted in a more stable operation. The result of the hydrogen sulphide oxidation was mostly elemental sulphur, partially accumulated in the headspace of the digester, where different sulphide-oxidising bacteria were found.

Hydrogen sulfide degradation characteristics of Bordetella sp. Sulf-8 in a biotrickling filter

The applicability of Bordetella sp. Sulf-8 to degrade Hydrogen Sulfide (H(2)S) gas in a biotrickling system was investigated. The isolate is a heterotrophic gram-negative, catalase- and oxidase-positive, rod-shaped bacterium which can metabolize thiosulfate or sulfide into sulfate. The mesophilic Bordetella sp. Sulf-8 can grow within a wide pH range using yeast as carbon source, with or without the presence of sulfur. In batch experiments, kinetic constants such as maximum specific growth rate (μ (max) = 0.12 1/h), saturation constant (K (S) = 0.017 g/L), and specific sulfur removal rate (88 mg S/g cells h) were obtained. In biotrickling experiments removal efficiencies were satisfactory, but the system performance was observed to be more influenced by empty bed residence time than by H(2)S feed gas concentration. Critical and maximum elimination capacities were 78.0 and 94.5 g H(2)S/m(3) day, respectively. Macrokinetic analysis of the biotrickling system revealed maximum H(2)S removal rate V (max) = 15.97 g S/kg media-day and half saturation constant K (S') = 12.45 ppm(v).