Anaerobic Biotrickling Filter Research Articles

Bioreduction of selenate in an anaerobic biotrickling filter using methanol as electron donor

The anaerobic bioreduction of selenate, fed in step (up to 60 mg.L−1) or continuous (∼7 mg.L−1) trickling mode, in the presence of gas-phase methanol (4.3–50 g m−3.h−1) was evaluated in a biotrickling filter (BTF). During the 48 d of step-feed and 41 d of continuous-feed operations, average selenate removal efficiencies (RE) > 90% and ∼68% was achieved, corresponding to a selenate reduction rate of, respectively, 7.3 and 4.5 mg.L−1.d−1. During the entire period of BTF operation, 65.6% of the total Se fed as SeO42− was recovered. Concerning gas-phase methanol, the maximum elimination capacity (ECmax) was 46.4 g m−3.h−1, with a RE > 80%. Methanol was mainly utilized for acetogenesis and converted to volatile fatty acids (VFA) in the liquid-phase. Up to 5000 mg.L−1 of methanol and 800 mg.L−1 of acetate accumulated in the trickling liquid of the BTF.

Performance of Anaerobic Biotrickling Filter and its Microbial Diversity for the Removal of Stripped Disinfection Byproducts.

The objective of this research was to evaluate the biodegradation of chloroform by using biotrickling filter (BTF) and determining the dominant bacteria responsible for the degradation. The research was conducted in three phases under anaerobic condition, namely, in the presence of co-metabolite (Phase I), in the presence of co-metabolite and surfactant (Phase II) and in the presence of surfactant but no co-metabolite (Phase III). The results showed that the presence of ethanol as a co-metabolite provided 49% removal efficiency. The equivalent elimination capacity (EC) was 0.13 g/(m3.hr). The addition of Tomadol 25 - 7 as a surfactant in the nutrient solution increased the removal efficiency of chloroform to 64% with corresponding EC of 0.17 g/(m3.hr). This research also investigated the overall microbial ecology of the BTF utilizing culture-independent gene sequencing alignment of the 16S rRNA allowing identification of isolated species. Taxonomical composition revealed the abundance of deltaproteobacteria and deltaproteobacteria with species level of 97%. A. oryzae (formally dechlorosoma suillum), A. restrica and Geobacter spp. together with other similar groups were the most valuable bacteria for the degradation of chloroform.

Methanethiol removal from biogas by biological conversion in an anaerobic biotrickling filter

In this study, methanethiol(MT)-degradation bacteria were cultivated by using MT, methanol and trimethylamine as carbon sources under anaerobic conditions. It was found that the batch bacteria used MT and methanol as carbon sources grew faster than those used trimethylamine. The enriched bacteria used MT and methanol as the carbon sources were respectively inoculated in different biotrickling filters. The biological conversion performance of MT under anaerobic conditions was investigated in biotrickling filters. The results showed that the performance of the biotrickling filter inoculated with the bacteria enriched using MT was better than that inoculated with the bacteria enriched using methanol. When the inlet concentration of MT was 0.005vol%(50,ppm), the empty bed residence time was 50 s, pH value was 8.0, and the flow rate of the nutrient solution was 10 L/h, the removal efficiency of MT reached 95.3%. Adding methanol stimulated the growth of the biomass and the degradation of MT, but caused that some bacteria only degrading methanol outcompeted the bacteria only degrading MT. The concentration of sodium bicarbonate in the nutrient solution needed to be controlled lower than 30 g/L, otherwise, it would be harmful to the degradation of MT.

Performance and mechanism of anaerobic biotrickling filter for removal of sulfite, sulfate, and hydrosulfite

A biotrickling filter (BTF) was designed for removal of sulfite (SO32−), sulfate (SO42−), and hydrosulfite (HSO−3) produced from flue gas adsorbent during dual-alkali flue gas desulfurization. With an SO32− concentration of 0.89 g-S/(L packing), BTF could completely remove SO32− within 3 h with an elimination capacity (EC) of 296 g-S/(m3h). With an SO42− concentration of 0.60 g-S/(L packing), the removal efficiency (RE) of SO42− reached 90.3% at 5.25 h and 95% at 24 h. With an HSO−3 concentration of 0.74 g-S/(L packing), HSO−3 could not be detected in the trickling liquid at 2 h with an EC of 370 g-S/(m3h). The difference in desulfurization performance of the BTF was minor when sodium lactate and sodium acetate were used as carbon sources. Acetate was more superior when taking both the carbon/sulfur ratio (C/S) and RE into account. The total dissolved sulfide yield was over 70% with sodium acetate as the carbon source, which was 15–20% higher than that with sodium lactate. Sodium lactate was not completely degraded and acetic acid was produced. All oxidation–reduction potential values were lower than −370 mV, indicating a perfect anaerobic condition in the BTF. The BTF could efficiently treat sulfite, sulfate, and hydrosulfite and could replace the regeneration stage of the dual-alkali process.

Research on the Removal Results of Hydrogen Sulfide of the Treatment of Coal Gasification Wastewater Biogas in the Anaerobic Biotrickling Filter

The uncertainty of operating parameters hinders the practical application of the biological desulfurization. To solve this problem, this study which was conducted in room temperature, pH around seven conditions, investigated the effects of the operating parameters on the hydrogen sulfide (H2S) removal performance in the biotrickling filter, including inlet H2S concentration, inlet flow rate or gas retention time, inlet volume load and circulating liquid spraying flux. The results showed that, the inlet H2S concentration should be controlled within 800mg/m3, 650mg/m3, 400mg/m3, 300mg/m3 respectively while the inlet flow rate was 150L/h, 200L/h, 250L/h, 300L/h, at those conditions, the outlet H2S concentrations were lower than 8mg/m3 and the H2S removal efficiencies were more than 98%. The optimum gas retention time was 12.37s, corresponding to the inlet flow rate of 200L/h, at this time, even if the inlet H2S concentration as high as 700mg/m3, the removal efficiency could be still more than 98%, the outlet concentration of H2S was only 13.1mg/m3. The maximum inlet volume load was 130g/(m3•h), in this condition, the outlet concentration of H2S could be controlled below 12mg/m3, the removal efficiency could above 98.4%.

Bioaugmentation of an anaerobic biotrickling filter for enhanced conversion of trichloroethene to ethene

During biological reduction of trichloroethene (TCE), incomplete reduction to partially dechlorinated intermediates cis-1,2-dichloroethene (cis-DCE) and vinyl chloride (VC) can occur due to kinetic and inhibitory limitations. In this study, an anaerobic biotrickling filter was inoculated initially with a mixed culture containing Dehalococcoides spp. that contained the TceA and VcrA reductive dehalogenases. After significant accumulation of cis-DCE and VC was observed in the bioreactor effluent, it was hypothesized that bioaugmentation with Dehalococcoides strain BAV1, which contains the BvcA dehalogenase responsible for the metabolic dechlorination of cis-DCE and VC, would improve the conversion of TCE to ethene. It was found that at TCE loadings of 8–9gmbed−3h−1, bioaugmentation with strain BAV1 resulted in 45% conversion of TCE to ethene, as opposed to less than 10% prior to bioaugmentation. Strain BAV1 was found to grow to the same density (106–107cells per g of packing material) as Dehalococcoides strains containing the TceA and VcrA dehalogenases. Strain BAV1 was also confirmed to be active, as determined by RT-qPCR of the BvcA mRNA. This study shows that it is possible to enhance the performance of continuously fed dechlorinating bioreactors by using a consortium that contains all three known reductive dehalogenases in the TCE dechlorination pathway. This is also the first study where a gas-phase biotrickling filter has been bioaugmented with a single strain to result in improved performance.

Kinetics and Inhibition of Reductive Dechlorination of Trichloroethene, cis-1,2-Dichloroethene and Vinyl Chloride in a Continuously Fed Anaerobic Biofilm Reactor

Anaerobic bioreactors containing Dehalococcoides spp. can be effective for the treatment of trichloroethene (TCE) contamination. However, reductive dehalogenation of TCE often results in partial conversion to harmless ethene, and significant production of undesired cis-1,2-dichloroethene (cis-DCE) and vinyl chloride (VC) is frequently observed. Here, a detailed modeling study was conducted focusing on the determination of biokinetic constants for the dechlorination of TCE and its reductive dechlorination intermediates cis-DCE and VC as well as any biokinetic inhibition that may exist between these compounds. Dechlorination data from an anaerobic biotrickling filter containing Dehalococcoides spp. fed with single compounds (TCE, cis-DCE, or VC) were fitted to the model to determine biokinetic constants. Experiments with multiple compounds were used to determine inhibition between the compounds. It was found that the Michaelis-Menten half-saturation constants for all compounds were higher than for cells grown in suspended cultures, indicating a lower enzyme affinity in biofilm cells. It was also observed that TCE competitively inhibited the dechlorination of cis-DCE and had a mild detrimental effect on the dechlorination of VC. Thus, careful selection of biotreatment conditions, possibly with the help of a model such as the one presented herein, is required to minimize the production of partially dechlorinated intermediates.

Analysis of the rate-limiting step of an anaerobic biotrickling filter removing TCE vapors

A detailed analysis of a biotrickling filter treating trichloroethene (TCE) vapors anaerobically is presented and discussed. The biotrickling filter relies on mixed cultures containing bacteria from the genus Dehalococcoides that reductively dechlorinate TCE to ethene. After about 200 days of steady operation, as biomass in the packed bed increased, a partial loss in treatment performance was observed which prompted the present investigations. Analysis of TCE and of its degradation metabolites in the gas phase and in the trickling liquid combined with the calculation of global effectiveness factors revealed that significant mass transfer limitations existed. Depending on the conditions, either the gas film or the liquid film limited the removal of TCE. These findings were confirmed by the determination of gas and liquid films mass transfer coefficients. In all cases, removal of TCE was greater without trickling of liquid. The most plausible reason for the onset of mass transfer limitations was the decrease in the specific interfacial area brought by important biomass growth over time. Overall, this study illustrates how complex kinetic and transport limitations can vary with the operating conditions in biotrickling filters.

Reductive Dehalogenation of Trichloroethene Vapors in an Anaerobic Biotrickling Filter

Until now, it has not been possible to use biofiltration to treat trichloroethene (TCE) from waste gases generated by soil vapor extraction or dual-phase extraction at remediation sites because aerobic biodegradation of TCE is possible only via cometabolism, which is difficult to engineer on a large scale. This study looks at the possibility of conducting anaerobic gas-phase biotreatment of TCE vapors. The vision is that nitrogen sparging could be substituted for air sparging, resulting in TCE contaminated oxygen-free gas streams which require treatment A lab-scale anaerobic biotrickling filter inoculated with a mixed culture containing multiple Dehalococcoides strains was used for the proof of concept TCE vapors were removed via reductive dechlorination and converted to ethene, cis-1,2-dichloroethene (cis-DCE), and vinyl chloride (VC). Sodium lactate, a fermentable substrate, was provided to the reactor through the recirculating liquid as a source of hydrogen, the electron donor for Dehalococcoides strains. The biotrickling filter was able to remove >90% TCE at loadings of up to 4 g m(bed)(-3) h(-1) and sustained performance for over 200 days. The distribution of the intermediates of TCE biological reduction was found to be affected by the pH of the recirculating liquid. At pH 8.3, the primary accumulating productwas cis-DCE (approximately 92% of the TCE removed); while at pH 6.85-6.9, conversion to ethene, the intended end product, was 50-67% of the TCE removed. Kinetic determinations using batch biotrickling filter operation showed that VC reduction and not cis-DCE reduction was the sloweststep. Overall, the study shows that sustained anaerobic biotreatment of TCE vapors in biotrickling filters is possible.