Biotrickling Filter Reactor Research Articles

PH-Optimized Biomethane Production: Evaluating Carrier Materials for Ex-situ Biomethanation

Choosing the appropriate carrier material for ex-situ biomethanation is a critical factor to consider when developing biogas upgrading technologies. The chosen material for biomethanation in a biotrickling filter reactor functions as a substrate that immobilises microorganisms, which act as catalysts in the reaction for producing biomethane. This study conducted experiments on waste-derived materials, including glass foam and vulcanised wood ash material, in addition to polyurethane foam and expanded clay pellets. Pretreratment of wood ash was done to lower the pH of material. The manometric test measured the rate of CH4 generation by quantifying pressure fluctuations. The validity of these results was confirmed by analysing product gas samples using a Shimadzu Nexis GC-2030 gas chromatograph, which was equipped with two parallel lines, a flame ionisation detector (FID) and a thermal conductivity detector (TCD). In order to enhance the biomethane concentration in the end product, two strains of Methanobacterium alcaliphilum were evaluated alongside biogas sludge as the inoculum. These strains of microorganisms are methanogens that utilise hydrogen and can thrive in a high pH environment. Thus, they have the potential to demonstrate improved biomethane production outcomes when a vulcanised wood ash filter is used as the carrier material.

Analyses of deodorization performance of mixotrophic biotrickling filter reactor using different industrial and agricultural wastes as packing material

In this study, to efficiently remove malodorous gas and reduce secondary pollution under mixotrophic conditions, pine bark, coal cinder, straw and mobile bed biofilm reactor (MBBR) fillers were used as packing materials in a biological trickling filter (BTF) to simultaneously treat high-concentration H2S and NH3. The results showed that the removal rate of BTF-A filled with pine bark was the highest, which was 86.31% and 94.06% under the H2S and NH3 loading rates of 53.59 g/m³·h while the empty bed residence time (EBRT) was 40.5 s. The theoretical maximum load was obtained by fitting the kinetic curve, and the value were 90.09 g H2S m-³·h−1 and 172.41 g NH3 m-³·h−1. Meanwhile, after treating with 720 ppm of NH3, the average concentration of NO3- in the BTF circulating fluid was only 127.58 mg/L, indicating the better performance of secondary pollutants control. Microbiological analysis showed that Dokdonella, Micropruina, Candidatus_Alysiosphaera, Nakamurella and Thiobacillus possessed high abundance at the genus level, and their entire percentage in four BTF reactors were 62.87%, 46.32%, 47.98%, and 57.35% respectively. It is worthwhile that the genera Comamonas and Trichococcus with heterotrophic nitrification and aerobic denitrification capabilities and proportion of 3.66%, 1.45%, 5.43%, and 3.23% were observed in four reactors.

The microbial community in a moving bed biotrickling filter operated to remove hydrogen sulfide from gas streams

The information available on the microbial communities responsible for pollutant degradation is increasingly accessible. Its use to optimize process design and operation is an important challenge in the field of effluent treatment research. Therefore, a prototype of a moving bed biotrickling filter (MBBTF) reactor was designed and, for the first time, operated at full-scale for the removal of sulfides desorbing from tannery industrial wastewater. The bacterial community operating in this innovative reactor was studied, and its composition and response to different operating conditions were characterized. A stable biomass, dominated by sulfur-oxidizing bacteria of the genus Acidithiobacillus was selected from inside the MBBTF reactor, and temperature, pH and bed rotation were shown to be the main factors driving the community structure. Moreover, data from different approaches indicated an uneven spatial distribution of biofilm inside the studied reactor, due to the combined effect of fluid dynamics and substrate gradients within the bed volume. Despite the high removal efficiency achieved by this innovative prototype (80% on average), the data suggested that the result could be improved by adopting solutions for a more stable and even biofilm distribution. It was shown that short frequent bed rotations, rather than long scattered rotations, ensured biomass stability. Furthermore, diversifying biofilm support media as a function of expected local pollutant concentrations should be considered. Data obtained from the bacterial community can therefore provide indications for possible further improvement of MBBTF reactor design and performance.

Isolation and Identification of a Chlorobenzene-degrading Bacterium and Its Degradation Characteristics

A bacterium strain LW26 which could utilize chlorobenzene (CB) as sole carbon and energy source was isolated from a biotrickling filter reactor treating CB-contaminated off-gas. Based on its morphological and physiological characteristics, as well as the analysis of 16S rRNA gene sequence and Biolog test, the strain LW26 was identified as Delftia tsuruhatensis. To our best knowledge, it is the first time that the strain Delftia tsuruhatensis was applied for CB purification. In this study, the effects of temperature, pH, initial CB concentration and Cl- concentration on the biodegradation were investigated. The results showed that the optimal temperature and pH for CB biodegradation were 25℃ and 7.0,respectively; the maximum CB tolerated concentration for LW26 was as high as 500 mg·L-1; when the concentration of Cl- was above 0.14 mol·L-1, the CB degradation was significantly restrained. The degrading process of the strain LW26 followed the Haldane kinetic model and the maximum specific growth rate and the maximum specific degradation rate were 0.42 h-1 and 2.53 h-1, respectively.GC-MS analysis of the metabolites revealed that CB was firstly converted to o-chlorophenol by strain LW26. Combined with the activity of catechol dioxygenase, it can be speculated that CB was finally mineralized to CO2, or converted to cell biomass after processes of ortho cleavage,dechlorination and oxidation.

Biodegradation of Methanol Using Thiosulphate as an Electron Acceptor Under Anaerobic Conditions.

Background.Methanol is a volatile organic compound commonly found in the effluent of the pulp and paper industries. Because of its toxicity, methanol can cause metabolic acidosis, neurologic sequelae, and even death when ingested. Information on biokinetic activity such as biodegradation rate of methanol and thiosulphate, biomass growth rate and biomass yield coefficient is limited in the literature.Objectives.To study the biomass growth rate and biomass yield coefficients of methanol and thiosulphate biodegradation. This research aims to increase knowledge of how to reduce the emission of toxic gas to the environment.Methods.The biodegradation trends of both methanol and thiosulphate were studied under anaerobic conditions using batch experiments at ambient temperature and alkaline conditions. Both supplement each other for their degradation. Methanol is an electron donor, whereas thiosulphate acts as an electron acceptor. A mixed culture from a previously used biomass in a biotrickling filter reactor from theUnited Nations Educational, Scientific and Cultural Organization (UNESCO), International Graduate Water Education Facility and fresh activated sludge from the Harnaschpolder wastewater treatment plant were used as a biomass source.Results.A specific biomass growth rate of biomass ranging from 0.04 to 1.7g per day was observed. The thiosulphate is biologically degraded by the biomass grown inside the reactor. The biodegradation rate of thiosulphate in the reactor varied from 0.02 to 0.80g per unit gram of biomass per day. A biodegradation rate of methanol in the reactor was observed in the range between 0.04 to 3.9g per unit gram of biomass per day. Bacterial biomass was grown as per the amount of methanol present inside the reactor. A maximum biomass yield coefficient of 0.7g biomass per gram of methanol was recorded. Thiosulphate was converted to sulphate that indirectly served as an electron acceptor for methanol degradation. Both degradation of methanol and thiosulphate in this experiment were in the range of the degradation rate shown for sulphate and organic compounds in other studies.Conclusion.Simultaneous removal of thiosulphate and methanol using an anaerobic bioreactor is promising and can be applied on an industrial scale. This finding is an important contribution to public health as it reduces the emission of toxic gas to the environment.

Formaldehyde removal mechanisms in a biotrickling filter reactor

Formaldehyde (FA) is one of toxic, mutagen, suspected carcinogen and teratogen pollutants presented in contaminated air and might be commonly released from a wide range of the industrial activities. Even though many studies have been made to remove FA from synthetic contaminated air stream (SCAS) using a biotrickling filter reactor (BTFR), the mechanisms of FA removal by a BTFR treatment process must to be verified. The aim of this study was to perform the laboratory-scale BTFR experiments to remove FA from the SCAS during a period of 21 days after passing an adaptation phase of 90 days. The mechanisms of FA removal from SCAS in biofilter must pass through two successive stages: (1) the first diffuses FA from gas phase to aqueous phase to form formic acid and methanol and (2) the second guarantees that the predominant microorganisms are able to metabolise the chemicals-derived FA from aqueous phase for growth and maintenance of life. The research findings may lead to better understanding of the BTFR design and operations to reduce air pollutants in order to maintain or improve air quality.

Degradation of hydrogen sulfide by immobilized Thiobacillus thioparus in continuous biotrickling reactor fed with synthetic gas mixture

In this work, a sulfur-oxidizing bacteria, Thiobacillus thioparus (immobilized on Mavicell B support) was employed to develop a microaerobic, biotrickling filter reactor for the efficient elimination of H2S from synthetic (bio)gas. To test the capability of this particular strain in oxygen-limited atmosphere, fixed bed reactor was operated under 0.25–5 vol.% O2 concentrations and its H2S decomposing ability was statistically evaluated. It was found that the system achieved 100% H2S elimination efficiency when at least 2.5 vol.% oxygen was provided. Further decrease of O2 levels to 0.25–1 vol.% cut the reliability and caused the loss of H2S biodegradation performance. The results of this study contributed to understand the behavior of T. thioparus under microaerobic conditions and thus may help to design efficient gas purification processes for biogas technology.

Performance of a combined system of biotrickling filter and photocatalytic reactor in treating waste gases from a paint-manufacturing plant

A pilot-scale biotrickling filter (BTF) was established in treating the waste gases that are intermittently produced from an automobile paint-manufacturing workshop. Results showed that the BTF required longer time to adapt to the aromatic compounds. The removal efficiencies (REs) for all aliphatic compounds reached more than 95% on day 80. Aromatic compounds were not easily removed by the BTF. The REs obtained by the BTF for toluene, ethylbenzene, m-xylene, o-xylene and p-xylene on day 80 were 72.7%, 77.2%, 71.9%, 74.8% and 60.0%, respectively. A maximum elimination capacity (EC) of 13.8 g-C m−3 h−1 of the BTF was achieved at an inlet loading rate of 19.4 g-C m−3 h−1 with an RE of 72%. Glucose addition promoted the biomass accumulation despite the fact that temporal decrease of REs for aromatic compounds occurred. When the inlet loading rates exceed 11.1 g-C m−3 h−1, the REs of the aromatic compounds decreased by 10% to 15%. This negative effect of shock loads on the performance of the BTF can be attenuated by the pre-treatment of the photocatalytic reactor. Nearly all components were removed by the combined system with REs of 99%.

Removal of formaldehyde from polluted air in a biotrickling filter reactor

Optimization of biotrickling filter reactor (BTFR) for the removal of formaldehyde contained in synthetic contaminated air was investigated. The importance of formaldehyde from contaminated air is necessary mainly because it is toxic, carcinogen, and mutagen for humans. Although several studies have been conducted on formaldehyde removal by using BTFR from contaminated air, but optimum conditions for formaldehyde removal is not being studied using a trustable method. The determination of optimum condition to remove formaldehyde was carried out with Taguchi experimental design method. The influence of different factors (pH, nitrogen, phosphorus, formaldehyde concentration) on formaldehyde removal efficiency in BTFR was determined, and the optimum condition for maximizing this response was obtained. The result shows that pH has a greater effect on BTFR efficiency for formaldehyde removal. By operating BTFR in optimum condition, the removal rate increased up to 98%. Thus, the operation of BTFR at optimum condition to remove formaldehyde is considered to be essential in minimizing the pollutants present in the atmosphere.

Calculation of optimal gas retention time using a logarithmic equation applied to a bio-trickling filter reactor for formaldehyde removal from synthetic contaminated air

Formaldehyde (FA) removal from contaminated air has been extensively studied using a bio-trickling filter reactor (BTFR). However, the effect of different volumetric air flow rates (VAFRs) on FA removal efficiency needs to be verified for better BTFR design with optimal operating conditions. This study uses a laboratory-scale BTFR, operating with the three different VAFRs to remove FA from synthetic contaminated air. Mathematical models to determine the optimal retention time of contaminated air flow through the BTFR system are developed. The effect of different pH values on the FA removal efficiency is evaluated. FA removal efficiencies of 99, 96 and 95% are verified for VAFRs of 90, 291 and 1512 L h−1, respectively. Optimal retention times of 141, 50 and 26 s are verified for BTFR experiments operating at 90, 291 and 1512 L h−1 VAFR, respectively. The logarithmic models are proposed as a new approach for determining the optimal retention time and hoped to make a significant contribution to future biotechnological developments and air quality improvement analysis.

Evaluation of gas retention time effects on the bio-trickling filter reactor performance for treating air contaminated with formaldehyde

The effect of different gas retention times (GRTs) on the efficiency of formaldehyde (FA) removal has been studied using a bio-trickling filter reactor (BTFR) for obtaining the optimal operating conditions. Mathematical models to determine the optimum process conditions of the BTFR system for FA removal from contaminated air are developed. Approximately 66% of the FA introduced into the BTFR treatment process dissolved in the nutrient solution, and about 34% of the residual FA was still present in the air. The predominant bacteria on the surface of supporting materials are identified as the five bacterial colonies Salmonella bongori, Salmonella choleraesuis subsp. arizonae, Salmonella typhimurium, Serratia entomophila and Serratia ficaria, and they have the ability to metabolise FA from two-phases (gas and liquid), as a source of carbon and energy. The optimum removal efficiencies of 450 mg FA L−1 of contaminated air ranged from 95 to 99% are verified for GRTs ranging from 100 to 150 s. Exponential models are proposed as a new approach for determining the optimal operating conditions of the BTFR system and can make significant contributions to improving the air quality.

Operational aspects of the desulfurization process of energy gases mimics in biotrickling filters

Biological removal of reduced sulfur compounds in energy-rich gases is an increasingly adopted alternative to conventional physicochemical processes, because of economical and environmental benefits. A lab-scale biotrickling filter reactor for the treatment of high-H 2S-loaded gases was developed and previously proven to effectively treat H 2S concentrations up to 12,000 ppm v at gas contact times between 167 and 180 s. In the present work, a detailed study on selected operational aspects affecting this system was carried out with the objective to optimize performance. The start-up phase was studied at an inlet H 2S concentration of 1000 ppm v (loading of 28 g H 2S m −3 h −1) and inoculation with sludge from a municipal wastewater treatment plant. After reactor startup, the inlet H 2S concentration was doubled and the influence of different key process parameters was tested. Results showed that there was a significant reduction of the removal efficiency at gas contact times below 120 s. Also, mass transfer was found to be the main factor limiting H 2S elimination, whereas performance was not influenced by the bacterial colonization of the packed column after the initial startup. The effect of gas supply shutdowns for up to 5 days was shown to be irrelevant on process performance if the trickling liquid recirculation was kept on. Also, the trickling liquid velocity was investigated and found to influence sulfate production through a better use of the supplied dissolved oxygen. Finally, short-term pH changes revealed that the system was quite insensitive to a pH drop, but was markedly affected by a pH increase, affecting both the biological activity and the removal of H 2S. Altogether, the results presented and discussed herein provide new insight and operational data on H 2S removal from energy gases in biotrickling filters.

Model Sensitivity Analysis for Biotrickling Filter Treatment of Graywater Simulant and Waste Gas. II

A detailed sensitivity analysis was conducted to identify key parameters for a biotrickling filter simultaneously treating graywater and waste gas containing ammonia and hydrogen sulfide contaminants. Sampling-based approaches were applied to quantitatively assess the sensitivity of both design and intrinsic model parameters. Specifically, the sensitivity of contaminant removal rates under system conditions was investigated. Results suggested that contaminant removal rates can be substantially improved by increasing the fraction of wetted area in a biotrickling filter. Although recirculation flow rate is insensitive when considering liquid contaminant removal, increasing this parameter improves gas removal efficiency and also increases wetted area within the biotrickling filter. Reactor performance can also be improved by increasing gas and liquid residence times. Contaminant diffusivity through the biofilm is an important parameter and should be accurately assessed. This study differentiated key from insignificant biotrickling filter reactor design parameters for the biotrickling filter and provides guidance for similar research applications.

Interactions of hydrophobic and hydrophilic solvent component degradation in an air‐phase biotrickling filter reactor

AbstractInteractions amongst the degradation rates of toluene, xylenes, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and n‐butyl acetate (n‐BA) were investigated. Experiments were performed in a biotrickling filter reactor packed with polypropylene Pall rings in a counter‐current air–water mode of operation. Under pseudo‐steady‐state conditions, the removal efficiency (RE) of the individual components in the middle of and at the effluent above the reactor bed was evaluated. By using a mixed microbial culture as the biocatalyst, the results revealed that an increased loading of toluene and xylene had a competitive effect on the RE of MIBK. After reaching a saturation point of the overall catabolic capacity of the biocatalyst, variations of RE were observed for the different components. This was most pronounced under conditions of overloading with the water‐soluble components mixture. Despite such variations, the system was able to efficiently degrade this complex pollutant mixture for a period of 1 yr. © 2006 American Institute of Chemical Engineers Environ Prog, 2006

Operation of a Full-Scale Biotrickling Filter Reactor to Treat Off-Gas Emissions Generated from an Industrial Wastewater Treatment Plant

Operation of a Full-Scale Biotrickling Filter Reactor to Treat Off-Gas Emissions Generated from an Industrial Wastewater Treatment Plant

Resolving operational and performance problems encountered in the use of a pilot/full‐scale biotrickling filter reactor

AbstractA pilot/full‐scale biotrickling filter reactor experiment was performed at an industrial site to treat styrene laden waste gas. The engineered system consisted of two stainless steel tanks in series, each with filter bed volumes of 4.0 m3, filled with 3.5‐inch plastic spheres. The system treated 340 m3 h−1 of air laden with styrene concentrations ranging up to 0.8g m−3. Over the five‐month study, styrene elimination was demonstrated up to 24g m−3 h−1 (35g m−3 h−1 across the first tank in series) with 70 to 85% removal. Operational and performance problems we re identified that differ from those developed under controlled, laboratory set‐ups. Op e rational problems typically involved equipment malfunctions, with the most prone to failure pieces of equipment being the air sampling system and water level sensors. Performance problems were identified that possibly limited the styrene re m oval. The transient operation of the plant, producing discontinuous, unsteady‐state concentrations, made it difficult to establish a stable biofilm on the packing material. Experiments we reperformed indicating both biological and mass transfer limitations may have occurred.