Inlet Loading Research Articles

Analysis on the Performance of Steam Absorption Chiller at Various Operating Conditions

Steam Absorption Chiller (SAC) is the main component of Cogeneration Plant which provides chilled water by utilizing the steam as system input for the cooling purpose. In this paper, the performance of a double effect lithium bromide-water steam absorption chiller was analyzed by conducting the energy and exergy analysis. An excel spreadsheet program was developed to calculate the exergy destructions within the systems and total exergy loss of the system in guiding future improvement of the plant. Various operating conditions like steam inlet temperature, chilled water inlet temperature and load factor were analyzed in detail. The result showed that the highest exergy destruction occurred at the high temperature generator followed by the absorber. Increasing the load factor, steam and chilled water inlet temperature will increase the system performance.

Removal of toluene vapor in the absence and presence of a quorum-sensing molecule in a biotrickling filter and microbial composition shift

Toluene is highly toxic and mutagenic, and it is generally used as an industrial solvent. Thus, toluene removal from air is necessary. To solve the problem of reducing high toluene concentrations with a short gas retention time (GRT), a quorum-sensing molecule [N-(3-oxododecanoyl)-L-homoserine lactone] (OHL) was added to a biotrickling filter (BTF). In this study, a BTF was used to treat synthetic and natural waste gases containing toluene. An extensive analysis was performed to understand the removal efficiency, removal characteristics, and bacterial community of the BTF. The addition of 20 μM OHL to the BTF significantly improved toluene removal, and more than 99.2% toluene removal was achieved at a GRT of 0.5 min when natural waste gas containing toluene (590–1020 ppm or 2.21–3.83 g m−3) was introduced. The maximum inlet load for toluene was 337.9 g m−3 h−1. Moreover, the BTF exhibited satisfactory adaptability to shock loading and shutdown operations. Pseudomonadaceae (33.0%) and Comamonadaceae (26.3%) were predominant bacteria in the system after a 98-day operation. These bacteria were responsible for toluene degradation. The optimal moisture content and low pressure drop for system operations demonstrated that the BTF was energy and cost efficient. Therefore, processing through a BTF with OHL is a favorable technique for toluene treatment.

Effects of n-butanol presence, inlet loading, empty bed residence time and starvation periods on the performance of a biotrickling filter removing cyclohexane vapors from air

This paper presents the results of investigations on the removal of cyclohexane vapors from air using a peat-perlite packed biotrickling filter. Effects of basic process parameters i.e. inlet loading and empty bed residence time as well as introduction of n-butanol to the treated air stream and starvation periods on the process performance were evaluated. The results show that the introduction of hydrophilic n-butanol results in an enhanced removal of hydrophobic cyclohexane comparing to the experiments where only cyclohexane was treated. Additionally, the biotrickling filter performance after the starvation events is regained to more extent for mixed system than for the single cyclohexane. A novel and interesting element of the paper is the application of an electronic nose for the process monitoring. Obtained results are discussed in the perspective of an influence of the presence of a compound with different affinity to aqueous phase on the removal efficiency of the compound with opposite chemical properties.

‏Methane biofiltration under different strategies of nutrient solution addition

Two biofilters B1 and B2 packed with non-porous inorganic materials were operated for 283 days to eliminate methane (CH4), an important greenhouse gas. The biofilters ran under a constant empty bed residence time of 6 min at CH4 inlet loads of 7–63 g m−3.h−1. B1 was fed with a fresh nutrient solution every day (2 L d−1, flow rate of 1 L min−1) whereas B2 was supplied by a recycled nutrient solution from a 10 L tank. The flexibility of both biofilters were evaluated and compared in absence of nutrient solution for 35 days. Also, the performance of both biofilters under a different nutrient solution addition frequency (0.5 L every 6 h, flow rate of 1 L min−1) was investigated. B2 performed appropriately with an average removal efficiency of 62 ± 3% for an inlet load of 13 g m−3.h−1. B1 showed an average removal efficiency of 66 ± 4% for the same inlet load as B2. Analysis of nutrient solution in the recycle tank showed that the highest nutrient consumption over the time was at an inlet load of 63 g m−3.h−1. B1 and B2 were tolerant to nutrient solution deprivation for 25 and 21 days, respectively. Frequent addition of nutrient solution (0.5 L every 6 h, flow rate of 1 L min−1) improved the performance with corresponding average removal efficiency of 64 ± 4% for B1, compared to 57 ± 4% with nutrient solution addition of 2 L every 24 h with a flow rate of 1 L min−1, while no significant change was observed in B2.

Moving from alcohol to methane biofilters: an experimental study on biofilter performance and carbon distribution

AbstractBACKGROUNDBiofilters can be used to eliminate different gaseous pollutants including alcohols (e.g. methanol, ethanol) and methane (CH4) individually or in a mixture. In this regard, the biofilter adaptability to feed composition variation is an industrial requisite. Inlet gas composition changes also give a better insight about carbon input and end‐points in biofilters. In this study, the gradual conversions of two biofilters from methanol and ethanol to CH4 were investigated.RESULTSBoth biofilters reached 100% removal efficiencies for the alcohols with no initial inoculation. Keeping the total inlet load constant (30 ± 1.3 g m−3 h−1), CH4 was progressively substituted in the feed with corresponding alcohol:CH4 mass ratios of 3:1, 1:1, 1:3 and 0 galcohol:gCH4. Maximum CH4 removal efficiencies of 52% and 29% were obtained (respectively) for biofilters started with methanol and ethanol. By moving from alcohols to CH4 biofilters, the gas phase output carbon increased from 273 to 666 gcarbon day−1 and from 377 to 681 gcarbon day−1 respectively for the methanol‐ and ethanol‐based biofilters.CONCLUSIONThis study showed a successful treatment based on inlet pollutant alteration from methanol or ethanol to CH4 in two separate biofilters. However, the methanol‐based biofilter displayed a better performance and a shorter acclimation time for CH4 conversion. © 2019 Society of Chemical Industry

Application of Response Surface Methodology for H2S Removal from Biogas by a Pilot Anoxic Biotrickling Filter

In this study, a pilot biotrickling filter (BTF) was installed in a wastewater treatment plant to treat real biogas. The biogas flow rate was between 1 and 5 m3·h−1 with an H2S inlet load (IL) between 35.1 and 172.4 gS·m−3·h−1. The effects of the biogas flow rate, trickling liquid velocity (TLV) and nitrate concentration on the outlet H2S concentration and elimination capacity (EC) were studied using a full factorial design (33). Moreover, the results were adjusted using Ottengraf’s model. The most influential factors in the empirical model were the TLV and H2S IL, whereas the nitrate concentration had less influence. The statistical results showed high predictability and good correlation between models and the experimental results. The R-squared was 95.77% and 99.63% for the ‘C model’ and the ‘EC model’, respectively. The models allowed the maximum H2S IL (between 66.72 and 119.75 gS·m−3·h−1) to be determined for biogas use in a combustion engine (inlet H2S concentration between 72 and 359 ppmV). The ‘C model’ was more sensitive to TLV (–0.1579 (gS·m−3)/(m·h−1)) in the same way the ‘EC model’ was also more sensitive to TLV (4.3303 (gS·m−3)/(m·h−1)). The results were successfully fitted to Ottengraf’s model with a first-order kinetic limitation (R-squared above 0.92).

The styrene purification performance of biotrickling filter with toluene-styrene acclimatization under acidic conditions

ABSTRACT The obvious disadvantages of biotrickling filters (BTFs) are the long start-up time and low removal efficiency (RE) when treating refractory hydrophobic volatile organic compounds (VOCs), which limits its industrial application. It is worthwhile to investigate how to reduce the start-up period of the BTF for treating hydrophobic VOCs. Here, we present the first study to evaluate the strategy of toluene induction combined with toluene-styrene synchronous acclimatization during start-up in a laboratory-scale BTF inoculated with activated sludge for styrene removal, as well as the effects of styrene inlet concentration (0.279 to 2.659 g·m−3), empty bed residence time (EBRT) (i.e., 136, 90, 68, 45, 34 sec), humidity (7.7% to 88.9%), and pH (i.e., 4, 3, 2.5, 2) on the performance of the BTF system. The experiments were carried out under acidic conditions (pH 4.5) to make fungi dominant in the BTF. The start-up period for styrene in the BTF was shortened to about 28 days. A maximum elimination capacity (ECmax) of 126 g·m−3·hr−1 with an RE of 80% was attained when styrene inlet loading rate (ILR) was below 180 g·m−3·hr−1. The highest styrene RE(s) [of BTF] that could be achieved were 95% and 93.4%, respectively, for humidity of 7.7% and at pH 2. A single dominant fungal strain was isolated and identified as Candida palmioleophila strain MA-M11 based on the 26S ribosomal RNA gene. Overall, the styrene induction with the toluene-styrene synchronous acclimatization could markedly reduce the start-up period and enhance the RE of styrene. The BTF dominated by fungi exhibited good performance under low pH and humidity and great potential in treating styrene with higher inlet concentrations. Implications: The application of the toluene induction combined with toluene-styrene synchronous acclimatization demonstrated to be a promising approach for the highly efficient removal of styrene. The toluene induction can accelerate biofilm formation, and the adaptability of microorganisms to styrene can be improved rapidly by the toluene-styrene synchronous acclimatization. The integrated application of two technologies can shorten the start-up period of biotrickling filters markedly and promote its industrial application.

Feedback and Feedforward Control of a Biotrickling Filter for H2S Desulfurization with Nitrite as Electron Acceptor

Biotrickling filters’ control for H2S removal has special challenges because of complexity of the systems. Feedback and feedforward control were implemented in an anoxic biotrickling filter, operated in co-current flow mode and using nitrite as an electron acceptor. The feedback controller was tuned by three methods—two based on Ziegler-Nichols’ rules (step-response and maintained oscillation) and the third using the Approximate M-constrained Integral Gain Optimization (AMIGO). Inlet H2S staircase step perturbations were studied using a feedforward control and the effect of EBRT considered by feedback control. The tuning method by maintained oscillation shows the lower errors. The selected controller was a PI, because unstable behavior at the lowest H2S inlet loading was found under a PID controller. The PI control was able to maintain an outlet H2S concentration of 14.7 ± 0.45 ppmV at three EBRT, studied at 117 s, 92 s and 67 s. Therefore, desulfurized biogas could be used to feed a fuel cell. Feedforward control enhances BTF performance compared to the system without control. The maximum outlet H2S concentration was reduced by 26.18%, although sulfur selectivity did not exceed 55%, as elemental sulfur was the main oxidation product.

Effects of nutrient load from St. Jones River on water quality and eutrophication in Lake George, Florida

Nutrient contamination in surface waters can pose a health risk for humans and aquatic life. The influx of Nitrogen and Phosphorus can cause an increase in algal blooms resulting in eutrophication of the water body. Eutrophication describes the trophic state or the health of a water body as it relates to the level of algae biomass. Water quality for this research is represented by the presence of chlorophyll a (Chl-a) which is an indicator of the activity within the water body. In this study, trophic state analysis and relations between Chl-a and nutrients in Lake George, Florida, have been conducted. Three zones within Lake George are established to prepare a succinct analysis of the existing monthly and seasonal averages across the water body. Statistical analyses, including multiple regression analysis, were used in this study to establish the relationship between Chl-a and nutrients, Total Nitrogen (TN) and Total Phosphorus (TP). Traditional single-variable regression analysis shows good correlations between the Chl-a and TN loading and poor relationship with TP, which indicate that TN loading is the controlling factor. Single-variable regression was also used to compare the inlet load contributions to the lake loading which was found to be conclusive. Multivariate regression analysis for all three zones were conducted to obtain acceptable to good relationship between Chl-a and nutrient (TN, TP) with the monthly R values for zones 1, 2, 3, are 0.72, 0.82, and 0.80 respectively, indicating nutrient is the dominant factor for eutrophication in the lake. Multivariate regression equations between Chl-a and nutrient (TN,TP) were used to investigate scenarios to reduce nutrient load at the inlet so as to control Chl-a concentrations in the lake to avoid eutrophic conditions. It was found that the TN inlet loading would have to be reduced by more than 75% for zone 1, 65% in zone 2 and less than 25% for zone 3 in order to not exceed the current EPA approved numeric criteria for Florida Lakes. It was also determined that both TN and TP concentrations are co-limiting in the lake based on Carlson’s criteria. Assessments by both Trophic State Index (TSI) method and Total Nutrient Status Index (TNI) methods indicate eutrophic conditions in the lake under current conditions.

Effects of ozone treatment on performance and microbial community composition in biofiltration systems treating ethyl acetate vapours

Ozone (O3) treatment is an effective strategy in maintaining high efficiency and control of biomass accumulation in gas phase biofiltration. However, little is known about the long-term impact of O3 on the microbial communities. In the present study, two biofilters treating gaseous ethyl acetate were operated continuously for 230 days with inlet loads up to 180 g m−3∙h−1. A biofilter operated under continuous O3 addition (90 ppbv) yielded consistently higher removal efficiency (RE) and elimination capacity (EC) compared to the control system. After 120 days of operation, a lower biomass content accompanied by a pH of 1.5 was observed in the ozonated biofilter, which was 2 units lower compared to the control reactor. Both reactors developed a distinct microbial community composition over the course of 230 days. The bacterial community was dominated in both biofilters by Beijerinckia and Gluconacetobacter, while Rhinocladiella similis, Trichosporon veenhuissi and Exophilia oligosperma were abundant in the fungal community. These findings suggest that ozonation of the biofiltration systems not only reduced clogging, but also contributed to the selection of biomass suitable for degradation of ethyl acetate.

Enhanced biological removal of intermittent VOCs and deciphering the roles of sodium alginate and polyvinyl alcohol in biofilm formation

Developing a robust biofilm is a prerequisite for a biotrickling filter to obtain the good performance in removing volatile organic compounds (VOCs). But the biofilm formation can be seriously disturbed under intermittent loading condition due to carbon starvation stress in idle time. In this study, a biotrickling filter, with its packing materials being modified by 3% sodium alginate and 5% polyvinyl alcohol (v/v = 1:3), was employed to treat intermittent VOCs. Results showed that the removal efficiencies of toluene, ethylbenzene, p-xylene, m-xylene, and o-xylene was significantly enhanced in the BTF compared to the control one. Under relatively lower inlet loading, nearly complete removal of the five pollutants was achieved. A quantitative analysis showed that the concentration of total organic compound (TOC) in the leachate maintained at a high level, and had a strongly positive correlation with the divergence of microbial communities. The capacity of biofilm formation in the BTF was approximately four-fold higher than the control BTF, while the quantity of EPS secreted was more than ten-fold. EPS comprised largely of protein, and to less extent, polysaccharide. The biofilm formed on the modified packing materials maintained higher levels of microbial diversity and stability, even when modifiers were complete depleted or the VOCs inlet loading was increased. This study highlights the importance of packing materials for reducing the gap in performance between laboratory and industrial applications of BTFs.

Abatement of dimethyl sulfide using anoxic biotrickling filter

AbstractBACKGROUNDThis study aimed to use a lab‐scale anoxic biotrickling filter (ABTF) for the bioconversion of dimethyl sulfide (DMS) gas to produce less harmful byproducts, i.e. elemental sulfur and/or sulfate. It examined the exploitation of nitrate as an electron acceptor in the oxidation of malodorous DMS‐containing gas in combination with other parameters: gas/liquid (G/L) ratio (40, 60, 80, 100, 150), empty bed residence time (EBRT) (10, 30, 60, 90, 120 s) and inlet loading (IL) (9, 18, 48, 90 g m−3 h−1).RESULTSThermodynamic analysis and half‐reactions showed that at DMS/NO3− molar yield ratios 0.75 and 0.34, elemental sulfur and sulfate were the main metabolic products respectively. Overall, 58% of the sulfur element in DMS was bioconverted to elemental sulfur. Mass balance calculations revealed high denitrification efficiency, i.e. 52.7% of inlet NO3− was converted to N2. The optimal EBRT was found as 30 s (corresponding to removal efficiency (RE) 89%) for inlet concentration 150 mg m−3 and as 60 s (corresponding to RE 78%) for inlet concentration 1500 mg m−3. However, the maximum elimination capacity (EC) was 70.3 g m−3 h−1 at EBRT 60 s and G/L ratio 80. The relative abundance of bacterial communities was dominated by Proteobacteria (56.1%) and Alphaproteobacteria (27.3%) at phylum and class levels respectively.CONCLUSIONThe study revealed that ABTF has a reliable biodegradation capacity in DMS oxidation under anoxic conditions; however, process improvement on mass transfer enhancement for low waste gas concentrations is still required. © 2019 Society of Chemical Industry

Mathematical modeling and sensitivity analysis of xylene removal in a scoria‐compost biofilter

AbstractMathematical modeling of biofiltration systems improves our understanding and design of such complex systems. This study focused on the theoretical and technical aspects of the modeling of xylene biofiltration in the absence and presence of a nonionic surfactant. In this regard, a mathematical model was developed based on mass balance principles in gas and biofilm phases. The developed model was calibrated and validated using the experimental data obtained from a lab‐scale scoria‐compost biofilter, which operated for 151 days in the absence and presence of Tween‐20, a nonionic surfactant. First, the model was calibrated using the experimental data obtained at empty bed retention time (EBRT) of 90 s and then validated with the data obtained at two other EBRTs. The biofilter provided maximum elimination capacities (ECmax) of 97.5 and 93.6 g m−3 hr−1, respectively, in the absence and presence of the surfactant at EBRT of 90 s. The corresponding predicted ECmax values were 99.9 and 95.7 g m−3 hr−1, respectively. Both model output and experimental data revealed that the nonionic surfactant improved the performance of the biofilter at moderate inlet loading rates. Various statistical measures, including fractional bias, average absolute relative error, and coefficient of determination (R2), showed good agreement between experimental data and estimated model predictions. Sensitivity analysis of the model showed that the specific surface area and bioreactor length affected strongly the results of the model. In general, the results of this study would in turn form the design basis for engineering purposes.

Isolation of formaldehyde-degrading bacteria and the evaluation of the degradation characteristics

A formaldehyde-degrading bacteria strain, B1, was isolated. Strain B1 was characterized morphologically, physiologically and biochemically, and it was identified as Pseudomonas putida. Then, the formaldehyde biodegradation characteristics were evaluated in a biofilter. A formaldehyde removal rate above 90% was maintained when inlet loading was below 38.9 mg L−1 h−1. In addition, strain B1 quickly became dominant bacteria when the reactor was restarted following a 30-days’ disruption, illustrating that the strain is both adaptable and resilient. The numerical simulation results demonstrate that the maximum degradation rates in the biofilter with strain B1 are better fitted with the Haldane model.

Stochastic Method for Evaluating Removal, Fate and Associated Uncertainties of Micropollutants in a Stormwater Biofilter at an Annual Scale

A stochastic method for evaluating the in situ mass balance of micropollutants in a stormwater biofilter, accounting for inlet and outlet loads and the evolution of pollutant mass in the filter media (ΔMsoil) at an annual scale, is proposed. In the field context, this type of calculation presents a number of methodological challenges, associated with estimating water quality for unsampled rain events, reconstituting missing or invalidated flow data and accounting for significant uncertainties associated with these estimations and experimental measurements. The method is applied to a biofiltration swale treating road runoff for two trace metals, Cu and Zn and six organic micropollutants: pyrene (Pyr), phenanthrene (Phen), bisphenol-A (BPA), octylphenol (OP), nonylphenol (NP) and bis(2-ethylhexyl) phthalate (DEHP). Pollutant loads were reduced by 27–72%. While organic micropollutants are likely to be lost to degradation or volatilization processes in such systems, dissipation could not be demonstrated for any of the organic micropollutants studied due to emissions from construction materials (case of BPA, OP, NP and DEHP) or high uncertainties in ΔMsoil (case of Pyr and Phen). The necessary conditions for establishing an in situ mass balance demonstrating dissipation, which include acquisition of data associated with all terms over a period long enough that uncertainty propagation is limited and the absence of additional sources of pollutants in the field, are discussed.

A rapid regulation with different response intensities of the pmoA gene guarantees process robustness towards methane surges in continuous and feast-famine bioreactors

A rapid recovery of methanotrophic activity from process fluctuations such as surges in CH4 inlet load is of utmost importance in bioreactors to guarantee a robust abatement of this potent greenhouse gas. However, the response of methanotrophs in CH4 abatement engineered ecosystems facing recurrent operational upsets has not been systematically investigated. The genetic and process performance response of methanotrophs to a gradual 2.8-fold increase in CH4 inlet load in continuous and feast-famine bioreactors was characterized by measuring their pmoA gene transcripts and the CH4 degradation capacities and CO2 production rates, respectively. Both bioreactors exhibited a high robustness in terms of CH4 removal towards CH4 inlet load increase. Higher CH4 elimination and CO2 production during shock load suggested the occurrence of CH4 mass transfer limitations. Consistently, a rapid regulation of the pmoA gene (less than one hour after CH4-shock load), characterized by several transient events of increased expression, was observed in both bioreactors. However, the pmoA gene expression in the feast-famine bioreactor exhibited a less intense response to the increase in CH4 load compared to the continuous system, which suggested a possible adaptation of the pmoA transcriptional response of methanotrophs to the previous history of the culture.

The influence of biochar and compost mixtures, water content, and gas flow rate, on the continuous adsorption of methane in a fixed bed column

Biofiltration is an excellent alternative for the treatment of diffuse emissions of methane (CH4) that cannot be treated by physical/chemical means or recovered for energy. Despite the advances on CH4 biological treatment technologies, they are limited by the low aqueous solubility of CH4 into the biofilm where CH4 mineralization occurs. In this study, the CH4 adsorption kinetics, adsorption capacity and transport behavior of CH4 was studied in batch experiments and in a fixed-bed column by varying the biochar and compost mixtures under 5-levels, 3 different water contents (dry, 15% and 30% water holding capacity), and 2 inlet flow rates. Experimental results were formally tested using analysis of variance (ANOVA) in order to draw objective conclusions based on statistical inference. As CH4 biofiltration requires water addition to maintain microbial activity, these results indicate adsorption capacity is not lost with water addition if biochar content is the dominant packing material. The Langmuir isotherm described the data best (R2 = 0.99). Maximum adsorption capacity by monolayer adsorption, or qmax, is relatively similar with or without the addition of water as long as the biochar component is the dominant material at 3.5 mg CH4/g medium for a 7:1 biochar: compost, v/v mixture. Empirical regression models for qo, kTh, (Thomas model) and τ and KYN (Yoon-Nelson model) were developed for the break through curves of CH4. The current work demonstrates the applicability of utilizing biochar, a relatively inexpensive adsorbent, can compensate for the low solubility of CH4 and overcome the rate-limiting step of mass transfer from the gas phase and into the methanotrophic biofilm. Further, biochar may be a reliable back-up system for CH4 storage especially for fluctuating inlet loads that may be encountered in industrial applications adsorbing up to 13 mg CH4/g biochar under dry conditions.

Trickling filter technology for biotreatment of nitrogenous compounds emitted in exhaust gases from fishmeal plants

Odour emissions are a major environmental issue associated with fishmeal production. Laboratory-scale biotrickling filters (BTFs) were inoculated with microbial consortia derived from sewage sludge, with the goal to study the biotreatment of low-loads of methylamines and ammonia that are main components of odorous exhaust gases produced by fishmeal processing plants. A BTF packed with ceramic rings was subjected to a real fishmeal plant emission containing trimethylamine (TMA), dimethylamine (DMA) and monomethylamine (MMA). The highest elimination capacities (ECs) obtained were 372 mg TMA m−3 h−1, 5.518 mg DMA m−3 h−1 and 1.038 mg MMA m−3 h−1, with maximal removal efficiencies of 92% (TMA), 83% (DMA) and 95% (MMA) after 30 days operation. In a different experiment, a polyurethane foam packing was employed to treat ammonia (NH3) at low inlet loads, reaching an EC of 47.19 mg N m−3 h−1 with 99.8% efficiency (inlet load of 47.27 mg N m−3 h−1). Likewise, the microbial community of the polyurethane-associated biofilm was diverse and stable during operation. These results suggested that elimination of volatile amino-compounds using BTFs inoculated with a methylotrophic microbial consortium holds potential for odour removal. In addition, sequencing analysis of 16S rDNA gene fragments allowed the identification of heterotrophic ammonia-oxidizing bacteria that are promising candidates to effectively maintain ammonia elimination in a biotreatment operation of nitrogenous compounds present in exhaust gases from fishmeal facilities.

Performance and microbial community evolution of toluene degradation using a fungi-based bio-trickling filter

Fungi have their unique advantages in capturing and degrading hydrophobic VOCs. To study the performance of fungi-based bio-trickling filters (BTFs) with respect to the degradation of toluene, and the succession process of the fungal colony under different operating conditions, a three-layer BTF packed by dominant Fusarium oxysporum immobilized with ceramic particles were set up. The fungal BTF started quickly within 7 days and restarted less than 7 days after starvation; its average RE was higher than 92.5% when the toluene inlet loading rate (ILR) ranging from 7.0 to 100.9 g m-3 h-1 at steady state. Moreover, the maximum elimination capacity (EC) of 98.1 g m-3 h-1 was obtained at a toluene ILR of 100.3 g m-3 h-1. The microorganism analysis of time and space revealed that the dominant fungi Fusarium were replaced by Paramicrosporidium saccamoebae after a certain evolutionary period. The intermediate layer had more microbes and a more complex community than the other two layers, and was more suitable for the survival of the varieties of microbes.

Transient-state strategies for the removal of toluene vapor in a two-liquid phase biotrickling filter: Experimental study and neural network analysis

Abstract The performance of a two-liquid phase biotrickling filter (TLP-BTF) packed with pall ring and pumice in the presence of silicone oil, as the organic solvent (10% v/v), was evaluated for the treatment of toluene vapor under various transient conditions. The experiments were done at EBRT of 1 min and inlet loading rates (ILRs) of 150-180 g m−3 h-1 and comprise of shock loading, intermittent loading for 10 h day-1, and aeration without toluene loading during shutdown periods. The TLP-BTF removal efficiency (RE) attained steady state (RE = 66%) in less than 40 min after loading initiation in different operating strategies. The TLP-BTF was subjected to a 5.5-fold increase at ILRs from 34 to 186 g m−3 h-1, however, RE declined only 10% within 2 h after shock loading. Nevertheless, RE decreased to 44% due to dominating the kinetic-limitation regime and silicone oil saturation. The variations of TLP-BTF performance were analyzed by using artificial neural networks (ANNs) modeling by means of casual index (CI) values. Lower discrepancies for CI-values in TLP-BTF (-8.05 > CI > -10.68) in comparison to the single-liquid phase BTF (-9.19 > CI >14.04) indicated the role of silicone oil for decreasing the negative impact of different intermittent loading types on the BTF performance.