Biofiltration of xylene using wood charcoal as the biofilter media under transient and high loading conditions

Air biofilters for a mixture of organic gaseous pollutants: an approach for industrial applications

Hazardous airborne pollutants are frequently emitted to the atmosphere in the form of a gaseous mixture. Air biofilters as the primary biotechnological choice for waste gas treatment (low inlet concentration and high gas flow rate) should run properly when the feed contains multiple pollutants. Simultaneous removal of pollutants in biofilters has been extensively studied over the last 10 years. In this review, the results and findings of the mentioned studies including different groups of pollutants, such as methane (CH4) and volatile organic compounds (VOCs) are discussed. As the number of pollutants in a mixture increases, their elimination might become more complicated due to interactions between the pollutants. Parallel batch studies might be helpful to better understand these interaction effects in the absence of mass transfer limitations. Setting optimum operating conditions for removal of mixtures in biofilters is challenging because of opposing properties of pollutants. In biofilters, concerns, such as inlet gas composition variation and stability while dealing with abrupt inlet load and concentration changes, must be managed especially at industrial scales. Biofilters designed with multi-layer beds, allow tracking the fate of each pollutant as well as analyzing the diversity of microbial culture across the filter bed. Certain strategies are recommended to improve the performance of biofilters treating mixtures. For example, addition of (bio)surfactants as well as a second liquid phase in biotrickling filters might be considered for the elimination of multiple pollutants especially when hydrophobic pollutants are involved.

Chicken Cartilage-Derived Carbon for Efficient Xylene Removal

Chicken cartilage was used for the first time as a raw material for the microwave-assisted synthesis of biochar and activated carbon. Various microwave absorbers, i.e., commercial active carbon, scrap tyres, silicon carbide, and chicken bone-derived biochar, as well as various microwave powers, were tested for their effect on the rate of pyrolysis and the type of products formed. Biochars synthesised under 400 W in the presence of scrap tyres and chicken bone-derived biochar were activated with KOH and K₂CO₃ with detergent to produce activated carbon with a highly developed porous structure that would be able to effectively adsorb xylene vapours. All carbons were thoroughly characterised (infrared spectroscopy, X-ray fluorescence spectrometry, nitrogen adsorption/desorption, Raman spectroscopy, proximate and ultimate analysis) and tested as xylene sorbents in dynamic systems. It was found that the activation causes an increase of up to 1042 m²·g^-1 in the specific surface area, which ensures the sorption capacity of xylene about 300 mg·g^-1. Studies of the composition of biogas emitted during pyrolysis revealed that particularly valuable gaseous products are formed when pyrolysis is carried out in the presence of silicon carbide as a microwave absorber.

Abatement of binary gaseous chlorinated VOC by biotrickling filter: Performance, interactions, and microbial community

The treatment of waste-gas containing chlorinated volatile organic compounds (CVOCs) has become a difficult issue in current air pollution control. Biotrickling filters (BTFs) have been recognized to be applicable for the treatment of CVOCs, but research on the biodegradation of binary gaseous CVOCs is rare. Herein, a BTF inoculated with Methylobacterium (M.) rhodesianum H13, Starkeya sp. T-2 and activated sludge was established to investigate the biodegradation of the gaseous dichloromethane (DCM) and 1,2-dichloroethane (1,2-DCE) and their interactions implicated. The bioaugmented BTF showed a faster startup (13 days), better removal efficiencies of DCM (80%) and 1,2-DCE (72%), and superior mineralization (65.9%) than that inoculated with activated sludge alone. The ECs of DCM and 1,2-DCE were positively related with the inlet load when the total inlet load was <50 g m^-3 h^-1. However, inlet loads higher than 50 g m^-3 h^-1 led to dramatic drop of the RE of DCM and 1,2-DCE due to the limitation of the degradation capacity of microorganisms and the toxic effect of high-concentration substrates. Besides, BTF could stand a lower shock load of 400 mg m^-3, while higher shock loads would deteriorate the RE of DCM and 1,2-DCE. And BTF showed better impact resistance toward DCM than 1,2-DCE, probably because the 1,2-DCE biodegrading bacteria was more sensitive to the concentration change. For the same reason, the removal recovery of DCM after starvation was quicker than 1,2-DCE. Kinetic interactions were quantified by the EC-SKIP model, results of which revealed that DCM cast negative effect on 1,2-DCE biodegradation, while 1,2-DCE could promote DCM biodegradation. Moreover, both the results of real-time PCR and high-throughput sequencing showed M. rhodesianum H13 had stronger competitiveness and adaptability than Starkeya sp. T-2. The survived M. rhodesianum H13 and Starkeya sp. T-2 after starvation robustly demonstrated the success of bioaugmentation as well as its great potential of engineering application.

Enhancing recovery performance of the toluene-removing biofilter after the short/long interference-shutdown period

In this study, the feasibility of three methods on enhancing the recovery performance of biofilter after the interference and starvation periods was evaluated. Results show that despite the pressure drop risk, supplementation of 7.5% (w/v) Polyethylene glycol-600 (PEG-600) resulted in quick recovery on removal efficiency in both short- and long-term interference shutdown experiments. Tinidazole Tablets (2 mg/L), a Bacteroidetes-specific antibiotic, are more suitable to apply as a one-time shot to improve recovery of biofilter as the second dose of Tinidazole Tablets was no longer effective presumably caused by the increased drug resistance. It is worth noting that the maximum elimination capacity of 134 g/(m³·h) was observed with Pseudomonas putida (P. putida) BRJC1032 addition. The biodegradation kinetic, biological characteristics and microbial community evolution in biofilters were systematically analyzed for finding the suitable methods to enhance recovery performance, which is of great value for the further industrial application of the biofilter technology.

Interaction of tetrahydrofuran and methyl tert-butyl ether in waste gas treatment by a biotrickling filter bioaugmented with Piscinibacter caeni MQ-18 and Pseudomonas oleovorans DT4

Bioaugmented biotrickling filter (BTF) seeded with Piscinibacter caeni MQ-18, Pseudomonas oleovorans DT4, and activated sludge was established to investigate the treatment performance and biodegradation kinetics of the gaseous mixtures of tetrahydrofuran (THF) and methyl tert-butyl ether (MTBE). Experimental results showed an enhanced startup performance with a startup period of 9 d in bioaugmented BTF (25 d in control BTF seeded with activated sludge). The interaction parameter I_2,1 of control (7.462) and bioaugmented BTF (3.267) obtained by the elimination capacity-sum kinetics with interaction parameter (EC-SKIP) model indicated that THF has a stronger inhibition of MTBE biodegradation in the control BTF than in the bioaugmented BTF. Similarly, the self-inhibition EC-SKIP model quantified the positive effects of MTBE on THF biodegradation, as well as the negative effects of THF on MTBE biodegradation and the self-inhibition of MTBE and THF. Metabolic intermediate analysis, real-time quantitative polymerase chain reaction, biofilm-biomass determination, and high-throughput sequencing revealed the possible mechanism of the enhanced treatment performance and biodegradation interactions of MTBE and THF.

Removal of ammonium, phosphate, and sulfonamide antibiotics using alum sludge and low-grade charcoal pellets

Powder adsorbents perform well due to their large surface area but are difficult to use because of aggregation and channeling. In this study, pelletization of adsorbents was proposed as a solution to these operating problems. A three-component mixture was extruded into pellets and calcined under air or nitrogen conditions The pellet adsorbent removed 47, 71, 97, and 72% of ammonium, phosphate, sulfathiazole, and sulfamethoxazole, respectively. Bentonite improved greatly the strength of pellets, and a 10 wt% of bentonite was sufficient to maintain pellet shape and mass. No significant difference in individual adsorption and multi-pollutant adsorption was found. Pellet adsorbents with alum sludge, bentonite, and low-grade charcoal are low-cost materials that effectively remove multi-pollutants from the aqueous phase.

Water condition in biotrickling filtration for the efficient removal of gaseous contaminants

Biofiltration (BF) facilitates the removal of organic and inorganic compounds through microbial reactions. Water is one of the most important elements in biotrickling filters that provides moisture and nutrients to microbial biofilms. The maintenance of proper trickle watering is very critical in biotrickling filtration because the flow rate of the trickling water significantly influences contaminant removal, and its optimal control is associated with various physicochemical and biological mechanisms. The lack of water leads to the drying of the media, creating several issues, including the restricted absorption of hydrophilic contaminants and the inhibition of microbial activities, which ultimately deteriorates the overall contaminant removal efficiency (RE). Conversely, an excess of water limits the mass transfer of oxygen or hydrophobic gases. In-depth analysis is required to elucidate the role of trickle water in the overall performance of biotrickling filters. The processes involved in the treatment of various polluted gases under specific water conditions have been summarized in this study. Recent microscopic studies on biofilms were reviewed to explain the process by which water stress influences the biological mechanisms involved in the treatment of hydrophobic contaminated gases. In order to maintain an effective mass transfer, hydrodynamic and biofilm conditions, a coherent understanding of water stress and the development of extracellular polymeric substances (EPS) in biofilms is necessary. Future studies on the realistic local distribution of hydrodynamic patterns (trickle flow, water film thickness, and wet efficiency), integrated with biofilm distributions, should be conducted with respect to EPS development.

Biochar for remediation of agrochemicals and synthetic organic dyes from environmental samples: A review

Application of agrochemicals in farming sector to control insects and pests; and use of synthetic organic dyes to color the products are increasing continuously due to the rapid growth of industries. During the application process many industries releases toxic agrochemicals and dyes in to the aquatic environment and on land without the proper treatment. Due to their toxicity the disposal of such chemicals is of utmost importance. Biochar offers the ability to remediate these substances from environmental matrices because of their high sorption ability of pollutants from water and soil. This review highlights the development and advancement of biochar-based treatment for abatement of agrochemicals and synthetic organic dyes, involving its technical aspects and the variables connected with removing these kinds of pollutants. Several optimization parameters like temperature, pH, chemical concentration, biochar properties, time, and co-existing ions have been elaborated. Literature survey shows that most of the researches on biochar application have been conducted in the batch mode. Hence there is an urgent need to apply this beneficial technique for the remediation of pollutants at the larger scale in the real water and soil samples. A comprehensive summary on sorption kinetics and adsorption isotherms with regards to pollutant removal is also presented. This review also covers the cost analysis of various techniques where biochar has been used as an adsorbent. Thus this review makes an easy roadmap for the further development in biochar and biochar based composites and expansion of these demanding areas of research in biochar and their applications.

Preparation and Evaluation of a Composite Filler Micro-Embedded with Pseudomonas putida for the Biodegradation of Toluene : Preparation of composite filler with high toluene removal efficiency

The main objective of this study was to evaluate the performance of a self-developed filler micro-embedded with Pseudomonas putida (P. putida) for toluene removal in a biofilter under various loading rates. The results show that the biofilter could reach 85% removal efficiency (RE) on the eighth day and remain above 90% RE when the empty bed residence time (EBRT) was 18 s and the inlet loading was not higher than 41.4 g m−3 h−1. Moreover, the biofilter could tolerate substantial transient shock loadings. After two shut-down experiments, the removal efficiency could be restored to above 80% after a recovery period of three days and six days, respectively. Sequence analysis of the 16S rRNA gene of fillers in four operating periods revealed that the highly efficient bacterial colonies in fillers mainly included Firmicutes, Actinobacteria and Proteobacteria and that the abundance of Bacteroidetes increased significantly during the re-start period.

Adsorption of Patent Blue V from Textile Industry Wastewater Using Sterculia alata Fruit Shell Biochar: Evaluation of Efficiency and Mechanisms

Biochar prepared from Sterculia alata fruit shell showed a better performance for dye removal than the biomass from Sterculia alata fruit shell. The important process parameters—namely the pH, the amount of biochar, the initial dye concentration and the contact time—were optimized in order to maximize dye removal using biochar of Sterculia alata fruit shell as the bio-sorbent. The results from this study showed that the maximum adsorption of dye on the biochar was obtained at a biochar dosage of 40 g/L, at a contact time of 5 h, and an initial dye concentration of 500 mg/L (pH 2.0; temperature 30 ± 5 °C). The increase in the rate adsorption with temperature and the scanning electron microscopic (SEM) images indicated the possibility of multilayer type adsorption which was confirmed by better fit of the Freundlich adsorption isotherm with the experimental data as compared to the Langmuir isotherm. The values n and R2 in the Freundlich isotherm were found to be 4.55 and 0.97, respectively. The maximum adsorption capacity was found to be 11.36 mg/g. The value of n > 1 indicated physical nature of the adsorption process. The first and second order kinetics were tested, and it was observed that the adsorption process followed the first-order kinetics (R2 = 0.911).

Evidence of inter-species swing adsorption between aromatic hydrocarbons

In this research, the competitive adsorption characteristics between aromatic hydrocarbons were investigated. It is well-known that an industrial effluent may contain a mixture of pollutants. The composition of effluents is usually highly variable in nature to depend upon the feedstock. Hence, one of the pollutants that is present in larger amounts may have the potential to dominate the sorption processes. Although many studies have investigated the competitive adsorption of volatile organic compounds (VOCs) onto activated carbon (AC) in detail, little is known about how the overall process is influenced when a fresh incoming VOC molecule encounters a sorbent bed pre-loaded with other VOCs. Consequently, the objective of the present study was to investigate the stability of pre-adsorbed VOC molecules in the presence of other potentially competitive VOCs in the influent stream. In this regard, the sorbent bed of AC was first preloaded with benzene (50 ppm (0.16 mg L^-1)) and subsequently challenged by either high purity nitrogen or a stream of xylene (at 10, 50, or 100 ppm (0.043, 0.22, or 0.43 mg L^-1)). The desorption rate of preloaded benzene and uptake rate of challenger xylene were assessed simultaneously. The maximum desorption rates of benzene (R_b) against two challenge scenarios (e.g., 100 ppm (0.43 mg L^-1) xylene and pure N₂) were very different from each other, i.e., 663 vs. 257 g kg^-1 h^-1, and their final benzene recoveries were 84% and 42%, respectively. The initially high desorption rate for the former quickly decreased with decreasing benzene residual capacity (C, mg g^-1). Interestingly, the adsorption capacity of xylene increased considerably after the preloading of benzene (relative to no preloading). As such, 10% breakthrough volumes (BTV10) of 100, 50, and 10 ppm (0.43, 0.22, and 0.043 mg L^-1) xylene challenge scenarios increased significantly from 100 to 186, 43.4 to 694, and 600 to 1000 L atm g^-1, respectively. The prevalent mechanisms were analyzed using density functional theory (DFT)-based modelling approaches. The results demonstrated effective replacement of pre-adsorbed molecules with weaker affinity (e.g., benzene) when challenged by molecules with stronger affinity (e.g., xylene) toward the sorbent; this was accompanied by noticeable synergistic enhancement in the adsorption capacity of the latter.

Computational tomography and CFD simulation of a biofilter treating a toluene, formaldehyde and benzo[α]pyrene vapor mixture

In this work, a 3D computational tomography (CT) of the packing material of a laboratory column biofilter is used to model airflow containing three contaminants. The degradation equations for toluene, formaldehyde and benzo[α]pyrene (BaP), were one-way coupled to the CFD model. Physical validation of the model was attained by comparing pressure drops with experimental measurement, while experimental elimination capacities for the pollutants were used to validate the biodegradation kinetics. The validated model was used to assess the existence of channeling and to predict the impact of the three-dimensional porous geometry on the mass transfer of the contaminants in the gas phase. Our results indicate that a physically meaningful simulation can be obtained using the techniques and approach presented in this work, without the need of performing experiments to obtain macroscopic parameters such as gas-phase axial and radial dispersion coefficients and porosities.

Utilization of activated carbon as an effective replacement for a commercialized three-bed sorbent (Carbopack) to quantitate aromatic hydrocarbons in ambient air

The potential use of activated carbon (AC) as an inexpensive and effective alternative sorbent material in thermal desorption is presented and validated for the analysis of aromatic volatile organic compounds (VOCs) such as benzene, toluene, m-xylene, and styrene (BTXS) in air. The optimum desorption conditions of an AC sampling tube (2 mg AC bed) were determined and compared with a commercial three-bed (Carbopack; C + B + X) tube sampler as a reference. The AC sampler exhibited good linearity (R² > 0.99) and reproducibility (RSE of 2.38 ± 0.21%) for BTXS analysis. The AC tube sampler showed good storability (up to 3 d) and excellent recyclability (up to 50 cycles). An analysis of BTXS in ambient air showed excellent agreement between AC and CBX (bias < 5%). The 1% breakthrough volume values for 2 mg AC, when tested at 100 ppb of benzene as a sole component or in a BTXS mixture, were 10,000 or 5000 L g^-1, respectively. The results of this study support the performance of AC as a suitable medium for sampling VOCs as reliable as high-cost commercial sorbent products.

Shift of microbial diversity and function in high-efficiency performance biotrickling filter for gaseous xylene treatment

Xylene is the main component of many volatile industrial pollution sources, and the use of biotechnology to remove volatile organic compounds (VOCs) has become a growing trend. In this study, a biotrickling filter for gaseous xylene treatment was developed using activated sludge as raw material to study the biodegradation process of xylene. Reaction conditions were optimized, and long-term operation was performed. The optimal pH was 7.0, gas-liquid ratio was 15:1 (v/v), and temperature was 25 °C. High-throughput sequencing technique was carried out to analyze microbial communities in the top, middle, and bottom layers of the reactor. Characteristics of microbial diversity were elucidated, and microbial functions were predicted. The result showed that the removal efficiency (RE) was stable at 86%-91%, the maximum elimination capacity (EC) was 303.61 g·m^-3·hr^-1, residence time was 33.75 sec, and the initial inlet xylene concentration was 3000 mg·m^-3, which was the highest known degradation concentration reported. Kinetic analysis of the xylene degradation indicated that it was a very high-efficiency-activity bioprocess. The r_max was 1059.8 g·m^-3·hr^-1, and K_s value was 4.78 g·m^-3 in stationary phase. In addition, microbial community structures in the bottom and top layers were significantly different: Pseudomonas was the dominant genus in the bottom layer, whereas Sphingobium was dominant in the top layer. The results showed that intermediate metabolites of xylene could affect the distribution of community structure. Pseudomonas sp. can adapt to high concentration xylene-contaminated environments. Implications: We combined domesticated active sludge and reinforced microbial agent on biotrickling filter. This system performed continuously under a reduced residence time at 33.75 sec and high elimination capacity at 303.61 g·m^-3·hr^-1 in the biotrickling reactor for about 260 days. In this case, predomestication combined with reinforcing of microorganisms was very important to obtaining high-efficiency results. Analysis of microbial diversity and functional prediction indicated a gradient distribution along with the concentration of xylene. This implied a rational design of microbial reagent and optimizing the inoculation of different sites of reactor could reduce the preparation period of the technology.

Performance of a biofilter with compost and activated carbon based packing material for gas-phase toluene removal under extremely high loading rates

The main aim of this work was to evaluate the performance of a biofilter packed with a mixture of compost and activated carbon, for gas-phase toluene removal under very high loading rates. Plaster of Paris was used as a binder to improve the mechanical strength and durability of the packing media. The biofilter was operated continuously for a period of ∼110 days and at four different flow rates (0.069, 0.084, 0.126 and 0.186 m^-3 h^-1), corresponding to toluene loading rates of 160-8759 g m^-3 h^-1. The maximum elimination capacity (EC) achieved in this study was 6665 g m^-3 h^-1, while the removal efficiency (RE) varied from ∼70 to >95% depending on the loading rate tested. The biofilter was able to remove >99% of toluene using Pseudomonas sp. RSST (MG 279053) as the dominant toluene degrading biocatalyst.

Competitive adsorption of gaseous aromatic hydrocarbons in a binary mixture on nanoporous covalent organic polymers at various partial pressures

Covalent-organic polymers (COPs) are recognized for their great potential for treating diverse pollutants via adsorption. In this study, the sorption behavior of benzene and toluene was investigated both individually and in a binary mixture against two types of COPs possessing different -NH₂ functionalities. Namely, the potential of COPs was tested against benzene and toluene in a low inlet partial pressure range (0.5-20 Pa) using carbonyl-incorporated aromatic polymer (CBAP)-1-based diethylenediamine (EDA) [CD] and ethylenetriamine (DETA) [CE]. The maximum adsorption capacity and breakthrough values of both COPs showed dynamic changes with increases in the partial pressures of benzene and toluene. The maximum adsorption capacities (A_max) of benzene (as the sole component in N₂ under atmospheric conditions) on CD and CE were in the range of 24-36 and 33-75 mg g^-1, respectively. In contrast, with benzene and toluene in a binary mixture, the benzene A_max decreased more than two-fold (range of 2.7-15 and 6-39 mg g^-1, respectively) due to competition with toluene for sorption sites. In contrast, the toluene A_max values remained consistent, reflecting its competitive dominance over benzene. The adsorption behavior of the targeted compounds (i.e., benzene and toluene) was explained by fitting the adsorption data by diverse isotherm models (e.g., Langmuir, Freundlich, Elovich, and Dubinin-Radushkevich). The current research would be helpful for acquiring a better understanding of the factors affecting competitive adsorption between different VOCs in relation to a given sorbent and across varying partial pressures.

The application of aged refuse in nitrification biofilter: Process performance and characterization

High adsorption capacity, good biocompatibility and low cost are highly demanded for biofilter used in ammonium-rich wastewater treatment. In this study, we used SEM, BET, XRD and 16S rRNA to document the evidence for good performance in adsorption and biodegradation in aged refuse. Parallel experiment between raw and inert refuse showed ammonium adsorption occurred at the initial week, with the highest ammonium removal efficiency of 90.36%, but saturated during the subsequent long-term operation. Meanwhile, over 6months' operation of an aged refuse biofilter was conducted to confirm that nitrification was the main pathway of ammonium conversion. The maximum nitrogen loading rate could reach up to as high as 1.28kg/m³/d, with ammonium removal efficiency at 99%. Further, high nitrifier biodiversity were detected with 'Nitrosomonas' and 'Nitrospira' in domination in the refuse. However, Nitrospira would outcompete Nitrosomonas under the oxygen limiting condition and resulted in the failure of partial nitrification. The physicochemical and biological analysis show that biodegradation is the main ammonium conversion pathway, which is the critical finding of this work. This investigation would help to accelerate the application of the aged refuse process in ammonium-rich wastewater treatment.

Bacteria enhanced lignocellulosic activated carbon for biofiltration of bisphenols in water

There are eight bisphenol analogues being identified and characterized; among them, bisphenol A (BPA) is on the priority list on the basis of its higher level of uses, occurrence, and toxicity. The endocrine system interfered by BPA has been inventoried as it has the same function as the natural hormone 17β-estradiol and binds mainly to the estrogen receptor (ER) to exhibit estrogenic activities. The BPA concentration in surface waters (14-1390 ng/L) in many parts of the world, such as Japan, Korea, China, and India, was also a significant concern. Research efforts are focusing on restricting BPA consumption as well as removing BPA in our environment especially in drinking water. Current opinion is that lignocellulosic activated carbon stimulated with BPA-degrading bacteria could have the potential to provide solution for recent challenges faced by water utilities arising from BPA contamination in water. This technology has some new trends in the low-cost biofiltration process for removing BPA. This review is to provide in-depth discussion on the fate of BPA in our ecosystem and underlines methods to enhance the efficacy of activated carbon in the presence of BPA-degrading bacteria in the biofiltration process.

Effects of concentration and gas flow rate on the removal of gas-phase toluene and xylene mixture in a compost biofilter

The aim of this work was to study the performance of a compost/ceramic bead biofilter (6:4 v/v) for the removal of gas-phase toluene and xylene at different inlet loading rates (ILR). The inlet toluene (or) xylene concentrations were varied from 0.1 to 1.5gm^-3, at gas flow rates of 0.024, 0.048 and 0.072m³h^-1, respectively, corresponding to total ILR varying between 7 and 213gm^-3h^-1. Although there was mutual inhibition, xylene removal was severely inhibited by the presence of toluene than toluene removal by the presence of xylene. The biofilter was also exposed to transient variations such as prolonged periods of shutdown (30days) and shock loads to envisage the response and recuperating ability of the biofilter. The maximum elimination capacity (EC) for toluene and xylene were 29.2 and 16.4gm^-3h^-1, respectively, at inlet loads of 53.8 and 43.7gm^-3h^-1.

Treatment of gaseous volatile organic compounds using a rotating biological filter

Rotating biological filter (RBF), which provides higher oxygen mass transfer has been developed for treating gaseous volatile organic compounds (VOCs) such as BTEX (Benzene, toluene, ethylbenzene and xylene) at higher concentrations. The screening of enriched cultures has been done initially to enhance the performance of RBF for treating xylene, toluene and xylene, and BTEX at various loading rates. The removal efficiency of BTEX was maximum (82%), higher than toluene and xylene (79%), and xylene (72%). The presence of xylene enhanced the removal of toluene in the mixture. In the BTEX, toluene was found to be highly biodegradable followed by ethylbenzene, benzene and xylene. The RBF also removed nutrients from wastewater along with VOCs. The stability study of RBF showed that supply of nutrient media influenced the RBF performance more. Further, the predominant strain identified in the mixed culture was Enterobacter cloacae SP4001, responsible for biodegradation of BTEX.

Biodegradation and kinetic study of benzene in bioreactor packed with PUF and alginate beads and immobilized with Bacillus sp. M3

Benzene removal in free and immobilized cells on polyurethane foam (PUF) and polyvinyl alcohol (PVA)-alginate beads was studied using an indigenous soil bacterium Bacillus sp. M3 isolated from petroleum-contaminated soil. The important process parameters (pH, temperature and inoculums size) were optimized and found to be 7, 37°C and 6.0×10⁸CFU/mL, respectively. Benzene removals were observed to be 70, 84 and 90% within 9days in a free cell, immobilized PVA-alginate beads and PUF, respectively under optimum operating conditions. FT-IR and GC-MS analysis confirm the presence of phenol, 1,2-benzenediol, hydroquinone and benzoate as metabolites. The important kinetic parameter ratios (µ_max/K_s; L/mg·day₎ calculated using Monod model was found to be 0.00123 for free cell, 0.00159 for immobilized alginate beads and 0.002016 for immobilized PUF. Similarly inhibition constants (K_i; mg/L) calculated using Andrew-Haldane model was found to be 435.84 for free cell, 664.25 for immobilized alginate beads and 724.93 for immobilized PUF.