A comprehensive review and perspective research in technology integration for the treatment of gaseous volatile organic compounds.

Volatile organic compounds (VOCs) are harmful pollutants emitted from industrial processes. They pose a risk to human health and ecosystems, even at low concentrations. Controlling VOCs is crucial for good air quality. This review aims to provide a comprehensive understanding of the various methods used for controlling VOC abatement. The advancement of mono-functional treatment techniques, including recovery such as absorption, adsorption, condensation, and membrane separation, and destruction-based methods such as natural degradation methods, advanced oxidation processes, and reduction methods were discussed. Among these methods, advanced oxidation processes are considered the most effective for removing toxic VOCs, despite some drawbacks such as costly chemicals, rigorous reaction conditions, and the formation of secondary chemicals. Standalone technologies are generally not sufficient and do not perform satisfactorily for the removal of hazardous air pollutants due to the generation of innocuous end products. However, every integration technique complements superiority and overcomes the challenges of standalone technologies. For instance, by using catalytic oxidation, catalytic ozonation, non-thermal plasma, and photocatalysis pretreatments, the amount of bioaerosols released from the bioreactor can be significantly reduced, leading to effective conversion rates for non-polar compounds, and opening new perspectives towards promising techniques with countless benefits. Interestingly, the three-stage processes have shown efficient decomposition performance for polar VOCs, excellent recoverability for nonpolar VOCs, and promising potential applications in atmospheric purification. Furthermore, the review also reports on the evolution of mathematical and artificial neural network modeling for VOC removal performance. The article critically analyzes the synergistic effects and advantages of integration. The authors hope that this article will be helpful in deciding on the appropriate strategy for controlling interested VOCs.

Phase Behavior of the Mixtures of 2- and 3-Components for Poly(styrene-co-octafluoropentyl methacrylate) by Dispersion Polymerization under CO2.

The dispersed-phase polymerization of poly(styrene-co-2,2,3,4,4,4-octafluoropentyl methacrylate), also known as p(styrene-co-OFPMA), took place in supercritical carbon dioxide (sc-CO2). The chemical and physical properties of p(styrene-co-OFPMA) were studied by varying the styrene-to-OFPMA ratios (40:1, 30:1, and 20:1) and 2,2'-azobis(isobutyronitrile) (AIBN) initiator amounts (wt %: 1.0, 2.0, 3.0). The cloud-point data were obtained for various systems, including the binary mixtures of p(styrene-co-OFPMA) (30:1 ratio, AIBN wt %: 1.0, 2.0, 3.0) with supercritical solvents such as sc-CO2, sc-CH3OCH3, sc-C3H6, sc-C4H8, and sc-CHClF2. Phase behavior (i.e., mixtures) was studied at temperatures of 324-455 K and pressure below 201 MPa. In the binary system of p(styrene-co-OFPMA) + sc-CH3OCH3, a lower critical solution temperature (LCST)-type curve was observed, characterized by a positive slope. Conversely, the binary systems of p(styrene-co-OFPMA) + (sc-C3H6, sc-C4H8, sc-CHClF2) exhibited an upper critical solution temperature (UCST) behavior with a decreasing slope. The phase equilibrium curves were obtained for p(styrene-co-OFPMA) [30:1; 1.0% (Mw = 42,400), 2.0% (Mw = 33,800), and 4.0% (Mw = 24,100); AIBN: 1.0 wt %] + sc-C3H6, sc-C4H8, and sc-CHClF2 mixtures. These curves exhibited an increasing slope for p(styrene-co-OFPMA) + sc-CH3OCH3 and a negative slope for p(styrene-co-OFPMA) + (sc-C3H6, sc-C4H8, sc-CHClF2) systems, indicating distinct phase behavior. Tetramethyl orthosilicate (TMOS) addition (0.0-68.9 wt %) to P(styrene-co-OFPMA) (30:1; AIBN wt %: 1.0) + solvents altered the phase equilibrium, switching from UCST to LCST, as evidenced by changes in the pressure-temperature slope.

Neuro-fuzzy modelling of a continuous stirred tank bioreactor with ceramic membrane technology for treating petroleum refinery effluent: a case study from Assam, India.

A continuous stirred tank bioreactor (CSTB) with cell recycling combined with ceramic membrane technology and inoculated with Rhodococcus opacus PD630 was employed to treat petroleum refinery wastewater for simultaneous chemical oxygen demand (COD) removal and lipid production from the retentate obtained during wastewater treatment. In the present study, the COD removal efficiency (CODRE) (%) and lipid concentration (g/L) were predicted using two artificial intelligence models, i.e., an artificial neural network (ANN) and a neuro-fuzzy neural network (NF-NN) with a network topology of 6-25-2 being the best for NF-NN. The results revealed the superiority of NF-NN over ANN in terms of determination coefficient (R2), root mean square error (RMSE), and mean absolute percentage error (MAPE). Three learning algorithms were tested with NF-NN; among them, the Bayesian regularization backpropagation (BR-BP) outperformed others. The sensitivity analysis revealed that, if solid retention time and biomass concentrations were maintained between 35 and 75 h and 3.0 g/L and 3.5 g/L, respectively, high CODRE (93%) and lipid concentration (2.8 g/L) could be obtained consistently.

Dosimetry of pulsed magnetic field towards attaining bacteriostatic effect on Enterococcus faecalis: Implications for endodontic therapy.

AIM: To examine in a laboratory setting the efficacy of moderate to high strength magnetic fields, as a potential bacteriostatic stimulus, against Enterococcus faecalis, one of the causative agents for infection during root canal treatments. METHODOLOGY: Four different strengths (1, 2, 3 and 4 T) of the pulsed magnetic field (PMF) were applied in thirty repetitions to bacterial suspension. A pickup coil setup was used to measure the electromotive force induced inside the bacterial suspensions. The optical density (OD) was monitored over time (for 16 h 40 min) during the post-treatment period to assess bacterial growth. Along with the change in OD values, live/dead assay, membrane depolarization study, atomic force microscopy (AFM), scanning electron microscopy (SEM) and reactive oxygen species (ROS) assay on selected samples were studied to evaluate the effect of PMFs. All results were analysed using one-way ANOVA followed by post hoc Tukey test and considered significant at p < .05. Regression analysis (at a confidence of 95%, α = 0.05) was performed on the bacterial growth and membrane depolarization studies to determine progressive changes of the outcomes. RESULTS: The peak value of the induced electromotive force was recorded as 0.25 V, for the 4 T magnetic field pulse with a pulse width of 16 ms. There was a significant arrest of bacterial cell growth after an exposure to PMFs of 1 T, 3 T and 4 T (ANOVA score: F (4, 495) =395.180 at p = .05). The image-based qualitative results of the live/dead assay using fluorescence microscopy techniques indicated that an exposure to higher PMFs (3 T/ 4 T) induced a bacteriostatic effect in a longer post-exposure timescale. Evidence of altered membrane potential within the 2 h of exposure to 4 T PMF was supported by the incidence of elevated ROS. For the ROS assay, a significant difference occurred for 4 T exposed samples (ANOVA score: calculated F (1, 3) =20.2749 at p = .05). SEM and AFM observations corroborated with the outcomes, by portraying significant membrane damage. CONCLUSION: In a laboratory setting, PMFs with higher magnitudes (3 T and 4 T) were capable of inducing bacteriostatic effects on E. faecalis.

Design of Site-Specific Microwave Phased Array Hyperthermia Applicators Using 434 MHz Reduced Cavity-Backed Patch Antenna.

Cancers of the neck, breast, and lower extremities are common malignancies diagnosed in India with a higher incidence of advanced-stage disease. Phased array (PA) applicators reported for hyperthermia treatment (HT) of the breast have small focal region and high cross-coupling, and those reported for lower extremities provide regional heating and limited steering. In this study, we present the numerical design of site-specific PA applicators for HT of large solid tumors in the neck, breast, and lower extremities using a miniaturized 434 MHz cavity-backed water-loaded patch antenna. The fabricated antenna has 38 × 36 mm2 aperture, more than 90% power coupling, 25 MHz bandwidth, and good agreement between simulated and measured specific absorption rate (SAR) in phantom. The site-specific applicators demonstrated less power reflection (<-17.9 dB) and cross-coupling (<-26.8 dB) for 5 mm inter-ring spacing. SAR indicators for 64 cc tumor at varying locations in simplified layered three-dimensional (3D) tissue models of the neck, breast, and leg showed average power absorption ratio (aPAratio ) ≥ 3.16, target to hotspot quotient (THQ) ≥ 0.57, 25% iso-SAR coverage (TC25 ) ≥ 81%, and 50% iso-SAR coverage (TC50 ) ≥51.8%. Simulation results of site-specific applicators for 3D inhomogeneous patient models showed aPAratio ≥ 5.98, THQ ≥ 0.9, TC50 ≥ 86%, and 100% TC25 for all sites. It is concluded that the 434 MHz miniaturized cavity-backed patch antenna can be used to develop high-density PA applicators with 12-24 antennas for HT of large solid tumors (≥4 cm) in the neck, breast, and lower extremities with 3D steering ability and less cross-coupling (≤-26.8 dB). © 2020 Bioelectromagnetics Society.

Gas-phase trichloroethylene removal by Rhodococcus opacus using an airlift bioreactor and its modeling by artificial neural network.

This study evaluated the biological removal of trichloroethylene (TCE) by Rhodococcus opacus using airlift bioreactor under continuous operation mode. The effect of inlet TCE concentration in the range 0.12-2.34 g m-3 on TCE removal has studied for 55 days. During the continuous bioreactor operation, a maximum of 96% TCE removal was obtained for low inlet TCE concentration, whereas the highest elimination capacity was 151.2 g m-3 h-1 for the TCE loading rate of 175.0 g m-3 h-1. The carbon dioxide (CO2) concentration profile from the airlift bioreactor revealed that the degraded TCE has primarily converted to CO2 with a fraction of organic carbon utilized for bacterial growth. The artificial neural network (ANN) based model was able to successfully predict the performance of the bioreactor system using the Levenberg-Marquardt (LM) back propagation algorithm, and optimized biological topology is 3:12:1. The prediction accuracy of the model was high as the experimental data were in good agreement (R2 = 0.9923) with the ANN predicted data. Overall, from the bioreactor experiments and its ANN modeling, the potential strength of R. opacus in TCE biodegradation is proved.

Experimental studies and neural network modeling of the removal of trichloroethylene vapor in a biofilter.

In this study, bamboo carrier based lab scale compost biofilter was evaluated to treat synthetic waste air containing trichloroethylene (TCE) under continuous operation mode. The effect of inlet TCE concentration and gas flow rate and its removal was investigated. Maximum TCE removal efficiency was found to be 89% under optimum conditions of inlet 0.986 g/m3 TCE concentration corresponding to a loading rate of 43 g/m3 h and 0.042 m3/h gas flow rate at empty bed residence time (EBRT) of 2 min. For the first time, Artificial Neural Network (ANN) was applied to predict the performance of the compost biofilter in terms of TCE removal. The ANN model used a three layer feed forward based Levenberg-Marquardt algorithm, and its topology consisted of 3-25-1 as the optimum number for the three layers (input, hidden and output). An excellent match between the experimental and ANN predicted the value of TCE removal was obtained with a coefficient of determination (R2) value greater than 0.99 during the model training, validation, testing and overall. Furthermore, statistical analysis of the ANN model performance mediated its prediction accuracy of the bioreactor to treat TCE contaminated systems.

A novel carbon monoxide fed moving bed biofilm reactor for sulfate rich wastewater treatment.

In this study, a moving bed biofilm reactor was used for biodesulfuruization using CO as the sole carbon substrate. The effect of hydraulic retention time (HRT), sulfate loading rate and CO loading rate on sulfate and CO removal was examined. At 72, 48 and 24 h HRT, the sulfate removal was 93.5%, 91.9% and 80.1%, respectively. An increase in the sulfate loading reduced the sulfate reduction efficiency, which, however, was improved by increasing the CO flow rate into the MBBR. Best results in terms of sulfate reduction (>80%) were obtained for low inlet sulfate and high CO loading conditions. The CO utilization was very high at 85% throughout the study, except during the last phase of the continuous bioreactor operation it was around 70%. An artificial neural network based model was successfully developed and optimized to accurately predict the bioreactor performance in terms of both sulfate reduction and CO utilization. Overall, this study showed an excellent potential of the moving bed biofilm bioreactor for efficient sulfate reduction even under high loading conditions.

Ultrasound-Based Regularized Log Spectral Difference Method For Monitoring Microwave Hyperthermia.

The feasibility of using normalized cumulative difference attenuation (NCDA) map for tracking the spatial and temporal evolution of temperature during microwave hyperthermia experiment on in-vitro phantoms is explored in this study. The NCDA maps were estimated from the beamformed ultrasound radio frequency (RF) data using a regularized log spectral difference (RLSD) technique. The NCDA maps were estimated at different time instants for the entire period of the experiment. The contour maps of the NCDA and the ground truth temperature map, obtained using an infra-red(IR) thermal camera corresponding to the ultrasound imaging plane, showed that NCDA was able to locate the axial and lateral co-ordinates of the hotspot with the error of <; 1.5 mm axially and <; 0.1 mm laterally. The error in the estimated hotspot area was less than 8 %. This preliminary in-vitro study suggests that NCDA maps estimated using RLSD may have potential in evaluating the spatio-temporal evolution of temperature and may help in the development of ultrasound-based image-guided temperature monitoring system for microwave hyperthermia.

Biodegradation of gaseous toluene with mixed microbial consortium in a biofilter: steady state and transient operation.

Petroleum oil refineries are massive emitters of risky volatile organic compounds (VOCs). Among the VOCs, toluene is taken into account as a significant pollutant. In the present study, a compost biofilter is used to treat the toluene vapor. However, an elimination capacity and removal efficiency of the biofilter was investigated for a wide range of toluene concentrations (0.29-3.8 g m-3) and operated for 54 days effectively. Elimination capacity of 93 g m-3 h-1 was recorded as maximum value at a toluene inlet concentration of 114 g m-3 h-1. An elimination capacity was perpetually better at the lower section of the biofilter, and therefore, the value was around 40-60 g m-3 h-1. The high removal efficiency of 97% was obtained at inlet toluene load of 60.55 g m-3 h-1. Hence, the biofilm was quite sensitive to handling transient loading conditions. The pressure drop had no vital impact on the biofilter performance. An Ottengraf model was applied to all phase of biofilter operation in each of the diffusion limiting region and reaction limiting region. The parameters of the model K 1 (75.95 g1/2 m-3/2 h-1) and K 0 (90.51 g m-3 h-1) were obtained from diffusion and reaction limiting region severally. However, K 1 was used to calculate the theoretical elimination capacities, and therefore, K 0 was used to discover the biofilm thickness. By the way, the average biofilm thickness was found to be 0.98 mm from reaction limiting region.