A review of passive acid mine drainage treatment by PRB and LPB: From design, testing, to construction.

An extensive volume of acid mine drainage (AMD) generated throughout the mining process has been widely regarded as one of the most catastrophic environmental problems. Surface water and groundwater impacted by pollution exhibit extreme low pH values and elevated sulfate and metal/metalloid concentrations, posing a serious threat to the production efficiency of enterprises, domestic water safety, and the ecological health of the basin. Over the recent years, a plethora of techniques has been developed to address the issue of AMD, encompassing nanofiltration membranes, lime neutralization, and carrier-microencapsulation. Nonetheless, these approaches often come with substantial financial implications and exhibit restricted long-term sustainability. Among the array of choices, the permeable reactive barrier (PRB) system emerges as a noteworthy passive remediation method for AMD. Distinguished by its modest construction expenses and enduring stability, this approach proves particularly well-suited for addressing the environmental challenges posed by abandoned mines. This study undertook a comprehensive evaluation of the PRB systems utilized in the remediation of AMD. Furthermore, it introduced the concept of low permeability barrier, derived from the realm of site-contaminated groundwater management. The strategies pertaining to the selection of materials, the physicochemical aspects influencing long-term efficacy, the intricacies of design and construction, as well as the challenges and prospects inherent in barrier technology, are elaborated upon in this discourse.

Enhanced Escherichia coli removal from stormwater with bermudagrass-derived activated biochar filtration systems.

Stormwater treatment and reuse can alleviate water pollution and scarcity while current sand filtration systems showed low treatment performance for stormwater. For enhancing E. coli removal in stormwater, this study applied the bermudagrass-derived activated biochars (BCs) in the BC-sand filtration systems for E. coli removal. Compared with the pristine BC (without activation), the FeCl3 and NaOH activations increased the BC carbon content from 68.02% to 71.60% and 81.22% while E. coli removal efficiency increased from 77.60% to 81.16% and 98.68%, respectively. In all BCs, the BC carbon content showed a highly positive correlation with E. coli removal efficiency. The FeCl3 and NaOH activations also led to the enhancement of roughness of BC surface for enhancing E. coli removal by straining (physical entrapment). The main mechanisms for E. coli removal by BC-amended sand column were found to be hydrophobic attraction and straining. Additionally, under 105-107 CFU/mL of E. coli, final E. coli concentration in NaOH activated BC (NaOH-BC) column was one order of magnitude lower than those in pristine BC and FeCl3 activated BC (Fe-BC) columns. The presence of humic acid remarkably lowered the E. coli removal efficiency from 77.60% to 45.38% in pristine BC-amended sand column while slightly lowering the E. coli removal efficiencies from 81.16% and 98.68% to 68.65% and 92.57% in Fe-BC and NaOH-BC-amended sand columns, respectively. Moreover, compared to pristine BC, the activated BCs (Fe-BC and NaOH-BC) also resulted in the lower antibiotics (tetracycline and sulfamethoxazole) concentrations in the effluents from the BC-amended sand columns. Therefore, for the first time, this study indicated NaOH-BC showed high potential for effective treatment of E. coli from stormwater by the BC-amended sand filtration system compared with pristine BC and Fe-BC.

Iron-ozone catalytic oxidation reactive filtration of municipal wastewater at field pilot and full-scale with high-efficiency pollutant removal and potential negative CO2 e with biochar.

Iron-ozone catalytic oxidation (CatOx) shows promise in addressing challenging wastewater pollutants. This study investigates a CatOx reactive filtration (Fe-CatOx-RF) approach with two 0.4 L/s field pilot studies and an 18-month, 18 L/s full-scale municipal wastewater deployment. We apply ozone to leverage common sand filtration and iron metal salts used in water treatment into a next-generation technology. The process combines micropollutant and pathogen destructive removal with high-efficiency phosphorus removal and recycling as a soil amendment, clean water recovery, and the potential for carbon-negative operation with integrated biochar water treatment. A key process innovation is converting a continuously renewed iron oxide coated, moving bed sand filter into a "sacrificial iron" d-orbital catalyst bed after adding O3 to the process stream. Results for the Fe-CatOx-RF pilot studies show >95% removal efficiencies for almost all >5 × LoQ detected micropollutants, with removal rates slightly increasing with biochar addition. Phosphorus removal for the pilot site with the most P-impacted discharge was >98% with serial reactive filters. The long-term, full-scale Fe-CatOx-RF optimization trials showed single reactive filter 90% TP removal and high-efficiency micropollutant removals for most of the compounds detected, but slightly less than the pilot site studies. TP removal decreased to a mean of 86% during the 18 L/s, 12-month continuous operation stability trial, and micropollutant removals remained similar to the optimization trial for many detected compounds but less efficient overall. A >4.4 log reduction of fecal coliforms and E. coli in a field pilot sub-study suggests the ability of this CatOx approach to address infectious disease concerns. Life cycle assessment modeling suggests that integrating biochar water treatment into the Fe-CatOx-RF process for P recovery as a soil amendment makes the overall process carbon-negative at -1.21 kg CO2 e/m3 . Results indicate positive Fe-CatOx-RF process performance and technology readiness in full-scale extended testing. Further work exploring operational variables is essential to establish site-specific water quality limitations and responsive engineering approaches for process optimization. PRACTITIONERS POINTS: Adding ozone to WRRF secondary influent flows into tertiary ferric/ferrous salt dosed sand filtration amplifies a mature reactive filtration technology into a catalytic oxidation process for micropollutant removal and disinfection. Expensive catalysts are not used. Iron oxide compounds used to remove phosphorus and other pollutants act as sacrificial catalysts with ozone, and these rejected iron compounds can be returned upstream to aid in secondary process TP removal. Biochar addition to the CatOx process improves CO2 e sustainability and phosphorus removal/recovery for long-term soil and water health. Short duration field pilot scale and 18-month full-scale operation at three WRRFs with good results demonstrate technology readiness.

Meta-omics profiling of full-scale groundwater rapid sand filters explains stratification of iron, ammonium and manganese removals.

Rapid sand filters (RSF) are an established and widely applied technology for groundwater treatment. Yet, the underlying interwoven biological and physical-chemical reactions controlling the sequential removal of iron, ammonia and manganese remain poorly understood. To resolve the contribution and interactions between the individual reactions, we studied two full-scale drinking water treatment plant configurations, namely (i) one dual-media (anthracite and quartz sand) filter and (ii) two single-media (quartz sand) filters in series. In situ and ex situ activity tests were combined with mineral coating characterization and metagenome-guided metaproteomics along the depth of each filter. Both plants exhibited comparable performances and process compartmentalization, with most of ammonium and manganese removal occurring only after complete iron depletion. The homogeneity of the media coating and genome-based microbial composition within each compartment highlighted the effect of backwashing, namely the complete vertical mixing of the filter media. In stark contrast to this homogeneity, the removal of the contaminants was strongly stratified within each compartment, and decreased along the filter height. This apparent and longstanding conflict was resolved by quantifying the expressed proteome at different filter heights, revealing a consistent stratification of proteins catalysing ammonia oxidation and protein-based relative abundances of nitrifying genera (up to 2 orders of magnitude difference between top and bottom samples). This implies that microorganisms adapt their protein pool to the available nutrient load at a faster rate than the backwash mixing frequency. Ultimately, these results show the unique and complementary potential of metaproteomics to understand metabolic adaptations and interactions in highly dynamic ecosystems.

Influence of operation modes on gravity-driven membrane process in treating the secondary effluent: Flux improvement and biocake layer property.

A low flux level of the gravity-driven membrane (GDM) process constrained its extensive application in treating the secondary effluent. In this study, different operation modes were introduced to the GDM process without aeration, backwashing, and chemical cleanings, hoping to develop simple and economic flux regulating strategies, and their influences on the filtration performances and biocake layer characteristics were systematically investigated. The results indicated that the stable fluxs in the intermittent GDM systems elevated by 40%-100% relative to the continuous GDM case, attributing to the synergetic effects of forming more permeable, mushroom-like structures and reducing the concentrations of EPS and SMP within biocake layers. The quantitative analysis of biocake layer properties suggested that the structural parameters of porosity and absolute roughness were closely related to the flux variation compared to the thickness and relative roughness. Besides, the intermittent GDM system generated an apparent detachment of the biocake layer from the membrane surface along with a persistent flux increase than in the continuous GDM case during long-term filtration, achieving its self-sustained operation in a higher flux level without any interferences. The periodical flux recovery and decline occurred daily in each intermittent GDM system since the biocake layer attached to the membrane surface was mainly reversible. Although there were no significant differences in removing dissolved organic pollutants under different operation modes, the manganese removals decreased by 0%-25% in the intermittent GDM filtrations compared to the continuous GDM scenario. The optimized daily operation mode was 16 h on / 8 h off (operation of 16 h, interruption of 8 h), considering the trade-off effects between membrane flux level and water production. These findings provide a new simply-feasible optimized GDM process operation strategy and benefit promoting the application of the GDM system in the reclamation of wastewater.

Improving the filtration properties for manganese tetroxide mud utilizing perlite particles to drill wide-range permeability sandstone formation.

A required feature of any drilling formulation is to mitigate the formation damage by having an excellent filtration and filter cake properties. The key factor for preventing and limiting formation damage is to improve the sealing qualities of the planned drilling fluid. In this study, a new novel filtration agent called "perlite" was introduced for improving the manganese tetroxide mud cake ability for better sealing features. The perlite particles were loaded to formulation containing the manganese tetroxide as weighting agent. The water-based drilling mud was designed at high densities (14.25 and 17.2 ppg). Perlite was added in varied concentrations to reach the optimum performance. The filtration test conducted at reservoir temperature of 250 °F and a differential pressure of 300 psi to form the filter cake. The tests were performed using sandstone cores with two different permeability categories (low and high permeabilities) as the filtration media. This gave the full picture of perlite performance as implemented for different formation properties and considering the drilling fluid properties. The formed filter cake structure and chemical composition was evaluated using scanning electron energy-dispersive X-ray (SEM-EDS). The presented results illustrated how the perlite was compatible to be added to the manganese tetroxide weighting agents in the same formulation. In addition, it has the capacity to improve the filter cake's sealing qualities, lowering the filtration volume by 41% and the filter cake internal and external layers permeability by 58% and 25%, respectively. Moreover, the EDS analysis showed that the perlite particles are concentrated generally in the internal layer of the filter cake.

Exploring organic micropollutant biodegradation under dynamic substrate loading in rapid sand filters.

Microbial removal of trace organic micropollutants (OMPs) from drinking water sources remains challenging. Nitrifying and heterotrophic bacteria in rapid sand filters (RSFs) are capable of biodegrading OMPs while growing on ammonia and dissolved organic matter (DOM). The loading patterns of ammonia and DOM may therefore affect microbial activities as well as OMP biodegradation. So far, there is very limited information on the effect of substrate loading on OMP biodegradation at environmentally relevant concentrations (∼ 1 µg/L) in RSFs. We investigated the biodegradation rates of 16 OMPs at various substrate loading rates and/or empty bed contact times (EBCT). The presence of DOM improved the biodegradation of paracetamol (41.8%) by functioning as supplementary carbon source for the heterotrophic degrader, while hindering the biodegradation of 2,4-D, mecoprop and benzotriazole due to substrate competition. Lower loading ratios of DOM/benzotriazole benefited benzotriazole biodegradation by reducing substrate competition. Higher ammonia loading rates enhanced benzotriazole removal by stimulating nitrification-based co-metabolism. However, stimulating nitrification inhibited heterotrophic activity, which in turn inhibited the biodegradation of paracetamol, 2,4-D and mecoprop. A longer EBCT promoted metformin biodegradation as it is a slowly biodegradable compound, but suppressed the biodegradation of paracetamol and benzotriazole due to limited substrate supply. Therefore, the optimal substrate loading pattern is contingent on the type of OMP, which can be chosen based on the priority compounds in practice. The overall results contribute to understanding OMP biodegradation mechanisms at trace concentrations and offer a step towards enhancing microbial removal of OMPs from drinking water by optimally using RSFs.

Combined Platelet and Erythrocyte Salvage: Evaluation of a New Filtration-based Autotransfusion Device.

BACKGROUND: The SAME device (i-SEP, France) is an innovative filtration-based autotransfusion device able to salvage and wash both red blood cells and platelets. This study evaluated the device performances using human whole blood with the hypothesis that the device will be able to salvage platelets while achieving a erythrocyte yield of 80% and removal ratios of 90% for heparin and 80% for major plasma proteins without inducing signification activation of salvaged cells. METHODS: Thirty healthy human whole blood units (median volume, 478 ml) were diluted, heparinized, and processed by the device in two consecutive treatment cycles. Samples from the collection reservoir and the concentrated blood were analyzed. Complete blood count was performed to measure blood cell recovery rates. Flow cytometry evaluated the activation state and function of platelets and leukocytes. Heparin and plasma proteins were measured to assess washing performance. RESULTS: The global erythrocyte yield was 88.1% (84.1 to 91.1%; median [25th to 75th]) with posttreatment hematocrits of 48.9% (44.8 to 51.4%) and 51.4% (48.4 to 53.2%) for the first and second cycles, respectively. Ektacytometry did not show evidence of erythrocyte alteration. Platelet recovery was 36.8% (26.3 to 43.4%), with posttreatment counts of 88 × 109/l (73 to 101 × 109/l) and 115 × 109/l (95 to 135 × 109/l) for the first and second cycles, respectively. Recovered platelets showed a low basal P-selectin expression at 10.8% (8.1 to 15.2%) and a strong response to thrombin-activating peptide. Leukocyte yield was 93.0% (90.1 to 95.7%) with no activation or cell death. Global removal ratios were 98.3% (97.8 to 98.9%), 98.2% (96.9 to 98.8%), and 88.3% (86.6 to 90.7%) for heparin, albumin, and fibrinogen, respectively. The processing times were 4.4 min (4.2 to 4.6 min) and 4.4 min (4.2 to 4.7 min) for the first and second cycles, respectively. CONCLUSIONS: This study demonstrated the performance of the SAME device. Platelets and red blood cells were salvaged without significant impact on cell integrity and function. In the meantime, leukocytes were not activated, and the washing quality of the device prevented reinfusion of high concentrations of heparin and plasma proteins.

Characterization of a novel strain of Aspergillus aculeatinus: From rhamnogalacturonan type I pectin degradation to improvement of fruit juice filtration.

Aspergillus spp. are well-known producers of pectinases commonly used in the industry. Aspergillus aculeatinus is a recently identified species but poorly characterized. This study aimed at giving a comprehensive characterization of the enzymatic potential of the O822 strain to produce Rhamnogalacturonan type I (RGI)-degrading enzymes. Proteomic analysis identified cell wall degrading enzymes (cellulases, hemicellulases, and pectinases) that accounted for 92 % of total secreted proteins. Twelve out of fifty proteins were identified as RGI-degrading enzymes. NMR and enzymatic assays revealed high levels of arabinofuranosidase, arabinanase, galactanase, rhamnogalacturonan hydrolases and rhamnogalacturonan acetylesterase activities in aqueous extracts. Viscosity assays carried out with RGI-rich camelina mucilage confirmed the efficiency of enzymes secreted by O822 to hydrolyze RGI, by decreasing viscosity by 70 %. Apple juice trials carried out at laboratory and pilot scale showed an increase in filtration flow rate and yield, paving the way for an industrial use of enzymes derived from A. aculeatinus.

Removal of antibiotic resistance genes from swine wastewater by membrane filtration treatment.

Antibiotic resistance genes (ARGs) have attracted extensive attention as an emerging environmental contaminant potentially threatening humans. One of the main emission sources of ARGs is swine wastewater. In this study, integrated membrane filtration including ultrafiltration and two-stage reverse osmosis was conducted for swine wastewater treatment. The abundances of 16 target ARGs, which accounted for 72.64% of the total ARGs in swine wastewater according to metagenomic sequencing, were quantified by quantitative real-time PCR (qPCR) during each stage of the membrane filtration process. The results showed that integrated membrane filtration could reduce more than 99.0% of conventional pollutants and 99.79% of ARGs (from 3.02 × 108 copy numbers/mL to 6.45 × 105 copy numbers/mL). Principal component analysis (PCA) indicated that the removal efficiency of ARGs subtype by membrane filtration did not depend on ARGs type. However, strong correlations were found between ARGs and the wastewater quality indicators TP, SS and EC according to Cooccurrence patterns, indicating that ARG removal was closely associated with insoluble solid particles and soluble ions in swine wastewater. These results showed that membrane filtration could not only remove conventional pollutants such as nitrogen and phosphorus but also reduce the emerging pollutant of ARGs and decrease the risk of ARGs flowing into natural water.

A filtration-assisted approach to enhance optical detection of analytes and its application in food matrices.

Analysis of target analytes in food and environmental samples often required sophisticated instrumentation, which restrains the accessibility and portability of the analysis. Herein, we developed an instrument-free approach for rapid quantification of target analytes. The reported filtration-assisted approach enables image analysis of aggregates formed via interaction between analytes and silver nanoparticles (AgNPs). Two model analytes were chosen for aggregating AgNPs, potassium phosphate for neutralizing the charges and a di-thiol molecule (2,2'-(ethylenedioxy) diethanethiol (EDT)) for cross-linking. The mixtures of AgNPs and analytes were filtered onto filter membranes and analyzed using grey color intensity analysis. Based on the AgNPs-EDT platform, we demonstrated the detection of 1 µg/mL acrylamide in instant coffee and biscuit matrices was achievable. The filtration-assisted method provides a simple, fast and inexpensive approach for optical detection and quantification of analytes in food matrices.

Impacts of operating conditions on efficiency of electrokinetically enhanced filtration for de-watering of orange juice and malt extract.

The effects of operational factors an on an electrokinetic-enhanced filtration (EKEF) application to dewater orange juice (OJ) and malt extract (ME) was investigated. EKEF improved dewatering of both foodstuffs and resulted in net dewatering efficiencies of 7.4% and 4.9% for OJ and 10.7% and 6.3% for ME after 5.5 h processing under 30 V and 15 V, respectively. Dry matter content was increased by 19.2% and 15.6% for OJ after 5.5 h and 14.8% and 12.8% for ME after 3.5 h under 30 V and 15 V, respectively, compared with 14.9% and 10.3% under the control conditions for OJ and ME, respectively. The EKEF process effectively improved dewatering of high moisture-content foods with positive impacts on process efficiency by increased voltage, pressure, and the pore size of filters. The initial distance between electrodes had a negative impact as the distance increased. EKEF is a useful adjunct to improve high pressure filtration of foodstuffs.

Amidoximated cellulose fiber membrane for uranium extraction from simulated seawater.

Uranium extraction from seawater is considered as an efficient strategy to meet the increasing demands of uranium. Amidoxime has been reported as one of the most efficient groups for uranium affinity. Herein, amidoximated cellulose fibers were synthesized by grafting polyacrylonitrile (PAN) onto cellulose fibers followed by amidoxime modification. The amidoximated cellulose fibers showed maximum adsorption capacity of 52.88 mg g-1 (pH = 5.0), and its static adsorption process was well fitted with Langmuir model and Pseudo-second-order kinetics. The adsorption mechanism was attributed to the chelating reaction between uranyl complexes and amidoximated cellulose fibers. The prepared fibers were further fabricated into nonwoven membrane for dynamic adsorption, and the breakthrough curves were well fitted to Dose-Response model. The amidoximated cellulose fiber membrane showed a good adsorption capacity of 1.22 mg g-1 at pH 8.0 after filtrating 10.0 L simulated seawater, demonstrating promising efficient engineering materials for uranium extraction from seawater.

Simultaneous denitrification, phosphorus recovery and low sulfate production in a recirculated pyrite-packed biofilter (RPPB).

The simultaneous removal of nitrate (15 mg N-NO3- L-1) and phosphate (12 mg P-PO43- L-1) from nutrient-polluted synthetic water was investigated in a recirculated pyrite-packed biofilter (RPPB) under hydraulic retention time (HRT) ranging from 2 to 11 h. HRT values ≥ 8 h resulted in nitrate and phosphate average removal efficiency (RE) higher than 90% and 70%, respectively. Decrease of HRT to 2 h significantly reduced the RE of both nitrogen and phosphorus. The RPPB showed high resiliency as reactor performance recovered immediately after HRT increase to 5 h. Solid-phase characterization of pyrite granules and backwashing material collected from the RPPB at the end of the study revealed that iron-phosphate, -hydroxide and -sulfate precipitated in the bioreactor. Thermodynamic modeling predicted the formation of S0 during the study. Residence time distribution tests showed semi-complete mixing hydrodynamic flow conditions in the RPPB. The RPPB can be considered an elegant and low-cost technology coupling biological nitrogen removal to the recovery of phosphorus, iron and sulfur via chemical precipitation.

Dynamic performance of a fungal biofilter packed with perlite for the abatement of hexane polluted gas streams using SIFT-MS and packing characterization with advanced X-ray spectroscopy.

The use of Fusarium solani fungi in an expanded perlite packed biofilter was investigated for the treatment of a hexane polluted waste gas stream using selected ion flow tube mass spectrometry (SIFT-MS). The latter analytical technique proved to be of utmost importance to evaluate the performance of the biofilter at high time resolution (seconds) under various transient conditions, analogous to industrial situations. The biofilter was operational for 277 days with inlet loads varying between 1 and 14 g m-3 h-1 and applying an empty bed residence time of 116 s. The results showed a positive behaviour of the biofilter against different types of disruptions such as: (i) changes in the relative humidity of the inlet gas, (ii) stopping the carbon supply for 1, 5 and 10 days, (iii) varying the inlet hexane concentration (step increases and intermittent pulses) and (iv) limiting the availability of nutrients. X-ray imaging (both conventional 2D µCT and X-ray fluorescence, XRF) was applied for the first time on biofilter media in order to get insight in the internal structure of expanded perlite and to visualise the biomass growth. The latter in combination with online porosity measurements using SIFT-MS provides fundamental information regarding the biofiltration process.

Performance enhancement of a biofilter with pH buffering and filter bed supporting material in removal of chlorobenzene.

Acidic substances, which produced during chlorinated volatile organic compounds, will corrode the commonly used packing materials, and then affect the removal performance of biofiltration. In this study, three biofilters with different filter bed structure were established to treat gaseous chlorobenzene. CaCO3 and 3D matrix material was added in filter bed as pH buffering material and filter bed supporting material, respectively. A comprehensive investigation of removal performance, biomass accumulation, microbial community, filter bed height, voidage, pressure drops, and specific surface area of the three biofilters was compared. The biofilter with CaCO3 and 3D matrix material addition presented stable removal performance and microbial community, and greater biomass density (209.9 kg biomass/m3 filter bed) and growth rate (0.033 d-1) were obtained by using logistic equation. After 200 days operation, the height, voidage, pressure drop, specific surface area of the filter bed consisted of perlite was 27.4 cm, 0.39, 32.8 Pa/m, 974,89 m2/m3, while those of the filter bed with CaCO3 addition was 28.2 cm, 0.43, 21.3 Pa/m, and 1021.03 m2/m3, and those of the filter bed with CaCO3 and 3D matrix material addition was 28.7 cm, 0.55, 17.4 Pa/m, and 1041.60 m2/m3. All the results verified the biofilter with CaCO3 and 3D matrix material addition is capable of sustaining the long-term performance of biofilters. CaCO3 could limit the changes of removal efficiency, microbial community and filter bed structure by buffering the pH variation. And 3D matrix material could maintain the filter bed structure by supporting the filter bed, regardless of the buffering effect.

Synergistic effects of combining ozonation, ceramic membrane filtration and biologically active carbon filtration for wastewater reclamation.

In this study, we proposed to apply an integrated process which is comprised of in situ ozonation, ceramic membrane filtration (CMF) and biologically active carbon (BAC) filtration to wastewater reclamation for indirect potable reuse purpose. A pilot-scale (20 m3/d) experiment had been run for ten months to validate the prospect of the process in terms of treatment performance and operational stability. Results showed that the in situ O3 + CMF + BAC process performed well in pollutant removal, with chemical oxygen demand, ammonia, nitrate nitrogen, total phosphorus and turbidity levels in the treated water being 5.1 ±â€¯0.9, 0.05 ±â€¯0.01, 10.5 ±â€¯0.8, <0.06 mg/L, and <0.10 NTU, respectively. Most detected trace organic compounds were degraded by>96%. This study demonstrated that synergistic effects existed in the in situ O3 + CMF + BAC process. Compared to pre-ozonation, in situ ozonation in the membrane tank was more effective in controlling membrane fouling (maintaining operational stability) and in degrading organic pollutants, which could be attributed to the higher residual ozone concentration in the tank. Because of the removal of particulate matter by CMF, water head loss of the BAC filter increased slowly and prolonged the backwashing interval to 30 days. BAC filtration was also effective in removing ammonia and N-nitrosodimethylamine from the ozonated water.

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.

A comparative study of biological activated carbon based treatments on two different types of municipal reverse osmosis concentrates.

A study was conducted to understand the impact of reverse osmosis concentrate (ROC) characteristics on the efficacy of biological activated carbon (BAC) based treatments for removing organics and nutrients from two ROC streams (ROCa derived from municipal waste input with high salinity, and ROCb derived from domestic waste plus industrial trade waste with markedly lower salinity). Fluorescence excitation and emission matrix spectra and molecular weight analysis demonstrated that ROCa and ROCb had a significantly different composition of organic compounds due to the petrochemical processing and abattoir waste compounds in ROCb. Although the sequence of coagulation, UV/H2O2 and BAC gave the highest organic removal from the two ROCs (67% DOC for ROCa and 62% for ROCb), UV/H2O2 followed by BAC achieved satisfactory removal (>55%) for both ROC types. Sequential treatment involving coagulation gave better phosphorus removal (>90%) than any single treatment (<65%). Total nitrogen (TN) removal was fairly low (<50%) for all the treatment options and the salinity level had insignificant impact on nitrogen removal. Analysis of bacterial communities suggested that higher phosphorus removal and lower total nitrogen and nitrate removal from ROCb than ROCa was related to the presence of various denitrifying or phosphorus accumulating bacteria in the BAC.

VOC Removal Performance of a Joint Process Coupling Biofiltration and Membrane-Filtration Treating Food Industry Waste Gas.

This study aimed to assess the efficiency of removal of volatile organic compounds (VOCs) from process gases from a food industry plant in East Poland, producing high-quality animal (goose, duck, and pig) and vegetable fats, using a two-stage method which is a combination of biological purification and membrane-separation. The research, conducted on the semi-technical scale, compared the effects of traditional and two-stage biofiltration carried out under the same process conditions. The concentrations of VOCs in process gases were measured by means of a multi-gas detector. Additionally the temperature and humidity of gases were determined by a thermoanemometer under filter bed, following the EU and Polish National Standard Methods Two different types of filling materials (the mix of stumpwood chips and bark, and the mix of stumpwood chips, bark, and compost) and two types of membranes (three-layer semi-permeable membrane fabrics were used, with differences in air permeability and water tightness) were analyzed. During all processes basic operational parameters, the biofilters were controlled, including surface load, volumetric load, duration of gas contact with the filling layer, flow rate, and pressure drops (in the biofilter and on the membrane). The analyzed gases were characterized by very high variability of VOC concentrations (ranging from 350 ppb to 11,170 ppb). The effectiveness of VOC removal (REvoc) was calculated by comparing the analytical results of raw and purified gases. The effectiveness of VOC removal with the application of traditional biofiltration during the experiment varied between 82% to 97% and was related to different parameters of the filling materials (mainly specific surface and moisture), reaching lower value for the mix of stumpwood chips and bark filling. The obtained results showed that the application of membrane improved the efficiency of biofiltration in all the analysed cases from 7% to 9%. The highest effectiveness was obtained using the filter bed in the form of stumpwood chips, bark, and compost in connection with the more permeable membrane. It was maintained between 96% to 99%, reaching an average value of 98%. The selection of the membrane should be determined by its permeability and the values of flow resistance.