Production of bio-oil from Tung seed residues in a fluidized-bed reactor

The current paper presents research on bio-oil production from Tung seed residues fed at 500 g/h via fast pyrolysis in a fluidized-bed. The objective was to investigate the influence of temperature on bio-oil production in a pyrolysis process. Three portions Tung residues were studied, Tung seed outer shells (TO), Tung seed inner shells (TI), and pressed residues of oil seeds (RS), all having particle sizes of 0.150-0.500 mm. The process temperatures were 350-500 °C. The physical and chemical properties of pressed residue particles were characterized by ASTM standard methods. Bio-oil component identification was done using GC-MS. Experimentally derived data showed an optimal pyrolysis temperatures for all three types of Tung residues (TO, TI and RS) of 400 °C, yielding respective maximum bio-oil yields of 53.46, 52.81, and 62.85 wt% on a dry basis (db). Apart from having highest bio-oil yield, RS produced bio-oil with the highest carbon content, leading to its greatest lower heating value (LHV), 28.05 MJ/kg (db). The main bio-oil components were acids, nitrogen compounds, and hydrocarbons. Char yield was reduced with increased temperature. Tung seed outer shells produced the highest char level (39.26 wt%) while RS gave highest char quality in term of density and heating value.

Two problems in one shot: Vinasse and glycerol co-digestion in a thermophilic high-rate reactor to improve process stability even at high sulfate concentrations

Anaerobic co-digestion (AcoD) of sugarcane vinasse and glycerol can be profitable because of the destination of two biofuel wastes produced in large quantities in Brazil (ethanol and biodiesel, respectively) and the complementary properties of these substrates. Thus, the objective of this study was to assess the effect of increasing the organic loading rate (OLR) from 2 to 20 kg COD m^-3 d^-1 on the AcoD of vinasse and glycerol (50 %:50 % on a COD basis) in a thermophilic (55 °C) anaerobic fluidized bed reactor (AFBR). The highest methane production rate was observed at 20 kg COD m^-3 d^-1 (8.83 L CH₄ d^-1 L^-1), while the methane yield remained stable at around 265 NmL CH₄ g^-1 COD_rem in all conditions, even when influent vinasse reached 1811 mg SO₄^2- L^-1 (10 kg COD m^-3 d^-1). Sulfate was not detected in the effluent. Bacterial genera related to sulfate removal, such as Desulfovibrio and Desulfomicrobium, were observed by means of shotgun metagenomic sequencing at 10 kg COD m^-3 d^-1, as well as the acetoclastic archaea Methanosaeta and prevalence of genes encoding enzymes related to acetoclastic methanogenesis. It was concluded that process efficiency and methane production occurred even in higher sulfate concentrations due to glycerol addition.

Biotransformation of chloramphenicol by white-rot-fungi Trametes versicolor under cadmium stress

The recalcitrant chloramphenicol (CAP) combined with heavy metals cadmium (Cd) commonly co-existed in the environment, posing threat to environment health. The capacity of Trametes versicolor to remove/biodegrade CAP in air-pulse fluidized-bed reactor was evaluated, even under Cd stress. T. versicolor could remove 44 % CAP of 5 mg/L in 15 days, even 51 % CAP under 1 mg/L Cd stress. Sustained Cd stress inhibited CAP biodegradation and Cd removal in a 5-batches of a 5-days cycle sequential batch reactor. Nine transformation products and two novel pathways were proposed, with initial multi-step transformation reaction into CP2 and allylic alcohol, respectively. Furthermore, the main mechanism of Cd removal by T. versicolor was extracellular surface bioadsorption and intracellular accumulation. This study filled the gap of the mechanism of simultaneous CAP removal/biodegradation and Cd removal by white-rot fungi T. versicolor, which offer a theoretical basis for future application of biological removal of CAP containing wastewater.

Fungal treatment of agricultural washing wastewater: Comparison between two operational strategies

Agricultural washing wastewater (AWW) is an important source of pesticides that, given its intrinsic characteristics, has a high potential to be treated by fungal bioremediation using white rot fungi. In the present study, two AWW treatment strategies were compared: a fluidized-bed reactor (FBR) with T. versicolor pellets and a rotating drum bioreactor (RDB) with T. versicolor immobilized on wood. The RDB effluent showed better results in all studied parameters compared to those of the FBR, including pesticide removal (87%), toxicity, laccase activity, COD, absorbance and microbial communities. Additionally, the fungal assemblage showed that T. versicolor was successfully immobilized in the RDB, which triggered a major shift in the initial community. Afterwards, solid by-products were treated in a fungal biopile-like system reaching high biodegradation rates. Therefore, this study validates the fungal RDB as a viable alternative for AWW treatment, opening up the possibility of a further in-situ and full-scale application.

The efficacy of the VUV/O3 process run in a continuous-flow fluidized bed reactor for simultaneous elimination of favipiravir and bacteria in aqueous matrices

The efficacy of the Vacuum UV/Ozonation (VUV/O₃) process was evaluated for the degradation of favipiravir (FAV). It was found that coupling O₃ and VUV resulted in a considerable synergistic catalytic effect on FAV removal. The VUV/O₃ process performed better in moderately alkaline conditions than in acidic ones; complete FAV degradation and 99.4% TOC removal were achieved within 10 and 60 min, respectively. HO^• played the dominant role in FAV degradation, with a second-order reaction rate constant with HO^• at 1.05 × 10¹⁰ M^-1 s^-1. The VUV/O₃ process could effectively treat tap water spiked with FAV. Efficient FAV and TOC removal, as well as total bacterial inactivation, was attained when treating municipal secondary effluent by the VUV/O₃ process. Finally, the VUV/O₃ process was operated in a continuous-flow mode in a fluidized-bed (FBR) reactor for treating FAV-spiked tap water. Complete degradation and 75.1% mineralization of 10 mg/L FAV were obtained at a hydraulic retention time of 1 and 8 min, respectively. The findings clearly suggest that the VUV/O₃ process operated in a continuous-flow FBR is a promising, efficient technology for the removal of novel and emerging contaminants, such as the antiviral FAV.

Vacuum UV pre-treatment coupled with self-generated peroxide stimulation of biomass: An innovative hybrid system for detoxification and mineralization of toxic compounds

The degradation of p-nitrophenol (pNP) was investigated in the chemical-less UVC/VUV process (Advanced Oxidation/Reduction Process, AORP), the packed bed bioreactor (PBR), and the hybrid of AORP/PBR system. The control UVC/VUV process degraded and mineralized pNP with rate constants of 0.098 and 0.032 min^-1, respectively, at neutral initial pH. Operating the UVC/VUV process in a fluidized bed reactor improved the rate of pNP degradation by 21 % at a packing ratio of 0.5 %. The fluidized bed AORP was operated under continuous-flow mode, where 79 % degradation and 28 % mineralization of pNP were obtained along a significant improvement in the biodegradability (41 %) at a hydraulic retention time of 20 min. The oxidation with HO and reduction with e_aq^- simultaneously contributed to the degradation of pNP in the UVC/VUV process. In comparison, degradation and mineralization of pNP in a single PBR process (without pretreatment) was found to be 84.7 % and 47.2 %, respectively, during 30 h biotreatment. Coupling the fluidized bed UVC/VUV with the PBR attained complete biodegradation of the residual pNP within 1 h and over 89 % of TOC reduction during 3 h post treatment in the PBR. Accordingly, the hybrid, fluidized bed UVC/VUV reactor coupled with the PBR is an efficient and promising technology for treating toxic environmental contaminants.

Comparison between two reactors using Trametes versicolor for agricultural wastewater treatment under non-sterile condition in sequencing batch mode

Agricultural wastewater is a major source of herbicides, which pose environmental and health concerns owing to their substantial use and poor elimination rate in conventional wastewater treatment plants. White-rot fungi are versatile in degrading xenobiotics; however, the key problem encountered with their application in actual scenarios is competition with indigenous microorganisms, mainly bacteria. To address this barrier, two different strategies were implemented in the present study. One strategy was to set up a trickle bed with Trametes versicolor immobilized on pine wood, and another strategy was to employ a T. versicolor-pelleted, fluidized-bed reactor to remove diuron and bentazon from actual wastewater under non-sterile conditions. The residence time in the trickle bed was estimated using three methodologies. With 10 batches of a 3-day cycle operation, although the trickle-bed reactor possessed a shorter contact time (8.5 h per cycle) and lower laccase activity compared with those of the fluidized-bed reactor, it demonstrated a higher removal yield and lower bacterial counts. In addition, the utilization of pine wood as a carrier obviously reduced the cost since no additional nutrients were required. Hence, after evaluating all advantages and limitations of both bioreactors, for the purpose of treating over the long term and scaling up, a trickle-bed reactor is the preferred choice.

Cartap removal from simulated water matrices by fluidized-bed Fenton process: optimization of process parameters

Cartap is a thiocarbamate pesticide widely-used to protect rice crops, one of the most mass-produced cereals worldwide. Effluents containing cartap pose serious environment and health risks due to the acute toxicity of this emerging contaminant. This work evaluates the capabilities of the Fenton process to efficiently remove cartap from water matrices. Process parameters such as hydrogen peroxide dosage, ferrous ion concentration and operating pH were optimized using Box-Behnken design. Results showed complete cartap removal with Fenton oxidation in a fluidized-bed reactor while eliminating sludge generation during treatment. Fluidized-bed Fenton process had improved reduction in chemical oxygen demand and total organic carbon due to the contribution of heterogeneous Fenton catalysis to the overall degradation of cartap species compared to conventional Fenton in a batch reactor. Furthermore, competitive reactions and scavenging effects in complex natural water matrices were simulated with the use of inorganic ions such as nitrate, chloride, and phosphate. Results demonstrated the detrimental effect of phosphate ions on Fenton oxidation due to the precipitation of soluble catalysts as iron phosphates, which stops the catalytic Fenton cycle and thus the production of oxidants for contaminant degradation.

Beyond carbon capture towards resource recovery and utilization: fluidized-bed homogeneous granulation of calcium carbonate from captured CO2

Atmospheric carbon dioxide (CO₂) imbalance due to anthropogenic emissions has direct impact in climate change. Recent advancements in the mitigation of industrial CO₂ emissions have been brought about by a paradigm shift from mere CO₂ capture onto various adsorbents to CO₂ conversion into high value products. The present study proposes a system which involves the conversion of CO₂ into high purity, low moisture, compact and large CaCO₃ solids through homogeneous granulation in a fluidized-bed reactor (FBR). In the present study, synthetic solutions of potassium carbonate (K₂CO₃) and calcium hydroxide (Ca(OH)₂) were used as sources of carbonate and precipitant, respectively. The effects of the degree of supersaturation (S) as chemical loading and influx flow rate (Q_T) as hydraulic loading on CaCO₃ granulation efficiency were investigated. In the study, S was varied from 10.2 to 10.8 and Q_T from 40 to 80 mL min^-1 while the operating pH and calcium-is-to-carbonate molar ratio ([Ca²⁺]/[CO₃^2-]) were set at 10 ± 0.2 and 1.50, respectively. Results showed that carbonate ions end product distribution had a highest carbonate granulation efficiency at [Carbonate]_G of 95-96% using S of 10.6 and Q_T of 60 mL min^-1. Characterization of the granules confirmed high purity calcium carbonate. Overall, the transformation of industrial CO₂ emissions into a valuable solid product can be a significant move towards the mitigation of climate change from anthropogenic emissions.

Heterogeneous Fenton reaction for elimination of Acid Yellow 36 in both fluidized-bed and stirred-tank reactors: Computational fluid dynamics versus experiments

Heterogeneous Fenton process is a kind of advanced oxidation processes (AOPs) that is significant for wastewater treatment. In the first part of this study, acid yellow 36 (AY36) degradation process has occurred in two kinds of reactors: fluidized-bed and stirred-tank reactors. Performances of these two semi-pilot reactors are compared by evaluating the removal ratio of the dye and pH changes during the process. Pyrite has been used as a heterogeneous catalyst. For obtaining the characteristics of pyrite, XRD, SEM, and FT-IR analysis have been carried out. In the second part of this study, a modified computational fluid dynamics (CFD) method has been utilized to solve the momentum and mass balances for heterogeneous Fenton process in both reactors. In AOPs, free radicals are reactive and have a short lifetime, so that turbulence mixing would be a limiting factor for the reactions that radicals are involved. By introducing a new parameter, named turbulence mixing rate, as a reaction rate for reactive species like hydroxyl radicals, the results of removal ratio and pH changes during the process showed a good agreement between the experiments and the CFD simulations, compared with not including the mixing rate in the CFD simulations (conventional kinetic modeling). In addition, the results revealed the high performance of the fluidized-bed reactor for this process in both experiments and CFD simulation.

Effects of different nickel species on autotrophic denitrification driven by thiosulfate in batch tests and a fluidized-bed reactor

Nickel is a common heavy metal and often occurs with nitrate (NO₃^-) in effluents from mining and metal-finishing industry. The present study investigates the effects of increasing concentrations (5-200mgNi/L) of NiEDTA^2- and NiCl₂ on autotrophic denitrification with thiosulfate (S₂O₃^2-) in batch tests and a fluidized-bed reactor (FBR). In batch bioassays, 50 and 100mgNi/L of NiEDTA^2- only increased the transient accumulation of NO₂^-, whereas 25-100mgNi/L of NiCl₂ inhibited denitrification by 9-19%. NO₃^- and NO₂^- were completely removed in the FBR at feed NiEDTA^2- and NiCl₂ concentrations as high as 100 and 200mgNi/L, respectively. PCR-DGGE revealed the dominance of Thiobacillus denitrificans and the presence of the sulfate-reducing bacterium Desulfovibrio putealis in the FBR microbial community at all feed nickel concentrations investigated. Nickel mass balance, thermodynamic modeling and solid phase characterization indicated that nickel sulfide, phosphate and oxide precipitated in the FBR during NiCl₂ injection.

Central composite design optimization of pilot plant fluidized-bed heterogeneous Fenton process for degradation of an azo dye

Optimization of Acid Yellow 36 (AY36) degradation by heterogeneous Fenton process in a recirculated fluidized-bed reactor was studied using central composite design (CCD). Natural pyrite was applied as the catalyst characterized by X-ray diffraction and scanning electron microscopy. The CCD model was developed for the estimation of degradation efficiency as a function of independent operational parameters including hydrogen peroxide concentration (0.5-2.5 mmol/L), initial AY36 concentration (5-25 mg/L), pH (3-9) and catalyst dosage (0.4-1.2 mg/L). The obtained data from the model are in good agreement with the experimental data (R(2 )= 0.964). Moreover, this model is applicable not only to determine the optimized experimental conditions for maximum AY36 degradation, but also to find individual and interactive effects of the mentioned parameters. Finally, gas chromatography-mass spectroscopy (GC-MS) was utilized for the identification of some degradation intermediates and a plausible degradation pathway was proposed.

Arsenic removal from acidic solutions with biogenic ferric precipitates

Treatment of acidic solution containing 5g/L of Fe(II) and 10mg/L of As(III) was studied in a system consisting of a biological fluidized-bed reactor (FBR) for iron oxidation, and a gravity settler for iron precipitation and separation of the ferric precipitates. At pH 3.0 and FBR retention time of 5.7h, 96-98% of the added Fe(II) precipitated (99.1% of which was jarosite). The highest iron oxidation and precipitation rates were 1070 and 28mg/L/h, respectively, and were achieved at pH 3.0. Subsequently, the effect of pH on arsenic removal through sorption and/or co-precipitation was examined by gradually decreasing solution pH from 3.0 to 1.6 (feed pH). At pH 3.0, 2.4 and 1.6, the highest arsenic removal efficiencies obtained were 99.5%, 80.1% and 7.1%, respectively. As the system had ferric precipitates in excess, decreased arsenic removal was likely due to reduced co-precipitation at pH<2.4. As(III) was partially oxidized to As(V) in the system. In shake flask experiments, As(V) sorbed onto jarosite better than As(III). Moreover, the sorption capacity of biogenic jarosite was significantly higher than that of synthetic jarosite. The developed bioprocess simultaneously and efficiently removes iron and arsenic from acidic solutions, indicating potential for mining wastewater treatment.

CO2 sequestration using accelerated gas-solid carbonation of pre-treated EAF steel-making bag house dust

Mineral CO2 sequestration is a promising process for the reduction of carbon dioxide emissions to the atmosphere. In this paper, alkaline calcium-rich dust particles collected from bag filters of electric arc furnaces (EAF) for steel making were utilized as a viable raw material for mineral CO2 sequestration. The dust particles were pre-treated through hydration, drying and screening. The pre-treated particles were then subjected to direct gas-solid carbonation reaction in a fluidized-bed reactor. The carbonated products were characterized to determine the overall sequestration capacity and the mineralogical structures. Leaching tests were also performed to measure the extracted minerals from the carbonated dust and evaluate the carbonation process on dust stabilization. The experimental results indicated that CO2 could be sequestered using the pre-treated bag house dust. The maximum sequestration of CO2 was 0.657 kg/kg of dust, based on the total calcium content. The highest degree of carbonation achieved was 42.5% and the carbonation efficiency was 69% at room temperature.

Fluidized-bed denitrification of mining water tolerates high nickel concentrations

This study revealed that fluidized-bed denitrifying cultures tolerated soluble Ni concentrations up to 500 mg/L at 7-8 and 22°C. From 10 to 40 mg/L of feed Ni, denitrification resulted in complete nitrate and nitrite removal. The concomitant reduction of 30 mg/L of sulfate produced 10 mg/L of sulfide that precipitated nickel, resulting in soluble effluent Ni below 22 mg/L. At this stage, Dechloromonas species were the dominant denitrifying bacteria. From 60 to 500 mg/L of feed Ni, nickel remained in solution due to the inhibition of sulfate reduction. At soluble 60 mg/L of Ni, denitrification was partially inhibited prior to recover after 34 days of enrichment by other Ni-tolerant species (including Delftia, Zoogloea and Azospira) that supported Dechloromonas. Subsequently, the FBR cultures completely removed nitrate even at 500 mg/L of Ni. Visual Minteq speciation model predicted the formation of NiS, NiCO3 and Ni3(PO4)2, whilst only Ni3(PO4)2 was detected by XRD.

Pyrolucite fluidized-bed reactor (PFBR): a robust and compact process for removing manganese from groundwater

The purpose of this paper is to introduce a pyrolucite fluidized-bed reactor (PFBR) as a potential drinking water process to treat groundwater containing high levels of dissolved manganese (Mn(II)) (0.5-3 mg/L) and reduce its concentration to <0.02 mg/L in treated water. A pilot-scale study was conducted under dynamic conditions using synthetic groundwater (SGW), to elucidate the effect of operational conditions and groundwater composition on manganese (Mn) removal achieved by the PFBR. Results demonstrated almost complete Mn removal (close to 100%) in less than 1 min under all tested operational conditions (influent Mn concentration of 0.5-3 mg/L, calcium (Ca(2+)) hardness of 0-200 mg CaCO3/L, pH of 6.2-7.8, temperature of 9 & 23 °C and high hydraulic loading rate (HLR) of 24-63 m/h (i.e., bed expansion of 0-30%)). Improved Mn removal profile was achieved at higher water temperature. Also, the results showed that adsorption of Mn(II) onto pyrolucite and subsequent slower surface oxidation of sorbed Mn(II) was the only mechanism responsible for Mn removal while direct oxidation of Mn(II) by free chlorine did not occur even at high concentrations of Mn(II) and free chlorine and elevated temperatures. Higher average mass transfer coefficient and consequently adsorption rate was achieved at elevated HLR. Increasing effluent free chlorine residuals from 1.0 to 2.0-2.6 mg Cl2/L allowed increasing the operation time needed for media regeneration from 6 days to >12 days. Turbidity was maintained around 0.2 NTU during the entire test periods indicating good capture of MnOx colloids within the PFBR.