Inlet Loading Research Articles

Integration of Moving Bed Biofilm Reactor (MBBR) and algal PhotoBioReactors (aPBR) for achieving carbon neutrality in wastewater treatment

Carbon neutrality is a primary goal for wastewater treatment plants (WWTPs), as they are responsible for significant greenhouse gas (GHG) emissions as well as unpleasant odour emissions.The paper shows a new modular biotechnology that enables simultaneous treatment of gaseous emissions and biofixation of CO2.A comparative assessment of system performances in removing target pollutants (toluene, p-xylene and hydrogen sulphide) was implemented. Results showed that the highest removal efficiency (RE) was recorded for the toluene, equaling 99.9 ± 0.1 %, for an inlet load (IL) of 9.91 ± 3.44 g m−3 d−1. During the experimental tests regarding hydrogen sulphide removal, the system recorded the highest CO2 assimilation, equal to −3.03 ± 0.93 g m−3 d−1. However, this assimilation rate did not correspond to the maximum volumetric biomass productivity (MVBP), equal to 1.3 g L−1 d−1, recorded with toluene treatment, with a maximum lipid productivity (MLP) of 450 mg L−1 d−1.The results demonstrated the complete adaptability of the investigated system, which can help to fill the gaps in the current technological landscape, providing an innovative biotechnology that can be directly implemented and environmentally sustainable.

Bioremediation of textile wastewater using Bacillus cereus isolated from refinery site: Comparative analysis of free and immobilized cells systems

The textile industries consume a considerable amount of freshwater and discharge untreated or semi-treated pollutants to the environment. Azo dyes, generally employed in textile manufacturing industries, have a hazardous impact on the ecosystem. Incomplete treatment of wastewater containing azo dyes discharges into the aquatic system, which has recalcitrant and toxic properties. Hence, the need for cost-effective and high-performing technologies is essential. In this direction, bacterial degradation is considered an economically viable and efficient technique for the treatment of Active blue (AB) dye. Polyurethane foam (PUF) is a low-cost and hydrophilic material with a microporous structure, which offers an excellent surface-to-volume ratio. Hence, PUF was preferred for the immobilization of isolated bacterial species. For this, a dye-degrading gram-positive bacteria namely Bacillus cereus GS2 IIT (BHU) was isolated from the petroleum sludge. A comparative analysis between free and immobilized cell systems was carried out by varying the process parameters, i.e., batch time, pH, temperature, glucose concentration, and initial AB dye concentration. The corresponding optimum conditions were found to be 6.0 days, 6.5, 30 °C, 1.0 g/L, and 50 mg/L, respectively. The immobilized cell system exceeds the dye removal efficiency (RE) by 10. 7 % compared to the free cell system. The packed bed bioreactor could be able to deliver 98.56 % of dye removal at an inlet loading rate of 30 mg/L d and 50 mg/L of initial dye concentration.

Treatment of gaseous toluene in an anoxic hybrid bioreactor: Optimization using response surface methodology

This study focuses on treating gaseous toluene emissions from chemical and petrochemical industries using an anoxic hybrid bioreactor (AnHBR) and optimizing the process using response surface methodology (RSM). By varying the gas flow rate (0.05–0.25 LPM) of toluene, the gas residence time (GRT) within the AnHBR ranged from 0.53 to 2.67 h, resulting in an inlet loading rate (ILR) between 0.36 to 14.33 g/m3 h. Simultaneously, the hydraulic retention time (HRT) of the liquid feed was varied from 24 to 72 h in the AnHBR. The operating parameters were varied to determine the optimal combination to achieve the maximum toluene removal, which remained above 96% throughout the operation. At the optimized combinations (flow rate: 0.15 LPM, GRT: 0.89 h, and HRT: 48 h) in AnHBR, toluene removal reached ∼99%, with end products generated consisting of 1.8% CO2 and 92.9% N2 gas. Metagenomics analysis revealed a dominance of toluene degraders (∼38%), highlighting their potential to degrade toluene in the AnHBR. The RSM enhanced toluene treatment in the AnHBR, demonstrating robustness in handling high pollutant loads and its potential for industrial applications.

Highly efficient degradation of ethanol, acetaldehyde, and ethyl acetate removal by bio-trickling filter reactors with various fillers

This study investigates the purification performance of bio-trickling filters (BTFs) using different media to treat ethanol, acetaldehyde, and ethyl acetate in kitchen waste malodorous gases. The media compared included a custom composite medium, pine bark, hollow polyhedral spheres, and ceramic particles. Over 25 days, the composite medium outperformed the traditional media, achieving removal rates of 90.13 % for ethanol, 63.89 % for acetaldehyde, and 82.56 % for ethyl acetate during the biofilm initiation phase, with the others below 60 %. Even under low empty bed residence time and high inlet concentrations, the maximum elimination capacity for ethanol, acetaldehyde, and ethyl acetate was 8.34–14.70 g/m3·h, 9.55–15.06 g/m3·h, and 6.18–10.45 g/m3·h. Kinetic analysis showed the Michaelis-Menten model fit well, indicating enhanced removal potential. High-throughput of 16S rDNA sequencing identified dominant microorganisms like Enterobacteriaceae (13.89 %), Stenotrophomonas (29.23 %), and Acinetobacter (4.09 %) in the composite medium, which thrived even at high pollutant concentrations. Principal component analysis (PCA) demonstrated differences in the microbial composition of the custom composite medium compared to traditional media under varying inlet concentrations and loads. This study provides technical support for the treatment of complex malodorous gas mixtures.

Exploring naphthalene vapor biofiltration: performance and microbial community dynamics with diverse inoculums

AbstractBackgroundNaphthalene is a polycyclic aromatic hydrocarbon, highly dangerous for human health. It is produced as a byproduct of incomplete combustion of organic material and is frequently present in the air. Biofilters offer an effective alternative for its treatment. The aim of this work was to study the treatment of naphthalene vapors through biofiltration using two biofilters: one inoculated with a consortium composed of Fusarium solani and Rhodococcus erythropolis (BF1), and the other inoculated with a consortium of microbial isolates obtained from a previous biofilter eliminating naphthalene vapors.ResultsThe results demonstrate that inoculating a biofilter with a reconstructed consortium of microbial isolates from a naphthalene vapor‐eliminating biofilter allowed a reduction of the startup time from 35 to 5 days, while maintaining a consistent removal capacity (6 g m−3 h−1, equivalent to 80% removal efficiency). It was also observed that the biofilter inoculated with the reconstructed consortium exhibited comparable robustness to a biofilter previously operated for 4 months with naphthalene, with a maximum removal capacity of 14 g m−3 h−1 for a naphthalene inlet load of 17 g m−3 h−1. The study of microbial communities indicates an increase in the bacterial variability, while fungal variability remains low, with Fusarium solani being predominant at 97%.ConclusionsResults obtained during the startup of both biofilters and by challenging biofilters to increasing naphthalene concentrations or decreasing empty bed residence time showed that startup time can be reduced sevenfold by selecting the microbial consortium. An equivalent performance, in the long run, was achieved for both biofilters. © 2024 Society of Chemical Industry (SCI).

Effect of applying a magnetic field on the biofiltration of hexane over long-term operation period.

The present study reports on the effect of magnetic field (MF) intensity on the biofiltration of hexane vapors. MF ranging from 0 to 30 mT (millitesla) was used to evaluate the biofiltration of hexane for 191days under a fixed inlet load of 40gm-3h-1. A homogeneous MF generated by Helmholtz coils was used. The performance of the reactors was evaluated in terms of removal efficiency (RE), elimination capacity (EC), biomass content, and exopolysaccharide (EPS) production. Maximal removal efficiencies of 25%, 36%, and 40% were found for the control (H0), 10 mT (H10), and 30 mT (H30) reactors, corresponding to ECs of 14.2, 15, and 18gm-3h-1, respectively. In the last period (days 94 to 162), H10 and H30 showed 40% of RE improvement compared with Ho. Also, the removal occurred all along the bioreactor height for biofilters exposed to MF. Reactors achieved a total biomass content of 152, 180, and 147mg VS (volatile solids) g-1 dry perlite for H0, H10, and H30, correspondingly, associated with EPS production of 30, 30, and 40mg EPS g-1 VS. The main components of EPS affected by the MF were carbohydrates and glucuronic acid; proteins were slightly affected. Experiments with MF pulses of 4 and 2h confirmed that MF exposure improved the removal efficiency of hexane, and after the pulse, removal enhancement was maintained for 5days. Thus, the MF application by pulses could be an economically and friendly technology to improve the RE of volatile organic compounds (VOCs).

Impact of p-cresol on hydrogen sulfide and ammonia treatment by biotrickling filter and the production of nitrous oxide

Biotrickling filter (BTF) is often used for purification of waste gas from swine houses, with vital information still needed regarding interaction effects among multiple gas pollutants removal and also the formation of byproducts especially nitrous oxide (N2O, a strong greenhouse gas) due to the relative high NH3 concentration level compared to other gases. In this study, gas removal and N2O production were compared between two BTFs, where the inlet gas of BTF-1 contained NH3 and H2S while p-cresol was additionally supplied to BTF-2. At inlet load (IL) between 3.67 and 18.91 g m−3 h−1, removal efficiencies of NH3 exceeded 95% for both BTFs. As alternative strategy, adding thiosulfate improved H2S removal. Interestingly, presence of p-cresol to some extent promoted H2S removal at IL of 0.56 g m−3 h−1possibly due to effect on pH value of circulating solution. Similar to NH3, removal efficiencies of p-cresol were higher than 95% at an average IL of 2.98 g m−3 h−1. Gas residence time, pH of circulating solution and inlet loading were identified as key factors affecting BTF performance, but the response of individual gas compound to these factors was not consistent. Overall, p-cresol enhanced N2O generation although the effects were not always significant. High-throughput sequencing results showed that Proteobacteria accounted for the largest proportion of relative abundance and BTF-2 had much richer microbial diversity compared to BTF-1. Thermomonas, Comamonas, Rhodanobacter and other bacterial genus capable of denitrification were detected in both BTFs, and their corresponding abundances in BTF-2 (10.9%, 8.7% and 5.2%) were all greater than those in BTF-1 (0.4%, 0.3% and 2.0%), indicating that more denitrification may occur within BTF-2 and higher N2O could have been generated. This study provided evidence that organic gas components, served as carbon source, may increase the N2O production from BTF when treating waste gases containing NH3.

Development and application of modified biocarrier immobilized with Bacillus sp. for azo dye degradation: batch and continuous study

The rapid growth of the industry and urbanization induces the consumption of large amounts of freshwater. In the meantime, untreated or partial treatment of industrial (especially textile) wastewater creates a threat to the living system. Azo dyes are generally used in textile industries and cause hazardous effects due to their recalcitrant and toxic nature. The present work emphasized the synergetic effect of adsorption and biodegradation of a modified biocarrier on Congo red (CR) dye removal. The modified biocarrier was developed by entrapping the polyurethane foam and activated carbon with sodium alginate. The adsorption effect was better explained by the Langmuir isotherm than Freundlich isotherm. Various independent factors, including pH, dissolved oxygen (DO), and dye concentration, were optimized in a fixed bed bioreactor (FBBR) filled with Bacillus sp. immobilized modified biocarrier. The highest removal of 95.43% was evaluated at a pH of 7.0, DO of 5.0 mg O2/L, and inlet CR dye concentration of 100 mg/L. Moreover, the continuous operation of FBBR achieved a 91.13% dye removal at an inlet loading rate of 216 mg/L. d at an initial dye concentration of 300 mg/L. The present approach could be an efficient technology for azo dye treatment.

Carbon neutrality in wastewater treatment plants: An integrated biotechnological-based solution for nutrients recovery, odour abatement and CO2 conversion in alternative energy drivers

Wastewater treatment plants play a crucial role in water security and sanitation, ensuring ecosystems balance and avoiding significant negative effects on humans and environment. However, they determine also negative pressures, including greenhouse gas and odourous emissions, which should be minimized to mitigate climate changes besides avoiding complaints. The research has been focused on the validation of an innovative integrated biological system for the sustainable treatment of complex gaseous emissions from wastewater treatment plants. The proposed system consists of a moving bed biofilm reactor coupled with an algal photobioreactor, with the dual objective of: i) reducing the inlet concentration of the odourous contaminants (in this case, hydrogen sulphide, toluene and p-xylene); ii) capturing and converting the carbon dioxide emissions produced by the degradation process into exploitable algal biomass. The first reactor promoted the degradation of chemical compounds up to 99.57% for an inlet load (IL) of 22.97 g m−3 d−1 while the second allowed the capture of the CO2 resulting from the degradation of gaseous compounds, with biofixation rate up to 81.55%. The absorbed CO2 was converted in valuable feedstocks, with a maximum algal biomass productivity in aPBR of 0.22 g L−1 d−1. Dairy wastewater has been used as alternative nutrient source for both reactors, with a view of reusing wastewater while cultivating biomass, framing the proposed technology in a context of a biorefinery within a circular economy perspective. The biomass produced in the algal photobioreactor was indeed characterized by a high lipid content, with a maximum percentage of lipids per dry weight biomass of 35%. The biomass can therefore be exploited for the production of alternative and clean energy carrier. The proposed biotechnology represents an effective tool for shifiting the conventional plants in carbon neutral platform for implementing principles of ecological transition while achieving high levels of environmental protection.

Chemical structure of hydrocarbons significantly affects removal performance and microbial responses in gas biotrickling filters

The control of emissions of short-chain hydrocarbons with different structures is critical for the petrochemical industry. Herein, three two-carbon-containing (C2) hydrocarbons, ethane, ethylene, and acetylene, were chosen as pollutants to study the effects of chemical structure of hydrocarbons on removal performance and microbial responses in biotrickling filters. Results showed that the removal efficiency (RE) of C2 hydrocarbons followed the sequence of acetylene > ethane > ethylene. When the inlet loading rate was 30 g/(m3·h) and the empty bed residence time was 60 s, the RE of ethane, ethylene, and acetylene was 57 ± 4.0 %, 49 ± 1.0 %, and 84 ± 2.7 %, respectively. The high water solubility resulted in the high removal of C2 hydrocarbons, while a low surface tension enhanced the removal of C2 hydrocarbons. Additionally, the microbial community, enzyme activity, and extracellular properties of microorganisms also contributed to the difference in C2 hydrocarbon removal. These results could be referred for the effective control of light hydrocarbon emissions.

Formaldehyde degradation using Biofilter loaded with Compost, Vermiculite and Activated Carbon: Performance and Optimization

<p>Formaldehyde is one of the typical indoor pollutants causing theprevalence of acute health issues among those residing in indoor environments. Biofiltrationis a commonly adopted technique to treat indoor air pollutants. In this investigation, a biofilter was fabricated and compactly filled with compost, vermiculite and activated carbon (65:25:10) as a media composition for enhanced formaldehyde degradation. The influence of formaldehyde inlet concentration (0.01 – 1 gm-3g/m3) and EBRT (30 – 180 s) was studied to evaluate the biofilter performance. Their progression was assessed with dynamic operations in five phases with two stages each. The formaldehyde removal was achieved between the range of 32% to 98% with regular intervals of EBRT at 30, 60, 90, 120, 150 and 180 seconds, which depend upon varying their flow rate and inlet loading rate. The biofilter performance lasted for over 202 days with a 98% formaldehyde removal and 23 g/m3h-1biofilter capacity under the maximum EBRT (180 s) and inlet formaldehyde concentration (1 gm-3g/m3). The experimental findings demonstrated the efficacy of biofilter in withstanding substantial formaldehyde loading rate while maintaining an acceptable EBRT. The primary microbe responsible for formaldehyde degradation was identified to be as gram-negative bacteria.</p>

Biodesulfurization of landfill biogas by a pilot-scale bioscrubber: Operational limits and microbial analysis.

Biogas serves as a crucial renewable energy vector to ensure a more sustainable energy future. However, the presence of hydrogen sulfide (H2S) limits its application in various sectors, emphasizing the importance of effective H2S removal techniques for maximizing its potential. In the present study, the limits of a pilot-scale bioscrubber for biogas desulfurization was study in a real scenario. An increase in the superficial liquid velocity resulted in significant improvements in the H2S removal efficiency, increasing from 76 ± 8% (elimination capacity of 6.2 ± 0.5 gS-H2S m−3 h−1) to 97.7 ± 0.5% (elimination capacity of 8 ± 1 gS-H2S m−3 h−1) as the superficial liquid velocity increased from 50 ± 3 m h−1 to 200 ± 8 m h−1. A USL of 161.4 ± 0.5 m h−1 was able to achieve outlet H2S concentrations as low as 3 ± 1 ppmv (H2S removal efficiency of 97 ± 1%) for 7 days. High superficial liquid velocity favoured the aerobic H2S oxidation reducing the nitrate demand. The maximum EC reached throughout the operation was 50.8 ± 0.6 gS-H2S m−3 h−1 (H2S removal efficiency of 96 ± 1%) and a sulfur production of 60%. Studies in batch flocculation experiments showed sulfur removal rates up to 97.6 ± 0.9% with a cationic flocculant dose of 75 mg L−1. Microbial analysis revealed that the predominant genus with sulfo-oxidant capacity during periods of low H2S inlet load was Thioalkalispira-sulfurivermis (61–69%), while in periods of higher H2S inlet load, family Arcobacteraceae was the most prevalent (11%).

Assessment of pathogen removal efficiency of vertical flow constructed wetland treating septage

Septage refers to the semi-liquid waste material that accumulates in septic tanks and other onsite sanitation systems. It is composed of a complex mixture of human excreta, wastewater, and various solid particles. Septage is a potential source of water pollution owing to presence of high organic content, significant pathogen concentrations, and a range of nutrients like nitrogen and phosphorus. The harmful impacts of septage pollution poses significant risks to public health through the contamination of drinking water sources, eutrophication of water bodies and spread of water borne diseases. Conventional septage treatment technologies often face limitations such as high operational costs, energy requirements, and the need for extensive infrastructure. Therefore, with an aim to treat septage through an alternative cost effective and energy-efficient technology, a laboratory-scale constructed wetland (CW) system (0.99 m2) consisting of a sludge drying bed and a vertical flow wetland bed was utilized for the treatment of septage. The sludge drying bed and vertical flow beds were connected in series and filled with a combination of gravel with varying sizes (ranging from 5 to 40 mm) and washed sand. Canna indica plants were cultivated on both beds to facilitate phytoremediation process. The system was operated with intermittent dosing of 30 Ltrs of septage every day for 2 months. The HRT of the system was fixed at 48 h. The average inlet loads of Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), and Total Suspended Solids (TSS) were measured as 150 ± 65.7 g m−2 day−1, 713 ± 443.9 g m−2 day−1, and 309 ± 66.3 g m−2 day−1, respectively. After treatment, the final effluent had an average load of 6 g m−2 day−1 for BOD5, 15 g m−2 day−1 for COD, and 51 g m−2 day−1 for TSS, indicating that the CW system achieved an average removal efficiency of 88% for BOD, 87% for COD, and 65% for TSS. The average load of total coliforms and helminthes eggs in the influent was recorded as 4 × 108 Colony-Forming Units (CFU) m−2 day−1 and 3 × 107 eggs m−2 day−1, respectively. However, the CW system demonstrated significant effectiveness in reducing microbial contamination, with an average removal efficiency of 99% for both total coliforms and helminthes eggs. The vertical flow constructed wetland system, equipped with pretreatment by sludge drying bed, has proven to be efficient in treatment of septage.

Biofiltration of Volatile organic compounds Using Chir Pine Cone Nuts Inoculated with Pseudomonas putida

Volatile organic compounds (VOCs) and hazardous air pollutants (HAPs) are the major pollutants in industrial and agricultural emissions. This study targets the efficiency and applicability of biofiltration to remove methanol and n-hexane, two common air pollutants, using Chir pine cone nuts as filter media and Pseudomonas putida as the inoculant. The designed biofilter was operated between 25-35°C, with an airflow rate of 0.35 m3 h-1 and nutrient supply of 1-2 L Day-1. From a 60-day operating period, methanol's removal efficiency was higher than n-hexane, with a maximum removal efficiency of 93.91% achieved at an inlet loading rate of 101.39 g m-3h-1 for methanol and 87.96% at 398.46 g m-3h-1 for n-hexane. The effects of varying loading rates on the elimination capacity for both pollutants were also studied. In addition, the temperature profile of the biofilter, microbial analysis, and the BOD concentration of leachate was also studied during the operation period. The findings offer insights into the potential use of Chir pine nuts as filter media for the biodegradation of methanol and n-hexane and provide a foundation for future research to optimize the biofilter system's design and operation to increase its removal efficiency of other contaminants.

Effect of inoculum type, packing material and operational conditions on the biofiltration of a mixture of hydrophobic volatile organic compounds in air

The emission of volatile organic compounds (VOCs) into the atmosphere causes negative environmental and health effects. Biofiltration is known to be an efficient and cost-effective treatment technology for the removal of VOCs in waste gas streams. However, little is known on the removal of VOC mixtures and the effect of operational conditions, particularly for hydrophobic VOCs, and on the microbial populations governing the biofiltration process. In this study, we evaluated the effect of inoculum type (acclimated activated sludge (A-AS) versus Rhodococcus erythropolis) and packing material (mixture of compost and wood chips (C + WC) versus expanded perlite) on the removal of a mixture of hydrophobic VOCs (toluene, cyclohexane and hexane) in three biofilters (BFs), i.e., BF1: C + WC and R. erythropolis; BF2: C + WC and A-AS; and BF3: expanded perlite and R. erythropolis. The BFs were operated for 374 days at varying inlet loads (ILs) and empty bed residence times (EBRTs). The results showed that the VOCs were removed in the following order: toluene > cyclohexane > hexane, which corresponds to their air-water partitioning coefficient and thus bioavailability of each VOC. Toluene is the most hydrophilic VOC, while hexane is the most hydrophobic. BF2 outperformed BF1 and BF3 in each operational phase, with average maximum elimination capacities (ECmax) of 21 ± 3 g toluene m−3 h−1 (removal efficiency (RE): 100 %; EBRT: 82 s), 11 ± 2 g cyclohexane m−3 h−1 (RE: 86 ± 6 %; EBRT: 163 s) and 6.2 ± 0.9 g hexane m−3 h−1 (RE: 96 ± 4 %; EBRT: 245 s). Microbial analysis showed that despite having different inocula, the genera Rhodococcus, Mycobacterium and/or Pseudonocardia dominated in all BFs but at different relative abundances. This study provides new insights into the removal of difficult-to-degrade VOC mixtures with limited research to date on biofiltration.

Biodegradation of formaldehyde gas pollutant by a novel immobilized haloalkaliphilic Salipaludibacillus agaradhaerens strain NRC-R isolated from hypersaline soda lakes

Indoor formaldehyde (HCHO) exceeding the recommended level, is harmful to human health. The goal of this study was to test the performance of a novel haloalkaliphilic (HAP) Salipaludibacillus agaradhaerens strain NRC-R isolated from hypersaline soda lakes and immobilized in alginate-PVA-chitosan gel composite to biodegrade HCHO gas in a stream of air containing various inlet HCHO concentrations (0.7 ppm and 7 ppm) in laboratory scale. The surface images of the immobilized cells/beads were examined by scanning electron microscopy (SEM). The maximum efficiency of HCHO removal was almost 90% with an inlet loading concentration of 0.7 ppm. Stepwise 10 times augment in the HCHO inlet concentration (7 ppm) showed that the immobilized strain was able to control this very high concentration and removed about 60% over 72 h of the treatment. Although several studies have been reported on the isolation of HAP bacteria from various environments, but to our knowledge, this is the first report on the isolation and immobilization of highly HCHO-controlled HAP bacterial strain from soda lakes of hypersaline in Egypt. This bio-system has a high biodegradation capacity via HCHO gas pollutant even with the higher concentrations (7 ppm). It is assumed that HAP S. agaradhaerens NRC-R strain could be utilized in the remediation and biodegradation of HCHO air pollutants. Furthermore, this novel strategy may be considered in employing such bacteria as a biotechnological treatment technique that reduces the environmental pollution rate and might be useful to control other organic compound pollutants in many industrial fields.

A synergistic approach combining Adsorption and Biodegradation for effective treatment of Acid Blue 113 dye by Klebsiella grimontii entrapped Graphene Oxide-Calcium Alginate Hydrogel Beads

This study investigated the degradation of Acid Blue 113 (AB 113) dye using Klebsiella grimontii entrapped Graphene Oxide-Calcium Alginate Hydrogel beads (KG-GO-CA) in a Fluidized Bed Bioreactor (FBBR) under varying inlet loading rates. The minimum fluidization velocity of the KG-GO-CA hydrogel beads in FBBR was found to be 0.15 mm/s. The KG-GO-CA beads showed a maximum removal efficiency of 94.6% at an inlet flow rate of 20 mL/h over 15 days. Reusability studies indicated a removal efficiency of 70.6 ± 2.5% for AB 113 after the 12th cycle. Langmuir adsorption isotherm showed the best fit (R2 = 0.98724) with model parameters of Qm (203.83 mg/g) and Ki (0.0101 L/g). The study also confirmed that treated wastewater was more environmentally safe for domestic and commercial uses than untreated wastewater. The research highlights the potential use of KG-GO-CA hydrogel beads for removing dyes from wastewater.

Experimental and numerical study of a liquid metal magnetohydrodynamic generator for thermoacoustic power generation

Combining a thermoacoustic cycle engine with a liquid metal magnetohydrodynamic (LMMHD) generator will result in a thermal power generation system with no mechanical moving parts and high reliability. This disruptive technology has drawn much attention in space nuclear power generation, especially in recent years. It requires an LMMHD generator to work at a higher frequency than conventional LMMHD generators targeted for ocean wave energy conversion. However, the operating characteristics and loss mechanisms of LMMHD generators at high operating frequencies remain poorly understood, and experimental characterization of such a generator is lacking. In this work, a three-dimensional transient numerical analysis of a high-frequency LMMHD generator is performed based on multi-physics field simulation software COMSOL, to understand the operating characteristics of the generator, and the effects of inlet velocity, load resistance, and operating frequency on the generator’s performance. Furthermore, an LMMHD generator prototype was designed, constructed, and tested under different inlet velocities, load resistances, and frequencies by using a linear compressor for the first time. When the operating frequency and inlet velocity are 15 Hz and 4.3 m/s, the output voltage and current of the generator prototype reached 113 mV and 1720 A, with an output power of 68 W at a corresponding acoustic-to-electric efficiency of 24 %. A discrepancy between the numerical predictions and the experimental results was found, which gave insight into where further improvements can be made. This work reveals the operating characteristics and losses mechanism of LMMHD generators operating at higher frequencies and contributes to the development of high-efficiency generators for thermoacoustic power generation.

An indigenous tubular ceramic membrane integrated bioreactor system for biodegradation of phthalates mixture from contaminated wastewater.

Endocrine-disrupting phthalates (EDPs) are widely used as plasticizers for the manufacture of different plastics and polyvinyl chloride by providing flexibility and mechanical strength. On the other hand, they are categorized under priority pollutants list due to their threat to human health and the environment. This study examined biodegradation of a mixture of dimethyl, diethyl, dibutyl, benzyl butyl, di-2-ethylhexyl, and di-n-octyl phthalates using a CSTB (continuous stirred tank bioreactor) operated under batch, fed-batch, continuous, and continuous with biomass recycle operation modes. For operating the CSTB under biomass recycle mode, microfiltration using an indigenous tubular ceramic membrane was employed. Ecotoxicity assessment of the treated water was carried out to evaluate the toxicity removal efficiency by the integrated bioreactor system. From the batch experiments, the EDPs cumulative degradation values were 90 and 75% at 1250 and 1500mg/L total initial concentration of the mixture, respectively, whereas complete degradation was achieved at 750mg/L. In the fed-batch study, 93% degradation was achieved at 1500mg/L total initial concentration of the mixture. In continuous operation mode, 94 and 85% degradation efficiency values were achieved at 43.72 and 52.08mg/L⋅h inlet loading rate of phthalate mixture. However, continuous feeding with 100% biomass recycle revealed complete degradation at 41.67mg/L⋅h inlet loading rate within the 84h operation period. High seed germination index and low mortality percentage of brine shrimps observed with phthalate degraded water from the integrated bioreactor system revealed its excellent potential in the treatment and toxicity removal of phthalates contaminated environment.

Effects of filling methods on the degradation of ethyl acetate and the microbial community in biofilters

Two biofilters (BFs) for treating ethyl acetate (EA) were constructed with magnetite, activated carbon, perlite and gravel added via layered filling (BF1) or mixed filling (BF2). This study demonstrated the effect of filling method on the degradation of EA and the microbial community in the BFs. The results indicated that the EA removal efficiency (RE) of BF1 and BF2 reached 86.3 ± 3.0 % and 88.9 ± 2.1 %, respectively, under low inlet load (L-IL; (224 g/(m3·h)). Meanwhile, BF2 exhibited stabler RE than BF1 at high IL. BF1 achieved the highest REs of total phosphorus (TP), total nitrogen (TN) and ammonia nitrogen (NH4+-N) under moderate inlet load (M-IL; 336 g/(m3·h)), with average values of 95.8 ± 3.5 %, 83.4 ± 0.4 %, and 85.7 ± 0.3 %, respectively. The removal of TP, TN and NH4+-N in BF2 was superior than BF1 at L-IL and M-IL condition. Moreover, the genera Burkholderia, Acinetobacter, unclassified_Rhizobiales and unclassified_Burkholderiales were the dominant EA-degrading bacteria in BF1, while the EA-degrading bacteria in BF2 were dominated by unclassified_Chloroflexi, unclassified_Bacteroidetes and unclassified_Anaerolineaceae. Furthermore, the mechanism investigation of the mechanism revealed that the types of filling method affect EA degradation by shifting the abundance and diversity of key microorganisms in biodegradation. This study provides an effective strategy for improving the biodegradation efficiency of volatile organic compounds VOCs.