Semi-continuous Operation Research Articles

Evaluating the influence of calcined eggshells and ultrasonication in the Co-digestion of avoidable and unavoidable Food Waste and OLS regression analysis of the reactor system

The technological advancements in the bio-conversion of food waste (FW) into biogas signify substantial advancements in the field of waste management. However, persistent operational challenges like rapid acidification and difficulties in maintaining the C/N ratio in mono-digestion remain, despite extensive research efforts. The present study aims to evaluate the reactor performance in co-digestion, specifically using a 1:1 ratio of unavoidable food waste (UAFW) and avoidable food waste (AFW), with the addition of calcined eggshells as an additive. Further, the study employs Ordinary Least Square (OLS) regression modeling to predict the biogas production from the co-digestion process. The experimental process involves ultrasonication pretreatment, focusing on calcined eggshells for their ability to preserve carbohydrates via Ca(OH)2, an alkaline material. The semi-continuous operation of the reactor spanned for 120 days and was divided into three phases with varying Organic Loading Rates (OLR) from 0.6 to 2.2 gVS/l/d. Characterization studies such as SEM, FTIR and TGA-DTA were performed to validate the pretreatment method and addition of egg-shells. Results indicated increased OLR led to higher Volatile Solids (VS) reduction. This was attributed to the calcined eggshells' role in adsorbing NH4+ and NO3− ions while maintaining pH levels, resulting in significantly higher biogas production. The multiple regression models used in the study yielded promising results, surpassing simple linear regression, with an adjusted R-squared value > 0.9 and p-value <0.05. The model effectively anticipated the specific methane yield, demonstrating the capability to improve energy production by co-digesting AFW and UAFW. The study presents an opportunity to divert organic waste from landfills, reduce greenhouse gas emissions, and promote sustainable waste management by using bio-waste additives, reducing reliance upon synthetic chemicals.

Batch and semi-continuous treatment of cassava wastewater using microbial fuel cells and metataxonomic analysis

The treatment of agroindustrial wastewater using microbial fuel cells (MFCs) is a technological strategy to harness its chemical energy while simultaneously purifying the water. This manuscript investigates the organic load effect as chemical oxygen demand (COD) on the production of electricity during the treatment of cassava wastewater by means of a dual-chamber microbial fuel cell in batch mode. Additionally, specific conditions were selected to evaluate the semi-continuous operational mode. The dynamics of microbial communities on the graphite anode were also investigated. The maximum power density delivered by the batch MFC (656.4 μW m-2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{-2}$$\\end{document}) was achieved at the highest evaluated organic load (6.8 g COD L-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{-1}$$\\end{document}). Similarly, the largest COD removal efficiency (61.9%) was reached at the lowest organic load (1.17 g COD L-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{-1}$$\\end{document}). Cyanide degradation percentages (50–70%) were achieved across treatments. The semi-continuous operation of the MFC for 2 months revealed that the voltage across the cell is dependent on the supply or suspension of the organic load feed. The electrode polarization resistance was observed to decreases over time, possibly due to the enrichment of the anode with electrogenic microbial communities. A metataxonomic analysis revealed a significant increase in bacteria from the phylum Firmicutes, primarily of the genus Enterococcus.

Anaerobic Co-Digestion of Fish Sludge Originating from a Recirculating Aquaculture System

Anaerobic co-digestion (AcoD) of fish sludge (FS) with food waste (FW), and fruit and vegetable waste (FVW) for biogas and methane production was optimised in small-scale bioreactors, and batch and semi-continuous pilot-scale digesters, under mesophilic (37 ℃) conditions. An experimental mixture design was first applied to small-scale biomethane potential (BMP) tests, to determine the optimal mixture proportions of the AcoD of FS, FW, and FVW that maximise the specific methane yield (SMY in NmLCH4 gVS−1). The optimal mixture proportion was 67%FS:18%FW:19%FVW (w/w), producing 401 mLCH4 gVS−1, which was 8 times higher than the SMY when FS was mono-digested (48 mLCH4 gVS−1). The SMY achieved in batch pilot-scale digesters were 70–82% of methane yields obtained in BMP tests under the same operating conditions, with stable biogas production and no apparent inhibition during the batch run. Semi-continuous operation of the pilot-scale digester was undertaken with organic loading rates (OLRs) of 1, 2, and 3 gVSL-1d-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$gVS{L}^{-1}{d}^{-1}$$\\end{document}, provided intermittently. However, the digester did not achieve stable biogas production at all of the evaluated OLRs, due to the intermittent feeding and accumulation of volatile fatty acids (VFAs): Improved process stability was achieved at an OLR of 2 gVSL-1d-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$gVS{L}^{-1}{d}^{-1}$$\\end{document}, compared to OLRs of 1 and 3 gVSL-1d-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$gVS{L}^{-1}{d}^{-1}$$\\end{document}. Optimisation of the AcoD process resulted in attractive biomethane yields from FS with FW and FVW co-feeds, indicating that producing biogas from co-digestion of FS with relevant substrates is a valuable managing tool for FS, while simultaneously providing renewable energy. The work provides novel data that elucidated optimal proportions in which to combine FS, FW and FVW to obtain optimal biogas production, and provided important new information relevant for the scale up and continuous operation of an AD process for treating FS.Graphical

Anaerobic digestion of winery solid waste in a two-stage membrane process: Effect of loading rate on biomethane production

The wine industry causes a high amount of solid waste with high organic content at different parts of the production line. One of the best strategies to overcome organic solid waste management problem is anaerobic digestion, as It allows renewable energy production and waste reduction together. The OLR is considered one of the most important operating parameters in continuous or semi-continuous anaerobic operations, as it affects the overall performance of anaerobic digestion systems. Therefore, appropriate OLR determination plays a crucial role in anaerobic digestion. This study investigated the effect of OLR on the performance of a TAnMBR treating (winery solid waste) WSW in terms of biogas and biomethane production. To this end, the production of biogas and biomethane from WSW via a TAnMBR at four different OLRs (0.5 0.75 1.0 1.5 gVS/Lreac d) was investigated. Biogas production rates were 677, 850, 1265, and 566 ml/gVS and biomethane production rates were 352, 450, 679, and 251 ml/gVS respectively, during 0.5 0.75 1.0 1.5 gVS/Lreac d OLR operating conditions. Results revealed that proper biogas and biomethane production can continue until the OLR is 1.5. VFA accumulation can be considered as the main inhibition reason, at 1.5 OLR VFA/Alk ratio increased up to 1.6 with 1864 mgHAc/L VFA concentration. Additionally, phenol and sulfate concentrations were below 45 and 48 mg/L during operation, respectively, therefore it is considered that no inhibition occurred due to these parameters.

Development of a hybrid bio-purification process of lactic acid solutions employing an engineered E. coli strain in a membrane bioreactor

BackgroundA potential alternative to lactic acid production through sugar fermentation is its recovery from grass silage leachate. The separation and purification of lactic acid from fermentation broths remain a key issue, as it amounts to up to 80% of its industrial production cost. In this study, a genetically engineered E. coli strain (A1:ldhA), that cannot catabolize lactic acid, has been used to selectively remove impurities from a synthetic medium comprising typical components (i.e., glucose and acetic acid) of green grass silage leachate. A systematic approach has been followed to provide a proof-of-concept for a bio-purification process of lactic acid solutions in a membrane bioreactor operating in semi-continuous mode.ResultsThe synthetic medium composition was initially optimized in shake-flasks experiments, followed by scale-up in bench-scale bioreactor. Complete (i.e., 100%) and 60.4% removal for glucose and acetic acid, respectively, has been achieved in batch bioreactor experiments with a synthetic medium comprising 0.5 g/L glucose and 0.5 g/L acetic acid as carbon sources, and 10 g/L lactic acid; no lactic acid catabolism was observed in all batch fermentation tests. Afterwards, a hybrid biotechnological process combining semi-continuous bioreactor fermentation and ultrafiltration membrane separation (membrane bioreactor) was applied to in-situ separate purified medium from the active cells. The process was assessed under different semi-continuous operating conditions, resulting in a bacteria-free effluent and 100% glucose and acetic acid depletion, with no lactic acid catabolism, thus increasing the purity of the synthetic lactic acid solution.ConclusionsThe study clearly demonstrated that a bio-purification process for lactic acid employing the engineered E. coli strain cultivated in a membrane bioreactor is a technically feasible concept, paving the way for further technological advancement.

Significance of homogeneous operation in light-assisted fixed-bed bioprocess under ammonia stress: Optimization, long-term operation and metagenomic analysis

Activating microbes with light is a promising strategy for addressing ammonia-stressed anaerobic digestion (AD). However, as a critical in-process parameter, homogenous operation, in light-assisted AD amended by bio-fixed bed has received limited attention. This research endeavors to establish a uniform-illuminated biosystem and assess its practical feasibility through a 90-day semi-continuous operation at pilot scale under solar light illumination. With optimal stirring mode (intermittent stirring for 3 min every 15 min), robust methane yields were achieved across various organic loads, reaching 88.7–94.3% of theoretical yield under high ammonium stress (3500 mg/L). The metagenomic analysis unveiled that uniform illumination triggered synergistic effects in AD, fostering a diversified microbial consortium, enhancing carbohydrate and methane metabolism, and facilitating the formation of an electroactive bio-cluster. This study underscores the significance of homogenous illumination in AD systems for efficient waste-to-energy conversion, highlighting the implementation of solar light as a greener approach for scale-up application.

Emerging Frontiers in Multichannel Membrane Capacitive Deionization: Recent Advances and Future Prospects.

Capacitive deionization (CDI) has emerged as a promising desalination technology and recently promoted the development of multichannel membrane capacitive deionization (MC-MCDI). In MC-MCDI, the independent control of multiflow channels, including the feed and electrolyte channels, enables the optimization of electrode operation in various modes, such as concentration gradients and reverse voltage discharge, facilitating semicontinuous operation. Moreover, the integration of redox couples into MC-MCDI has led to advancements in redox-mediated desalination. Specifically, the introduction of redox-active species helps enhance the ion removal efficiency and reduce energy consumption during desalination. This systematic approach, combining principles from CDI and electrodialysis, results in more sustainable and efficient desalination. These advancements have contributed to improved desalination performance and practical feasibility, rendering MC-MCDI an increasingly attractive option for addressing water scarcity challenges. Despite the considerable interest in and potential of this process, there is currently no comprehensive review available that covers the operational features and applications of MC-MCDI. Therefore, this Review provides an overview of recent research progress, focusing on the unique cell configuration, vital operation principles, and potential advantages over conventional CDI. Additionally, innovative applications of MC-MCDI are discussed. The Review concludes with insights into future research directions, potential opportunities in industrial desalination technology, and the fundamental and practical challenges for successful implementation.

Valorization of organic carbon in primary sludge via semi-continuous dark fermentation: First step to establish a wastewater biorefinery

In this study, lab-scale, bench-scale, and pilot-scale experiments were carried out to optimize short-chain fatty acids production from primary sludge. Batch tests showed the requirement of short retention times and semi-continuous operation mode showed a plateau of maximum daily productivity at 36-hours hydraulic retention time with minimal methanation. Optimization from pH 5 to pH 10 at 36 h-hydraulic retention time under long-term semi-continuous operating mode revealed that production of short-chain fatty acids was pH dependent and highest yields could be achieved at pH 7 by establishing optimum redox conditions for fermentation. Pilot-scale experiments at 32 °C showed that daily productivity (3.1 g∙Lreactor-1∙dHRT-1) and yields (150 mg∙gVS-1; OLR = 21 gVS∙Lreactor-1∙dHRT-1; pH 7) of short-chain fatty acids could be significantly improved, specifically for acetic and propionic acids. From these results, a robust dark fermentation step for recovery of valuable products from the solids treatment step in a biorefinery can be achieved.

Electrocoagulation Technique for Treating Swine Slaughterhouse Wastewater from Batch to Semicontinuous Operation Mode

In this study, industrial swine slaughterhouse wastewater was treated by electrocoagulation process using batch and semicontinuous operation systems. Electrochemical technique was carried out in batch operation mode during 2.5 h applying different current densities in sulfate and chloride media. After finding the best operating parameters in batch mode (lab-scale), the process was transferred to a semicontinuous pre-pilot scale process using a filter-press FM01-LC type electrochemical reactor fitted with flat plate aluminum electrodes. In this stage, distinct current densities and mean linear flow rates were assessed.Total organic carbon, chemical oxygen demand, total phosphorus, total nitrogen, and potassium among other parameters were analyzed during both treatments. The industrial swine slaughterhouse wastewater contained TOC 333 mg L–1, COD 1765 mg L–1, TP 13.55 mg L–1, TN 327 mg L–1, K 45 mg L–1, turbidity 102 NTU, color –absorbance 0.90 A.U. at 415 nm–, conductivity 1.9 mS cm–1, and pH 6.9. The highest TOC removal efficiency (72.7%), in semicontinuous process, was found at j = 25 mA cm-2 and ur = 0.64 cm s-1 with an energy consumption of 19.80 kW h m-3. Residual COD and TP concentrations met the international standard limits. Moreover, complete discoloration and disinfection were achieved. EDXRF, SEM, EDAX, XRD, and FTIR analyzes indicate pollutants were removed by adsorption on aluminum/iron hydroxides/oxyhydroxides.

Integrated Semi-Continuous Manufacturing of Lentiviral Vectors Using a HEK-293 Producer Cell Line

There have been considerable efforts on improving the lentiviral vector (LV) system and their production. However, there remains the persisting challenge of producing a sufficient quantity of LVs at manufacturing scale to support treatments beyond early clinical trials. Furthermore, their innately labile nature poses an equally important obstacle in LV production. As LVs lose function over time and they are sensitive to environmental factors in each unit operation in the bioprocess workflow, integrated continuous manufacturing is an attractive strategy for process intensification. This manuscript describes the implementation of nuclease treatment, clarification, and capture step in a semi-continuous mode. Combining the clarification and loading of the capture step as well as operating those steps in parallel to the purification of the capture step expedite the processing time, reducing it by 4-fold as compared to processing the same volume in batch mode using the same membrane size. This semi-continuous operation also improves the recoveries of functional vector particles and total vector particles by 26% and 18%, respectively, showing an added benefit in loading the capture membranes in series in continuous flow chromatography. Building on previously published upstream work using a scalable cell retention device in perfusion mode, this manuscript demonstrates the integration of upstream and downstream in a semi-continuous manner, reducing processing and hold times as well as showing improvements in LV product quality and recovery.

Enhancing industrial swine slaughterhouse wastewater treatment: Optimization of electrocoagulation technique and operating mode

In this study, industrial swine slaughterhouse effluents were treated by an electrocoagulation process (EC) with aluminum and iron electrodes. Batch and semicontinuous operation were performed. EC tests were carried out in batch operating mode for 2.5 h using fixed current densities (j = 10, 20, and 30 mA cm−2) in sulfate and chloride media. At the laboratory scale, higher TOC removal efficiencies were observed using aluminum electrodes at 20 mA cm−2 without the addition of a supporting electrolyte (82.7%). However, the EC process with Fe electrodes consumed 43.6% less energy.After the best operating parameters were found at the laboratory scale, the process was tested as a semicontinuous prepilot process using a filter-press FM01-LC-type electrochemical reactor equipped with flat plate aluminum electrodes. In this stage, current densities and mean linear flow rates were assessed. The highest TOC removal efficiency of 72.7% (i.e., residual TOC concentration of 85.18 mg L−1) in the semicontinuous process was achieved by the application of j = 25 mA cm−2 and ur = 0.64 cm s−1 with an energy consumption of 19.80 kW h m−3. The residual COD and TP concentrations met the international standard limits. Moreover, complete decoloration and disinfection were accomplished. EDXRF, SEM, EDAX, XRD, and FTIR analyses indicated that pollutants were removed by adsorption on aluminum/iron hydroxides/oxyhydroxides.

Treatment of mixed wastewater by vertical rotating microalgae-bacteria symbiotic biofilm reactor

A novel vertical rotating microalgae-bacteria symbiotic biofilm reactor was built to treat the mixed wastewater containing municipal and soybean soaking wastewater. The reactor was operated in both sequential batch and semi-continuous modes. Under the sequential batch operation mode, the maximum removal rates for Chemical Oxygen Demand (COD), Total Nitrogen (TN), Total Phosphorus (TP), and Ammonia Nitrogen (NH4+-N) of the mixed wastewater were 95.6 %, 96.1 %, 97.6 %, and 100 %, respectively. During the semi-continuous operation, the water discharge indices decreased gradually and eventually stabilized. At stabilization, the removal rates of COD, TN, and NH4+-N achieved 98 %, 95 %, and 99.9 %, respectively. The maximum biomass productivity of the biofilm was 2.69 g·m−2·d-1. Additionally, the carbohydrate, protein and lipid comprised approximately 22 %, 51 % and 10 % of the dry weight of Chlorella. This study demonstrates the great potential of the microalgae-bacteria symbiotic biofilm system to treat food and domestic wastewater while harvesting microalgal biomass.

Numerical analysis of two-bed adsorption thermophysical battery

Air conditioning systems powered by waste energy sources, such as solar-driven adsorption air conditioning systems, hold significant importance. The present study delves into the performance assessment of a silica gel-based adsorption thermophysical battery (ATB) under varying operational conditions. Advanced cycles featuring a two-bed configuration have been devised to enable semi-continuous operation and refrigeration. This novel design presents a compact ATB that integrates the evaporator and condenser within a single heat exchanger, referred to as the Evaporator-Condenser Unit (ECU), thereby reducing the overall size and cost of the ATB system. The operating and design characteristics of the two-bed adsorption system were thoroughly explored using a theoretical model developed through MATLAB software. Evaluations were conducted on various performance metrics of the ATB, encompassing the coefficient of performance (COP), cooling capacity, specific cooling power, adsorption isotherm, and kinetics. A theoretical approach was formulated using the lumped parameter (LPM) and modified Freundlich adsorption equations. It can be deduced that the inlet temperature of the hot coolant exhibited a direct proportion with both refrigeration effect (RE) and specific cooling power (SCP) while inversely affecting the coefficient of performance (COP). A decrease in coolant temperature from 313 to 303 K resulted in a noteworthy 13.4 %. Furthermore, it was observed that COP exhibited a direct proportionality with the flow rate of chilled and cooled water while inversely relating to the flow rate of hot water.

Enhancing biogas production from cheese whey using Zero-Valent Iron: A comparative analysis of batch and semi-continuous operation modes

Cheese whey (CW) is the primary by-product of dairy industries, and its anaerobic treatment presents several challenges. Among these is the production of high levels of volatile fatty acids (VFAs) due to rapid biodegradation, which leads to a drop in pH and adversely impacts methanogenesis. This study aims to evaluate the impact of Zero-Valent Iron (ZVI) on the anaerobic digestion of CW under both semi-continuous and batch conditions. Since ZVI generates H2 and increases pH under soluble CO2 conditions, the study also focuses on the effects of ZVI on solubilization/hydrolysis, acidification, and microbial response. Three anaerobic bioreactors (R25-PZVI with 25 g/L powder ZVI, R50-SZVI with 50 g/L scrap ZVI, and R-Control without ZVI), at semi-continuous mode, treated cheese whey at varying organic loading rates. After 118 days, R25-PZVI showed the highest CH4 yield and best COD removal, followed by R50-SZVI. Despite NaOH additions, it maintained a lower VFA/ALK ratio than the control. Under semi-continuous mode, CH4 composition in R25-PZVI was 59%, rising to over 95% under batch conditions due to the higher pressure and subsequent solubilization of H2 and CO2. The ZVI mainly impacted methanogenesis and acidogenesis and not solubilization/hydrolysis. 25-PZVI's superior performance was due to its increased H2 generation and alkalinity over 50 g/L SZVI, as was found in the abiotic test. Under semi-continuous conditions, Methanobacterium (a hydrogenotrophic methanogen) and Methanosarcina were the dominant genera in the R25-PZVI reactor. Under batch conditions, Methanothrix displayed a higher abundance, which explained the increased acetic acid utilization.

Selective chromium and copper recovery from wastewater using flow-electrode capacitance deionization: In-situ reduction mechanism regulating metal charging characteristics

Recovering valuable metal resources from industrial wastewater has environmental and economic significance. Flow-electrode capacitive deionization (FCDI) has been successfully used to remove salt and heavy metals. However, the use of this technology in heavy metal treatment has several limitations, including low selectivity, poor long-term stability, and production of low-quality metal products. In this study, a new strategy for recovering chromium (Cr) from wastewater was proposed using an in-situ reduction method. A liquid membrane chamber (LMC) was introduced into a classic three-chamber FCDI and an extraction solution containing Na2SO3 and NaCl was used to capture Cr in wastewater. During FCDI operation, the CrO42− ions entered the LMC were immediately reduced to Cr3+ and retained in the extraction solution. Completing anions (i.e., Cl−) in the extraction solution maintained the concentration of SO32− ions, and thereby reducing the consumption of reagents. The improved FCDI system exhibited satisfactory separation performance and high stability during semi-continuous operation. Freshwater, Cr, and copper were obtained in the separation chamber, LMC, and flow electrode chamber, respectively. The facile approach may open the doors for the separation and recovery of metal resources from water/wastewater with high scalability and universality.

Semi-Continuous Descent Operation: A Fuel-Efficient Interval Management Algorithm

This paper presents a fuel-efficient interval management algorithm called semi-continuous descent operation (semi-CDO) to support air traffic controllers in issuing altitude and velocity instructions to arriving aircraft to ensure proper separation. The control logic of semi-CDO is stated as an optimization problem of minimizing the fuel consumption of the descending trajectory based on the prediction model under the separation constraints. Numerical experiments simulating the arrival traffic at Kansai International Airport in Japan were performed to verify the effectiveness of the proposed algorithm. The results showed that semi-CDO achieves the fuel-efficient descent for multiple arrival aircraft while maintaining proper separation between them.

Enhancing crotonaldehyde biodegradation in petrochemical wastewater: Role of electron donors in microbial electron transfer systems

Crotonaldehyde is typical inhibitory compound of wastewater discharged in the petrochemical industry. To resolve the inhibition of crotonaldehyde on microorganism, electron donors (cellose, glucose and ethanol) were dosed to accelerate the biodegradation of crotonaldehyde by semi-continuous operation experiments. The results indicated that crotonyl alcohol was the most dominant biodegradable product of crotonaldehyde, and its conversion rates dosing ethanol, glucose and cellose as electron donors (2000 mgCOD/L) were 1.84, 1.46 and 1.21 times higher than that in control test when the initial concentrations of crotonaldehyde was 500 mg/L, respectively. Furthermore, the ethanol as electron donor was superior to cellose and glucose in relieving the inhibition of crotonaldehyde on the processes of acidogenesis, acetogenesis, and methanogenesis duo to the more electron release, faster electron transfer efficiency, less electron competition. Last, the enrichment of electro-active bacteria such as Syntrophobacter, Geobacter and the bacteria associated with reverse β-oxidation pathway (RBO) such as Clostridium_sensu_stricto_12 also proved that higher electron transfer system (ETS) activity was obtained in the reactor dosed ethanol as electron donor. This study suggests that dosing electron donors is an efficient strategy to accelerate the biodegradation of crotonaldehyde, and the results could be referred to pretreat wastewater containing aldehyde pollutants.

Enhanced degradation of bisphenol S in water using a combination process of electrochemical oxidation with periodate activation

This paper proposed a new system, electrochemically activated periodate (E/PI) with a Ti/RuO2-IrO2 anode, for the efficient degradation of endocrine disrupting chemical bisphenol S (BPS). The results suggested that the degradation efficiency reached 100 % after 30 min at the conditions of PI 0.25 mM, current density 2 mA/cm2 and pH 7.2. In comparison to other activators of PI (e.g., ultrasonic or visible light) and electrochemically activated different oxidants (e.g., persulfates or H2O2), the E/PI system was found to be more effective in degrading BPS. The system showed a faster degradation rate with increasing current density or PI dose, and demonstrated a strong anti-interference capability against the humic acid and inorganic anions present in water. The system also demonstrated excellent stability, and can still remove 100 % of BPS even after 40 intermittent semi-continuous operations (20 h). The singlet oxygen (1O2) was identified as the primary reactive oxygen species (ROS) for the BPS degradation, as revealed by the free radical quenching and the electron paramagnetic resonance (EPR) experiment. In addition, the intermediates of BPS during its degradation process and main degradation pathways were proposed. The E/PI system can be used as a new AOPs and has practical application potential in water treatment.

Constructing carbon-based materials loaded with MOFs to realize efficient anaerobic digestion of rural organic waste

The application of anaerobic digestion (AD) technology could convert rural organic waste (ROW) into renewable energy such as methane, which can help to mitigate the scarcity of fossil fuels and positively impact the global environment. However, the inhibition of ammonia nitrogen remains a significant obstacle to the methane production process with high concentrations of AD. Hence, in this study, three adsorption materials for ammonia nitrogen, namely FeMn-MOF, FeMn/MOF-CFs, and FeMn/MOF-CFC, were synthesized through distinct protocols. Their ability to mitigate the effect of ammonia nitrogen inhibition was investigated in a Continuous Stirred-Tank Reactor (CSTR) with total solid (TS) concentration of 10% under a semi-continuous operation of ROW digestion system. The results show that the addition of Metal-Organic Frameworks (MOFs) material substantially mitigated the inhibition of ammonia nitrogen and enhanced methane production. Compared with the control group, FeMn/MOF-CFC exhibited the best performance, with a 40.21% decrease in ammonia nitrogen concentration and 66.96 L/L-reactor cumulative methane production. Furthermore, the potential mechanisms underlying microbial community characteristics were explored, indicating that the addition of FeMn/MOF-CFC to AD provides the optimal enhancement of methane production. The addition of FeMn/MOF-CFC can enrich Methanosarcina, enhance the acetoclastic pathway for methane production, and increase the relative activity of coenzyme F420, achieving a 193.68% increase.

Process for nutrient recycling from intensive aquaculture through microalgae-bacteria consortium

This work studies a biological process based on a microalgae-bacteria consortium for recycling nutrients in a recirculating aquaculture system (RAS) implanted in an intensive marine aquaculture farm. Additionally, some techniques were used for microalgae biomass harvesting and tested the effectiveness of filtration by a column with multi-layer sand to reduce the solids concentrations in the effluent.The consortium was grown in photobioreactors in batch and semi-continuous operation modes using the solids concentrated stream generated in the RAS system. The semi-continuous operation showed a high percentage of TDN and TDP removal, achieving final concentrations of 1.09 ± 0.02 mg·L−1 and 0.01 ± 0.01 mg·L−1, respectively, while DOC was reduced to 3.87 ± 0.06 mg·L−1. The values of productivity 44 ± 9 mg TSS·L−1 indicated that the studied stream is a suitable culture medium for the growth of the microalgae-bacteria consortium.A combination of harvesting techniques was studied, coagulation-flocculation-settling and coagulation-flocculation-flotation. The first step was to optimise the dose of FeCl3 through the coagulation-flocculation test to pre-concentrate the biomass generated, achieving an optimal dose of 0.106 mg Fe·mg TSS−1. Then, two separation processes were applied to the stream and compared: settling and flotation. The maximum removal efficiency (90.2 ± 0.3 %) was obtained in the settling process, so the coagulation-flocculation-settling was select as the best combination of harvesting techniques.Finally, sand filtration was studied as an effluent refining process to improve solids reduction of the water obtained in the harvesting step resulting in an effluent with 17.18 ± 1.49 mg TSS·L−1.The proposed sequence process is capable of recycling nutrients from an intensive marine aquaculture farm by using these resources via transformation into microalgae biomass and generating quality effluent.