Gas Sparging Research Articles

Impact of preacidification on the functionality and insoluble calcium levels of Low-Moisture Part-Skim Mozzarella made from high-casein milk

The use of low-concentration factor ultrafiltered (LCF-UF) milk for cheesemaking has become popular in recent years. Research on using LCF-UF milk to make low-moisture part-skim (LMPS) Mozzarella manufacture is limited due to concerns about the negative impact of the higher casein content on functional properties, such as melt and stretch. Pre-acidification (PA) (reflects acid added to milk before the addition of the starter culture) has been used in low-fat and nonfat Mozzarella cheeses to lower calcium levels and improve their texture and melting properties. We explored the use of PA to reduce the insoluble calcium content of cheese (calcium that is a crosslinking material for the casein proteins) and its impact on the functionality of LMPS Mozzarella made from high casein (4.2%) milk. Seven vats of LMPS Mozzarella, with a control (no PA), 2 pH values for PA (6.40 and 6.00) and 3 different acidification methods (use of acetic, citric, or carbonic acid from carbon dioxide) were evaluated for their impact on solubilization of colloidal calcium phosphate during LMPS manufacture. Composition, proteolysis, microstructural and functional changes in the LMPS cheeses were monitored during 90 d of refrigerated storage. All cheeses had similar composition except for the cheese made with milk PA with carbonic acid, which had a lower fat-in-dry matter probably due to foaming observed in this sample during the gas sparging. The cheese made with milk PA with citric acid to pH 6.00 had the lowest amount of total and insoluble calcium compared with other cheeses at all steps during cheese manufacture and storage, likely due to the calcium chelating ability of citric acid. The cheese that was made with milk PA with citric acid to pH 6.40 had a trend of slightly lower (not significant) total and insoluble calcium during cheese manufacture compared with other cheeses that were made with milk PA to pH 6.40. The pH value in all the cheeses remained similar throughout 90 d of storage, whereas the cheese that was made with milk PA with citric acid to pH 6.00 had the lowest pH values during storage. Treatment significantly (P < 0.05) impacted instrumental hardness, the maximum loss tangent during heating, the melting temperature and the storage modulus values measured at 70°C. Proteolysis was not impacted by treatment suggesting that typical aging should occur. Cheese that was PA with citric acid to pH 6.00 initially had lower maximum loss tangent values and higher hardness, possibly due to the lower pH value of this cheese. The performance of cheeses on pizza was assessed using Sensory Spectrum® method and quantitative descriptive analysis. The PA of cheese milk with citric acid helped to reduce the insoluble Ca level and at 30 and 90 d of storage, these cheeses had lower first chew hardness, lower chewiness, and lower strand thickness values compared with other cheeses. The use of PA could help improve the functionality of LMPS Mozzarella made from milk high in casein with citric acid being the most efficient in dissolving the insoluble calcium from casein.

Destruction of perfluorooctane sulfonic acid (PFOS) in gas sparging incorporated UV-indole reductive treatment system – Benefits and challenges

Ultraviolet (UV) reductive treatment systems that generate hydrated electrons (eaq-) have emerged as a promising technology for the destruction of chemically inert per- and polyfluoroalkyl substances (PFAS). Here, we report on the evaluation of an indole derivative-based UV reductive treatment system that utilizes the amphipathic properties of PFAS at the gas-water interface (via nitrogen (N2) sparging) for more energy-efficient destruction of perfluorooctane sulfonic acid (PFOS). Results from this work illustrated that N2 sparging within UV systems can enhance the degradation and defluorination of PFOS compared to non-sparged conditions, but their overall treatment efficiency is low to industry standard. The inadequate system performance is likely originated from the insufficient accumulation of electron sources at the gas-water interface and their low water solubility level. In addition, carbonate species, which are ubiquitous in natural water and commonly applied as buffers in UV reductive treatment systems, negatively impact PFOS defluorination when indole is the electron source. The species-specific quenching imposed by carbonate species (e.g., HCO3- > H2CO3*) indicates that naturally occurring constituents and varying reactor conditions can substantially influence the remediation of PFOS. Other notable findings in this work include: 1) gramine, a cationic indole derivative, was able to remove > 99 % PFOS mass via electrostatic interaction within 0.5 h of reaction, signifying the electron source's structural property importance in UV reductive treatment systems, and 2) energy consumption calculations showed indole species are less energy-efficient as electron sources for PFOS destruction comparing to sulfite-iodide, but performance tradeoffs exist in both systems. The results of this work revealed both the benefits and challenges of utilizing N2 sparging and indole derivatives in UV-PFAS reductive treatment processes and provided critical information needed to improve the prediction and design of similar PFAS destruction technologies.

Recommendation on the selection of powdered activated carbon as carrier to enhance performance of polymeric UF membrane

The addition of powdered activated carbon (PAC) has been widely accepted as a solution to alleviate membrane fouling and maintain a sustainable flux in membrane bioreactor (MBR) and anaerobic membrane bioreactor (AnMBR). This is due to PAC's unique characteristics, such as serving as a supportive medium for bacterial attachment and growth, achieving adsorption of organic foulants and providing abrasion effect that minimizes the formation of cake layers on membrane surfaces. While majority of ultrafiltration (UF) membranes used in MBR and AnMBR application are polymeric, no study has yet investigated the integrity of polymeric UF membranes with the addition of PAC adsorbents. The abrasive effects of PAC on membrane surfaces under gas sparging in AnMBR or air scouring in MBR have not been studied, and no guidelines have been established for selecting a reliable PAC for such purposes. To address these concerns, this study systemically investigated the integrity of polymeric UF membranes with five different types of PACs to establish recommendations for PAC selection. Based on the integrity testing of polymeric UF membranes, a recommendation for PAC selection was formulated, highlighting bulk density and Gold Number (GN) as pivotal criteria. Five distinct types of PACs were studied to determine the optimal characteristics for polymeric UF membranes, considering variations in raw materials (coal-based and wood-based), activation methods (chemical and steam), particle morphology (sharp and granular), bulk densities (ranging from 0.23 to 0.6 kg/L) and GNs (spanning from 0.1 to > 6.0). The investigation extended beyond 100 d or until irreversible defects were observed in the UF membranes. This study provides guidelines for selecting PACs to be used with polymeric UF membranes, aiming to improve membrane performance while minimising their impact on membrane surfaces.

A real-time oxygen uptake rate monitoring approach suitable for the antibody production process

Significant progress has been achieved in large-scale mammalian cell culture technology for biotherapeutics manufacturing over the past decades, necessitating the Process Analytical Technology (PAT) for the real-time measurement of critical quality attributes and the guidance for precise process control to ensure productivity, quality, and consistency. The Oxygen Uptake Rate (OUR) serves as a crucial indicator for characterizing the energy metabolism of mammalian cells, offering insights into cellular state and metabolism dynamics. However, current cellular OUR monitoring in antibody production depends mainly on costly gas analyzers or periodic manual sampling. Here, we introduce a novel method for in-line monitoring of cellular OUR in bioreactors based on the stationary liquid phase balance (SLPB) theory, which extends its applicability to diverse aeration and foam conditions without additional equipment or labor expenditures. We modeled the kLa of the aerated stirred bioreactor, assessed the influence of foam on liquid surfaces induced by gas sparging on oxygen transfer, and processed raw OUR data using a sliding filter. The established method was applied to monitoring the real-time OUR of Chinese Hamster Ovary (CHO) cell cultures for antibody production, demonstrating its excellent accuracy, sensitivity and readability. Aligned with the Quality by Design (QbD) concept, this real-time OUR estimation enables rapid detection of metabolic changes, revealing cellular physiology and facilitating precise feedback control in biotherapeutics manufacturing.

Modeling and Evaluation of PFOS Retention in the Unsaturated Zone above the Water Table

AbstractUnderstanding the retention of per‐ and polyfluoroalkyl substances (PFAS) in the vadose zone is vital to the management of impacted sites. This paper examines PFAS retention in the unsaturated zone above the water table using a mathematical model, MODFLOW‐USG‐Transport PFAS or “USGT‐PFAS.” The USGT‐PFAS model incorporates adsorption onto air‐water interfaces, providing a more comprehensive understanding of PFAS retention near the water table and release to groundwater. Modeling of a hypothetical perfluorooctane sulfonic acid (PFOS) site under various idealized site conditions illustrated that the impacts on PFOS retention from smallest to largest were water table fluctuations, low episodic recharge, constant recharge, moderate episodic recharge, constant recharge with water table fluctuations, and high episodic recharge. PFOS retention also varied by sand type, with greater retention occurring in simulations incorporating coarse sand with low capillary potential versus fine sand with high capillary potential. PFAS management strategies were also explored, including the adaptation of gas sparging, a method traditionally used for volatile organic compounds. Gas sparging can concentrate PFAS in groundwater and the vadose zone around the water table, facilitating retention or removal. Model simulations for a simplified hypothetical site demonstrated that PFAS can be substantially retained in the unsaturated zone once gas sparging results in an upward concentration of PFAS in groundwater and the unsaturated zone near the water table. Modeling can aid in understanding PFAS behavior but requires simulation of multiple interrelated processes to correctly predict PFAS fate and transport in subsurface conditions.

Microbial electrolysis cells designed for BioH2 production: Potential improvements with carbon dioxide and nitrogen

The long-term feasibility and efficiency of microbial electrolysis cells (MECs) depend primarily upon several crucial parameters. However, they show promise for sustainably producing biohydrogen (bioH2). This study investigates a newly designed biohydrogen reactor by studying the effects of several variables on the production of bioH2, including applied voltage, electrode material, and gas sparging with CO2 and N2. The study aims to optimize the system for improved efficiency and production performance. The results of this study show that both electrode type and applied voltage affect bioH2 production where choosing the right inoculum has a significant impact on the catalytic efficiency. The aluminum electrodes significantly help produce the most bioH2 production at 2.0 V with 884 mL/L in 11.25 min, while emphasizing the significance of material characteristics. The reduced partial pressure from CO2 sparging, up to a point, improves bioH2 generation. The N2 gas sparging further demonstrates an increased efficiency where the ideal flow rates are dependent on the size of the MEC system. The highest bioH2 production rates for CO2 and N2 sparging are measured as 821 mL/L and 813 mL/L in 4.25 min and 11.50 min at a volume of 400 mL/min and 300 mL/min, respectively. The results of this study further advance our knowledge of and ability to optimize MEC systems for long-term, sustainable bioH2 production.

Measurement and control of foam generation in a mammalian cell culture.

Foam is generated in mammalian cell cultures by excessive agitation or gas sparging. This occurs particularly in cultures that generate recombinant proteins at high cell concentrations. Three antifoam agents were tested for their compatibility with antibody-producing Chinese hamster ovary (CHO) cells. One agent (antifoam 204) was completely inhibitory to growth at a concentration of 10 ppm, one agent (antifoam C) showed partial inhibition and a third (antifoam SE-15) showed no inhibition at this concentration. A novel foam image analyzer (LabCam) was used to evaluate two antifoams (C and SE-15) for their ability to dissipate foam generated in cell culture media by enhanced agitation. The presence of antifoam in the media reduced significantly the foam layer that was generated and this was shown to be rapidly dissipated in the presence of 10 ppm SE-15. The antifoams were also tested for foam dissipation in cultures of CHO cells at >106 cells/mL. Supplementation of the cultures with SE-15 resulted in dissipation of foam generated by excessive gas sparging within 2 min. Under equivalent conditions 75% of foam dissipated in the presence of antifoam C, within 2 min but there was a residual foam layer up to 25 min. This study showed the value of an optical monitoring system (LabCam) for measuring foam generation and dissipation in a bioreactor to assess the efficiency of antifoam agents to reduce foam in a bioreactor. This has the potential for use as a control system that could be designed for continuous monitoring and foam control in a mammalian cell bioprocess.

Pilot scale application of a rotating hollow fibre membrane for direct membrane filtration of domestic wastewater

This study investigates the direct ultrafiltration process of municipal wastewater (MWW) at pilot scale. Short-term trials were conducted with two membrane modules to assess the fouling mechanisms using different physical cleaning methods: gas sparging (hydraulic cleaning) and rotation (mechanical cleaning). This work demonstrates that membrane rotation effectively erodes and re-disperses external fouling during the backwashing stages. Consequently, shear stress generated by the rotational movement enables the operation with permeate fluxes ranging between 24 and 30 L/hm2, above the threshold flux value (22–24 L/hm2), while maintaining fouling rates (rf) below 10 Pa/s. In contrast, rf values increases up to 12.4–17.8 Pa/s when gas sparging is employed. Furthermore, the feasibility of up-concentrating municipal wastewater up to 12 times while operating with a net permeate flux of 20 L/hm2 is demonstrated through a long-term trial. The increase in suspended solids concentration (TSS = 5750 mg/L and VSS = 4750 mg/L) favours the rapid formation of a reversible cake on the membrane surface during filtration, at moderate transmembrane pressures (26 cmHg). These operating conditions avoid cake layer compression and protect the inner surface of the membrane module from severe internal residual fouling with an energy consumption of 0.027 kWh/m3.

Dissolved Oxygen Removal in Wines by Gas Sparging, Its Optimization and Chemical Impact

Sparging is a technique to remove an excess of dissolved oxygen from the wine with inerting gases before bottling to avoid negative consequences for its chemical and sensory properties. However, its effectiveness on these properties has not been studied in depth. This work investigates the effectiveness of different inerting gases (N2, CO2, and argon) in removing dissolved oxygen in different volumes of a model wine. The efficacy of these gases was also studied in white and red wine, as was their effect on the physicochemical characteristics. Sparging with N2 in the model wine gave the best results in terms of cost–benefits, and with CO2 the worst. The scaling in tanks of different sizes allowed us to establish that the N2 expenditure ranged between 0.09 L and 0.23 L of gas per liter of model wine, establishing an index (Lgas/Lwine) that can be very useful for wineries to remove the dissolved oxygen. Sparging treatments in white and red wine showed very similar results to the model wine. The effect on the chemical properties of the wines was, in some cases, different for white and red wine and for each gas used. The incorporation of oxygen and the subsequent sparging produced a significant loss of some volatile compounds of sensory interest and increased the content of others that have a negative sensory effect. In addition, it had a negative effect on the chromatic properties of red wines.

Kilogram-scale production of high purity 2,5-furandicarboxylic acid via sustainable leap in continuous electrochemical oxidation of 5-hydroxymethylfurfural

Electrochemical oxidation of 5-hydroxymethylfurfural (HMFOR) stands out as an efficient and sustainable approach for 2,5-furandicarboxylic acid (FDCA) production. However, despite numerous catalyst advancements, the industrial adoption of this process faces significant challenges, stemming from limitations in scalability and high device costs. To address this gap, we developed a scalable HMFOR process for continuous FDCA production. Key parameters such as electrolyte concentration, anodic and cathodic catalysts, types of sparge gas, and current density were found to be critical to the yield and quality of the isolated FDCA products. NiFeOOH anode and Pt cathode operated at 33.3 mA cm−2 in 0.33 M KOH and O2 environment were chosen as they provided the fastest oxidation kinetic and minimized HMF degradation rate, hence producing FDCA with high yield and purity. Using the optimal conditions identified in a milligram-scale batch reactor, we constructed a 2-liter CSTR with a novel electrode design accommodating 100 A of current. This process achieved an unprecedented FDCA production rate of ∼2 kg per day and space–time yields of up to 295 μmol h−1 cm−2, along with exceptional stability for 48 h. The isolated FDCA demonstrated comparable purity and color to commercial products. This simple and robust continuous reactor design can be applied to other electrochemical biomass valorization processes, potentially replacing conventional electrolyzers.

Enhanced biohydrogen production from high loads of unpretreated cattle manure by cellulolytic bacterium Caldicellulosiruptor bescii at 75 °C

Caldicellulosiruptor bescii is the most thermophilic cellulolytic bacterium capable of fermenting crystalline cellulose identified to date, and it also has a superior ability to degrade plant biomass without any pretreatment. This study is the first to assess the potential of utilizing unpretreated cattle manure (UCM) as a feedstock for hydrogen (H2) production by C. bescii at a concentration range between 2.5–50 g volatile solids (VS)/L. At 50 g VS/L UCM concentrations, H2 production ceased due to inhibition of C. bescii. To alleviate the impacts of inhibition, two strategies were adopted: (i) reduction of H2 build-up in the reactor headspace via gas sparging and (ii) adaptation of C. bescii to UCM via adaptive laboratory evolution (ALE). The former increased H2 yield by 47% compared to the control reactors, where no sparging was applied. The latter increased H2 yield by 142% compared to the control reactors inoculated by the wild type C. bescii. The UCM-adapted C. bescii demonstrated a remarkable H2 yield of 161.3 ± 1.6 mL H2/g VSadded at 15 g VS/L. This yield represents a twofold increase compared to the maximum H2 yield reported in the literature amongst fermentation studies utilizing manure as feed. At 15 g VS/L, around 73% of UCM was solubilized, and the carbon balance indicated that most of the effluent carbon was in the sugar- and acid-form. The remarkable ability of C. bescii to produce H2 from UCM under non-sterile conditions presents a significant potential for sustainable biohydrogen production from renewable feedstocks.

Nitrogen-sparging assisted anoxic biological drinking water treatment system.

Existing heterotrophic denitrification reactors rely on microorganisms to consume dissolved oxygen (DO) and create conditions suitable for denitrification, but this practice leads to excessive microbial growth and increased organic carbon doses. An innovative reactor that uses nitrogen gas sparging through a contactor to strip DO was developed and tested in the lab. It reduced influent nitrate from 15 to <1 mg/L as N with nitrite accumulation <1 mg/L as N. It maintained a consistent flow rate and developed minimal headloss, making it easier to operate than the denitrifying dual-media filter that was operated in parallel. Gravel, polyvinyl chloride pieces, and no packing media were assessed as options for the nitrogen-sparged contactor, and gravel was found to support denitrification at the highest loading rate and was resilient to nitrogen-sparging shutoffs and intermittent operation. This innovative reactor appears promising for small drinking water systems.

Effects of gas saturation and sparging on sonochemical oxidation activity under different liquid level and volume conditions in 300-kHz sonoreactors: Zeroth- and first-order reaction comparison using KI dosimetry and BPA degradation

The sonochemical oxidation activity was investigated for gas saturation and gas sparging under various liquid levels and volumes in 300 kHz sonoreactors. The liquid levels and volumes ranged from 5λ (25 mm, 0.47 L) to 50λ (250 mm, 4.30 L) and two gas mixtures, Ar:O2 (75:25) and N2:O2 (75:25), were used. Two types of reaction kinetics were observed to quantitatively analyze the sonochemical oxidation reactions: zero-order (KI dosimetry: C0 = 60.2 mM) and first-order (Bisphenol A (BPA) degradation: C0 = 0.043 mM). The masses of the sonochemical oxidation reactions were calculated and compared rather than the concentrations to more accurately compare the sonochemical oxidation activity under different liquid volume conditions. First, as the liquid level or volume increased for the zero-order reactions, the concentration of I3- ions representing the volume-averaged activity decreased substantially for gas saturation owing to the increase in liquid volume. However, gas sparging substantially enhanced sonochemical oxidation activity, and the mass of I3- ions representing the total activity remained constant as the liquid level increased from 20λ because of the improved liquid mixing and a shift in the sonochemical active zone. Second, as evidenced by the zero-order reactions, the concentration of BPA decreased considerably as the liquid level or volume increased in the first-order reactions. When gas sparging was used, higher reaction constants were obtained for both gas mixtures, ranging from 40λ to 50λ. However, a comparison of the sonochemical oxidation activity in terms of the degraded mass of BPA was inapplicable as the concentration of BPA decreased substantially and a lack of reactants occurred for the lower liquid level and volume conditions as the irradiation time elapsed. Instead, using the first-order reaction constant, a comparison of the required reaction times for a specific removal efficiency (30%, 60%, and 90%) was proposed. Gas sparging can substantially reduce the reaction time required for a liquid level of 40λ or higher.

Effects of sparging gas entrainment on void and temperature coefficients in the Transatomic Power molten salt reactor core

A model of the Transatomic Power Molten Salt Reactor core was simulated using the Monte Carlo code Serpent 2 to determine the effects of sparging gas entrainment on the void and temperature coefficients. The reactor core showed a positive void coefficient of around + 170 pcm per 1% increase in void and a shift in transition temperatures from negative to positive temperature coefficient of around –24 K per 1% increase in void. These observations were similar for the homogeneous model chosen in this work and for a heterogeneous (explicit bubble) model. The observed characteristics were caused by decreased fuel mixture self–shielding as gas entrainment levels increase and its synergistic effect with gas thermal expansion. Due to the important safety implications from the observed characteristics, similar reactor designs should be evaluated for their void and temperature coefficients with respect to gas entrainment levels.

H2 generation by the 10B(n,α)7Li reaction in high temperature water

H2 produced in water from the 10B(n,α)7Li fission reaction has been measured up to 300 °C. Thermal energy neutrons from the Rhode Island Nuclear Science Center's 2 MW reactor interact with boric acid-containing water in temperature-controlled high-pressure cells made from tubing of either titanium or zirconium alloy. After exposure for a minimum of 1 h, the solution sample is extracted and sparged with argon. The H2 entrained by the sparging gas is sampled with a small mass spectrometer. A small amount of sodium is included in the boric acid solution so that after sparging, samples can be collected for 24Na activation measurements in a gamma spectrometer to determine the neutron exposure and thus the total energy deposited in solution. The G-value (μmol/J) for H2 production is obtained for water at a pressure of 25 MPa, over a temperature range from 20 °C to 300 °C. The weak temperature dependence of this yield between 150 °C and 200 °C demonstrates that the bimolecular reaction of pairs of eaq− is a very minor source of H2 in high LET tracks.

Effect of dissolved gases on sonochemical oxidation in a 20 kHz probe system: Continuous monitoring of dissolved oxygen concentration and sonochemical oxidation activity

Dissolved gases have a substantial influence on acoustic cavitation and sonochemical oxidation reactions. Little research on the changes in dissolved gases and the resultant changes in sonochemical oxidation has been reported, and most studies have focused only on the initial dissolved gas conditions. In this study, the dissolved oxygen (DO) concentration was measured continuously during ultrasonic irradiation using an optical sensor in different gas modes (saturation/open, saturation/closed, and sparging/closed modes). Simultaneously, the resulting changes in sonochemical oxidation were quantified using KI dosimetry. In the saturation/open mode using five gas conditions of Ar and O2, the DO concentration decreased rapidly when O2 was present because of active gas exchange with the atmosphere, and the DO concentration increased when 100% Ar was used. As a result, the order of the zero-order reaction constant for the first 10 min (k0-10) decreased in the order Ar:O2 (75:25) > 100% Ar ≈ Ar:O2 (50:50) > Ar:O2 (25:75) > 100% O2, whereas that during the last 10 min (k20-30) when the DO concentration was relatively stable, decreased in the order 100% Ar > Ar:O2 (75:25) > Ar:O2 (50:50) ≈ Ar:O2 (20:75) > 100% O2. In the saturation/closed mode, the DO concentration decreased to approximately 70–80% of the initial level because of ultrasonic degassing, and there was no influence of gases other than Ar and O2. Consequently, k0-10 and k20-30 decreased in the order Ar:O2 (75:25) > Ar:O2 (50:50) > Ar:O2 (25:75) > 100% Ar > 100% O2. In the sparging/closed mode, the DO concentration was maintained at approximately 90% of the initial level because of the more active gas adsorption induced by gas sparging, and the values of k0-10 and k20-30 were almost the same as those in the saturation/closed mode. In the saturation/open and sparging/closed modes, the Ar:O2 (75:25) condition was most favorable for enhancing sonochemical oxidation. However, a comparison of k0-10 and k20-30 indicated that there would be an optimal dissolved gas condition that was different from the initial gas condition. In addition, the mass-transfer and ultrasonic-degassing coefficients were calculated using changes in the DO concentration in the three modes.

Electrocoagulation for the Treatment of Metals Machining Plants Effluents: Experimental and Modeling Study

AbstractTreatment of effluents discharged from mechanical machining of copper and copper alloys for removal of cutting oils and toxic copper ions by electrocoagulation was studied using a cell containing two steel electrodes and a built‐in heat transfer facility. Current density, initial pH of the solution, temperature, starting pollutants' concentrations, amount of NaCl supportive electrolyte, and the impact of gas sparging were investigated. Response surface methodology was used to correlate % oil removal, % copper removal, and electrical energy consumption to the affecting variables. The results imply that the cubic model fits well with the experimental results. The electrocoagulation of oil and copper from waste solutions was optimized using the response optimizer. The simultaneous removal of oil and Cu2+ in the same cell could lower the operational and capital expenses of wastewater treatment.

The foaming properties of sweet potato protein hydrolysates produced by Alcalase and Ficin.

The processing of sweet potatoes generates a waste by-product rich in sweet potato protein (SPP). In this study, the effects of the concentrations of Alcalase and Ficin, hydrolysis time and pH value on the foaming properties of SPP hydrolysates (SPPHs) determined via gas sparging method were investigated. The results showed that SPPH prepared by Alcalase exhibited a significantly higher foaming expansion (the highest of 576%) than that of the SPP (462%) but displayed a weaker liquid volume stability compared with SPPH hydrolyzed by Ficin. The molecular weight of SPPH prepared by Alcalase was distributed in 10-30 kDa. A good microbiological quality of the SPPH prepared by Alcalase in pH 13 has been confirmed, and it is suitable for food application with respect to its microbiological safety profile. SPPH (pH 13) could be further safely applied in food, especially as a food additive at low concentrations to create a better organic plant-based foaming agent for the food industry. © 2023 Society of Chemical Industry.

Macroalgal biochar synthesis and its implication on membrane fouling mitigation in fluidized bed membrane bioreactor for wastewater treatment

The intensification of biochar into fluidized bed membrane bioreactor was investigated to mitigate membrane fouling. Different biochars from algal biomass were produced and used as biomaterials for wastewater treatment. In this study, different macroalgal biochar was synthesized at different pyrolysis temperatures and characterized using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Brunauer Emmett-Teller (BET) and Fourier transform infrared spectroscopy (FTIR) techniques to implicate their effect on membrane fouling reduction in fluidized bed membrane bioreactor. The combined effect of macroalgal biochars and biocarriers with gas sparging was evaluated for fouling mitigation. Macroalgal biochar curtailed membrane fouling effectively at low gas sparging rate. Transmembrane pressure (TMP) was reduced to 0.053 bar; under the fluidization of biochar-650 and biocarriers with gas sparging; from 0.27 bar (gas sparging only). Combined effect of gas sparging, biocarriers and biochar-650 instigated 92.1% fouling reduction in comparative to gas sparging alone. Mechanical scouring driven by biocarriers could reduce fouling due to removing surface deposit of foulants from membrane surface effectively and biochar can efficiently adsorb foulants because of its active functional groups resulting in reduction of colloidal fouling. The addition of divalent ions (Ca2+) further enhanced the fouling reduction in fluidized bed membrane bioreactor.

Impact of Integration of FO Membranes into a Granular Biomass AnMBR for Water Reuse

The granular sludge based anaerobic membrane bioreactor (G-AnMBR) has gained emphasis in the last decade by combining AnMBR advantages (high quality permeate and biogas production towards energy positive treatment) and benefits of granular biomass (boosted biological activity and reduced membrane fouling). With the aim to further reduce energy costs, produce higher quality effluent for water reuse applications and improve system efficiency, a forward osmosis (FO) system was integrated into a 17 L G-AnMBR pilot. Plate and frame microfiltration modules were step by step replaced by submerged FO ones, synthetic wastewater was used as feed (chemical oxygen demand (COD) content 500 mg/L), with hydraulic retention time of 10 h and operated at 25 °C. The system was fed with granular biomass and after the acclimation period, operated neither with gas sparging nor relaxation at around 5 L.m-2.h-1 permeation flux during at least 10 days for each tested configuration. Process stability, impact of salinity on biomass, the produced water quality and organic matter removal efficiency were assessed and compared for the system working with 100% microfiltration (MF), 70% MF/30% FO, 50% MF/50% FO and 10% MF/90% FO, respectively. Increasing the FO share in the reactor led to salinity increase and to enhanced fouling propensity probably due to salinity shock on the active biomass, releasing extracellular polymeric substances (EPS) in the mixed liquor. However, above 90% COD degradation was observed for all configurations with a remaining COD content below 50 mg/L and below the detection limit for MF and FO permeates, respectively. FO membranes also proved to be less prone to fouling in comparison with MF ones. Complete salt mass balance demonstrated that major salinity increase in the reactor was due to reverse salt passage from the draw solution but also that salts from the feed solution could migrate to the draw solution. While FO membranes allow for full rejection and very high permeate purity, operation of G-AnMBR with FO membranes only is not recommended since MF presence acts as a purge and allows for reactor salinity stabilization.