Ozone Pretreatment Research Articles

Consumer Perception on the Redness and Off Flavor Upon Stored Red Chili Paste with Ozone Treatment

Since red chili has a high moisture content and a rapid respiration rate, it is regarded as a perishable item. The redness and scent of the chili can be used to detect a quality decline during storage. It has long been common practice to employ ozone to prevent horticultural products from degrading. The purpose of this study is to ascertain the impact of ozone pretreatment on the redness and scent of chili paste during storage as a quality indicator of customer perception level. Red chilies were treated by soaking in ozonated water for 15 minutes using an ozone generator, as opposed to the control treatment, which used only pure water. Samples were kept for seven days, and each day the redness and scent were evaluated. Data were obtained by calculating the average and standard deviation, then presented in a graph with error bars. The results showed that the redness value of control and ozone treatment started from 51.55 and 46.04 and on the seventh day became 42.94 and 43.81. The control treatment showed off-flavor on the third day of storage while the ozone treatment did not show off-flavor until seventh day of storage. In conclusion, ozone treatment slowed down the decrease of red chili paste’s redness value and off-flavor.

Ozone pretreatment alleviates ischemia[sbnd]reperfusion injury-induced myocardial ferroptosis by activating the Nrf2/Slc7a11/Gpx4 axis

Myocardial ischemiareperfusion injury (MIRI) is defined as the additional damage that occurs during the process of restoring blood flow to the heart tissue after ischemia-induced damage. Ozone is a powerful oxidizer, but low concentrations of ozone can protect various organs from oxidative stress. Some studies have demonstrated a link between ozone and myocardioprotection, but the mechanism remains unclear. To establish an in vivo animal model of ischemiareperfusion injury (I/R), this study utilized C57 mice, while an in vitro model of hypoxia-reoxygenation (H/R) injury was developed using H9c2 cardiomyocytes to simulate ischemiareperfusion injury. Ozone pretreatment was used in in vitro and in vivo experiments. Through this research, we found that ozone therapy can reduce myocardial injury, and further studies found that ozone regulates the expression levels of these ferroptosis-related proteins and transcription factors in the H/R model, which were screened by bioinformatics. In particular, nuclear translocation of Nrf2 was enhanced by pretreatment with ozone, inhibited ferroptosis and ameliorated oxidative stress by initiating the expression of Slc7a11 and Gpx4. Significantly, Nrf2 gene silencing reverses the protective effects of ozone in the H/R model. In summary, our results suggest that ozone protects the myocardium from I/R damage through the Nrf2/Slc7a11/Gpx4 signaling pathway, highlighting the potential of ozone as a new coronary artery disease therapy.

Desmodesmus sp. from biowaste to produce electrospinning membranes: Effect of ultrasounds and ozone pre-treatments

Desmodesmus sp. microalgae previously employed in wastewater management was reused as a raw material for producing green nanofibrous membranes through electrospinning. The reduction of biowastes as well as the replacement of common non-degradable plastics would benefit the process sustainability. In this work, different amounts of microalgae (1.25%, 2.5% and 5% wt) were dispersed in an acetic acid/water solution (80/20) and then electrospun at 0.3 mL/h, 25 kV. The presence of acetate cellulose (17%) was required to obtain nanofibres since the microalgae solutions were not sufficiently viscous for electrospinning processing. For the first time, the effect of ultrasound (50 and 125 kWh/kg), and ozone (9 mg/kg) on microalgae before the electrospinning process was evaluated. Ultrasound prompted cell rupture, which allowed both a greater release and higher exposure of the protein, which eventually enabled the formation of nanofibers from the microalgae waste. However, when the intensity of ultrasounds increased from 50 to 125 kWh/kg, a higher presence of aggregates and defects in the fibres could be observed, probably due to protein aggregation. Thus, nanofibrous mats with c.a. 50 nm fibre diameter were obtained when ultrasound pre-treatment at 50 kWh/kg was applied. Protein unfolding was also inferred from the rheological measurements, as higher viscosity values were obtained (∼ 4.1 Vs. 2.5 Pa·s for 50 and 125 kWh/kg ultrasounds, respectively). The present work highlights the potential that Desmodesmus sp. microalgae have in the production of green electrospun mats, still quite unexplored. These bio-based mats possess great potential in different applications that can range from filtering to scaffolds.

Ozone pretreatment combined with partial denitrification-anammox process for efficient nitrogen removal from nanofiltration concentrate of landfill leachate

Treatment of nanofiltration concentrate (NFC) from landfill leachate is challenging due to its complex composition and high concentration of refractory organic matter. This study proposed a combined process of ozone pretreatment and partial denitrification/anammox (PD/A) for treating NFC, exploring the feasibility of using ozone-oxidized NFC as a carbon source for partial denitrification. The ozone oxidation process was employed to degrade the refractory organic compounds. With an ozone flow rate of 1.2 L/min and a reaction time of 50 min, the chemical oxygen demand (COD) removal efficiency of NFC was 20.83%, and the volatile fatty acid (VFA) content reached a maximum value of 104.37 mg/L. Meanwhile, the process significantly increased the ammonia and nitrate concentrations in the NFC. Then, PD/A process was applied to remove nitrogen from the NFC. Results showed that PD/A can effectively remove nitrogen from the NFC without additional carbon source. Using VFA produced in the ozone oxidation stage as carbon source, the reactor achieved a nitrogen removal efficiency of approximately 70%, resulting in an effluent with a total nitrogen below 40 mg/L, which satisfied the relevant standards in China. This study provides new insights into the application of ozone oxidation and PD/A in treating NFC from leachate.

Controlling ultrafiltration membrane fouling in surface water treatment via combined pretreatment of O3 and PAC: Mechanism investigation on impacts of technological sequence

In this research, the effects of combined powdered activated carbon (PAC)-ozone (O3) pretreatment on ultrafiltration (UF) performance were comprehensively examined and compared with the conventional O3-PAC pretreatment. The performance of pretreatments on mitigating membrane fouling caused by Songhua River water (SHR) was evaluated by specific flux, membrane fouling resistance distribution, and membrane fouling index. Moreover, the degradation of natural organic matter in SHR was investigated by UV absorbance at 254 nm (UV254), dissolved organic carbon (DOC), and fluorescent organic matter. Results showed that the 100PAC-5O3 process was the most effective in improving the specific flux, with 82.89 % and 58.17 % reductions in the reversible fouling resistance and irreversible fouling resistance respectively. Additionally, the irreversible membrane fouling index was reduced by 20 % relative to 5O3-100PAC. The PAC-O3 process also exhibited superior performance in the degradation of UV254, DOC, three fluorescent components, and three micropollutants in the SHR system compared to O3-PAC pretreatment. The O3 stage played a major role in mitigating membrane fouling, while PAC pretreatment enhanced the oxidation in the subsequent O3 stage during the PAC-O3 process. Furthermore, the Extended Derjaguin-Landau-Verwey-Overbeek theory and pore blocking-cake layer filtration model fitting analysis were employed to explain the mechanisms of membrane fouling mitigation and fouling patterns transformation. It was found that PAC-O3 significantly increased the repulsive interactions between the foulants and the membrane, which restrained the formation of the cake layer filtration stage. Overall, this study evidenced the potential of PAC-O3 pretreatment in surface water treatment applications, providing new insights into the mechanism of controlling membrane fouling and improving the permeate quality.

Preparation of carboxymethyl cellulose (CMC) derived from palm fiber waste: Effect of ozone pretreatment on CMC properties

AbstractCarboxymethyl cellulose (CMC) was prepared using cellulose extracted from palm fiber (CPF). The effect of ozone pretreatment on the CMC properties degree of substitution (DS) and viscosity was investigated. After treatment of CPF with ozone, CMC was prepared by alkalization followed by etherification using sodium hydroxide (NaOH) and sodium monochloroacetic acid (NaMCA) in an alcoholic medium. The DS of CMC increased with increased ozone pretreatment time and with increased amounts of NaOH and NaMCA reagents. The CMC solubility increased with increasing DS. Therefore, the solubility increased with ozone pretreatment time. The favored treatment conditions were ozone pretreatment for 3 h, followed by the addition of 10 mL of 30% NaOH and 38.6 mM of NaMCA. Under these conditions, the DS, purity, and solubility were 1.05, 79.6%, and 94.6%, respectively. The viscosity of CMC prepared using cellulose treated with ozone decreased with increasing ozone pretreatment time, which was caused by the reduced degree of polymerization. Therefore, use of ozone pretreatment for CMC preparation is an effective method for controlling CMC properties.

A comparison of ultrasonic, ozone, and enzyme pre-treatments on cheese whey degradation for enhancement of anaerobic digestion

Lactose in cheese whey wastewater (CWW) makes it difficult to degrade under normal conditions. The effect of ultra-sonication (US), ozonation and enzymatic hydrolysis on increasing the bioavailability of organic matter in CWW and biogas production were evaluated. The pre-treatment conditions were: specific energy input varied from 2130 to 8773KJ/KgTS for a sonication time of 4.5–18.5 min, Ozone (O3) dosages ranging from 0.03 to 0.045gO3/gTS were applied for 4–16 min, pH (3.8–7.1), temperature (35°C–55°C), enzyme dosage (0.18–0.52%), was operated from 7.75 to 53 min for enzymatic hydrolysis by β-galactosidase. The results of the US reported a maximum sCOD solubilisation of 77.15% after 18.5 min of operation, while the corresponding values for ozonation and enzymatic methods were 64.8% at 16 min and 54.79%, respectively. The organic matter degradation rates evaluated in terms of protein and lactose hydrolysis were 68.78%,46.03%; 47.83%,16.15% and 54.22%,86.2%respectively, for US, ozonation and enzymatic methods. The cumulative methane yield for sonicated, ozonised and enzymatically hydrolysed samples were 412.4 ml/g VS, 361.2 ml/g VS and 432.3mlCH4/gVS, respectively. Regardless of the lower COD solubilisation rates attained, enzymatic pre-treatment showed maximum methane generation compared to US and ozonation. This could be attributable to the increased activity of β-galactosidase in hydrolysing whey lactose. The energy calculations revealed that the pre-conditioning of organic-rich CWW with enzymatic hydrolysis is more effective and efficient, yielding a net energy gain (gross output energy-input energy) of 9166.7 KJ and an energy factor (ratio of output to input energy) of 6.67. The modified Gompertz model well simulated all experimental values.

Performance of resin adsorption and ozonation pretreatment in mitigating organic fouling of reverse osmosis membrane

Effective pretreatment of reverse osmosis (RO) influent is of great importance for reducing membrane fouling risks during coking wastewater desalination. In this study, the combined resin adsorption and ozonation pretreatment was investigated on alleviating RO membrane organic fouling. The performance of combined process was compared with only resin adsorption or ozonation, which was evaluated in terms of changes in chemical oxygen demand (COD), ultraviolet-visible index, and three-dimensional excitation-emission matrix fluorescence spectra. RO membrane fouling tests were conducted to examine the effects of pretreatment on flux decline and filtration resistance. The surface morphology and functional groups of membrane before and after fouling was characterized by scanning electron microscopy and infrared spectroscopy. The correlation between major organic matter in the wastewater and normalized RO membrane flux was established via multiple linear regression equations. The results showed that ozonation was more effective in removing COD and fluorescent organics than resin adsorption. Moreover, the combined bifunctional resin adsorption/ozonation unit showed the best performance, with COD and UV254 removal rates of 49.4 % and 88.0 %, respectively. The fluorescence intensity of each component decreased significantly. Meanwhile, the polysaccharide and protein components of the RO membrane fouling layer were effectively reduced by 67.2 % and 80.8 %, respectively. Most importantly, the combined pretreatment substantially reduced the decline in membrane flux and filtration resistance. Meanwhile, the fulvic acid-like organics in the wastewater showed high correlations with normalized membrane flux. The regression equation was beneficial for RO membrane fouling evaluation.

Physicochemical changes in microplastics and formation of DBPs under ozonation

Microplastics (MPs) are substances that pose a risk to both human life and the environment. Their types and production are increasing year on year, and their potential to cause environmental pollution is a worldwide concern. Conventional water treatment processes, particularly coagulation and sedimentation, are not effective at removing all MPs. It is therefore important to assess the morphological changes in the MPs, i.e., the thermoplastic polyurethane (TPU) and polyethylene (PE), during ozonation and the dissolved organic carbon leaching as well as chloroform formation in the subsequent chlorination. The results show that the appearance and surface chemistry of the MPs changed during the ozonation process, most notably for TPU. The trichloromethane (CHCl3) generation during chlorination was 0.168 and 0.152 μmol/L for TPU and PE, respectively, and the ozone pretreatment significantly increased the CHCl3 yield of TPU, while it had a weak effect on PE. Additional disinfection byproducts (DBPs), including CHCl2Br, CHClBr2, and CHBr3, were produced in the presence of bromide ions in the water column, and the total amount of DBPs produced by PE, PE-O, TPU, and TPU-O was significantly increased to 0.787, 0.814, 0.931, and 1.391 μmol/L, respectively. The study provides useful information for the environmental risk assessment of two representative MPs, i.e., TPU and MPs, in disinfection procedures for drinking water.

Effect of ozone pretreatment on anaerobic digestibility of sewage sludge and the energy evaluation

Effect of ozone pretreatment on anaerobic digestibility of sewage sludge and the energy evaluation

THE EFFECT OF OZONATION, ULTRASONIC, AND HYBRID OZONATION-ULTRASONIC PRETREATMENT METHODS ON THE DELIGNIFICATION OF OIL PALM MESOCARP FIBERS

Oil palm mesocarp fiberis a by-product of the palm oil pressing process, which has great potential if used as a second-generation biofuel raw material. The main components of oil palm mesocarp fiber are cellulose, hemicellulose, and lignin commonly called lignocellulose. Cellulose is the most valuable component to be utilized in the bioenergy sector. However, the oil palm mesocarp fibers lignin layer, which binds cellulose and restricts cellulose accessibility, makes it difficult to use. Ozone pretreatment is considered to be an alternative and effective method of lignin breakdown. This study compares the ozonation, ultrasonic, and hybrid ozonation-ultrasonicmethods used to degrade lignin in oil palm mesocarp fibers. The operating conditions were set at pH (3, 4, 5, 6, 7, 8, 9, 10, 11), flow rate (1, 2, 3, 4, 5) L min-1, for (0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100) minutes, at 29±1 oC. The research indicates that using ozonation-ultrasonic hybridization results in a more significant degradation of lignin than using ozonation and ultrasonics individually. In this investigation, the hybrid ozonation-ultrasonic treatment gives the best lignin degradation results and the highest quantities of cellulose, reaching 91.99% after 60 minutes at a temperature of 29±1 oC, a pH of 9, and a flow rate of 2 L.min-1. Meanwhile, the degradation of lignin using ozone treatment is 72.75%, and ultrasound only 47.70%. Cellulose with the highest purity is 89.71%.

Mitigation of Chilling Stress by Ozone Pretreatment and Acclimation of Sweet Pepper Grown under Unheated Greenhouse Conditions

Ozone is an important air pollutant that causes many challenges for human health, such as lung diseases. The negative impacts of exogenous ozone on cultivated plants have been discussed in several publications, but the positive impacts are less investigated. The current study is an attempt to answer the following question: is there any positive contribution of ozone pretreatment in growing plants under stress? Plants grown in unheated plastic greenhouses suffer from cold stress during the winter when the temperature drops to 5–10 °C. This stress can also be enhanced under saline soil conditions in arid regions. Treatments involving different ozone application methods (seed priming and seedling foliar application) and cold pretreatment (4 °C for 36 h) were compared with untreated controls of two sweet pepper hybrids (Zidenka and Lirica) in an unheated plastic greenhouse. In general, the Lirica hybrid outperformed the Zidenka hybrid in growth and fruit yield and showed good adaptation to cold stress resulting from ozone treatment through foliar application on seedlings. Moreover, cold treatment was associated with higher values of the studied parameters compared to the control (untreated). A concentration of 20 ppm of ozone in the first season and as 30 ppm of ozone in the second season increased plant leaf area, proline content, and APX activity, all of which improved the plant’s defense mechanisms against cold stress. These benefits contributed to high fruit sets; early, total, and marketable fruit yields; and fruit quality under cold stress. The highest yield (16.52 kg m−2) was attained with 30 ppm ozone applied as a seedling spray, compared with 10.07 kg m−2 in the control. Therefore, the foliar application of ozone up to 30 ppm can be recommended for sweet pepper hybrids of Lirica under unheated plastic greenhouse conditions. Further investigations are needed to study the interaction of combined ozone and cold stress, as well as various levels of soil salinity.

Treatment of organic pollutants in coke plant wastewater by micro-nanometer catalytic ozonation, A/A/O and reverse osmosis membrane.

Coking wastewater has a complex and highly concentrated chemical composition which is toxic and does not biodegrade easily. Treating the organic pollutants in this wastewater is very challenging. The toxic substances in this wastewater make traditional biotechnological treatments inefficient. Current wastewater treatment studies are based on unit processes, and no full process studies could be found. This study used the micro-nanometer catalytic ozonation process as a pretreatment unit, and reverse osmosis membrane treatment as a depth processing unit to improve the effect of the coking wastewater degradation. The micro-nanometer catalytic ozonation pretreatment greatly improves the biodegradability of the coking wastewater and promotes the coking wastewater degradation in the anoxia/anaerobic/oxic (A/A/O) system. The integrated coagulation air flotation-micro-nanometer catalytic ozonation-A/A/O-reverse osmosis membrane system can remove 98% of the chemical oxygen demand, which meets the direct emission standard of the new national standard (China). The dominant genera in the A/A/O biochemical reactor were Thioalkalimicrobium, Proteiniphilum, Azoarcu, Bacillus, Fontibacter, and Taibaiella. This work provides a novel approach for the degradation of high-concentration organic wastewater and lays a solid foundation for the restoration of environmental water bodies.

Effect of ozone pretreatment on biogranulation with partial nitritation - Anammox two stages for nitrogen removal from mature landfill leachate.

Due to the extremely low C/N ratio, high concentration of ammonia nitrogen and refractory organic matter of mature landfill leachate (MLL), appropriate processes should be selected to effectively remove nitrogen and reduce disposal costs. Partial nitritation (PN) and anaerobic ammonia oxidation (AMX) have been used as the main nitrogen removal processes for MLL, and the sludge granulation in PN and AMX processes could contribute to high biological activity, good sedimentation performance, and stable resistance to toxicity. In this study, the O3-PN-AMX biogranules process was selected to effectively remove nitrogen from MLL without carbon addition and pH adjustment. Without uneconomical NH4+-N oxidation and wasting the alkalinity of MLL, ozone pretreatment achieved color removal, decreased humic- and fulvic-like acid substances, and alleviated the MLL toxicity on ammonia oxidizers. In addition, the ozonation of MLL could shorten the start-up time and improve the treatment efficiency and biogranules stability of PN and AMX processes. Efficient and stable nitritation was achieved in PN reactor without strict dissolved oxygen (DO) control, which was attributed to the unique structure of granular sludge, ozone pretreatment, and alternating inhibition of free ammonia and free nitric acid on nitrite oxidizers. Through the application of ozone pretreatment and granular sludge, the nitrogen removal rate (NRR) and nitrogen removal efficiency (NRE) of the O3-PN-AMX biogranules process reached 0.39kg/m3/day and 85%, respectively, for the undiluted MLL treatment. This study might provide a novel and effective operation strategy of combined process for the efficient, economical, and stable nitrogen removal from MLL.

Comparison of Different Volume Reactor for Batik Wastewater Pre-Treatment with Ozonation to Improve Biodegradability

Batik is a unique ethnic and heritage textile from Indonesia with low biodegradability (BOD5/COD) and demanding biological wastewater treatment. However, in its application a high biodegradability value is needed. To increase biodegradability the ozonation process can be used as pre-treatment. The purpose of this study is to determine the effectiveness of ozone pre-treatment in color removal, COD removal, and changes in biodegradability. This study was divided into two types of the reactor with a volume of 2 L and 16 L with each dose of 4 mg/min and 40 mg/min. The results of color removal in the reactor with a volume of 2 L showed a value of 85% for color removal and 34.6% for COD removal. The reduction in efficiency occurred in the color removal to 65% in reactor 16 L. The removal of COD with a volume of 16 L was not evenly distributed at each altitude of 43; 35; and 33% (50; 100; 150 cm). Biodegradability increased from 0.143 to 0,49 (2L reactor) and 0.4-0.45 (16L reactor), this allows for the application of higher biological wastewater treatment. Which the NH3-N and total phenol removal efficiencies of 12.9%-31.4% and 3-21.2%, respectively.

Specific degradation of phenolic compounds from palm oil mill effluent using ozonation and its impact on methane fermentation

In this study, the inhibition to anaerobic digestion of phenolic compounds present in palm oil mill effluent (POME) was quantified in batch and continuous operations to assess their effects on methane fermentation. Caffeic acid (CAF), at its concentration in POME, was found to be the most effective inhibitor of the microbial community in hydrolysis, acidogenesis, and methanogenesis phases. To mitigate the toxicity of anaerobic digestion (AD), the pretreatment of POME with various ozone dosages (0.1 to 0.4 gO3/Lwastewater) was performed to determine the effectiveness of specific phenolic compounds destruction. The ozone pretreatment was able to significantly degrade these phenolic molecules and alter their profile in POME over the wide ranges of ozone dosage. Ozone dosage of 0.2 gO3/Lwastewater was optimal to cause the individual concentration to drop below the strong inhibitory levels. When POME was ozonized, the overall total phenolic compounds in the effluent were reduced by 75 % from 613 to 155 mg/L. The overall volumetric biogas yields correspondingly increased by 67 % from 0.3 to 0.5 L/Lreactor.d with the improved specific methane yield from 6.3 ± 0.2 to 9.3 ± 0.1 LCH4/m3. The results demonstrated that the inhibitory effects of phenolic compounds could significantly be detoxified by pretreatment with ozone to enhance anaerobic digestion performance.

Freeze-Drying Processes Applied to Melon Peel: Assessment of Physicochemical Attributes and Intrinsic Microflora Survival during Storage.

Melon peel is recognized as a source of healthy nutrients and oxidant compounds. Being considered a non-edible part with no profit value, large amounts of melon rinds are discharged by fruit industries. Innovative food ingredients with potential health benefits may arise if these parts were conveniently transformed. The objective was to freeze-dry small melon peel cubes to attain a potential edible matrix. An ozone pre-treatment was applied seeking decontamination purposes and quality retention. The effect of these processes was assessed in terms of physicochemical parameters (moisture content, water activity and color), bioactive compounds (total phenolics, vitamin C and chlorophylls) and antioxidant capacity, during 7 weeks of storage at room temperature. Intrinsic microflora (mesophylls, yeasts and molds) were also monitored. Results showed that the freeze-drying process allowed retention of the most bioactive compounds analyzed, except for total phenolic content. In this case, the ozone pre-treatment was important for phenolics preservation. During the storage period, ozonated samples presented a higher content of bioactive compounds. In terms of microflora, the ozone and freeze-drying effects were not significant. Freeze-drying proved to be a suitable preservation method for melon peel. The ozone impact was not relevant in terms of decontamination.

Simultaneous study of the interaction effect of chemical and hydrothermal pretreatment on the yield of methane produced from municipal waste

Municipal waste has the potential to be a significant source of energy production. This study investigated pretreatment methods such as NaOH, hydrothermal, and ozonation to increase biomethane production from municipal waste. In addition, these pretreatments were further evaluated using ultrasonic pretreatment after achieving optimal conditions by RSM CCD methods. The optimum pretreatment conditions were observed to be 8% NaOH concentration, 132 °C hydrothermal temperature, and O3 equal to 0.19 g/g TS. The maximum biomethane produced and achieved during the tests was 394 mL/kg TS, which increased to 410 mL/kg TS after ultrasonic pretreatment. The best sCOD reduction in the optimal pretreatment conditions and after the ultrasonic pretreatment was 87% and 91%, respectively. Also, in the absence of ozone pretreatment, the highest yields of biomethane and biogas occurred at a 6.4% concentration of NaOH and a temperature of 135 °C; however, in the presence of ozone, the yield of biomethane and biogas produced was greater and the inhibitory effect of sodium hydroxide also occurs in higher amounts. Experiments have shown that ozonation increases biomethane production rather than increasing biogas production (hence the ratio of methane to biogas).

Structural Changes of Alkali Lignin under Ozone Treatment and Effect of Ozone-Oxidized Alkali Lignin on Cellulose Digestibility

In this study, the structural changes of alkali lignin induced by ozonation were investigated, and the effect of ozone-treated alkali lignin and its mechanism on Avicel enzymatic hydrolysis was examined. The physicochemical properties of alkali lignin were analyzed by FTIR, 1H-13C HSQC NMR, and GPC. It was revealed that ozone pretreatment increased the content of carboxyl and/or aldehyde groups and the negative zeta potential of alkali lignin, which enhanced the electrostatic repulsion between alkali lignin and cellulase; The S/G ratio was reduced, indicating the hydrophobic interaction was diminished. The Langmuir adsorption isotherm showed that the cellulase binding strength of ozone pretreated alkali lignin (OL-pH3, OL-pH7, and OL-pH12 were 16.67, 13.87, and 44.05 mL/g, respectively) was significantly lower than that of alkali lignin (161.29 mL/g). The 72 h hydrolysis yields of Avicel added with OL-pH3, OL-pH7, and OL-pH12 were 55.4%, 58.6%, and 54.9% respectively, which were 2.6–6.3% higher than that of Avicel added with AL (52.3%). This research aimed to reduce the non-productive adsorption between cellulase and lignin by investigating the structural changes of lignin caused by ozone treatment. For the first time, we discovered that ozone-treated alkali lignin has a further promotion effect on the enzymatic digestion of cellulose, providing a green and feasible pretreatment process for the enzymatic hydrolysis of lignocellulose and aiding in the more efficient utilization of biomass.

Enhancing nitrogen removal in mature landfill leachate by mixed microalgae through elimination of inhibiting factors

Nitrogen removal from landfill leachate (LL) using microalgae is a promising method and can realize CO2 mitigation. But the performances are usually inhibited by high chromaticity, high free ammonia (FAN) and some complex macro molecular organic matter (MOM) in the LL. To achieve efficient nitrogen removal from LL, this study firstly pretreated the mature LL with ozone, decolorizer and activated sludge (AS) respectively, and then inoculated with mixed microalgae. The results showed that the synergistic effect of ozonation and microalgae was the best among the three, with 99.7% ammonia removal, 0.77 g/L (dry weight) microalgae biomass, and a maximum growth rate of 160 mg/L/d. Ozonation pretreatment significantly reduced the chromaticity and macromolecular organic matter of LL, with the chromaticity reduced from 2225 to 225 times and the 3D fluorescence intensity representing MOM reduced from 4089 a.u. to 986.1 a.u.. And it was found that the mixed microalgae grown after pretreatment by three different methods all were mostly Chlorella and very few Microcystis, and the density of microalgal populations (number of cells per unit volume) after ozonation was up to 10,650 cells/μL. This work provides a feasible and an economical way to remove ammonia nitrogen (NH+ 4-N) from landfill leachate.