Acidification Process Research Articles

Potential and characteristics on nitrobenzene degradation by biological acidification.

Biological acidification, efficient and low-cost biotechnology, is crucial in treating pharmaceutical, pesticide water, and petrochemical wastewater. Nitrobenzene is a typical organic pollutant in petrochemical wastewater with high toxicity and long persistence. However, its effect on hydrolysis acidification is yet to be fully elucidated. The present study sought to investigate the inhibitory effect of nitrobenzene on biological acidification. Volatile fatty acid toxicity assays were performed to examine the acid production of sludge exposed to different concentrations of nitrobenzene over time. Extracellular polymeric substances (EPS) were measured by the phenol-sulfuric acid technique and Coomassie brilliant blue G250 to characterize the changes in extracellular polymers after exposure to different nitrobenzene concentrations. Enzyme-linked immunosorbent assay kits were employed to evaluate representative enzyme activities of acidified bacteria after exposure to nitrobenzene. Nitrobenzene and its products were respectively determined by liquid chromatography and gas chromatography-mass spectrometry, and the transformation properties of nitrobenzene were explored in the context of acid production, EPS, and changes in key enzymes. Results showed that nitrobenzene inhibited acid production at high concentrations (median effective concentration (EC50)=104.81mg/L), and acetic fermentation was predominant. Furthermore, the amounts of EPS significantly dropped when the nitrobenzene concentration was above 100mg/L. The contents of key enzymes decreased with an increase in nitrobenzene concentration. The process of nitrobenzene hydrolysis acidification was characterized as follows: EPS and anaerobic granular sludge adsorbed nitrobenzene, which is subsequently transformed to aniline by the joint action of microbial consortium reductase. Therefore, high concentrations of nitrobenzene should be pretreated before entering the biological treatment system since the capacity of bio-acidification to remove it is restricted.

Effect of black highland barley polysaccharides and low frequency-static magnetic field on casein-based coacervates: Formation, characterization, and probiotic encapsulation capacity.

To evaluate the combination effects of highland barley polysaccharides (HBP) and low-frequency static magnetic field (LF-SMF) treatment on the structure and properties of acid-induced casein (CS) coacervates, this study conducted a comprehensive investigation at various stages- before, during, and after coacervation-for the first time. Compared with native CS, adding HBP caused CS to denature owing to hydrophobic and electrostatic interactions, and LF-SMF treatment further promoted these changes. During the acidification (pH7.0-2.0) and coacervation processes, the integration of LF-SMF treatment with the addition of HBP enhanced the rate and extent of casein (CS) aggregation and crosslinking, attributable to alterations in the ζ-potential of CS. Among the formed coacervates, the yield and particle size of CS/HBP complex coacervates after being treated with LF-SMF (M-CS/HBP) increased from 67.9% to 78.4% and from 803.12nm to 1253.43nm, respectively. Additionally, M-CS/HBP demonstrated improved viscoelasticity and a more uniform, compact microstructure with denser packing. The alterations observed in CS-based coacervates were due to non-covalent interactions between CS and HBP, further promoted by LF-SMF treatment, leading to the unfolding and disordering of protein secondary structure. Consequently, M-CS/HBP complex coacervates demonstrated superior encapsulation efficiency for L. plantarum and provided enhanced protection for probiotics under adverse environments.

Acidification of Cocoa Nibs using Malic Acid to Modify the Color While Preserving the Bioactive Compounds.

The occurrence of non-fermented cocoa beans in the Indonesian market is still a huge challenge that needs to be solved. Unfermented cocoa beans are considered low-quality cocoa due to their low chocolate flavor and taste, and high bitterness and astringency levels. This limits its usability in the industries. An effort to utilize unfermented cocoa beans can be made through an alternative processing method utilizing an acidification process. Malic acid was used for acidification at various concentrations (0.01, 1, 2.5, and 5%). This acid solution was used to incubate the cocoa nibs for 1,3 and 5 hours. Physicochemical characteristics such as color changes, anthocyanin content, total phenolic content, and antioxidant activity of acidified cocoa nibs were analyzed. Fourier transform infrared spectroscopy analysis was also utilized to evaluate the changes in the functional groups. The results showed that the acidification of cocoa nibs using >1% malic acid significantly altered the color of cocoa nibs from brownish-purple to reddish color. Anthocyanin and phenolic content of cocoa nibs could be preserved to more than 61 and 65%, resulting in preserved antioxidant activity (>66%). The use of 2.5% malic acid followed by incubation for 3 hours resulted in cocoa nibs with bright red color and highly-preserved bioactive compounds.

Construction of Biogas Digester and Produce Biogas from Cow Dung and Chicken Droppings as an Alternative Source of Heat to the Existing LPG Gas

The study analyzed the compositions of cow dung and chicken droppings, revealing that cow dung has a higher proximate composition, containing more organic waste, leading to increased biogas output. Anaerobes break down raw materials through hydrolysis, acidification, and methanization processes. The densities of both materials were found to be different, with cow dung having a larger density than chicken droppings. This results in varying chances of becoming soluble in the digester's contents during fermentation periods. The calorific values of the two raw materials were 7.8 mj/kg for cow dung and 7.9 mj/kg for goat dung. Both materials have a high rate of biogas production and a decent calorific value. The pH values of the slurry for cow dung and chicken droppings were 7.8 and 7.9, respectively. For fermentation and regular gas generation, a pH of 7 to 8.5 is ideal. The modest pH variations between the two substrates might be explained by the type of organic feeds given to animals as ruminants. Gas production was usually started from the 5th day. The pH of the slurry was adjusted to the required value (5-8) by adding 1 N sodium bicarbonate solution. The daily production over 30 days' retention period for the slurry with different pH levels showed that biogas gas production was higher during initial days and decreasing gradually as the day passed. The maximum gas yield was obtained for pH 7 on the 16th day and 8th and 19th in 10 and 20% of cow dung and chicken droppings, followed by 33, 22, and 33, 38 ml for pH 5 on the 25th, 23rd, and 16th, 13th days in 10 and 20% of cow dung and chicken droppings, and 14, 22, and 15, 26.1 cm3 for pH 8 on the 20th, 23rd, and 11th, 18th days in 10 and 20% of cow dung and chicken droppings, respectively

Study on the Influence of Heterogeneity of Low-Permeability Reservoirs on Wormhole Morphology and Acidizing Process Parameters

Carbonate rocks typically exhibit strong heterogeneity, which can have a significant impact on the effectiveness of acidification processes. This article developed a non-homogeneous reservoir acidification process program based on the TSC model and open-source software FMOT, and studied the influence of heterogeneity intensity on wormhole morphology and acidizing process parameters. The results indicate that different heterogeneity intensities can produce different wormhole development patterns and wormhole morphology. In the early stage of acidizing, there is competitive development at low heterogeneity intensities and a transition to dominant wormhole development as the intensity increases. The differences in the wormholes morphology are mainly reflected in the branching wormholes. Low intensity forms fewer and wider branches, while high intensity forms more and narrower branches. As the heterogeneity intensity increases, the curve shows a downward trajectory characterized by a progressively diminishing rate of decline. However, this enhanced heterogeneity does not affect the optimal injection rate. The optimal injection rate increases with the increase in the acid injection temperature. Under high-heterogeneity conditions, the optimal injection rate increases more significantly with the increase in the inject temperature. Additionally, although typically there are increases with the rise in the inject temperature, this trend reverses under high injection rates.

Improving methane production from waste-activated sludge by coupling thermal hydrolysis with potassium ferrate pretreatment

Thermal hydrolysis (TH) is effective in improving the solubilization of waste-activated sludge, but opportunities for enhancement remain, particularly in increasing organic matter conversion and reducing the generation of refractory substances. This study proposed a novel pretreatment method combining TH and potassium ferrate (PF) and evaluated its performance in improving sludge methane production. The results indicated that the combined pretreatment increased the methane yield from 118 ± 2 mL/g VS to 215 ± 7 mL/g VS, an increase of 82.2 % compared to the control. Combined pretreatment promoted the exposure of functional groups in the extracellular polymeric substances (EPS) and altered protein secondary structure composition, thereby disrupting EPS. PF improved the biodegradability of TH-treated sludge by degrading humic acids and Maillard reaction products. In addition, Fe(III) produced by PF induces dissimilar iron reduction, which enhances microbial electron transfer activity and facilitates subsequent hydrolysis and acidification processes. Combined pretreatment increased the abundance of hydrolyzing and acidifying bacteria, but reduced hydrogenotrophic methanogens. This article reveals that PF improves the biodegradability of TH-treated sludge and provides new ideas for advanced TH technologies for sludge resource recovery.

Construction and application of fluorescent probe and sensing aerogel with ability to detect hydrogen sulfide

The dyeing, wastewater acidification and anaerobic treatment processes in the textile always produce a large amount of hydrogen sulfide (H2S), which will be harmful to the human beings. The fluorescent detection of H2S with highly specific and sensitive probe is of significance. Here, using the 2, 7-dichlorofluorescein (DCF) derivative DCF-MPYM as the fluorophore, a fluorescent probe M1 for specifically recognizing H2S was designed and synthesized by introducing 2-chloro-5-nitrobenzoic acid into the oxanthracene moiety of DCF-MPYM. The introduction of 2-chloro-5-nitrobenzoic acid results in DCF-MPYM being in a closed-loop state, thus, the fluorescence quantum yield (Φ) of the probe M1 was low. The characteristic of weak fluorescence plays an important role in the use of a fluorescent probe. The fluorescence titration and selectivity results demonstrated that the probe M1 could selectively detect H2S, and its detection limit for H2S was calculated to be 45.31 μM. The reaction mechanism of the probe was verified by the high-resolution mass spectrometry (HRMS) and liquid chromatography as the nucleophilic addition of H2S to the probe M1, which induced the cleavage of ester bond and subsequently restored the spectral properties of DCF-MPYM. To bring the probe M1 into practical application, the fluorescent aerogel CMC-M1 was constructed by mixing the probe M1 and carboxymethyl cellulose sodium (CMC-Na) aerogel, and the fluorescent aerogel can be applied in absorbing and removing H2S in water. The adsorption capacity and removal efficiency of CMC-M1 for H2S were 0.626 mg·g−1 and 99.36 %. The investigation of adsorption kinetic showed that the adsorption effect of CMC-M1 towards Na2S was mainly chemical adsorption. In addition, the fluorescent aerogel CMC-M1 can be applied for qualitative, quantitative detection and effective removal of H2S in dyeing and finishing wastewater.

Experimental Investigation on the Evolution of Physicochemical Properties and Dissolution Mechanism of High-Siliceous Shale with Acid Treatment

Summary The investigation of the influence of acidification conditions on the modification patterns of shale and the mechanisms of shale acidification processes is an indispensable aspect of further development within the field of shale acidizing theory. Prior research on shale acidizing has predominantly used hydrochloric acid (HCl) and carbonate-rich shale, which has restricted the scope of application for shale acidizing techniques and has not thoroughly examined the reaction kinetics of acid-rock interactions under reservoir conditions. This study focuses on siliceous shale, utilizing hydrogen fluoride (HF) in rotating disk experiments to assess the kinetic parameters of acid-rock reactions under varying acidification conditions, including duration, concentration, temperature, bedding direction, and acid flow velocity. Key influencing factors such as time, temperature, concentration, and experimental methods were selected for a comprehensive analysis, incorporating mineral composition [X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS)], microstructure (SEM), pore medium characteristics [mercury intrusion porosimetry (MIP) and low-temperature nitrogen adsorption (LNA)], surface morphology (3D laser scanning), and nanoindentation testing (NIT). The findings confirm the positive role of acid treatment in enhancing the permeability of shale oil and gas and in softening the reservoir rock, while also indicating potential negative impacts on hydrocarbon extraction, such as the formation of precipitated byproducts and the exfoliation of rock layers. This paper investigates the patterns of influence of HF acidizing parameters on siliceous shale and elucidates the mechanisms of action in shale acidification transformations, thereby providing a theoretical foundation for the modification of shale oil and gas reservoirs.

A feedback loop comprising RhMYB114 and RhMYB16 regulates anthocyanin accumulation and tissue acidification in Rosa hybrida

Coloration in rose (Rosa hybrida) petals is primarily determined by anthocyanin accumulation in vacuoles, and vacuolar acidification plays a central role in controlling the accumulation of this pigment. Nevertheless, the regulatory interplay between anthocyanin accumulation and tissue acidification processes remains somewhat unclear. The present study characterized an activator RhMYB114 and a repressor RhMYB16, which functioned synergistically in anthocyanin accumulation and tissue acidification in rose. Transforming tobacco and roses by overexpression, the introduction of RhMYB114 resulted in an increase in anthocyanin levels and a noticeable decrease in pH in the petal cells of both rose and tobacco, whereas RhMYB16 introduction led to inverse effects. To further clarify the underlying the regulatory mechanisms, the yeast two-hybrid (Y2H), bimolecular fluorescence complementation (BiFC) and dual-luciferase (LUC) were employed. The results showed that RhMYB16 competed with RhMYB114, bound to RhbHLH3 or RhbHLH33, and inhibited its ability to induce the expression of genes related to anthocyanin biosynthesis and acidification. Our findings revealed a feedback mechanism for the regulation of anthocyanin synthesis and tissue acidification involving RhMYB114, which stimulated the transcriptional expression of RhMYB16, whose encoded protein RhMYB16, in turn, negatively regulated the transcriptional expression of RhMYB114. Therefore, this study underscores the pivotal roles of the RhMYB114–RhMYB16 loop in regulating anthocyanin synthesis and tissue acidification, offering insights into metabolic manipulation to enhance the aesthetic appeal of roses.

Mapping Endocytic Vesicular Acidification with a pH-Responsive DNA Nanomachine.

Mapping the endocytic vesicular acidification process is of prior importance to better understand the health and pathological processes of cells. Herein, by integrating a pH-sensitive i-motif and a pair of fluorescence resonance energy transfer (FRET) into a tetrahedral DNA framework (TDF), we develop a pH-responsive DNA nanomachine, allowing for efficient sensing of pH from 7.0 to 5.5 via the pH-triggered spatial proximity modulation of FRET. The inheriting endo-lysosome-targeting ability of TDF enables spatiotemporal tracking of endocytic vesicle acidification during the endosomal maturation process. Analysis of pH-dependent FRET response at single fluorescent spot level reveals the significant difference of endocytic vesicular acidification between normal and cancer cells. The performance of pH-responsive DNA nanomachine underlines its potential for studies on vesicle acidification-related pathologies as a universal platform.

Purification of Crude Glycerol Recovered From Fish Processing Waste Biodiesel Process

Biodiesel and crude glycerol are byproducts of the esterification and transesterification reactions that occur between triglyceride molecules and alcohol in the presence of acid and base catalysts. Purification of crude glycerol is necessary to increase the economic sustainability of the biodiesel industry. This study was carried out for pre-treatment of crude glycerol sourced from fish processing waste during biodiesel manufacturing, treated through an acidification process using phosphoric acid (H3PO4), and then using further purification treatment with Jatropha curcas bio-adsorbent. Based on the measurement, the quantity of 0.1% phosphoric acid (H3PO4) solution was required to treat the crude glycerin. The reaction conditions include heating solution to 60°C and stirring it at 40 rpm for varying treatment periods such as 15, 30, 45, and 60 min. The crude glycerol's pH was adjusted to begin the acidification process, and soap was then converted into fatty acids and salts using phosphoric acid. The maximum purified glycerol yield of 76.6% by weight was obtained with treatment time of 15min using vacuum distillation at 120°C. The crude and purified glycerol’s density was measured as 1.013 g/mL and 1.001 g/mL, respectively. However, after bio-adsorbent treatment at temperature of 50°C and 10% loading weight of the Jatropha curcas bio-adsorbent, the best impurity elimination was accomplished in 15 min. The research findings demonstrated that, following acidification and bio-adsorbent treatments, the FFA% decreased from 2.82% to 2.24%, while its density increased from 1.002 g/mL to 1.032 g/mL, respectively. The purified glycerol properties were found in accordance with BS 2621-1979 standard, showing that the acidification method for purifying of crude glycerol, in conjunction with bio-adsorbent treatment is efficient in enhancing the glycerol purity. It also improves glycerol's application in generating high-value products that enhance revenue streams for the biodiesel production.

Purification Processes for Generating Cationic Lignin-Acrylamide Polymers.

Purification is an essential step in many polymerization processes for fabricating highly pure polymers. This study considered various purification methods for purifying the product of lignin, acrylamide (AM), and diallyl dimethylammonium chloride (DADMAC) copolymerization reactions at a laboratory scale. The charge density, yield, molecular weight, and solubility analyses confirmed that ethanol extraction and membrane filtration were the most effective processes for producing lignin-p(AM)-p(DADMAC). The 1H NMR analysis revealed that the membrane dialysis effectively removed unreacted AM and DADMAC monomers from the reaction medium. The produced samples of the ethanol-extraction and dialysis processes had higher solubility and yield compared to the product of the acidification process. Thermogravimetric studies confirmed that the ethanol-extracted and dialyzed samples had a degradation temperature (220 °C) higher than that of the acidified samples (160 °C). The rheological studies confirmed that the viscosities of the polymer solutions were influenced more by the solubility than by the molecular weight of the generated polymers within the molecular weight range examined in this study. The flocculation studies confirmed that the ethanol-extracted and dialyzed polymers were more effective flocculants than the acidified samples for the particles of a kaolinite suspension. Based on the above results, membrane filtration with a larger pore size could be an environmentally friendly method for effectively purifying lignin-p(AM)-p(DADMAC).

Use of embedding immobilized biofillers to improve hydrolysis acidification efficiency in domestic wastewater treatment

This study evaluated the effectiveness of embedding immobilization technology in wastewater treatment and its capacity to enhance the hydrolysis acidification process. Based on this technology, a stable anaerobic environment has been maintained. Results showed that the rates of dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) conversion both exceeded 98 % under short hydraulic retention time (HRT = 2h) and ambient temperature. Notably, acetic acid and propionic acid comprised up to 90.9 % of the total volatile fatty acids in the effluent, providing suitable carbon sources for downstream denitrification. 16S rRNA gene sequencing indicated that biofillers effectively enriched and retained functional bacteria, causing norank_Anaerolineaceae (11.6 %-29.7 %) and norank_Bacteroidetes_vadinHA17 (10.8 %-14.9 %) as the dominant genera in the reactor, which were crucial for refractory organic matter degradation. Immobilized biofillers effectively improved wastewater biodegradability, supporting a stable microbial community with high DON and DOP conversion rates as well as increased VFA accumulation.

Peracetic acid enhanced anaerobic co-digestion of excess sludge and food waste: performance and mechanism

ABSTRACT Anaerobic co-digestion of excess sludge (ES) and food waste (FW) has been proven to be a clean and efficient strategy for the resource recovery of organic waste. However, the methane production from the anaerobic co-digestion of ES and FW is not optimal. This study reports a new strategy of using peracetic acid (PAA) pretreatment to enhance the anaerobic co-digestion of ES and FW and reveals the underlying mechanisms. The results confirm that PAA can effectively promote the production of methane from the anaerobic co-digestion of ES and FW, with the maximum methane yield reaching 416 mL/g volatile suspended solids at a PAA content of 9% (w/w). Mechanistic analysis indicates that PAA efficiently facilitates the solubilization of organic matter, promoting the release of soluble proteins and polysaccharides, and accelerating the metabolic conversion of volatile fatty acids (VFAs) to prevent excessive acidification. The maximum output of VFA in the PAA group was 1,511–1,974 mg/L, which was lower than that in the control group. Batch experimental analysis revealed that PAA promoted the hydrolysis and acidification processes, but inhibited the methanogenic process. The PAA pretreatment technique provides a theoretical basis for the efficient treatment of organic matter in urban areas.

The effect of Fenton sludge on anaerobic digestion of papermaking wastewater in an upflow anaerobic sludge blanket reactor

An upflow anaerobic sludge blanket (UASB) reactor was used to investigate the effect of adding Fenton sludge (FS) on the anaerobic digestion of actual papermaking wastewater. The results showed that a one-time addition of 10 g/L FS could sustainably promote the performance of UASB for more than 40 days. The organic matter removal efficiency increased by 15.56%, and the biogas production increased by 24.52%. The proportion of methane in biogas increased by 12.87%. Adding FS increased the capacitance values of sludge extracellular polymeric substances and the electron transfer system activity in reactor increased by 1.76 times. The dehydrogenase activity and coenzyme F420 of the sludge increased by 1.54 and 2.11 times, respectively. Adding FS enriched the iron-reducing bacteria (Thermodesulfobacteriota) and hydrolytic acid-producing bacteria (Chloroflexota and Synergistota), thereby promoting the hydrolysis and acidification process. Adding FS was beneficial to the enrichment of methanogen, especially Methanosaeta, significantly increasing the methane production.

Enhancing short-chain fatty acids production from waste activated sludge anaerobic fermentation with addition of red mud: Performance and mechanisms

Red mud (RM) as hazardous waste produced from aluminum refining industry has threatened the environment and human health. In this study, RM was added into the fermenter to promote short chain fatty acids (SCFAs) production from waste activated sludge (WAS) anaerobic fermentation. Results showed that the addition of RM could effectively improve the SCFAs production, especially, acetic acid. In particular, the production of total SCFAs and acetic acid in 20 g/L RM added fermenter were 1108.1 mg COD/L and 415.5 mg COD/L, which were 116.0% and 1308.0% higher than that in control fermenter. Batch experiment revealed that RM could enhance the hydrolysis and acidification process. Further study indicated that the activity of enzyme related to hydrolysis-acidification, abundance of fermentative bacteria for SCFAs production and functional metabolism genome were all improved with the addition of RM. The potential mechanism maybe that the RM promoted the hydrolysis-acidification process with the contained varies Fe(Ⅲ) oxides as electron acceptor, and the produced Fe2+ could serve as necessary trace elements to synthesize enzyme and then stimulate the expression of enzyme genes.

Optimization of the Brewing of “Kablé-Missine”, Togo Northern Local Sorghum Beer

Kablé-missine is a traditional alcoholic beverage predominantly brewed in Northern region of Togo. Despite its widespread consumption and use in various festivities, its quality varies enormously depending on the individual brewing methods. This study aimed to optimize the brewing process of local sorghum beer, kablé-missine, with a particular focus on malting and mashing. Local sorghum grains were subjected to steeping, and key parameters including moisture content during malting, pH, and Brix of the wort were evaluated. The moisture content significantly increased during the steeping phase (39.77 ± 0.44%) and subsequently decreased during germination (37.93 ± 0.53%). The pH of the acidification process was adjusted to 3.11 ± 0.02, and the Brix level significantly increased with extended boiling time in both samples. Moreover, using a limited amount of water during mashing effectively reduced the boiling time.

Insights into multivalent metal removal-assistant anaerobic fermentation of waste activated sludge: Impact factor identification and mechanism clarification of metal removal

The study investigated the impact factors of metal removal and their role in enhancing anaerobic fermentation of waste activated sludge (WAS), aiming to identify key mechanisms. By optimizing the sludge concentration, it found that a sludge suspension solid range of 10–30 g/L significantly improved the efficiency of anaerobic fermentation, and yielded SCOD of 93.8–177.1 mg/g volatile suspension solid after 8 h, respectively, which was 3.67–4.77 times higher than the control. Correspondingly, the production of short-chain fatty acids (SCFAs) was significantly enhanced. At the optimal sludge suspension solid of 10–30 g/L, the SCFAs were 1.28–1.51 times higher than that of the control. Furthermore, the study evaluated the performance of different metal removal reagents and discovered that microporous COOH reagent outperformed gel SO3H and macroporous SO3H reagent. The macroporous COOH reagent achieved 1.54 and 1.22 times higher SCOD values and significantly enhanced the production of SCFAs, demonstrating its superiority in metal removal and fermentation enhancement. Moreover, the research revealed that sludge concentration and metal removal agent types influenced the activities of key enzymes involved in anaerobic fermentation. Additionally, the macroporous COOH reagent showed the most efficient ability to remove metal ions, contributing to increased nutrient recovery in terms of nitrogen (NH4+-N) and total phosphorus (TP) release during the acidification process. In summary, the enhancing mechanism of metal removal-assistant anaerobic fermentation was discussed from the sludge floc concentration, the skeleton structure and the ion exchange group type. The identified mechanism significantly improves fermentation efficiency and facilitate the organic recovery, representing an innovative approach for wide application in WAS management and resource recovery.

Volatile fatty acids (VFAs) production from sludge and chicken manure anaerobic co-fermentation: Effects of mixing ratio and microbial mechanisms

Aimed at exploring the effects of co-fermentation with different dewatered sludge (DS) and chicken manure (CM) ratios on volatile fatty acid (VFA) production, five experimental groups with different DS/CM ratios were set up, the microbial community and the activity of functional enzymes were discussed in this study. The highest concentration of VFAs reached 153.74 mgCOD/gVSS at the ratio of 1:3, and dominated by acetic and propionic acids, which was 1.37 times higher than the control group. The addition of CM contributed to the accumulation of soluble chemical oxygen demand (sCOD) and promoted the release of NH4+-N and PO43--P. High-throughput sequencing results indicated that co-fermentation enriched hydrolytic and acidogenic bacteria to promote the hydrolysis and acidification processes and facilitated the accumulation of VFAs. Firmicutes were the dominant phylum in all experimental groups, and 1:3 ratio was more satisfied with acidogenic bacteria (such as Bacillus and Clostridium_sensu_stricto_1). Meanwhile, the abundances of glycolysis/gluconeogenesis, amino sugar, and nucleotide sugar metabolisms exceeded other groups. Furthermore, this condition exhibited the highest abundances of acetyltransferase [EC: 2.3.1.8] and acetate kinase [EC: 2.7.2.1], which were 2.71 and 1.66 times higher than that in the control group, respectively.

Investigation of models for predicting the effectiveness of acid treatments in carbonate deposits

This article presents the results of an analysis of the available literature data on the acid treatment of carbonates based on the solution approach. The analysis of various acid treatment liquids, the choice of additives and modeling procedures was also carried out in order to optimally design the process of acid treatment of carbonates. Although theoretical models are designed to predict the effectiveness of acid treatments, their practical applicability for scaling at the field level remains uncertain. Scaling laboratory data to the optimal rate does not always lead to results corresponding to the usual values of processing at the field. In modern models, it is proposed to use the geometry of the pipe to calculate the dominant penetration of wormholes and take into account the competition between them, introducing the density of wormholes in a porous medium. However, assigning values that are sensitive to the rock structure and injection conditions is a major difficulty. Instead of predicting the length of dominant wormholes, it is preferable to focus on estimating the permeability resulting from acid injection. However, the permeability assessment is not possible without first calculating the dissolution coefficient. The simulation results demonstrate that the existence of various zones of recesses or cracks in the formation has a significant impact on the acidification process, especially on the direction of wormhole propagation. This direction can be partially controlled by adding deflecting or retarding agents.