Thermal Hydrolysis Research Articles

Enhancing flame retardancy and hydrolysis resistance of flame retardant copolyester fibers by reactive carbodiimide

Polyethylene terephthalate flame retardant copolyester (FRPET) copolymerized with 2-carboxyethyl (phenyl) phosphinic acid (CEPPA) is one of the major copolymerized commercial flame-retardant copolyesters. Similar to conventional PET fibers, the mechanical and flame retardant properties of FRPET fibers after alkaline water post-treatment are reduced. In this work, two kinds of carbodiimide-based masterbatches are added to FRPET fibers, the thermal processing stability, hydrolysis resistance and flame retardancy are significantly improved. The structural and physicochemical properties of the modified FRPET fibers were characterized. The processing thermal stability of FRPET is improved due to the reaction of the double bond structure in carbodiimide with the terminal carboxyl group of polyester to form an acyl urea structure. After melt extrusion, the viscosity reduction of the modified FRPET fiber is only 1.6 %, which is about 10 times lower compared to that of FRPET (17.6 %). After being treated with 50 g/L NaOH solution at 95 °C for 1 h, the tensile strength retention rates of the modified FRPET fibers are over 85.0 %, which is much higher than that of FRPET fibers (71.8 %), showing excellent hydrolysis resistance. In addition, the vertical burning performance of the modified FRPET fibers is improved from V-2 to V-0, and the limiting oxygen index could still reach 25.6 %. Besides that, the mechanism of the combustion process is further discussed.

Impact of Conditioning Agent Addition Sequence on Dewatering Performance of Advanced Anaerobic Digested Sludge

The advanced anaerobic digestion process enhances sludge resource utilization. However, thermal hydrolysis pretreatment of anaerobically digested sludge reduces dewatering efficiency due to excessive organic matter decomposition. This necessitates significant time and effort for sludge conditioning in wastewater treatment plants. Using conditioning agents can achieve high dewatering efficiency. This study investigates how the order of adding coagulants and flocculants impacts the dewatering performance of digested sludge. The results indicate that, compared to the flocculation–coagulation process with the same dosage, the coagulation–flocculation process leads to a 15–20% increase in the average particle size of digested sludge. The content of polysaccharides and proteins in S-EPS decreases by 28.8–30.8% and 10.1–11.3%, respectively. The filter cake solids content increases by 8.5%, and there is an increase in surface water channels within the flocs. This is because initially adding coagulants efficiently adsorbs small particles, forming larger aggregates that settle effectively. This promotes the breakdown of extracellular polymeric substances, releasing more bound water. Adding flocculants later bridges the aggregates, further enhancing settling and filtration performance, thereby improving sludge dewatering efficiency. These research findings contribute to a better understanding of the mechanisms of coagulant and flocculant co-conditioning for digested sludge and provide recommendations for optimizing sludge conditioning steps.

Assisting role of carbonaceous skeleton in sludge thermal hydrolysis and press filtration

As a key step in disposal and reutilization, sludge dewatering is very difficult, since extracellular polymers substances (EPS) binds the water, and compressible organic matter deforms and causes water filtration channels to collapse. Sludge dewaterability was demonstrated to enhance by carbonaceous skeleton (CSkel)-assisted thermal hydrolysis in our previously study. This work further investigated the assisting role of different types of CSkel in EPS decomposition during sludge thermal hydrolysis stage and channels reformation during press filtration stage. Two major types of CSkel, lignocellulosic waste (waste sawdust, waste straw, processing by-product) and protein-rich waste (shrimp shells, jatropha oil cake), were selected. The experimental results showed that in the thermal hydrolysis stage, the decomposition of lignocellulosic waste would increase fatty acids production by 28%, resulting in an acidic environment that reduced the total amount of three hydrophilic amino acids, i.e., glycine, serine and threonine. These promoted the release of water from the sludge. In the press filtration stage, average pore size of sludge was reduced by approximately 87% and nanoscale holes began to appear and increase. Assisting of CSkel rebuilt the filtration channels which brought good connectivity between the pores in sludge cake. Lignocellulosic waste proved significantly more effective than protein-rich waste in achieving a water removal rate of 88.63% under 1 MPa. This study provided a basis for selecting suitable CSkel to optimize sludge dewatering for subsequent utilization.

Can low-temperature thermal hydrolysis mitigate the oxidative stress of polystyrene nanoplastics on anaerobic digestion?

The presence of micro/nanoplastics (MPs/NPs) in sewage sludge has sparked considerable apprehensions over their potential negative effects on anaerobic digestion (AD) performance. The occurrence of MPs/NPs can trigger oxidative stress on the anaerobic microbiome, leading to potential inhibition of the AD process. While the thermal hydrolysis process (THP) is an extensively utilized sludge pretreatment method for AD, its impact on stress induced by MPs/NPs during AD remains poorly understood. In this study, we assessed the impacts of low-temperature THP (90 °C, 90 min) on AD of sewage sludge in the presence of 150 μg/L of polystyrene nanoplastics (PsNPs) under different solid retention times (SRTs) of 20, 15, and 10 d. The presence of PsNPs resulted in a higher reactive oxygen species (ROS) production and a higher abundance of antibiotic resistance genes (ARGs). Additionally, their presence caused a significant inhibition of methane production by 28.2%, 29.3%, and 38.8% for SRTs of 20, 15, and 10 d, respectively. Introducing low-temperature THP prior to the AD could partially recover methane production by mitigating ROS-induced stress and curbing the propagation of ARGs during the AD process. These results shed light on the potential benefits of THP and further optimization opportunities in alleviating the adverse effects of MPs/NPs-induced stress during sewage sludge AD.

Valorisation of waste activated sludge for protease production by Bacillus licheniformis

Waste activated sludge (WAS) is the main by-product of wastewater treatment plants. Its management is considered one of the major environmental challenges worldwide, due to the large volume generated, along with the presence of pathogens and hazardous substances. Nevertheless, the biopolymers present in its structure can make it a promising source of nutrients to obtain high value-added products. Therefore, this study is focused on the use of WAS as a renewable feedstock to produce proteases by Bacillus licheniformis. To this end, both thermal hydrolysis (TH) and wet oxidation (WO) were evaluated as strategies for the solubilization of the valuable compounds. The results revealed that an operation time of 90 min (at 140 °C) was optimal for both pretreatments, which allowed obtaining concentrations of carbohydrates, proteins and humic acids up to 2.7 ± 0.1 g/L, 5.3 ± 0.1 g/L and 5.1 ± 0.1 g/L, respectively. Regarding bioconversion processes, the initial pH of the medium significantly influenced the assimilation of the biopolymers, bacterial growth and enzyme biosynthesis. In this sense, a pH of 5.5 for the WAS pretreated by TH (WAS-TH) and 7.5 for the WAS pretreated by WO (WAS-WO) allowed maximizing the proteolytic activities, reaching values of 767 ± 2 U/mL and 838 ± 6 U/mL, respectively. Additionally, higher initial inoculation levels positively influenced the performance of the fermentative process. Consequently, a 30 % inoculum resulted in enzymatic activities of 828 ± 11 U/mL for WAS-TH and 903 ± 4 U/mL for WAS-WO. Partial purification of the medium with ammonium sulphate increased the enzymatic activity by 7 times for WAS-TH and 3 times for WAS-WO.

Synergistic effect of hydrothermal sludge and food waste in the anaerobic co-digestion process: microbial shift and dewaterability.

While thermal hydrolysis technology is commonly employed for sewage sludge treatment in extensive wastewater treatment facilities, persistent challenges remain, including issues such as ammonia-induced digestive inhibition and reduced productivity stemming from nutrient deficiency within the hydrothermal sludge. In this study, the effects of hydrothermal sludge-to-food waste mixing ratios and fermentation temperatures on anaerobic co-digestion were systematically investigated through a semi-continuous experiment lasting approximately 100days. The results indicated that anaerobic co-digestion of hydrothermal sludge and food waste proceeded synergistically at any mixing ratio, and the synergistic effect is mainly attributed to the improvement of carbohydrate removal and digestive system stability. However, thermophilic digestion did not improve the anaerobic performance and methane yield. On the contrary, mesophilic digestion performed better in terms of organic matter removal, especially in the utilization of soluble carbohydrates, soluble proteins, and VFAs. Microbial community analysis revealed that the transition from mesophilic to thermophilic anaerobic co-digestion prompts changes in the methane-producing pathways. Specifically, the transition entails a gradual shift from pathways involving acetoclastic and hydrogenotrophic methanogenesis to a singular hydrogenotrophic methanogenesis pathway. This shift is driven by thermodynamic tendencies, as reflected in Gibbs free energy, as well as environmental factors like ammonia nitrogen and volatile fatty acids. Lastly, it is worth noting that the introduction of food waste did lead to a reduction in cake solids following dewatering. Nevertheless, it was observed that thermophilic digestion had a positive impact on dewatering performance.

The novel application of polyoxometalates for achieving sludge deep dewatering using low-temperature thermal hydrolysis pretreatment

Traditional thermal hydrolysis pretreatment (THP) for sludge deep dewatering is energy-intensive and poses the risk of generating bio-toxic substances that affect downstream wastewater treatment processes. To address these challenges, this study introduces the novel application of polyoxometalates (POMs) in THP to achieve sludge deep dewatering at lower temperatures. Specifically, under the optimal conditions with a POMs dosage of 1.0 mM/g VSS and a THP temperature of 140 °C, a reduction of 30.36%, 88.31%, and 55.04% in WC, SRF, and CST, respectively, was achieved compared to 20-RS-THP. Further analysis revealed that both the acidity and the biological effect of POMs played the dominant role in enhancing sludge dewatering. Spectroscopic techniques and molecular simulations revealed changes in protein structure during THP induced the POMs-proteins interaction. Results revealed that at lower THP temperatures (<80 °C), POMs induced protonation of functional groups in amino acid residues, strengthening electrostatic interactions. As temperatures increased (80–140 °C), more binding sites in hydrophilic amino acid residues became available for hydrogen bonding with POMs. This interaction led to structural changes in proteins, facilitating water liberation and the formation of sludge colloidal aggregates with improved drainage channels. However, at higher temperatures (140–180 °C), the exposure of hydrophobic sites, the loss of hydrophilic amino acids, and the occurrence of the Maillard reaction in proteins partially offset POMs' binding effects. Moreover, the development of magnetized POMs-based materials may offer sustainability and economic benefits for POMs-based sludge treatment and disposal technologies.

Bioethanol Production from Marine Macroalgae Waste: Optimisation of Thermal acid Hydrolysis

Marine macroalgae waste, resulting from the accumulation of drifted algal biomass along the coastline, might be a relevant complementary raw material aiming sustainable bioethanol production. In the present study, the optimisation of thermal acid hydrolysis was performed using response surface methodology (RSM) considering the effect of three variables, namely, reaction time (10–60 min), acid concentration (0.1–2.5% (v/v) H2SO4) and biomass:acid ratio (5–15% (w/v)) on sugar concentration and yield. Under the best conditions, the resulting hydrolysates were fermented (7 days, 30 °C, 150 rpm, commercial yeast) to produce bioethanol. A statistically valid second-order model was obtained (r2 = 0.9876; Prob > F lower than 0.05), showing that sugar concentration is mostly influenced by the biomass:acid ratio while reaction time was not significant. The maximum predicted sugar concentration was 18.4 g/L, being obtained at 2.5% H2SO4 concentration and 15% (w/v) biomass:acid ratio, corresponding to a sugars yield of 12.5 g/100 g (less 36% than that obtained using 10% (w/v)). At the best conditions, the hydrolysates were fermented to obtain a bioethanol concentration up to 2.4 g/L and a 21 mgbioethanol/gbiomass yield, emphasizing the biomass potential for bioenergy production.Graphical

Sewage sludge-derived nutrients and biostimulants stimulate rice leaf photosynthesis and root metabolism to enhance carbohydrate, nitrogen and antioxidants accumulation

The production of high quality liquid nitrogen fertilizer with both nutrient comprehensive and biostimulant properties by alkaline thermal hydrolysis of sewage sludge has shown great potential in agricultural production. However, little is known about the effects of sewage sludge-derived nutrients, and biostimulants (SS-NB) on leaf photosynthesis and root growth in rice. Phenotypic, metabolic and microbial analyses were used to reveal the mechanism of SS-NB on rice. Compared to NF treatment, phenotypic parameters (fresh/dry weight, soluble sugar, amino acid, protein) were increased by SS-NB in rice. SS-NB can enhance the photosynthesis of rice leaves by improving the photoconversion efficiency, chlorophyll content, ATP synthase activity, Rubisco and NADPH production. Meanwhile, SS-NB also increased antioxidant capacity (SOD, POD, CAT and proline) in rice leaf and root tissues. Metabolomics revealed that SS-NB application increased the expression levels of metabolites in root and leaf tissues, including carbohydrate, nitrogen and sulfur metabolism, amino acid metabolism, antioxidants, and phytohormone. Most importantly, the regulation of metabolites in rice root tissues is more sensitive than in leaf tissues, especially to the higher levels of antioxidants and phytohormones (IAA and GA) in rice root tissues. Furthermore, SS-NB increased the abundance of photosynthetic autotrophic, organic acids-degrading and denitrifying functional bacteria in rice roots and recruited plant growth-promoting bacteria (Azospirillum and norank_f_JG30-KF-CM45), while the NF treatment group resulted in an imbalance of the microbial community, leading to the dominance of pathogenic bacteria. The results showed that SS-NB had great application potential in crop growth and stress resistance improvement.

Low-temperature thermal hydrolysis for enhancing sludge anaerobic digestion and antibiotic resistance management: Significance of digester solids retention time

Recently, there has been a growing inclination towards utilizing primary sludge (PS) fermentation prior to anaerobic digestion (AD) in water resource recovery facilities (WRRFs), where sludge liquor containing volatile fatty acids is used for biological nutrient removal. Nevertheless, using a low-temperature thermal hydrolysis process (THP) to improve AD in WRRFs adopting PS fermentation remains an area that has received limited research attention. Here, we studied the impact of THP (90 °C, 90 min) on anaerobic co-digestion of thickened waste activated sludge (TWAS) and fermented primary sludge (FPS) under varying solids retention times (SRTs) in semi-continuous mode. The study involved two THP schemes: scheme 1, where THP was done for both TWAS and FPS, and scheme 2, where THP was applied to TWAS only. The results demonstrated that reducing SRT from 20 to 15 and 10 d leads to decreased methane yield in both schemes. However, THP significantly enhances methane production, showing improvements of up to 37.9 % (scheme 1) and 31.2 % (scheme 2) under a 15-d SRT. Furthermore, while decreasing SRT increased the proliferation of antibiotic resistance genes (ARGs), thermal hydrolysis could effectively reduce most ARGs, indicating its potential to mitigate antibiotic resistance in the AD process. Overall, these results provide useful perceptions regarding the potential adoption of low-temperature THP in WRRFs with PS fermentation.

Germination Study of Some Protein-Based Gels Obtained from By-Products from the Leather Industry on Tomato and Pepper Seeds.

This study aimed to evaluate the biostimulant effects of three protein-based gels, GHC 1-B (20% gelatin (GPU-B) obtained by thermal hydrolysis from residual untanned leather and 80% collagen hydrolysates (HCE-B) obtained by alkaline-enzymatic hydrolysis from residual bovine-tanned leather), GHC 2-B (40% keratin hydrolysate (HKU-B) obtained by alkaline-enzymatic hydrolysis from sheep wool + 40% HCE-B + 20% GPU-B), and GHC 3-B (20% GPU-B + 80% hydrolyzed collagen (HPU-B) obtained by thermal and enzymatic hydrolysis from residual untanned leather). A germination study was carried out on pepper and tomato seeds at concentrations of 1%, 3%, and 10%. As a result of the study, it was found that all three protein-based gels showed a stimulatory effect on the tomato seeds at a 1% concentration, where the Gi (germination index) was ˂100%. The GHC 2-B variant had the highest stimulatory effect (Gi-190.23%). Pepper seeds have proven to be more sensitive to the gel's composition. The concentration at which it proved to be non-inhibitory (Gi-88.29%) was 1% in the case of GHC 2-B. It was found that the presence of hydrolyzed keratin in the composition can be a plus compared to the other two protein gels tested due to its composition, which is richer in phytonutrient compounds (e.g., sulfur molecules).

ScB2C2: The first high damage tolerant ultra-high temperature ceramic with hydrolysis resistance

The first high damage resistant ultra-high temperature ceramic ScB2C2 with excellent hydrolysis resistance was successfully prepared through boron carbon thermal reduction and hot pressing sintering using Sc2O3, B4C and graphite as raw materials. The Vickers hardness, flexural strength, fracture toughness, Young’s modulus, shear modulus, bulk modulus and Poisson’s ratio of as-prepared ScB2C2 ceramic are 6.0 ± 0.2 GPa, 246 ± 17 MPa, 4.11 ± 0.18 MPa·m1/2, 240 GPa, 101 GPa, 127 GPa and 0.18, respectively. In the a-b plane (B2C2 sheet) and along the c-axis direction, ScB2C2 exhibits extremely strong anisotropy of chemical bonds and elastic properties. The high residual strength, damage tolerance factor Dt and fracture toughness to strength ratio KIc/σf indicates that ScB2C2 has excellent damage tolerance. In addition, ScB2C2 displayed remarkable thermal shock resistance and hydrolysis resistance. These unique features endow ScB2C2 with significant potential for future ultra-high temperature applications.

Double Advantages of Nutrients and Biostimulants Derived from Sewage Sludge by Alkaline Thermal Hydrolysis Process for Agricultural Use: Quality Promotion of Soil and Crop.

Low-carbon alkaline thermal hydrolysis of sewage sludge for the production of high-quality plant-growth-promoting nutrients and biostimulants is a growing concern for sludge resource utilization in agriculture. Thus, this study aims to investigate functional characteristics and soil biochemical effects of sewage sludge-derived nutrients and biostimulants (SS-NB). The content of heavy metals in SS-NB decreased by 47.39-100%, and an increase in soil protease, invertase, and soil nutrient utilization rates are observed in SS-NB groups. SS-NB substituted for chemical fertilizer increased the diversity and evenness of microbial community and reduced the abundance of the soil-borne bacterial genus Arthrobacter. The dominant community of SS-NB100 group is mainly enriched in Microvirga, Ensifer, Novosphingobium, Bosea and Ellin6055, which are principally beneficial symbiotic bacteria of plants and participated in C and N cycles. Moreover, SS-NB reduced the accumulation of Ktedonobacteria and Nitrosospira, which are involved in the production of CO2 and N2O, and also enhanced the coordination of soil microorganisms with enzyme activities and nutrient utilization rate. In conclusion, the results suggest that SS-NB exerts a positive effect on reducing greenhouse gas emissions and preventing soil-borne diseases, and can further enhance collaboration with soil enzyme activity and soil nutrient utilization by stimulating soil microorganisms.

Analytical quality by design aided stability indicating a robust ultra‐performance liquid chromatographic technique for the quantification of sonidegib and its organic impurities in bulk drug substance

AbstractA simple quality by design aided stability indicating method was developed for quantification of sonidegib (SONI) and its process related impurities using on ultra‐performance liquid chromatography in bulk drug substance. AutoChrom and Design‐Expert software were used to predict physicochemical properties, draw Ionization graphs, and generate analytical target profile. SONI was subjected to forced degradation conditions, such as oxidative, acid hydrolysis, base hydrolysis, hydrolytic, thermal, and photolytic hydrolysis. All degradation products and process contaminants were separated using an Acquity Ethylene Bridged Hybrid C18 column in gradient elution mode with a mobile phase containing 0.02 M ammonium acetate buffer and acetonitrile: methanol (80:20 v/v). The predicted physicochemical properties are accurate and they facilitated for selection of robust conditions in development of chromatographic method with minimal trials. The developed method can be used for quantification of drug and its process related impurities in bulk drugs.

Review of Melanoidins as By-Product from Thermal Hydrolysis of Sludge: Properties, Hazards, and Removal

Melanoidins, as macromolecular heterogeneous organic polymers, are produced from the Maillard reaction between amino and carbonyl groups during the thermal hydrolysis pretreatment (THP) of sludge. The brown color and recalcitrance of melanoidins pose a serious threat to wastewater treatment systems, such as invalidating UV disinfection and decreasing the efficiency of anaerobic digestion; thus, they have gradually received much concern in recent years. However, currently the study on THP-origin melanoidins is limited by a lack of reliable extraction and quantification methods. This paper presents a comprehensive review of the physical, chemical, and biological properties of melanoidins from different sources to fill the research gap on THP-origin melanoidins. The adverse effects of melanoidins on the management of wastewater and sludge are discussed, and for the first time, special attention is paid to the potential environmental hazards of THP-origin melanoidins to natural ecosystems. The removal technologies of melanoidins are summarized and compared as well. Finally, the suggested areas that future studies should focus on are provided. This review is dedicated to providing guidance on melanoidin research and management for the better development of the THP industry.

Phosphorus release from sewage sludge and digestate driven by biological sulfate reduction: effect of feed sulfate concentration and thermal hydrolysis

Recovering phosphorus from sewage sludge is a strategic, circular approach to ensure long-term phosphorus availability for future generations, supporting sustainability and resource preservation.

STABILITY INDICATING UPLC METHOD FOR ESTIMATION OF BENAZEPRIL AND HYDROCHLOROTHIAZIDE IN BULK AND COMBINED DOSAGE FORM

Objective: The main objective was to develop stability indicating UPLC technique for simultaneous estimation of Benazepril and Hydrochlorothiazide in bulk and formulation. Methods: 0.1% Triethylamine phosphate: Methanol (25:75v/v) was used as the mobile phase. Benazepril linearity was found to be 4-20 µg/ml and Hydrochlorothiazide linearity was found to be 5-25 g/ml. The detection wavelength was 236 nm, and the retention period of Benazepril was 3.4 min and Hydrochlorothiazide was 5.4 min with a flow rate of 1.0 ml/min. According to the ICH guidlines, the proposed method was validated and stress studies revealed that the drugs are prone to alkali and peroxide stress conditions. Results: The calibration curve was plotted, and the regression equations for Benazepril were y = 2,01,491.67x+60,532.30 with a correlation coefficient (r2) of 0.9997 and Hydrochlorothiazide were y = 64,635.86x-74,607.10 with a correlation coefficient (r2) of 0.9994. According to the accuracy research, the percent recovery of Benazepril is 99.09-100.69 % and that of Hydrochlorothiazide is 98.27-101.88%, both of which are within the ICH recommendations. Benazepril has a limit of detection of 0.08 g/ml-0.24 g/ml and Hydrochlorothiazide has a limit of quantitation of 0.03 g/ml-0.10 g/ml. The procedure was found to be straightforward, linear, rapid, exact, repeatable, and robust. It was determined that the % RSD was within ICH norms. Stress degradation tests showed the drug's vulnerability to oxidative, thermal, photolytic, acid, basic, and neutral hydrolysis stress conditions. Under the circumstances of alkali and peroxide stress, it was discovered that the drug degraded most quickly. Conclusion: The developed chromatographic technique under consideration was suitable for the accurate, precise, and quick simultaneous measurement of hydrochlorothiazide and benazepril in both their bulk and medicinal dose forms.

Effects of carbon diversion to primary sludge production on thermal hydrolysis pretreatment-enhanced anaerobic digestion

Solid mass flow through the WRRF (a) without primary settling, (b) with primary settling and a PS-to-WAS ratio of 1 : 1, and (c) with primary settling and a PS-to-WAS ratio of 3 : 1.

Mesophilic, thermophilic and thermal hydrolysis process coupled anaerobic digestion of sewage sludge: Biomethane potential, pathogen removal and energy feasibility

Conventional Anaerobic digestion is one of the most preferred sludge management techniques however, it has limitations such as low hydrolysis rate, longer retention time, larger digester volume, and reduced methane generation etc., To overcome these problems, Thermal hydrolysis process (THP) has been used as an effective pretreatment method for enhancing methane generation. However, the effect of the thermal hydrolysis process in heavy metal solubilization and methane production from high SRT (solids retention time) sludge is still not clear. Anaerobic digestion of sewage sludge sourced from sequencing batch reactor (SBR) and conventional activated sludge process (CASP) systems were evaluated under mesophilic (MAD), thermophilic (TAD), and thermal hydrolysis process (THP) mediated anaerobic digestion (AD) in terms of methane generation and, VS and pathogen removal. THP resulted in almost 38% COD solubilization for SBR and CASP sludge. Anaerobic digestion of SBR sludge resulted in methane generation of 101, 166, and 390 mL/gVS under mesophilic, thermophilic, and THP pretreatment conditions, respectively. For CASP sludge, the highest methane generation was observed for THP pretreated sludge (587 mL/gVS), followed by thermophilic (298 mL/gVS) and mesophilic digestion (241 mL/gVS). The fecal coliforms in the mesophilic and thermophilic digested SBR sludge were 3000 and 620 MPN/g, respectively, while 6100 and 740 MPN/g were found in digested CASP sludge, respectively. The THP-MAD and TAD processed SBR, and CASP sludges met the Class A sludge fecal coliforms and Salmonella density criteria of <1000 MPN/g TS (dry basis) and 3 MPN/4g TS (dry basis), respectively, over MAD processed sludges. Even though THP pretreatment resulted in the release of heavy metals, the concentration of heavy metals in the THP effluent was lesser than the limits prescribed by USEPA. The energy demand of the THP unit (160 °C, 6 bar) was estimated to be 162 MJ/m3. The energy balance analysis revealed that THP pretreatment would lead to energy self-sufficiency upon integration in a wastewater treatment plant (WWTP). This study can provide an experimental basis to apply THP pretreatment to enhance hydrolysis rate in anaerobic digesters while maximizing methane production and achieving energy benefits over MAD and TAD.

Pure Hydrolysis of Polyamides: A Comparative Study

Polyamides (PAs) undergo local environmental degradation, leading to a decline in their mechanical properties over time. PAs can experience various forms of degradation, such as thermal degradation, oxidation, hydrothermal oxidation, UV oxidation, and hydrolysis. In order to better comprehend the degradation process of PAs, it is crucial to understand each of these degradation mechanisms individually. While this review focuses on hydrolysis, the data from degrading similar PAs under pure thermal oxidation and/or hydrothermal oxidation are also collected to grasp more perspective. This review analyzes the available characterization data and evaluates the changes in molecular weight, crystallinity, chemical structure, and mechanical properties of PAs that have aged in oxygen-free water at high temperatures. The molecular weight and mechanical strength decrease as the crystallinity ratio rises over aging time. This development is occurring at a slower rate than degradation in pure thermal oxidation. By combining the data for the changes in mechanical properties with the ones for molecular weight and crystallinity, the point of embrittlement can be not only predicted, but also modeled. This prediction is also shown to be dependent on the fibers, additives, types of PA, pH, and more.