Combined hydrothermal and free nitrous acid, alkali and acid pretreatment for biomethane recovery from municipal sludge

Kakar, Farokh Laqa; Purohit, Neha; Okoye, Frances; Liss, Steven N.; Elbeshbishy, Elsayed

doi:10.1016/j.wasman.2021.06.021

Cited by 18 publications

(9 citation statements)

References 43 publications

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“…The literature also reported that the COD solubilization for the thermo-alkaline pretreatment is higher than that of the thermo-acid pretreatment (Kakar et al, 2021). Other scholars have also broadly investigated the privilege of alkaline addition when using HTP (C. Since SC, temperature, and pH were substantial factors, the impact of retention time in a small range of 10-30 min was negligible.…”

Section: Discussionmentioning

confidence: 99%

“…Thus, suitable pretreatment is required to enhance digestibility by improving the hydrolysis stage Several studies have been conducted to evaluate the effect of hydrothermal pretreatment on municipal sludge (Kakar et al, 2021;Mu et al, 2021). Accordingly, most of the results confirmed a positive effect on the fermentation/acidification process and biogas production.…”

Section: Discussionmentioning

confidence: 99%

“…Fermentate and center of the fermentate from the four systems were used as the substrate for BMP tests.The samples' methane production rate and biodegradability fraction were determined using BMP testsRajput et al, 2018;Ryue et al, 2020). A previous study described the method and conditions used(Kakar et al, 2021).…”

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confidence: 99%

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Application of Hydrothermal Pretreatment for Improving the Fermentation and Anaerobic Digestion Processes for Resource Recovery from Municipal Solid Waste

Kakar

2024

Preprint

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<p>This thesis comprehensively investigated the hydrothermal pretreatment (HTP) parameters' impact on the sludge disintegration, volatile fatty acid (VFA), and methane production. It has also studied different process configurations and the development of a novel thermal-hydrolysis and vacuum fermentation for high-grade VFA recovery. Results confirmed the significant impact of HTP on all process parameters and a direct correlation between the retention time, sludge pH, and solid content with process parameters. The highest COD solubilization and solid destruction percentage were observed for the retention time of 30 minutes, pH 10, and solid content (SC) of 10%. It was found that fermentative bacteria prefer consuming sludge with lower solid content while methanogenesis produced higher methane consuming sludge with SC of 16%. The combination of thermal hydrolysis with chemical pretreatments also played a crucial role in resource recovery. Combining free nitrous acid and thermal hydrolysis demonstrated the highest methane production efficiency compared to the combination with typical acetic acid and sodium hydroxide. Moreover, the impact of HTP parameters on mesophilic and thermophilic fermentation was investigated and ultimately, 10-15% higher solubilization and VFA production occurred during thermophilic fermentation compared to mesophilic. Further, different process configurations of HTP with fermentation and anaerobic digestion were examined while hydrothermal pretreatment was found to have superior results for COD solubilization (25.5%), VFA production (65 g Acetate/L), and methane production (230 mL CH /g 4COD added) compared to the hydrothermal inter-treatment (HIT). Mathematical models developed by incorporating more than 100 sample points from studies mentioned above further defined the correlation of HTP and process response parameters. The best conditions of HTP from observations in the first phase were utilized to pretreat TWAS for the next phase. The pretreated TWAS and PS mixture was then used as the substrate of the novel integrated thermal hydrolysis and vacuum fermentation. Vacuum fermentation integrated with HTP demonstrated the highest (45%), VFA yield (0.32 g COD/g VSS added), and methane yield (267 mL CH4/g TCOD added) compared to the systems without pretreatment and vacuum. Microbial community analysis confirmed that HTP and vacuum application significantly impact the bacterial community's diversity. A bigger population of fermenters such as coprothermobacteraeota was observed in vacuum systems and for pretreated samples.</p>

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Application of Hydrothermal Pretreatment for Improving the Fermentation and Anaerobic Digestion Processes for Resource Recovery from Municipal Solid Waste

Kakar

2024

Preprint

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“…As FNA is a chemical requiring minimal acid addition for implementation as sludge pretreatment to AD, studies have been conducted to investigate further advantages that may be achieved by combining it with other pretreatment technologies. 1.8 g N/L of FNA was added after hydrothermal pretreatment of TWAS at 170°C for 30 minutes, increasing methane yield by 18% compared to the sole hydrothermal pretreatment (Kakar et al, 2021). FNA addition to the hydrothermal pretreatment showed better performance than acid (pH 3) and alkaline (pH 10)…”

Section: Free Nitrous Acid Treatment In Water Resource Recovery Facil...mentioning

confidence: 99%

“…Combining 1.8 mg HNO2-N/L with hydrothermal pretreatment at 170 °C for 30 minutes resulted in 43% increase in methane production compared to the untreated sludge (Kakar et al, 2021).…”

Section: Effect Of Combined Pretreatment On Anaerobic Digestionmentioning

confidence: 99%

Anaerobic Process Intensification With Vacuum and Combined Pretreatment Technologies

Okoye

2024

Preprint

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Anaerobic digestion and fermentation are essential processes for transforming wastewater treatment plants into robust energy, nutrient, and water recovery facilities. However, these processes' slow microbial growth rate and low yields limit their application to larger facilities. To improve their efficiency, intensifying anaerobic digestion and fermentation (to a lesser extent) has been the subject of numerous research studies. This dissertation explored the principle of vacuum evaporation for combining sludge thickening, decoupling of hydraulic and retention times, and nutrient recovery into a single treatment unit. Gaps, including the efficiency of vacuum sludge thickening at different solids content, its impact on anaerobic bacteria and the overall physio and biochemical processes, were investigated. In batch fermentation, establishing 400 mbar of absolute pressure led to 49% solubilization of primary sludge in 72 hours compared to the conventional fermentation in which 11% solubilization was achieved. During fermentation of TWAS at 400 mbar, deterioration of solubilization and VFA yield was observed. The vacuum technology was used to decouple the hydraulic and solids retention time (HRT/SRT) in semi-continuous fermentation of mixed sludge. At SRT of 3 days and HRT of 1.5 days, the vacuum-assisted fermenter yielded 660 mg sCOD/g VSS compared to the conventional fermenter which achieved 513 mg sCOD/g VSS with equal HRT and SRT of 3 days. Additionally, 50% of the ammonia produced in the fermenter was extracted in the condensate with no chemical alterations. The results led to the development of IntensiCarb, a patent-pending technology that combines sludge thickening, digestion, and dewatering into a single unit. This dissertation also investigated the use of combined chemical-mechanical and chemical-chemical pretreatment technologies with free nitrous acid (FNA) to enhance the anaerobic digestion of TWAS. FNA is an environment-friendly chemical that can be produced in wastewater treatment facilities. In this study, FNA concentrations from 0.7 to 2.8 mg HNO2-N/L were combined with ultrasonication energy input from 600 to 3,000 kj/kg TS to explore the feasibility of lower energy input for effective sludge disintegration and enhanced anaerobic digestion. The energy input for ultrasonication could be halved from 3,000 kj/kg TS to 1,500 kj/kg TS by adding 2.8 mg HNO2-N /L while improving solubilization by 43% and methane yield by 18%. FNA was also combined with hydrogen peroxide, an oxidizing chemical that has shown effectiveness in improving biodegradability at low pH. The results showed that the pretreatment combination with the lowest chemical concentrations of 0.7 mg HNO2-N /L and 25 mg H2O2/g TS was the most effective for maximizing methane yield, increasing it by 50% compared to the untreated TWAS.

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Sodium alginate/sinter gel spheres immobilized lysozyme producing strain SJ25 enhanced sludge reduction: Optimization and mechanism

Yan

Ali

et al. 2023

Bioresource Technology

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Combined hydrothermal and free nitrous acid, alkali and acid pretreatment for biomethane recovery from municipal sludge

Cited by 18 publications

References 43 publications

Application of Hydrothermal Pretreatment for Improving the Fermentation and Anaerobic Digestion Processes for Resource Recovery from Municipal Solid Waste

Application of Hydrothermal Pretreatment for Improving the Fermentation and Anaerobic Digestion Processes for Resource Recovery from Municipal Solid Waste

Anaerobic Process Intensification With Vacuum and Combined Pretreatment Technologies

Sodium alginate/sinter gel spheres immobilized lysozyme producing strain SJ25 enhanced sludge reduction: Optimization and mechanism

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