Effect of Hydrothermal Pretreatment on Volatile Fatty Acids Production from Source-Separated Organics

The main objective of this study was to evaluate the hydrothermal pretreatment’s retention time influence on the volatile fatty acids and biomethane production from thickened waste activated sludge under mesophilic conditions. Six different retention times of 10, 20, 30, 40, 50, and 60 min were investigated while the hydrothermal pretreatment temperature was kept at 170 °C. The results showed that the chemical oxygen demand (COD) solubilization increased by increasing the hydrothermal pretreatment retention time up to 30 min and stabilized afterwards. The highest COD solubilization of 48% was observed for the sample pretreated at 170 °C for 30 min. Similarly, the sample pretreated at 170 °C for 30 min demonstrated the highest volatile fatty acids yield of 14.5 g COD/Lsubstrate added and a methane yield of 225 mL CH4/g TCODadded compared to 4.3 g COD/Lsubstrate added and 163 mL CH4/g TCODadded for the raw sample, respectively. The outcome of this study revealed that the optimum conditions for solubilization are not necessarily associated with the best fermentation and/or digestion performance.

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Characterization of Leachate from a Woodwaste Pile

Water Quality Research Journal ◽

10.2166/wqrj.2005.051 ◽

2005 ◽

Vol 40 (4) ◽

pp. 476-483 ◽

Cited By ~ 23

Author(s):

Wendong Tao ◽

Ken J. Hall ◽

Arash Masbough ◽

Kevin Frankowski ◽

Sheldon J.B. Duff

Keyword(s):

Fatty Acids ◽

Chemical Oxygen Demand ◽

Volatile Fatty Acids ◽

Inorganic Nitrogen ◽

Oxygen Demand ◽

Aquatic Life ◽

Temperature And Precipitation ◽

Lower Oxygen ◽

Late Closure ◽

Leachate Quality

Abstract Leachate was generated when precipitation percolated through a pile of woodwaste, including trimmings, off-specification wood chips, shredded bark and roots, and sawdust from several cedar processing mills. The “young” woodwaste leachate produced in the pile's placement period was amber, acidic (pH 3.4–3.7), nutrient-poor (inorganic nitrogen 1.4–3.2 mg L-1, orthophosphate 3.3–4.3 mg P L-1), of very high oxygen demand (chemical oxygen demand 12,559–14,254 mg L-1, tannin and lignin 3066–5150 mg L-1 as tannic acid, volatile fatty acids 1564–2132 mg L-1), and very toxic to aquatic life (96-h median lethal concentration of 0.74% leachate). The leachate at 1.5 years old in the closure period had lower oxygen demand and higher ammonia, and became less acidic and darker. The leachate had a 5-day biochemical oxygen demand to chemical oxygen demand ratio of 0.33 in the placement period and 0.14 in the late closure period. Volatile fatty acids accounted for 6 to 34% chemical oxygen demand, varying as the pile developed and with woodwaste age. Tannin and lignin accounted for 33 to 45% chemical oxygen demand. More than 98% contaminants were in dissolved form. The monthly variation of leachate quality was likely a result of both temperature and precipitation. pH was significantly correlated to chemical oxygen demand, tannin and lignin, and volatile fatty acids.

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Riboflavin boosts fermentative valeric acid generation from waste activated sludge

BioResources ◽

10.15376/biores.15.2.3962-3969 ◽

2020 ◽

Vol 15 (2) ◽

pp. 3962-3969

Author(s):

Binfang Shi ◽

Jingang Huang ◽

Zhenjiang Yin ◽

Wei Han ◽

Shanshan Qiu ◽

...

Keyword(s):

Fatty Acids ◽

Activated Sludge ◽

Chemical Oxygen Demand ◽

Acid Production ◽

Volatile Fatty Acids ◽

Suspended Solids ◽

Oxygen Demand ◽

Valeric Acid ◽

Waste Activated Sludge ◽

Acid Generation

Fermentative valeric acid production is a promising way to recycle valuable resources from waste activated sludge (WAS). This study investigated the feasibility of using riboflavin (RF) to enhance volatile fatty acids (VFAs) production, especially valeric acid production from WAS coupled with solid reduction. The results indicated that RF (0.5 mM) promoted the VFAs production by up to 41.0%. Valeric acid accounted for the most abundance within the VFAs components. When RF dosages were 0.05 to 5.0 mM in the WAS fermentation systems, the chemical oxygen demand fractions of valeric acid to the total VFAs were 41.0% to 62.8%, which were much higher than those using other chemical supplements. Moreover, RF enhanced the reduction of mixed liquor volatile suspended solids (MLVSS). When RF dosage was 0.2 mM, MLVSS reduction achieved a maximum at 47.4%, compared to that in the RF-free control (33.9% reduction). Riboflavin in this study was considered as a feasible chemical to enhance the fermentative valeric acid generation coupled to MLVSS reduction, realizing the reduction of solids and the reutilization of valuable resources from WAS.

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Acidogenesis of dairy wastewater at various pH levels

Water Science & Technology ◽

10.2166/wst.2002.0331 ◽

2002 ◽

Vol 45 (10) ◽

pp. 201-206 ◽

Cited By ~ 70

Author(s):

H.-Q. Yu ◽

H.H.P. Fang

Keyword(s):

Fatty Acids ◽

Chemical Oxygen Demand ◽

Volatile Fatty Acids ◽

Biomass Yield ◽

Oxygen Demand ◽

Dairy Wastewater ◽

Alcohol Production ◽

Mixed Liquor ◽

Influence Of Ph ◽

Fatty Acids And Alcohols

Continuous experiments were conducted to study the influence of pH in the range 4.0–6.5 on the acidification of dairy wastewater at 37°C with 12 hours of hydraulic retention in an upflow reactor. Results showed that degradation of dairy pollutants increased with pH from pH 4.0 to 5.5. At pH 5.5, 95% of carbohydrate, 82% of protein and 41% of lipid were degraded. Based on chemical oxygen demand (COD), 48.4% of dairy pollutants were converted into volatile fatty acids and alcohols in the mixed liquor, 6.1% into hydrogen and methane in biogas, and the remaining 4.9% into biomass. The biomass yield at pH 5.5 was estimated as 0.32 mg-VSS/mg-COD. Further increase of pH, up to 6.5, increased degradation of carbohydrate, protein and lipid only slightly, but resulted in the lowering of overall acid and alcohol production due to their increased conversion into methane. Acetate, propionate, butyrate and ethanol are the main products of acidogenesis. Productions of propionate and ethanol were favored at pH 4.0−4.5, whereas productions of acetate and butyrate were favored at pH 6.0−6.5.

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Anaerobic Co-digestion of Fruit and Vegetable Waste and Sewage Sludge

International Journal of Chemical Reactor Engineering ◽

10.2202/1542-6580.1439 ◽

2007 ◽

Vol 5 (1) ◽

Cited By ~ 9

Author(s):

Maria Cristina Rizk ◽

Rosangela Bergamasco ◽

Célia Regina Granhen Tavares

Keyword(s):

Fatty Acids ◽

Sewage Sludge ◽

Chemical Oxygen Demand ◽

Volatile Fatty Acids ◽

Oxygen Demand ◽

Organic Load ◽

Vegetable Waste ◽

Fruit And Vegetable ◽

The World ◽

Vegetable Wastes

Fruit and vegetable wastes are generated in large quantities around the world. This kind of residue constitutes a source of nuisance in municipal landfills because of its high biodegradability. Another residue that is generated in large quantities around the world and also constitutes a source of nuisance is the sewage sludge. Both residues can be treated together by the anaerobic co-digestion process. In this sense, the aim of the present study was to evaluate the anaerobic co-digestion of fruit and vegetable waste and sewage sludge, in order to monitor the waste stabilization time and the biogas generation, among others. The study was conducted in a 70 litter stainless steel anaerobic reactor, with no mixing system, at room temperature (25±5ºC), during a period of 105 days. The fruit and vegetable wastes were collected in a central distribution market for food, and were shredded and blended before the experiment. The seed inoculum was collected in an anaerobic domestic sewage station of treatment. The parameters analyzed were: chemical oxygen demand, C/N and C/N/P ratios, pH, alkalinity, volatile fatty acids, and biogas generation. The results showed that the chemical oxygen demand was reduced around 20%. The parameters, pH, alkalinity and volatile fatty acids were stabilized, but the C/N wasnt stabilized. The final value obtained for C/N ratio was around 20/1. The biogas generation was around 331 litters and most of the biogas production occurred during the first month of the experiment. The low chemical oxygen demand removal, the high C/N ratio and the biogas generation almost always in the first few days of the experiment probably indicate that this residue, although being organic, presents difficulties in its degradation, maybe because of the high organic load that was applied to the reactor. The fact of the reactor being disproved by a mixing system can also have contributed to the low residue degradation.

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Effect of pH and hydraulic retention time on volatile fatty acids production from real waste in dark fermentation process

10.32920/ryerson.14657766.v1 ◽

2021 ◽

Author(s):

Muhammed Ali Abdullah Khan

Keyword(s):

Fatty Acids ◽

Activated Sludge ◽

Retention Time ◽

Volatile Fatty Acids ◽

Hydraulic Retention Time ◽

Oxygen Demand ◽

Biological Nutrient Removal ◽

Waste Activated Sludge ◽

Carbon Substrate ◽

Primary Sludge

Waste-derived volatile fatty acids (VFAs) is an important carbon substrate for microorganisms engaged in the production of bioenergy, biodegradable plastics, and biological nutrient removal process. In this project, the generation and applications of waste-derived VFA were examined. Three solid wastes were used Primary sludge (PS), thickened waste activated sludge (TWAS) which were collected from Ashbridges Bay and source separated organics (SSO) that was collected from Disco Road facility. All the water quality analyses such as pH, TCOD, SCOD, TVFA, TSS, VSS, NH3 and, alkalinity were monitored. The results of this study showed that with increasing the Hydraulic retention time (HRT), the percentage of acidification increased. Furthermore, the results showed that alkaline pH was better than the acid pHs. Keywords: Total Volatile Fatty Acids, Soluble Chemical Oxygen Demand, Primary Sludge, Thickened Waste Activated Sludge, Source Separated Organics.

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Effect of the solid retention time in the obtention of polyhydroxyalkanoates

F1000Research ◽

10.12688/f1000research.28852.1 ◽

2021 ◽

Vol 10 ◽

pp. 864

Author(s):

Rolando Calero ◽

Manuel Martínez

Keyword(s):

Fatty Acids ◽

Retention Time ◽

Volatile Fatty Acids ◽

Batch Reactor ◽

Oxygen Demand ◽

Solid Retention Time ◽

Dry Cell Weight ◽

Acidogenic Reactor ◽

Mixed Microbial Cultures ◽

Dry Cell

Background: The effect of solid retention time (SRT) over cheese whey substrates in a fermentation process drives changes in the composition of polyhydroxyalkanoates (PHAs) obtained. Volatile fatty acids produced in the first step of an anaerobic sequencing batch reactor were used as substrates to produce PHA using mixed microbial cultures under aerobic dynamic feeding conditions. Methods: Analytical methods were used for the standard analysis of parameters of interest including measuring the amount of ammonium and phosphate, chemical oxygen demand, among others. Results: The SRT increasing from 4 to 6 and 10 days produced changes in the distribution of volatile fatty acids produced. The polyhydroxybutyrate-hydroxyvalerate copolymers formed in the accumulation stage gave the following results: 58:42, 68:32 and 81:19 (%), referred to SRTs of 10, 6 and 4 days, respectively. The maximum PHA accumulation obtained at 10 days of SRT was 52% of the dry cell weight within 7 h, reaching a PHA productivity of 0.62 g L−1 h−1 and a storage yield of 0.37. Conclusion: The SRT variation impact on the distribution of volatile fatty acids in the acidogenic reactor and consequently on the PHA production and composition formed in the accumulation stage.

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Effect of pH and hydraulic retention time on volatile fatty acids production from real waste in dark fermentation process

10.32920/ryerson.14657766 ◽

2021 ◽

Author(s):

Muhammed Ali Abdullah Khan

Keyword(s):

Fatty Acids ◽

Activated Sludge ◽

Retention Time ◽

Volatile Fatty Acids ◽

Hydraulic Retention Time ◽

Oxygen Demand ◽

Biological Nutrient Removal ◽

Waste Activated Sludge ◽

Carbon Substrate ◽

Primary Sludge

Waste-derived volatile fatty acids (VFAs) is an important carbon substrate for microorganisms engaged in the production of bioenergy, biodegradable plastics, and biological nutrient removal process. In this project, the generation and applications of waste-derived VFA were examined. Three solid wastes were used Primary sludge (PS), thickened waste activated sludge (TWAS) which were collected from Ashbridges Bay and source separated organics (SSO) that was collected from Disco Road facility. All the water quality analyses such as pH, TCOD, SCOD, TVFA, TSS, VSS, NH3 and, alkalinity were monitored. The results of this study showed that with increasing the Hydraulic retention time (HRT), the percentage of acidification increased. Furthermore, the results showed that alkaline pH was better than the acid pHs. Keywords: Total Volatile Fatty Acids, Soluble Chemical Oxygen Demand, Primary Sludge, Thickened Waste Activated Sludge, Source Separated Organics.

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