Hydrogen and methane production by co-digestion of waste activated sludge and food waste in the two-stage fermentation process: Substrate conversion and energy yield

2013 ◽  
Vol 146 ◽  
pp. 317-323 ◽  
Author(s):  
Xinyuan Liu ◽  
Ruying Li ◽  
Min Ji ◽  
Li Han
Keyword(s):  
Activated Sludge ◽  
Food Waste ◽  
Methane Production ◽  
Fermentation Process ◽  
Waste Activated Sludge ◽  
Energy Yield ◽  
Two Stage ◽  
Substrate Conversion

scholarly journals Effects of Two-Stage Operation on Stability and Efficiency in Co-Digestion of Food Waste and Waste Activated Sludge

Energies ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2748 ◽  
Author(s):  
Xinyuan Liu ◽  
Ruying Li ◽  
Min Ji
Keyword(s):  
Activated Sludge ◽  
Food Waste ◽  
Oxygen Demand ◽  
Single Stage ◽  
Waste Activated Sludge ◽  
Energy Yield ◽  
Two Stage ◽  
Thermoanaerobacterium Thermosaccharolyticum ◽  
Organics Removal ◽  
Operation Stability

The two-stage anaerobic digestion (AD) technology attracts increasing attention due to its ability to collect both hydrogen and methane. A two-stage AD system feeding with food waste and waste activated sludge was investigated in order to achieve higher energy yield and organics removal. The two-stage process consists of a thermophilic H2-reactor and a mesophilic CH4-reactor, achieved the highest hydrogen and methane yields of 76.8 mL/g-VS and 147.6 mL/g-VS at hydraulic retention times (HRTs) of 0.8 d and 6 d, respectively. The co-digestion process in this study required much less external alkalinity to maintain the pH values than sole food waste digestion in the literature. Compared with the single-stage mesophilic methane AD process, the two-stage AD system had better performance on operation stability, biogas and energy yields, organics removal and chemical oxygen demand (COD) conversion at high organic loading rates (OLRs). According to the TA-cloning analysis, the dominant bacteria in H2-reactor was closely related to Clostridium sp. strain Z6 and species Thermoanaerobacterium thermosaccharolyticum. The dominant methanogens in two-stage and single-stage CH4-reactor were recognized as acetotrophic methanogens and hydrogenotrophic methanogens, respectively. The presence of the genus Nitrososphaera in the two CH4-reactors might contribute to the low NH4+-N concentration in digestate and low CO2 content in biogas.

Anaerobic Co-Digestion of Food Waste and Thermal Pretreated Waste Activated Sludge: Synergetic Effect and Energy Assessment

2021 ◽  
Author(s):  
Jian Zhang ◽  
Peng Gan ◽  
Ru-yi Wang ◽  
Tian Xie ◽  
Yang Liu ◽  
...  
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Food Waste ◽  
Methane Production ◽  
Synergetic Effect ◽  
Gompertz Model ◽  
Waste Activated Sludge ◽  
Thermal Pretreatment ◽  
Energy Assessment ◽  
Modified Gompertz Model

Abstract Thermal pretreatment was an effective method to improve the anaerobic digestion of waste activated sludge. However its application in China was still hindered by the high energy demand. In order to balance the energy consumption of sludge thermal pretreatment integrated with anaerobic digestion, food waste was introduced as co-substrate to achieve an energy self-sustainable sludge treatment system. Anaerobic biodegradability test was performed using thermal pretreated sludge and food waste in order to clarify the kinetics and mechanism of co-digestion, especially the synergetic effect on specific methane yield. The prominent synergetic effect was an initial acceleration of cumulative methane production by 20.7- 23.8% observed during the first 15 days, and the cumulative methane production of feedstock can be calculated proportionately from its composition. Between the evaluated models, modified Gompertz model presented a better agreement of the experimental results and it was able to describe the synergetic effect, assessed by the relative deviation between theoretical estimation and the experimental results of co-digestion tests. This feature made modified Gompertz model a suitable tool for methane production prediction of mono- and co-digestion. Energy assessment shown that co-digestion with food waste was a sustainable solution to maintain the integration of thermal pretreatment and anaerobic digestion energy neutral or even positive. Besides, the performance of sludge dewatering was a crucial factor for the energy balance.

Effects of thermochemical pretreatment on the anaerobic digestion of waste activated sludge

1997 ◽  
Vol 35 (8) ◽  
pp. 209-215 ◽  
Author(s):  
Shuzo Tanaka ◽  
Toshio Kobayashi ◽  
Ken-ichi Kamiyama ◽  
Ma. Lolita N. Signey Bildan
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Production Rate ◽  
Methane Production ◽  
Waste Activated Sludge ◽  
Batch Experiments ◽  
Industrial Wastewaters ◽  
Thermochemical Pretreatment ◽  
Chemical Heating ◽  
Methane Production Rate

Effects of pretreatment on the anaerobic digestion of waste activated sludge (WAS) were investigated in terms of VSS solubilization and methane production by batch experiments. The methods of pretreatment studied are NaOH addition (chemical), heating (thermal) and heating with NaOH addition (thermochemical) to the domestic WAS and to the combined WAS from domestic, commercial and industrial wastewaters. The thermochemical pretreatment gave the best result among three methods in the combined WAS, i.e., the VSS was solubilized by 40-50% and the methane production increased by more than 200% over the control when the WAS was heated at 130°C for 5 minutes with the dose 0.3 g NaOH/g VSS. In the domestic WAS, the VSS solubilization rate was 70-80% but the increase of the methane production was about 30% after thermochemically pretreated. The domestic WAS consists of 41% protein, 25% lipid and 14% carbohydrate on COD basis, and the solubilization rate of protein, which is the largest constituent of the WAS, was 63% in the thermochemical pretreatment. Although the effect of the thermochemical pretreatment on the methane production was higher to the combined WAS than to the domestic WAS, the methane production rate was 21.9 ml CH4/g VSSWAS·day in the domestic WAS and 12.8 ml CH4/g VSSWAS·day in the combined WAS.

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