scholarly journals Methane conversion efficiency as a simple control parameter for an anaerobic digester at high loading rates

2011 ◽  
Vol 64 (2) ◽  
pp. 534-540 ◽  
Author(s):  
W. Charles ◽  
N. P. Carnaje ◽  
R. Cord-Ruwisch
Keyword(s):  
Anaerobic Digestion ◽  
Production Rate ◽  
Conversion Efficiency ◽  
Methane Conversion ◽  
Control Parameter ◽  
Loading Rate ◽  
High Loading ◽  
Loading Rates ◽  
Ch4 Production ◽  
On Line

The anaerobic digestion process is globally applied to the treatment of highly concentrated wastes such as industrial and rural effluents, and sewage sludge. However, it is known to be relatively unstable. When loaded with high concentrations of organic material, unwanted volatile fatty acids (VFA) are often produced rather than methane (CH4) gas which can lead to digester acidification and failure. This study investigated digester behaviour under high loading rates, testing the usefulness of stoichiometric methane conversion efficiency as a digester control parameter at high loading rates. Our results show that, in general, the CH4 production rate was proportional to the feed rate (loading rate). However, at very high loading rates, the CH4 production rate was not proportional to the increase in the feeding rate. Consequently, VFA accumulated and the H2 partial pressure increased. The proportionality of the loading rate and gas production rate is stoichiometrically expressed as the conversion efficiency. We found that conversion efficiency was a useful indicator as an early warning of digester imbalance. The digester remained stable at conversion efficiencies above 75%. Dropping below 70% signified the onset of digester failure. As loading rate and methane production data are readily available on-line in most anaerobic digestion plants, the conversion efficiency can be monitored on-line and used as an efficient control technique to maintain safe operation of anaerobic digesters at high loading rates.

scholarly journals Stimulation of Biomethane Productivity in Anaerobic Digestion Using Electro-Conductive Carbon-Nanotube Hollow-Fiber Media

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 179
Author(s):  
Seongmin Yang ◽  
Seungyeob Han ◽  
Yeo-Myeong Yun ◽  
Seoktae Kang
Keyword(s):  
Carbon Nanotube ◽  
Anaerobic Digestion ◽  
Production Rate ◽  
Hollow Fiber ◽  
Laser Scanning ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Ch4 Production ◽  
Microscopic Morphology ◽  
Positive Effect

The production of biogas was promoted via direct interspecies electron transfer (DIET) by employing electro-conductive carbon-nanotube hollow-fiber media (CHM) in anaerobic digestion. Experimental results showed a positive effect of CHM presence on CH4 productivity with 34% higher CH4 production rate than that of in the presence of non-electroconductive polymeric hollow fiber media. An increased CH4 production rate was due to the shift in the microbiome with more abundant Pelobacter (10.0%), Geobacter (6.9%), and Methanosaeta (15.7%), which play key roles in promoting CH4 production via syntrophic metabolism associated with DIET. Microscopic morphology analysis, using confocal laser scanning microscopy and scanning electron microscopy, exhibited that several living cells were attached with electro-conductive pili on the CHM surface, thereby facilitated electron transport between microbial cells.

Dairy Waste Treatment with Anaerobic Stationary Fixed Film Reactors

1983 ◽  
Vol 15 (8-9) ◽  
pp. 359-368 ◽  
Author(s):  
L van den Berg ◽  
K J Kennedy
Keyword(s):  
Cheese Whey ◽  
Loading Rate ◽  
Cod Removal ◽  
High Loading ◽  
Loading Rates ◽  
Dairy Wastes ◽  
Plant Waste ◽  
Fixed Film ◽  
Dairy Plant ◽  
Removal Efficiencies

Cheese whey and a dilute waste from a cheese factory with a Chemical Oxygen Demand of 66,000 and 4,000 mg (COD)/L respectively, were treated at high loading rates in 0.7 to 1.2 L downflow anaerobic stationary fixed film reactors and an upflow sludge bed reactor. In downflow stationary fixed film reactors treating cheese whey, COD removal efficiencies of 97% were achieved at a loading rate of 5 kg COD/m3/day and 92% at a maximum loading rate of 22 kg COD/m3/day. With dairy plant waste, loading rates of up to 15 kg COD/m3/day were possible with COD removal efficiencies averaging 75%, decreasing slightly with increasing loading rates. In an upflow sludge bed reactor the COD removal efficiency of dairy plant waste, decreased from 87% at 5 kg COD/m3/day to 73% at 15 kg COD/m3/day. A stationary fixed film reactor treating a skim milk powder waste (4,000 ppm) could only be operated at up to 10 kg COD/m3/day with a treatment efficiency of 72%. Methane was produced from all wastes at rates corresponding to 0.32 m3 CH4 (0°C, 1 atm) per kg COD removed. Results show that stationary fixed film reactors are capable of treating dairy wastes at high loading rates and high COD removal efficiencies.

Dynamic Simulation of Crack Propagation with Dislocation Emission and Migration

1995 ◽  
Vol 408 ◽  
Author(s):  
N. Zacharopoulos ◽  
D. J. Rolovitz ◽  
R. A. Lesar
Keyword(s):  
Crack Propagation ◽  
Crack Growth ◽  
Dynamic Simulation ◽  
Loading Rate ◽  
High Loading ◽  
Spatial Evolution ◽  
Dislocation Emission ◽  
Loading Rates ◽  
Simulation Procedure ◽  
And Migration

AbstractWe present a simulation procedure for fracture that self-consistently accounts for dislocation emission, dislocation migration and crack growth. We find that the dislocation microstructure in front of the crack tip is highly organized and shows a complex temporal-spatial evolution. The final dislocation microstructure and the number of emitted dislocations immediately proceeding fracture varies rapidly with the loading rate. For high loading rates, fracture occurs at smaller loads with increasing loading rate. However, the load at fracture shows a maximum with respect to loading rates.

Loading Rate Effect Investigation of Through-Hole-Mounted Solder Joints

2005 ◽  
Author(s):  
Frank Z. Liang ◽  
Larry M. Palanuk ◽  
Mike Gabriel
Keyword(s):  
Solder Joint ◽  
High Speed ◽  
Loading Rate ◽  
High Loading ◽  
Static Tests ◽  
Loading Rates ◽  
Wide Range ◽  
Load To Failure ◽  
The Impact ◽  
Through Hole

This paper presents two simple and unique tests to extract shock-level loading limits for eutectic and lead free solders. A wide range of loading rates, from quasi-static to high speed, was applied to a through-hole-mounted anchor assembly test coupon. The high speed shock tests were conducted on a drop shock table where the impacting velocities were derived through table input adjustments. The quasi-static tests were done using controlled hydraulic linear actuator with a load cell. As would be assumed, the dynamic load to cause solder joint failure was found to increase with higher loading rate. However, at such a high loading rate range, the impact velocity did not change the load to failure. This study leads to an interesting hypothesis that at high loading rates, the solder joint strain rate may not see a significant change as observed at low rates.

Anaerobic co-digestion of sewage sludge and food waste using temperature-phased anaerobic digestion process

2004 ◽  
Vol 50 (9) ◽  
pp. 107-114 ◽  
Author(s):  
H.-W. Kim ◽  
S.-K. Han ◽  
H.-S. Shin
Keyword(s):  
Anaerobic Digestion ◽  
Sewage Sludge ◽  
Production Rate ◽  
Food Waste ◽  
Batch Reactor ◽  
Hydrolytic Activity ◽  
Organic Loading Rate ◽  
Methanogenic Activity ◽  
Ch4 Production ◽  
Low Efficiency

This study was performed to overcome the low efficiency of anaerobic digestion of sewage sludge and food waste by combining temperature-phased digestion, sequencing batch operation, and co-digestion technology. It was demonstrated that the temperature-phased anaerobic sequencing batch reactor (TPASBR) system for the co-digestion of sewage sludge and food waste resulted in enhanced volatile solids (VS) reduction and methane production rate. At the organic loading rate (OLR) of 2.7 g VS/l/d, the TPASBR system showed the higher VS reduction (61.3%), CH4 yield (0.28 l/g VSadded) and CH4 production rate (0.41 l CH4/l/d) than those (0.29 l CH4/l/d) of the mesophilic two-stage ASBR (MTSASBR). In the specific methanogenic activity (SMA) tests on thermophilic biomass of the TPASBR system, the average SMA of acetate (93 ml CH4/gVSS/d) was much higher than those of propionate (46 ml CH4/g VSS/d) and butyrate (76 ml CH4/g VSS/d). Also, higher specific hydrolytic activity (SHA, 217 mg COD/g VSS/d) of the biomass supported fast hydrolysis under thermophilic conditions. The track study revealed that the most active period of the 24 h cycle was between 6 and 12 h. The enhanced performance of the TPASBR system could be attributed to longer solids retention time, fast hydrolysis, higher CH4 conversion rate, and balanced nutrient condition of co-substrate. It was verified that this combination could be a promising and practical alternative for the simultaneous recycling of two types of organic fraction of municipal solid waste (OFMSW) with high stability.

The performance and microbial diversity of temperature-phased hyperthermophilic and thermophilic anaerobic digestion system fed with organic waste

2008 ◽  
Vol 57 (2) ◽  
pp. 283-289 ◽  
Author(s):  
M. Y. Lee ◽  
J. H. Cheon ◽  
T. Hidaka ◽  
H. Tsuno
Keyword(s):  
Anaerobic Digestion ◽  
Microbial Diversity ◽  
Conversion Efficiency ◽  
Methane Conversion ◽  
Organic Waste ◽  
Effect Of Temperature ◽  
High Concentration ◽  
Thermophilic Anaerobic Digestion ◽  
In Series ◽  
Increasing Temperature

The objective of this study was to evaluate the performances and microbial diversities for development of the effective hyperthermophilic digester system that consists of a hyperthermophilic reactor and hyperthermophilic or thermophilic reactor in series. Lab-scale reactors were operated continuously fed with artificial kitchen garbage. The effect of temperature on the acidification step was firstly investigated. Results indicated that 20.8% of COD solubilization was achieved at 70°C, with 12.6% at 80°C. The average protein solubilization reached 31% at 80°C. Methane conversion efficiency following the acidification was around 85% on average at 55°C, but decreased with increasing temperature and methane gas was not produced over 73°C. As well, bacteria affiliated with the methanogens dominated the population below 65°C, while those affiliated with acidogens were predominant over 73°C. These results indicated that the hyperthermophilic process has considerable benefits to treat wastewater or waste containing high concentration of protein.

A Potential Treatment Alternative for Swine Wastewater in the Tropics

1985 ◽  
Vol 17 (4-5) ◽  
pp. 819-831 ◽  
Author(s):  
P. Y. Yang ◽  
S. Y. Nagano
Keyword(s):  
Anaerobic Digestion ◽  
Production Rate ◽  
Algal Biomass ◽  
Energy Production ◽  
Loading Rate ◽  
Gas Production ◽  
Energy Utilization ◽  
Swine Wastewater ◽  
N Removal ◽  
The Tropics

Development of a low-cost and effective swine waste management system in the tropics is the main objective of this study. Because of the apppropriate temperature environment and abundance of sunlight, an integration of an anaerobic digestion and an algal biomass process was selected and investigated. A pilot, plant integrating a 20 m3 anaerobic digester with sludge recycling and a 120 m3 algal-biomass raceway were installed and evaluated. Maximum gas production rate of 1.527 liter/liter/day (69% methane content) can be achieved by a TVS loading rate of 4.23 gram/liter/day. A sludge production rate of 0.82-2.62 g TS/liter is obtained from a TVS loading rate of 0.76-4.23 g TVS/liter/day. Critical SRT for maximum gas production rate is 2.67. For the algal biomass raceway, a loading rate of 0.097 g SCOD/liter/day or 0.017 g NH4-N/liter/day would achieve SCOD and NH4-N removal efficiencies of 94.44% and 98.42%, respectively. Combining the previous analysis of energy input and land requirement for an algal biomass raceway and mass balance of energy production and utilization, integrating the energy production (anaerobic digestion) and energy utilization (dehydration of digested sludge and power requirement of raceway) provides a great potential for a swine wastewater treatment in the tropics.

Simultaneous treatment of sewage sludge and food waste by the unified high-rate anaerobic digestion system

2006 ◽  
Vol 53 (6) ◽  
pp. 29-35 ◽  
Author(s):  
H.-W. Kim ◽  
S.-K. Han ◽  
H.-S. Shin
Keyword(s):  
Anaerobic Digestion ◽  
Sewage Sludge ◽  
Production Rate ◽  
Food Waste ◽  
High Rate ◽  
Organic Loading Rate ◽  
Simultaneous Treatment ◽  
Methanogenic Activity ◽  
Ch4 Production ◽  
Methane Production Rate

This study aimed to evaluate the performance of the unified high-rate anaerobic digestion (UHAD) system treating co-substrate of sewage sludge and food waste. A 24-hr operating sequence consisted of four steps including fill, react, settle, and draw. The effects of co-substrate and organic loading rate (OLR) on the performance were investigated to verify the system applicability. In each OLR, the UHAD system showed higher CH4 recovery (>70%), CH4 yield (0.3 L CH4/g VSadded) and CH4 production rate (0.6 L CH4/L/d) than the control system. In the specific methanogenic activity (SMA) tests on thermophilic biomass of the UHAD system, the average SMA of acetate (102 mL CH4/gVSS/d) was much higher than those of butyrate (85 mL CH4/g SS/d) and propionate (42 mL CH4/gVSS/d). It was demonstrated that the UHAD system for co-digestion resulted in higher methane yield and methane production rate due to sequencing batch operation, thermophilic digestion, and co-digestion. The enhanced performance could be attributed to longer retention time of active biomass, faster hydrolysis, higher CH4 conversion rate, and balanced nutrient conditions of co-substrate in the UHAD system. Consequently, this optimized unification could be a viable option for the simultaneous treatment of two types of OFMSW with high stability.

Dynamic Simulation Of Crack Propagation With Dislocation Emission And Migration

1995 ◽  
Vol 409 ◽  
Author(s):  
N. Zacharopoulos ◽  
D.J. Srolovitz ◽  
R.A. LeSAR
Keyword(s):  
Crack Propagation ◽  
Crack Growth ◽  
Dynamic Simulation ◽  
Loading Rate ◽  
High Loading ◽  
Spatial Evolution ◽  
Dislocation Emission ◽  
Loading Rates ◽  
Simulation Procedure ◽  
And Migration

AbstractWe present a simulation procedure for fracture that self-consistently accounts for dislocation emission, dislocation migration and crack growth. We find that the dislocation microstructure in front of the crack tip is highly organized and shows a complex temporal-spatial evolution. The final dislocation microstructure and the number of emitted dislocations immediately proceeding fracture varies rapidly with the loading rate. For high loading rates, fracture occurs at smaller loads with increasing loading rate. However, the load at fracture shows a maximum with respect to loading rates.

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