Electrical conductivity as a state indicator for the start-up period of anaerobic fixed-bed reactors

2016 ◽  
Vol 73 (9) ◽  
pp. 2294-2300 ◽  
Author(s):  
A. Robles ◽  
E. Latrille ◽  
J. Ribes ◽  
N. Bernet ◽  
J. P. Steyer
Keyword(s):  
Electrical Conductivity ◽  
Production Rate ◽  
Methane Production ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Bicarbonate Concentration ◽  
Fixed Bed Reactors ◽  
Start Up ◽  
On Line ◽  
Methane Production Rate

The aim of this work was to analyse the applicability of electrical conductivity sensors for on-line monitoring the start-up period of an anaerobic fixed-bed reactor. The evolution of bicarbonate concentration and methane production rate was analysed. Strong linear relationships between electrical conductivity and both bicarbonate concentration and methane production rate were observed. On-line estimations of the studied parameters were carried out in a new start-up period by applying simple linear regression models, which resulted in a good concordance between both observed and predicted values. Electrical conductivity sensors were therefore identified as an interesting method for monitoring the start-up period of anaerobic fixed-bed reactors due to its reliability, robustness, easy operation, low cost, and minimum maintenance compared with the currently used sensors.

Physicochemical and Microbial Monitoring of UASB Sludge during Start-Up of Mesophilic Reactor

2005 ◽  
Vol 277-279 ◽  
pp. 552-558
Author(s):  
Yeong Hee Ahn ◽  
Young Jin Song ◽  
Hyo Seob Kim ◽  
You Jin Lee ◽  
Sung Hoon Park
Keyword(s):  
Production Rate ◽  
Removal Efficiency ◽  
Methane Production ◽  
Cod Removal ◽  
Laser Scanning Microscopy ◽  
Volume Index ◽  
Maximum Value ◽  
Cod Removal Efficiency ◽  
Start Up ◽  
Methane Production Rate

Anaerobically digested sludge was seeded in a mesophilic UASB reactor and the sludge was monitored for seven months to better understand the start-up process of the reactor. The reactor was fed with synthetic wastewater containing glucose. As the COD loading rate increased stepwise (from 1 to 4 g COD l-1 d-1), the methane production rate increased. COD removal efficiency was maintained to be greater than 90% after day 36. Maximum value of the methane production rate (6.0-6.5 l d-1) was achieved from day 152 and remained stable afterward. Although the reactor showed steady performance in terms of COD removal efficiency and methane production under constant hydraulic retention time (HRT) or COD loading rates, physicochemical and microbial properties of UASB sludge kept changing during the initial 5 months of operation. Specific methanogenic activity was initially negligible but increased until day 150, and then remained constant (0.72 + 0.11 g CH4-COD g-1 VSS d-1) afterward. Sludge volume index showed that the settling ability of UASB sludge gradually improved until it reached a plateau in day 120. Improved settling-ability could provide a basis for keeping bed height constant despite shortened HRT. The mean diameter of the UASB sludge gradually increased until approximately day 150 and maintained a maximum value (0.48 mm) afterward. Confocal laser scanning microscopy revealed F420-based autofluorescence of physical and optical sections of UASB sludge, suggesting the locations of autofluorescent methanogens in the UASB sludge during the start-up period. During the initial operation of the reactor, autofluorescence showed random and uneven distribution inside the sludge. However, autofluorescence appeared as an inner layer near the edge of the sludge with time, suggesting more abundant or active methanogens in this layer. The highest autofluorescence was observed in the range of 20 to 28 µm depth from the surface of granule as determined by optical slicing of UASB sludge. The results obtained in this study provide insight into UASB sludge development that involves dynamic changes in physicochemical and microbial aspects during the start-up period.

scholarly journals Effects of Nickel and Cobalt on Kinetics of Methanol Conversion by Methanogenic Sludge as Assessed by On-Line CH4 Monitoring

1999 ◽  
Vol 65 (4) ◽  
pp. 1789-1793 ◽  
Author(s):  
Graciela Gonzalez-Gil ◽  
Robbert Kleerebezem ◽  
Gatze Lettinga
Keyword(s):  
Production Rate ◽  
Methane Production ◽  
Dissolution Kinetics ◽  
Methanol Conversion ◽  
Pulse Mode ◽  
Metal Sulfides ◽  
On Line ◽  
Methane Production Rate ◽  
Temporary Decrease ◽  
Kinetics Of

ABSTRACT When metals were added in a pulse mode to methylotrophic-methanogenic biomass, three methane production rate phases were recognized. Increased concentrations of Ni and Co accelerated the initial exponential and final arithmetic increases in the methane production rate and reduced the temporary decrease in the rate. When Ni and Co were added continuously, the temporary decrease phase was eliminated and the exponential production rate increased. We hypothesize that the temporary decrease in the methane production rate and the final arithmetic increase in the methane production rate were due to micronutrient limitations and that the precipitation-dissolution kinetics of metal sulfides may play a key role in the biovailability of these compounds.

Role of filter media in an anaerobic fixed-bed reactor

1995 ◽  
Vol 31 (9) ◽  
pp. 137-144 ◽  
Author(s):  
T. Miyahara ◽  
M. Takano ◽  
T. Noike
Keyword(s):  
Anaerobic Bacteria ◽  
Fixed Bed ◽  
Methanogenic Bacteria ◽  
The Other ◽  
Fixed Bed Reactor ◽  
Filter Media ◽  
Fixed Bed Reactors ◽  
Attached Bacteria ◽  
The Relationship

The relationship between the filter media and the behaviour of anaerobic bacteria was studied using anaerobic fixed-bed reactors. At an HRT of 48 hours, the number of suspended acidogenic bacteria was higher than those attached to the filter media. On the other hand, the number of attached methanogenic bacteria was more than ten times as higher than that of suspended ones. The numbers of suspended and deposited acidogenic and methanogenic bacteria in the reactor operated at an HRT of 3 hours were almost the same as those in the reactor operated at an HRT of 48 hours. Accumulation of attached bacteria was promoted by decreasing the HRT of the reactor. The number of acidogenic bacteria in the reactor packed sparsely with the filter media was higher than that in the closely packed reactor. The number of methanogenic bacteria in the sparsely packed reactor was lower than that in the closely packed reactor.

Modeling of aerated upflow fixed bed reactors for nitrification

1999 ◽  
Vol 39 (4) ◽  
pp. 85-92 ◽  
Author(s):  
J. Behrendt
Keyword(s):  
Mathematical Model ◽  
Mass Transfer ◽  
Liquid Phase ◽  
Gas Phase ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Bulk Liquid ◽  
Initial Value ◽  
Fixed Bed Reactors ◽  
Number Of Cells

A mathematical model for nitrification in an aerated fixed bed reactor has been developed. This model is based on material balances in the bulk liquid, gas phase and in the biofilm area. The fixed bed is divided into a number of cells according to the reduced remixing behaviour. A fixed bed cell consists of 4 compartments: the support, the gas phase, the bulk liquid phase and the stagnant volume containing the biofilm. In the stagnant volume the biological transmutation of the ammonia is located. The transport phenomena are modelled with mass transfer formulations so that the balances could be formulated as an initial value problem. The results of the simulation and experiments are compared.

Biofilm formation on polypropylene during start‐up of anaerobic fixed‐bed reactors

Biofouling ◽  
1993 ◽  
Vol 6 (4) ◽  
pp. 345-361 ◽  
Author(s):  
Gerhard Zellner ◽  
Hans Diekmann ◽  
Ute Austermann‐Haun ◽  
Goetz Baumgarten ◽  
Carl‐Franz Seyfried
Keyword(s):  
Biofilm Formation ◽  
Fixed Bed ◽  
Fixed Bed Reactors ◽  
Start Up

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.

Online estimation of VFA, alkalinity and bicarbonate concentrations by electrical conductivity measurement during anaerobic fermentation

2012 ◽  
Vol 65 (7) ◽  
pp. 1281-1289 ◽  
Author(s):  
Cesar-Arturo Aceves-Lara ◽  
Eric Latrille ◽  
T. Conte ◽  
Jean-Philippe Steyer
Keyword(s):  
Electrical Conductivity ◽  
Hydrogen Production ◽  
Linear Regression ◽  
Regression Model ◽  
Linear Regression Model ◽  
Anaerobic Fermentation ◽  
Simple Linear Regression ◽  
Conductivity Measurements ◽  
Bicarbonate Concentration ◽  
On Line

This paper describes the use of electrical conductivity for measurement of volatile fatty acids (VFA), alkalinity and bicarbonate concentrations, during the anaerobic fermentation process. Two anaerobic continuous processes were studied: the first was a laboratory reactor for hydrogen production from molasses and the second was a pilot process for anaerobic digestion (AD) of vinasses producing methane. In the hydrogen production process, the total VFA concentration, but not bicarbonate concentration, was well estimated from the on-line electrical conductivity measurements with a simple linear regression model. In the methane production process, the bicarbonate concentration and the VFA concentration were well estimated from the simultaneous on-line measurements of pH and electrical conductivity by means of non-linear regression with neural network models. Moreover, the total alkalinity concentration was well estimated from electrical conductivity measurements with a simple linear regression model. This demonstrates the use of electrical conductivity for monitoring the AD processes.

Application of Biofilm Kinetics to Anaerobic Fixed Bed Reactors

1991 ◽  
Vol 23 (7-9) ◽  
pp. 1319-1326 ◽  
Author(s):  
I. E. Gönenç ◽  
D. Orhon ◽  
B. Beler Baykal
Keyword(s):  
Removal Rate ◽  
Fixed Bed ◽  
Experimental Studies ◽  
Pilot Scale ◽  
Cod Removal ◽  
Experimental Results ◽  
Fixed Bed Reactor ◽  
Removal Mechanism ◽  
Term Operation ◽  
Fixed Bed Reactors

Two basic phenomena, reactor hydraulics and mass transport through biofilm coupled with kinetic expressions for substrate transformations were accounted for in order to describe the soluble COD removal mechanism in anaerobic fixed bed reactors. To provide necessary verification, experimental results from the long term operation of the pilot scale anaerobic reactor treating molasses wastewater were used. Theoretical evaluations verified by these experimental studies showed that a bulk zero-order removal rate expression modified by diffusional resistance leading to bulk half-order and first-order rates together with the particular hydraulic conditions could adequately define the overall soluble COD removal mechanism in an anaerobic fixed bed reactor. The experimental results were also used to determine the kinetic constants for practical application. In view of the complexity of the phenomena involved it is found remarkable that a simple simulation model based on biofilm kinetics is a powerful tool for design and operation of anaerobic fixed bed reactors.

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