scholarly journals Effect of digester F/M ratio on gas production and sludge minimization of ultrasonically treated sludge

2010 ◽  
Vol 62 (7) ◽  
pp. 1510-1517 ◽  
Author(s):  
Gözde T. Köksoy ◽  
F. Dilek Sanin
Keyword(s):  
Oxygen Demand ◽  
Gas Production ◽  
Batch Reactors ◽  
Thermal Methods ◽  
Anaerobic Digesters ◽  
Sludge Pretreatment ◽  
Sludge Minimization ◽  
Effect Of Food ◽  
Soluble Chemical Oxygen Demand ◽  
Sonication Parameters

Sludge pretreatment by mechanical, chemical or thermal methods before anaerobic digestion has been applied to increase the digestability of excess sludge. Pretreatment processes rely on their ability to disrupt cell membranes and to release organic materials from the cells into the aqueous phase. Pretreatment by mechanical disintegration has grown rapidly in recent years in parallel with the advances in technology. Ultrasonic sludge disintegration –one of the most commonly used mechanical pretreatment methods- enables the occurrence of cavitation bubbles for the break-up of microorganism cells to extract intracellular materials. The purpose of this study was to conduct disintegration experiments to optimize sonication parameters and to operate subsequent batch anaerobic digesters to examine the effect of food to microorganism ratio (F/M) in sonicated and unsonicated samples. Results showed that high sonication powers and longer treatment times were effective in sludge disintegration in terms of soluble chemical oxygen demand release. Sonicated sludge digested in batch reactors with higher initial F/M ratio caused higher methane generations, higher sludge reductions and had better dewatering characteristics.

ADM1 performance using SS-OFMSW with non-acclimated inoculums

2012 ◽  
Vol 66 (9) ◽  
pp. 1885-1892 ◽  
Author(s):  
M. El-Fadel ◽  
R. Maroun ◽  
R. Bou Fakher Eldeen ◽  
S. Ghanimeh
Keyword(s):  
Feeding Rate ◽  
General Trend ◽  
Oxygen Demand ◽  
Gas Production ◽  
Organic Fraction ◽  
Anaerobic Digesters ◽  
Start Up ◽  
Acclimation Period ◽  
Soluble Chemical Oxygen Demand ◽  
The Mathematical Model

This paper assesses the anaerobic digestion (AD) of the source-sorted organic fraction of municipal solid waste (SS-OFMSW). For this purpose, an experimental programme was implemented involving the operation and monitoring of two bench-scale anaerobic digesters, continuously fed with SS-OFMSW. The mathematical model (ADM1) was then applied to simulate the process of AD of SS-OFMSW. While start-up of the digesters was relatively slow, re-inoculation with cattle manure with effluent dilution reduced the acclimation period and achieved better stability, accommodating a feeding rate at an OLR = 2.39 kg TVS m−3 day−1. The high recorded methane gas production rate, reaching (0.1–2.5 m3 CH4/m3 reactor day), confirms the excellent biodegradability of the type of waste used (SS-OFMSW) and its suitability for AD. Satisfactory simulations of soluble chemical oxygen demand (COD), pH, and methane composition of biogas were obtained, whereas volatile fatty acid (VFA) concentrations in both reactors were over-predicted albeit capturing its general trend.

The performance of the sludge pretreatment system with venturi tubes

2008 ◽  
Vol 57 (1) ◽  
pp. 131-137 ◽  
Author(s):  
H.J. Kim ◽  
D.X. Nguyen ◽  
J.H. Bae
Keyword(s):  
Energy Efficiency ◽  
High Speed ◽  
Fluid Dynamic ◽  
Oxygen Demand ◽  
Total Solid ◽  
Lower Efficiency ◽  
Primary Sludge ◽  
Sludge Pretreatment ◽  
In Series ◽  
Soluble Chemical Oxygen Demand

This research investigates the feasibility of the venturi cavitation system (VCS) for the sludge pretreatment to increase biodegradability. The performances of the VCS depended on the inclination angle of the venturi outlet, and better results obtained with 12° than with 8° or 15°. Although it is energy efficient to use several venturies in series, the number of the venturies should be determined with detailed fluid dynamic calculations. The linear relationship between total solid (TS) concentration and the increases in soluble chemical oxygen demand (ΔSCOD) was observed for both wasted activated sludge (WAS) and primary sludge, which might be related to the better conditions for cavitation development at high TS concentrations even with higher viscosity. The VCS achieved better energy efficiency in terms of ΔSCOD/kJ compared to high-speed homogenizer (HSH). On the other hand, the VCS showed a similar energy efficiency for mixed sludge with 1.8% TS, but lower efficiency for WAS with 4% TS when compared to ultrasonic disintegration.

Using excess sludge as carbon source for enhanced nitrogen removal and sludge reduction with hydrolysis technology

2010 ◽  
Vol 62 (7) ◽  
pp. 1536-1543 ◽  
Author(s):  
Yong-Qing Gao ◽  
Yong-Zhen Peng ◽  
Jing-Yu Zhang ◽  
Jian-Long Wang ◽  
Liu Ye
Keyword(s):  
Carbon Source ◽  
Nitrogen Removal ◽  
Wastewater Treatment Plants ◽  
Reduction Rate ◽  
Oxygen Demand ◽  
Domestic Wastewater ◽  
Batch Reactors ◽  
Sludge Reduction ◽  
Zero Order Kinetics ◽  
Soluble Chemical Oxygen Demand

In order to improve the nitrogen removal efficiency and to achieve the sludge reduction in traditional wastewater treatment plants, a combined hydrolysis-anoxic-oxic (H-A-O) pilot-scaled reactor was used in this study to investigate the possibility and validity of using excess activated sludge (EAS) fermentation liquids to enhance the nitrogen removal. The results clearly showed that sludge acidification rate in fermentation reactor can reach to 43.2%. The percentages of acetic acid, propionic acid and butyric acid in the fermentation liquids were 68.4, 25.3 and 6.3%, respectively, while those in domestic wastewater were 73.0, 12.2 and 13.8%, respectively. Bioavailability of soluble chemical oxygen demand (SCOD) from fermentation liquids and domestic wastewater were investigated in batch reactors with nitrate as the electron accepter as well. The corresponding specific denitrification rates were 0.15 g NO3−-N/g VSS d−1 and 0.09 g NO3−-N/g VSS d−1. When the substances were enough, the denitrification reaction appeared to follow the zero-order kinetics. The results also showed that, when the H-A-O pilot-scaled reactor was operated continuously and sludge fermentation liquids were applied as additional carbon source in the A-O reactor, the removal efficiencies of SCOD, NH4+-N and total nitrogen (TN) were higher than 90, 95 and 79%, respectively. EAS reduction rate in this system was able to reach 40.4%, and the sludge VSS/SS ratio decreased from 0.82 to 0.59 after hydrolysis step.

scholarly journals Biogas from slaughter house waste and optimization of the process

2016 ◽  
Vol 51 (3) ◽  
pp. 203-214 ◽  
Author(s):  
MA Rouf ◽  
MS Islam ◽  
T Rabeya ◽  
AK Mondal ◽  
M Khanam ◽  
...  
Keyword(s):  
Anaerobic Digestion ◽  
Stomach Content ◽  
Oxygen Demand ◽  
Gas Production ◽  
Batch Reactors ◽  
Volatile Solid ◽  
Optimum Conditions ◽  
Slaughter House ◽  
Destruction Efficiency ◽  
Volatile Solids

To assess the potential of biogas generation by anaerobic digestion from slaughter house waste (undigested stomach content) and to determine the optimum conditions for biogas generation from the substrate, different proportions of substrate were used in six batch reactors R1, R2, R3, R4, R5 and R6. The reactors were operated with initial volatile solid concentrations of 34.00, 50.80, 67.20, 51.60, 48.10 and 63.36 g/l and corresponding specific gas production obtained was 0.258, 0.200, 0.160, 0.270, 0.201 and 0.170 l/g respectively. The volatile solids (VS) destruction efficiency was 31.71%, 29.15%, 28.26%, 32.29%, 30.56 and 29.08% as well as chemical oxygen demand (COD)  reduction achieved in the test reactors were 40.31%, 44.44%, 49.40%, 53.24%, 48.55% and 51.26% in R1, R2, R3, R4, R5 and R6 respectively. Methane yield in different reactors varied from 72% to 76%. The optimum mix for generation of biogas from the substrate was 75% slaughter waste mixed with 25% cow dung.Bangladesh J. Sci. Ind. Res. 51(3), 203-214, 2016

Use of microwave pretreatment for enhanced anaerobiosis of secondary sludge

2004 ◽  
Vol 50 (9) ◽  
pp. 17-23 ◽  
Author(s):  
B. Park ◽  
J.-H. Ahn ◽  
J. Kim ◽  
S. Hwang
Keyword(s):  
Control System ◽  
Microwave Irradiation ◽  
Biogas Production ◽  
Irradiation Time ◽  
Oxygen Demand ◽  
Volatile Solid ◽  
Anaerobic Digesters ◽  
Secondary Sludge ◽  
Working Volume ◽  
Soluble Chemical Oxygen Demand

This work elucidates the effects of pretreatment of secondary sludge by microwave irradiation on anaerobic digestion. The soluble chemical oxygen demand (COD) concentration increased up to 22% as microwave irradiation time increased, which indicated the sludge particles disintegrated. Three identical automated bioreactors with working volume of 5 l were used as anaerobic digesters at mesophilic temperature (35°C). The reactors were separately fed with sludge with microwave pretreated- and controlsludge at different hydraulic retention times (HRT). The volatile solid (VS) reduction in the control operation was approximately 23.2 ± 1.3%, while it was 25.7 ± 0.8% for the reactors with the pretreated sludge. The average biogas production rate with the pretreated sludge at 8, 10, 12, and 15 days HRTs was 240 ± 11, 183 ± 9, 147 ± 8, and 117 ± 7 ml/l/d respectively, while those with the control sludge were134 ± 12 and 94 ± 7 ml/l/d at 10 and 15 days HRTs. Maximum rates of COD removal and methane production with the pretreated sludge were 64% and 79% higher than those of the control system, respectively.

scholarly journals Application of Ozone and Oxygen to Reduce Chemical Oxygen Demand and Hydrogen Sulfide from a Recovered Paper Processing Plant

2010 ◽  
Vol 2010 ◽  
pp. 1-6 ◽  
Author(s):  
Patricia A. Terry
Keyword(s):  
Hydrogen Sulfide ◽  
Chemical Oxygen Demand ◽  
Contact Time ◽  
Oxygen Demand ◽  
Gas Production ◽  
Injection System ◽  
Processing Plant ◽  
Short Contact Time ◽  
Production Of Hydrogen ◽  
Fox River

A pilot study was performed at the Fox River Fiber recovered paper processing company in DePere, Wisconsin, to determine the extent to which injection of oxygen and ozone could reduce the high chemical oxygen demand, COD, in the effluent and the effectiveness of the ozone/oxygen stream in suppressing production of hydrogen sulfide gas in downstream sewage lines. Adaptive Ozone Solutions, LLC, supplied the oxygen/ozone generation and injection system. Samples were analyzed both before and after oxygen/ozone injection. Hydrogen sulfide gas was continuously monitored at sewer stations downstream of Fox River Fiber. Results showed that with a very short contact time, effluent COD was reduced by over 15%. A simple kinetic model predicts that a contact time of fewer than 30 minutes could reduce COD by as much as 60%. In addition, downstream hydrogen sulfide gas production in the sewage mains was also better controlled, such that costly Bioxide applications could be reduced.

Anaerobic co-digestion of winery waste and waste activated sludge: assessment of process feasibility

2013 ◽  
Vol 69 (2) ◽  
pp. 269-277 ◽  
Author(s):  
C. Da Ros ◽  
C. Cavinato ◽  
F. Cecchi ◽  
D. Bolzonella
Keyword(s):  
Activated Sludge ◽  
Biogas Production ◽  
Oxygen Demand ◽  
Pilot Scale ◽  
Waste Activated Sludge ◽  
Organic Loading ◽  
Operational Conditions ◽  
Loading Rates ◽  
Thermophilic Conditions ◽  
Soluble Chemical Oxygen Demand

In this study the anaerobic co-digestion of wine lees together with waste activated sludge in mesophilic and thermophilic conditions was tested at pilot scale. Three organic loading rates (OLRs 2.8, 3.3 and 4.5 kgCOD/m3d) and hydraulic retention times (HRTs 21, 19 and 16 days) were applied to the reactors, in order to evaluate the best operational conditions for the maximization of the biogas yields. The addition of lee to sludge determined a higher biogas production: the best yield obtained was 0.40 Nm3biogas/kgCODfed. Because of the high presence of soluble chemical oxygen demand (COD) and polyphenols in wine lees, the best results in terms of yields and process stability were obtained when applying the lowest of the three organic loading rates tested together with mesophilic conditions.

Two-stage entrapped mixed microbial cell process for simultaneous removal of organics and nitrogen for rural domestic sewage application

2004 ◽  
Vol 49 (5-6) ◽  
pp. 281-288 ◽  
Author(s):  
S.J. Kim ◽  
P.Y. Yang
Keyword(s):  
Removal Efficiency ◽  
Loading Rate ◽  
Oxygen Demand ◽  
Domestic Wastewater ◽  
Microbial Cell ◽  
Two Stage ◽  
Rate Limiting Step ◽  
Soluble Chemical Oxygen Demand ◽  
Removal Efficiencies ◽  
Entrapped Mixed Microbial Cell

A two-stage entrapped mixed microbial cell (2SEMMC) process which separates nitrification and denitrification phases by the installation of the anoxic and oxic EMMC reactors packed with EMMC carriers was operated with 6, 4, 3, and 2 hours of hydraulic retention time (HRT) using simulated domestic wastewater. The activated sludge was immobilized using cellulose acetate for the EMMC carriers. Similar soluble chemical oxygen demand (SCOD) removal efficiencies of 90-97% were observed for all HRTs (SCOD loading rate of 0.84-2.30 g/L/d) applied. In order to achieve more than 80 % of TN removal efficiency, the HRT should be maintained higher than 4 hours (less than 0.24 g/L/d of TN loading rate). Denitrification was a rate-limiting step which controlled overall TN removal efficiency at TN loading rate of 0.15-0.31 g/L/d although nitrification efficiencies achieved 97-99 %. The effluent TSS of less than 25 mg/L in the 2SEMMC process was maintained at the SCOD loading rate of less than 1.23 g/L/d with back-washing intervals of 5 and 10 days in the anoxic and oxic EMMC reactors, respectively. The minimum HRT of 4 hours is required for high removal efficiencies of organics (average 95.6 %) and nitrogen (average 80.5 %) in the 2SEMMC process with 3 times of recirculation ratio.

scholarly journals Kinetics in vitro of ruminal fermentation of cocoa husks subjected to alkali and heat treatment

2015 ◽  
Vol 36 (6) ◽  
pp. 3897
Author(s):  
Flávio Moreira de Almeida ◽  
José Augusto Gomes Azevêdo ◽  
Ícaro Dos Santos Cabral ◽  
Luiz Gustavo Ribeiro Pereira ◽  
Gherman Garcia Leal de Araújo ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Alkali Treatment ◽  
Alkaline Treatment ◽  
Gas Production ◽  
Ruminal Fermentation ◽  
Thermal Methods ◽  
Final Volume ◽  
In Vitro Gas Production ◽  
Efficient Alternative

The objective was to evaluate the parameters of kinetics of ruminal fermentation of cocoa husks (CH) treated with alkali and thermal agents, using the semi-automated in vitro gas production technique. Cocoa husks samples were subjected to alkali and thermal methods (effect of time of exposure) treatment, as follows: control; alkaline treatment with calcium hydroxide ((Ca(OH)2) and calcium oxide (CaO), both doses of 15.0; 30.0 and 45.0 g kg-1 of CH; heat treatment in an autoclave at a pressure of 1.23 kg cm-2 (15 psi) and a temperature of 123°C for 30, 60 and 90 minutes. For statistical analysis, orthogonal contrasts and regression. The degradation rate and the final volume of gases of non-fiber carbohydrates decreased with the addition of Ca(OH)2 and CaO, however, for fibrous carbohydrates effects were positive. For each percentage of Ca(OH)2 and CaO included, it is estimated an increase of 5.74 and 2.9% in the final volume of the fiber, respectively. When the heat treatment, a decrease in all parameters was estimated. For each minute of exposure to heat, there was a decrease of 0.4% in total final volume of gases. The alkali treatment can be an efficient alternative for improving the digestibility of fibrous fractions of CH.

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