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Section Eight BIOLOGICAL: ANAEROBIC SYSTEMS 29 FEASIBILITY AND BENEFITS OF METHANOGENESIS UNDER OXYGEN-LIMITED CONDITIONS D.H. Zitomer, Assistant Professor J.D. Shrout. Research Assistant Civil and Environmental Engineering Marquette University Milwaukee, Wisconsin 53201 ABSTRACT Methanogenic and aerobic (or microaerophilic) biological processes are often considered mutually exclusive and separated as biological wastewater treatment options. However, under oxygen- limited conditions, both aerobic respiration and methanogenesis may be practically accomplished by a single mixed culture. This chapter describes sustained batch culture, oxygen-limited methanogenic serum bottle and bench-scale systems. Serum bottle cultures exhibited methanogenic activity similar to or greater than that of a strictly anaerobic culture maintained in parallel. The COD removal efficiencies of anaerobic, oxygen-limited, and aerobic bench-scale reactors receiving 30.000 mg/L of sucrose were comparable (94%), but a system receiving 1 g 0-,/LR-day achieved a lower final effluent COD than the strictly anaerobic reactor. After a shock-load of sucrose, the pH recovered in low-aeration batch reactors in 28 to 34 days, whereas anaerobic pH did not recover after 52 days of observation. In the future, methanogenesis under limited-aeration may be employed as an energy-efficient treatment option to achieve low final COD concentrations, minimal biosolids generation, and mineralization of a broad range of specific organic chemicals. INTRODUCTION Oxygen, which is classically considered to be the nemesis of methanogenic processes, may potentially enhance methanogenesis under some conditions. Although even low levels of dissolved oxygen are considered to be extremely toxic to methanogens. methanogens have been found to survive short periods in the presence of dissolved oxygen and to coexist with aerobic or microaerophilic organisms. For example, methane production by the methanogen Methanothrix soehngenii did not decline after oxygen was administered for 48 hours and then removed.1 Other methanogens. including Methanosarcina barker!2 Methanobacterium bryantii, Methanothrix soehngenii,* Methanobacterium thermoautotrophicum, and Methanobrevibacter arboriphilus4 all exhibit limited tolerance to low oxygen levels. Mixed cultures of methanogenic. acetogenic, and obligate aerobic microorganisms have been described, and methane production has been sustained over a wide range of oxygen supply rates.5 Obligate aerobes in these systems have been found to oxidize acetate and propionate produced by acetogenic anaerobes during lactose fermentation,'' and to transform acetamide in synergistic association with methanogens.7 Stoichiometric equations for propionate- and ethanol-fed methanogenic. oxygen-limited batch cultures have been developed using electron equivalent balances.8 The oxygen utilized by various cultures ranged from 10 to 30% of the added COD. whereas the remainder of removed COD was converted to methane. 52nd Purdue Industrial Waste Conference Proceedings. lou7, Ann Arbor Press. Chelsea. Miehigan 48118. Printed in U.S.A. 279
Object Description
Purdue Identification Number | ETRIWC199729 |
Title | Feasibility and benefits of methanogenesis under oxygen-limited conditions |
Author |
Zitomer, D. H. Shrout, J. D. |
Date of Original | 1997 |
Conference Title | Proceedings of the 52nd Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://earchives.lib.purdue.edu/u?/engext,20307 |
Extent of Original | p. 279-288 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital object copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Date Digitized | 2009-11-03 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Description
Title | page 279 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital object copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Transcript | Section Eight BIOLOGICAL: ANAEROBIC SYSTEMS 29 FEASIBILITY AND BENEFITS OF METHANOGENESIS UNDER OXYGEN-LIMITED CONDITIONS D.H. Zitomer, Assistant Professor J.D. Shrout. Research Assistant Civil and Environmental Engineering Marquette University Milwaukee, Wisconsin 53201 ABSTRACT Methanogenic and aerobic (or microaerophilic) biological processes are often considered mutually exclusive and separated as biological wastewater treatment options. However, under oxygen- limited conditions, both aerobic respiration and methanogenesis may be practically accomplished by a single mixed culture. This chapter describes sustained batch culture, oxygen-limited methanogenic serum bottle and bench-scale systems. Serum bottle cultures exhibited methanogenic activity similar to or greater than that of a strictly anaerobic culture maintained in parallel. The COD removal efficiencies of anaerobic, oxygen-limited, and aerobic bench-scale reactors receiving 30.000 mg/L of sucrose were comparable (94%), but a system receiving 1 g 0-,/LR-day achieved a lower final effluent COD than the strictly anaerobic reactor. After a shock-load of sucrose, the pH recovered in low-aeration batch reactors in 28 to 34 days, whereas anaerobic pH did not recover after 52 days of observation. In the future, methanogenesis under limited-aeration may be employed as an energy-efficient treatment option to achieve low final COD concentrations, minimal biosolids generation, and mineralization of a broad range of specific organic chemicals. INTRODUCTION Oxygen, which is classically considered to be the nemesis of methanogenic processes, may potentially enhance methanogenesis under some conditions. Although even low levels of dissolved oxygen are considered to be extremely toxic to methanogens. methanogens have been found to survive short periods in the presence of dissolved oxygen and to coexist with aerobic or microaerophilic organisms. For example, methane production by the methanogen Methanothrix soehngenii did not decline after oxygen was administered for 48 hours and then removed.1 Other methanogens. including Methanosarcina barker!2 Methanobacterium bryantii, Methanothrix soehngenii,* Methanobacterium thermoautotrophicum, and Methanobrevibacter arboriphilus4 all exhibit limited tolerance to low oxygen levels. Mixed cultures of methanogenic. acetogenic, and obligate aerobic microorganisms have been described, and methane production has been sustained over a wide range of oxygen supply rates.5 Obligate aerobes in these systems have been found to oxidize acetate and propionate produced by acetogenic anaerobes during lactose fermentation,'' and to transform acetamide in synergistic association with methanogens.7 Stoichiometric equations for propionate- and ethanol-fed methanogenic. oxygen-limited batch cultures have been developed using electron equivalent balances.8 The oxygen utilized by various cultures ranged from 10 to 30% of the added COD. whereas the remainder of removed COD was converted to methane. 52nd Purdue Industrial Waste Conference Proceedings. lou7, Ann Arbor Press. Chelsea. Miehigan 48118. Printed in U.S.A. 279 |
Resolution | 300 ppi |
Color Depth | 8 bit |
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