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Section Four BIOLOGICAL SYSTEMS-C. ANAEROBIC 40 IMPROVED ANAEROBIC DIGESTION WITH LOW LEVEL CHEMICAL PRETREATMENT R. V. Rajan, Doctoral Student University of Massachusetts at Amherst Amherst, Massachusetts 01003 Jih-Gaw Lin, Doctoral Candidate Bill T. Ray, Assistant Professor Southern Illinois University at Carbondale Carbondale, Illinois 62901 INTRODUCTION Sludge handling costs represent 30 to 40% of the capital cost and about 50% of the operating costs of a typical wastewater treatment facility.1 About two thirds of the volume of sludge in secondary treatment plants is waste activated sludge (WAS). WAS has to be stabilized sufficiently to reduce its organic content, odor problems and pathogen contamination, before its ultimate disposal. Thus, any new process or process modification that significantly improves WAS stabilization will reduce overall wastewater treatment plant costs. Anaerobic digestion is a commonly used form of secondary sludge stabilization. Digestion of WAS, in which most of the substrate is enclosed within cell membranes, requires conversion of cell bound substrate into more readily accessible forms before it can be utilized by viable anaerobes. In the context of this chapter, mechanical and chemical unit operations on sludge that improve substrate availability are referred to as "pretreatment" methods. Past research in the area of substrate modification has led to the development of pretreatment schemes that are energy intensive and impractical for WAS processing. These include thermal pretreatment of WAS at moderate (60 to 100°C)2 and high (175 to 225°C)3 temperatures and thermochemical pretreatment using high temperatures and chemical levels (300 mEq/L).* In this research project, a relatively simple, less expensive WAS pretreatment process was evaluated for its influence on particulate hydrolysis and the performance of anaerobic digesters. It was the intent of the first phase of this project to study the kinetics of alkaline hydrolysis and to determine the parameters that control the process. The rationale behind the use of an alkali, instead of an acid, is that residual alkalinity is compatible with subsequent anaerobic digestion, while acidity is not. This ambient temperature, alkaline pretreatment procedure is discussed and preliminary results of its effect on anaerobic digestion are presented in this chapter. METHODOLOGY WAS used in this project was collected from the Carbondale Northwest wastewater treatment plant in Carbondale, Illinois. Sludge was collected a day before subsequent hydrolysis experiments were performed. Samples in 20 liter carboys were immediately transferred to the laboratory to be stored at 1°C, while the sludge settled. The sludge readily settled to over 1.0% total solids (TS). When feed sludge over 2.0% TS was required, a portion of the sludge was centrifuged at 5000 rpm and adjusted to the appropriate strength with the settled sludge. Analyses performed in this study were based on the procedures recommended in the 16th edition of Standard Methods.* 43rd Purdue Industrial Waste Conference Proceedings, © 1989 Lewis Publishers, Inc., Chelsea, Michigan 48118. Printed in U.S.A. 327
Object Description
Purdue Identification Number | ETRIWC198840 |
Title | Improved anaerobic digestion with low level chemical pretreatment |
Author |
Rajan, R. V. Lin, Jih-Gaw Ray, Bill T. |
Date of Original | 1988 |
Conference Title | Proceedings of the 43rd Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://e-archives.lib.purdue.edu/u?/engext,39828 |
Extent of Original | p. 327-338 |
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 | 2009-08-13 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Description
Title | page 327 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Transcript | Section Four BIOLOGICAL SYSTEMS-C. ANAEROBIC 40 IMPROVED ANAEROBIC DIGESTION WITH LOW LEVEL CHEMICAL PRETREATMENT R. V. Rajan, Doctoral Student University of Massachusetts at Amherst Amherst, Massachusetts 01003 Jih-Gaw Lin, Doctoral Candidate Bill T. Ray, Assistant Professor Southern Illinois University at Carbondale Carbondale, Illinois 62901 INTRODUCTION Sludge handling costs represent 30 to 40% of the capital cost and about 50% of the operating costs of a typical wastewater treatment facility.1 About two thirds of the volume of sludge in secondary treatment plants is waste activated sludge (WAS). WAS has to be stabilized sufficiently to reduce its organic content, odor problems and pathogen contamination, before its ultimate disposal. Thus, any new process or process modification that significantly improves WAS stabilization will reduce overall wastewater treatment plant costs. Anaerobic digestion is a commonly used form of secondary sludge stabilization. Digestion of WAS, in which most of the substrate is enclosed within cell membranes, requires conversion of cell bound substrate into more readily accessible forms before it can be utilized by viable anaerobes. In the context of this chapter, mechanical and chemical unit operations on sludge that improve substrate availability are referred to as "pretreatment" methods. Past research in the area of substrate modification has led to the development of pretreatment schemes that are energy intensive and impractical for WAS processing. These include thermal pretreatment of WAS at moderate (60 to 100°C)2 and high (175 to 225°C)3 temperatures and thermochemical pretreatment using high temperatures and chemical levels (300 mEq/L).* In this research project, a relatively simple, less expensive WAS pretreatment process was evaluated for its influence on particulate hydrolysis and the performance of anaerobic digesters. It was the intent of the first phase of this project to study the kinetics of alkaline hydrolysis and to determine the parameters that control the process. The rationale behind the use of an alkali, instead of an acid, is that residual alkalinity is compatible with subsequent anaerobic digestion, while acidity is not. This ambient temperature, alkaline pretreatment procedure is discussed and preliminary results of its effect on anaerobic digestion are presented in this chapter. METHODOLOGY WAS used in this project was collected from the Carbondale Northwest wastewater treatment plant in Carbondale, Illinois. Sludge was collected a day before subsequent hydrolysis experiments were performed. Samples in 20 liter carboys were immediately transferred to the laboratory to be stored at 1°C, while the sludge settled. The sludge readily settled to over 1.0% total solids (TS). When feed sludge over 2.0% TS was required, a portion of the sludge was centrifuged at 5000 rpm and adjusted to the appropriate strength with the settled sludge. Analyses performed in this study were based on the procedures recommended in the 16th edition of Standard Methods.* 43rd Purdue Industrial Waste Conference Proceedings, © 1989 Lewis Publishers, Inc., Chelsea, Michigan 48118. Printed in U.S.A. 327 |
Resolution | 300 ppi |
Color Depth | 8 bit |
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