page328 |
Previous | 1 of 20 | Next |
|
|
Loading content ...
Static Aeration Systems — Problems and Performance R.O. BALL, Waste Consultant H.J. CAMPBELL, Jr., Waste Consultant Engineering Service Division E.I. Du Pont de Nemours & Company Wilmington, Delaware 19898 INTRODUCTION Since the discovery of the activated sludge process by Ardern and Lockett in 1914 (1), a variety of aeration systems have been investigated. Initially, large bubble, diffused aeration systems were used, mainly in municipal applications. For industrial applications, mechanical forms of aeration, such as high and low speed surface mixing and submerged turbine mixing, have been employed. In recent years, several types of high efficiency aeration systems have been proposed. It can be seen from the oxygen transfer equation that there are several ways that aeration efficiency can be improved: (1) where. Dt= -Kl Dt= DO deficit at time t Da = DO deficit at time zero K = mass transfer coefficient If the DO deficit is increased for example, then the aeration efficiency will be improved proportionally. Another method is to increase the mass transfer rate. The static aeration systems that have been developed thus far attempt to improve the mass transfer rate with respect to conventional diffused and mechanical types of aeration. DESCRIPTION OF STATIC AERATION SYSTEMS Two types of static aerators which have been developed and marketed were studied. The first type consists of a plastic tube 12 in in diameter, 5 ft in length with five helical elements. The elements are turned alternately left hand and right hand in the tube to provide greater turbulence. The second type of static aerator is 18 in in diameter, 6 ft in length, and has a continuous spiral element in the tube. This element is at approximately the same pitch as the individual elements in the other type of aerator. A cutaway view of the first type of aerator is shown in Figure 1, and the second in Figure 2. For each system, air is introduced through large diameter orifices beneath the tube. The large bubbles are sheared into very fine bubbles in the tube, which also acts as an air lift pump, thereby mixing the air and water. This provides for a very high surface area to volume ratio as well as providing intimate mixing. The benefits of using these types of aerators, exclusive of their efficiency, are numerous. The aerator tubes are constructed of plastics, without moving parts, and possess an advantage for use with industrial wastes where corrosion can be a problem. Also, as the orifices which deliver the air are approximately jSj-$J in diameter, the possibility of plugging in the air distribution system is minimized. Due to the relatively low surface turbulence inherent in these systems, surface misting and heat losses from the aeration tanks are reduced. The static aerators are also particularly suitable for deep aeration tanks where 328
Object Description
Purdue Identification Number | ETRIWC197433 |
Title | Static aeration systems : problems and performance |
Author |
Ball, Roy O. Campbell, Hugh J. |
Date of Original | 1974 |
Conference Title | Proceedings of the 29th Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://earchives.lib.purdue.edu/u?/engext,24462 |
Extent of Original | p. 328-337 |
Series | Engineering extension series no. 145 |
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 | 2009-06-05 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Description
Title | page328 |
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 | Static Aeration Systems — Problems and Performance R.O. BALL, Waste Consultant H.J. CAMPBELL, Jr., Waste Consultant Engineering Service Division E.I. Du Pont de Nemours & Company Wilmington, Delaware 19898 INTRODUCTION Since the discovery of the activated sludge process by Ardern and Lockett in 1914 (1), a variety of aeration systems have been investigated. Initially, large bubble, diffused aeration systems were used, mainly in municipal applications. For industrial applications, mechanical forms of aeration, such as high and low speed surface mixing and submerged turbine mixing, have been employed. In recent years, several types of high efficiency aeration systems have been proposed. It can be seen from the oxygen transfer equation that there are several ways that aeration efficiency can be improved: (1) where. Dt= -Kl Dt= DO deficit at time t Da = DO deficit at time zero K = mass transfer coefficient If the DO deficit is increased for example, then the aeration efficiency will be improved proportionally. Another method is to increase the mass transfer rate. The static aeration systems that have been developed thus far attempt to improve the mass transfer rate with respect to conventional diffused and mechanical types of aeration. DESCRIPTION OF STATIC AERATION SYSTEMS Two types of static aerators which have been developed and marketed were studied. The first type consists of a plastic tube 12 in in diameter, 5 ft in length with five helical elements. The elements are turned alternately left hand and right hand in the tube to provide greater turbulence. The second type of static aerator is 18 in in diameter, 6 ft in length, and has a continuous spiral element in the tube. This element is at approximately the same pitch as the individual elements in the other type of aerator. A cutaway view of the first type of aerator is shown in Figure 1, and the second in Figure 2. For each system, air is introduced through large diameter orifices beneath the tube. The large bubbles are sheared into very fine bubbles in the tube, which also acts as an air lift pump, thereby mixing the air and water. This provides for a very high surface area to volume ratio as well as providing intimate mixing. The benefits of using these types of aerators, exclusive of their efficiency, are numerous. The aerator tubes are constructed of plastics, without moving parts, and possess an advantage for use with industrial wastes where corrosion can be a problem. Also, as the orifices which deliver the air are approximately jSj-$J in diameter, the possibility of plugging in the air distribution system is minimized. Due to the relatively low surface turbulence inherent in these systems, surface misting and heat losses from the aeration tanks are reduced. The static aerators are also particularly suitable for deep aeration tanks where 328 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Tags
Comments
Post a Comment for page328