38    THE IMPACT OF ALPHA ON THE FEASIBILITY OF FINE
BUBBLE DIFFUSERS IN INDUSTRIAL WASTEWATER
Kevin R. Flanders, Engineer
Woodard & Curran Inc.
Portland, Maine 04112
Robert Reich, Senior Consultant
E.I. DuPont deNemours and Co., Inc.
Wilmington, Delaware 19899
Louis E. Himelreich, Jr., Consultant Associate
E.I. DuPont deNemours and Co.
Deepwater, New Jersey 07802
Gary Gilbert
Aeration Technologies, Inc.
North Andover, Massachusett 01061
James W. Morris, Senior Consultant
Woodard & Curran Inc.
Portland, Maine 04112
Harry W. Heath
HWH Consulting
Wilmington, Delaware 19899
BACKGROUND
The objective of this study was to determine the technical and economic feasibility of replacing the
coarse bubble aeration system at the DuPont Chambers Works facility (Chambers Works) with fine
bubble diffusers. The study included an onsite pilot study and extensive review and interpretation of
the data. The pilot study evaluated the performance of four fine bubble diffusers and one coarse
bubble diffuser. The four fine bubble diffusers were: a generic membrane tube (MT), commercial
membrane disk (MD), commercial ceramic disk (CD), and commercial plastic tube (PT). Another
diffuser was constructed to model the existing coarse bubble (CB) aeration system.
Fine bubble diffusers often provide significantly higher oxygen transfer efficiency (OTE) values
than coarse bubble diffusers. The fine bubble diffuser advantage lies in the much larger surface-to-
volume ratio of fine bubbles as compared to coarse bubbles. This results in a more rapid movement of
oxygen from a given mass of air across the gas-liquid interface, which is usually the rate limiting step
in oxygen transfer. This advantage results in lower air-volume requirements, less blower power
demand, and reduced energy costs. Because of this potential for significant energy costs savings,
DuPont decided to test, under simulated field conditions, the comparative oxygen transfer efficiencies
of the five aeration devices.
The MT fine bubble diffuser consisted of a 2.5-inch diameter, 24-inch long, plastic pipe frame with
a perforated elastomer membrane fastened over the pipe frame. The CD fine bubble diffuser consisted of a 9-inch diameter ceramic disc mounted on a rigid plastic frame. The MD fine bubble
diffuser consisted of a 22-inch diameter plastic disk covered by a perforated elastomer membrane
mounted on a rigid plastic frame. The PT fine bubble diffuser consisted of a 2.5-inch diameter, 24-
inch long, rigid porous plastic cylindrical tube. The CB diffuser consisted of a 2.5-inch diameter, 24-
inch long, plastic pipe with one orifice located at the bottom center of the diffuser.
Test results allow the pounds of oxygen required to treat each pound of BOD5 loading experienced
by the aeration tanks to be calculated, which lead to diffuser system sizing. This information was used
in a life cycle cost analysis to determine the extent of cost savings, if any, that would result from
replacing the existing coarse bubble aeration system with fine bubble diffusers.
49th Purdue Industrial Waste Conference Proceedings, 1994 Lewis Publishers, Chelsea, Michigan 48118. Printed in
U.S.A.
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