United States June
Environmental Protection 1983
Agency
• Sedalia, MO - 2.6 MGD
• Gallatin, MO - 0.225 MGD
These proposed innovative facility plans also in-
clude modifications such as a shorter hydraulic de-
tention time, peak flow clarifiers, propellor-type mix-
ers, and fine bubble aeration.that contribute in part
to the projected cost savings for the four facilities
shown in Figure 4.
Actual bid costs for the 40 MGD Little Blue Valley
project (Jan. 1983 $) were projected to be
$23,808,000 for the total treatment plant. Bid costs
relative to the Intrachannel Clarifier portion of the
project were $6,158,700 for two 10 MGD aeration-
clarification basins. This represents a cost of slightly
less than $.31 per gallon of treatment capacity.
v>EPA An Emerging
Technology
Intrachannel
Clarification
A Project
Assessment
For additional information contact:
EPA-OWPO(WH-547)
401 M Street, SW
Washington, DC 20460
(202)362-7370/7369
EPA Region 1
John F. Kennedy Federal Building
Boston, MA 02203
EPA Region 2
26 Federal Plaza
New York, NY 10278
EPA Region 3
6th & Walnut Streets
Philadelphia, PA 19106
EPA Region 4
345 Courtland Street, NE
Atlanta, GA 30308
EPA Region 5
230 South Dearborne Street
Chicago, IL 60604
EPA-MERL (489)
26 West St. Clair Street
Cincinnati, OH 45268
(513)684-7614
EPA Region 6
1201 Elm Street
Dallas, TX 75270
EPA Region 7
324 East 11th Street
Kansas City, MO 64106
EPA Region 8
1860 Lincoln Street
Denver, CO 80203
EPA Region 9
215 Fremont Street
San Francisco, CA 94105
EPA Region 10
1200 6th Avenue
Seattle, WA 98101
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Intrachannel Clarification - A Project Assessment of a Pi
Introduction
Community leaders are becoming more and
more cost conscious when selecting wastewater
treatment alternatives. Initial capital investments
will continue to be important, but operation and
maintenance costs will become a greater
consideration in process selection. This cost
awareness is leading consulting engineering
professionals to seek more innovative solutions
to meet their clients' needs. One example of this
approach is an Intrachannel Clarifier system
developed by Bums & McDonnell of Kansas
City, Missouri, in cooperation with the staff of the
Little Blue Valley Sewer District, Kansas City,
Missouri, Metropolitan Area. This cost-saving
approach to modify the oxidation ditch process
has become an integral part of the District's
planned 40 MGD treatment facility, which will
serve a 238 square mile watershed area.
Longitudinal Section
Figure 2 Clarifier Longitudinal Cross-Section
Mechanical
Skimming
Hydraulic
Skimming,
Note: TiifNne aerator was later replaced with
propeltor mixer and fine bubble aerator.
Waste
Sludge
^ Plant
^Effluent
Figure 1 Process Plan View for the original 1.0 MGD Little Blue Valley Pilot Plant
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pmising Process Modification
Sludge Age
Overflow Rate
Mixed Liquor
Concentration
Aeration
Effluent Quality
10 Days
600-800 gallon
per day per
sq. ft.
3,000-3,500 mg/l
10 hr.
mg/l BOD5
* 20 mg/l SS
Table 1 Typical Pilot Plant Operating Conditions
This process modification was tested and demons-
trated as part of a Step II construction grant from
the U.S. EPA and was selected as one of the Ten
Outstanding Achievements in the National Society
of Professional Engineers' 16th Annual Competition.
This fact sheet brings this emerging technology to the
attention of potential users. Although the fact sheet
describes the Bums & McDonnell Intrachannel
Clarifier design, there are currently two other designs
for this process which have been developed by
EIMCO and Beard Engineering, Inc.
The Process
The Intrachannel Clarifier is a modification of the
oxidation ditch process which combines the aeration
and clarification processes in one basin. The screened
wastewater enters the basin, is aerated, and then
passes under the Intrachannel Clarifier where a
mixture of the wastewater and activated sludge
(mixed liquor) rises through the clarifier bottom panels.
As the mixed liquor flows up into the clarifier, solids
settle, fall through the bottom openings and return to
the continuously flowing mixture. Effluent is removed
from the quiescent zone in the, upper portion of the
Intrachannel Clarifier via the submerged orifice effluent
pipe. Figure 1 to the left shows a plan view of the
original pilot process. Figure 2 shows a cross-
section of the clarifier.
Field Testing
The Intrachannel Clarification concept was tested
as a wastewater treatment solution that would re-
duce capital and O&M costs for the Little Blue Val-
ley Sewer District's planned 40 MGD facility. This
concept has been demonstrated via pilot-scale at
the site of the District's 20 MGD Interim Treatment
Plant. The pilot plant is an oval basin -110 feet
long by 32 feet wide - with a liquid depth of six feet.
The pilot plant was designed to treat 1 MGD of
screened wastewater and has operated at flow
rates from 0.3 MGD up to 1.3 MGD. Table 1 shows
typical operating conditions for the pilot plant. A
novel aeration system consisting of a slow rpm
propellor-type mixer and fine bubble aeration was
tested and is proposed for the full-scale 40 MGD
system. Figure. 3 below shows the process schematic
for the planned 40 MGD facility.
Projected Advantages
Pilot results indicate the Intrachannel. Clarifier eli-
minates many of the problems associated with con-
ventional secondary clarifiers. There are no sludge
blankets or compression zones, and the full depth
of the clarifier is available for maximum settling. As
the solids settle in the clarifier, they also act as a
nucleus to attract and remove material in the liquor
Influent ,
.—>Jpumps'
. '•>
Fir
Ae
e Bubble
ation
Propeller
Marific.jtion
Effluent
r<
X; ••••:•*$
Figure 3 Schematic of Planned Full-Scale System
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flowing upward into the quiescent zone. The under-
flow beneath the clarifier pulls the settling solids
back into the mixed liquor stream without the use of
a return sludge pump. Thus, no control over sludge
return is necessary and sludge age is easily controlled
by wasting mixed liquor.
Many pieces of equipment associated with conven-
tional activated sludge processes are not needed
with this system. The system also has a major
advantage over the conventional oxidation ditch be-
cause the hydraulic detention time is lower (10 hrs.
vs. 24 hrs.), resulting in a smaller basin volume and
associated cost savings.
Cost Comparisons
Projected capital and first year operation and
maintenance (O&M) costs for proposed facilities
which incorporate Intrachannel Clarification and for
conventional oxidation ditch technology are shown
in Figure 4. These curves are based on estimated
costs (1982 $) for the following four proposed muni-
cipal wastewater treatment plants:
• Little Blue Valley Sewer District
(Jackson County, MO) - 40 MGD
• Storm Lake, IA - 3.34 MGD
Total Annual O&M Costs
Flow (MGD)
Figure 4 Cost Curves
Original 1 MGD Pilot System at Little Blue Valley Sewer-District
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