vvEPA
United States
Environmental Protection
Agency
Decentralized Systems Technology Fact
Sheet
Control Panels
DESCRIPTION
In recent years, regulatory agencies have increased
performance requirements for onsite wastewater
treatment. This necessitates onsite alternatives that
provide higher levels of treatment than standard septic
tank drainfield systems are capable of achieving.
Alternative systems are more complex and typically
rely on uniform distribution and periodic dosing of
pretreated effluent. Pumps are the primary method for
dosing and distributing effluent, and dosing pump
control is typically performed with a control panel using
water level sensors, programmable timers, and other
controls. Control panels may also be able to provide
remote control and monitoring. This fact sheet
discusses the use of control panels in the management
of onsite wastewater treatment systems.
A control panel consists of controls and sensors that
ensure the onsite system will operate efficiently as well
as sound an alarm whenever malfunctions threaten
efficient performance. Typical control panel functions
may include high-water level alarm, pump start/stop
control, low-water level alarms, programmable timers,
and intrinsically safe control relays for pumping
locations in a hazardous or potentially explosive
environment. Telemetry, current sensing,
programmable controllers, and other special options
are generally considered too costly for residential
applications, but have been utilized with larger
commercial flows. Standard control panel features
may include circuit breakers, disconnects,
manual/off/automatic motor control operation,
audio/visual alarms (with silencer), and automatic reset
upon correction of alarm condition (Bounds 1995).
APPLICABILITY
Control panels are commonly used in municipal lift
stations and pumping stations to monitor various
parameters and conditions including liquid level and
pressure. As costs have decreased and technology has
improved, control panels are increasingly being applied
to the management of decentralized or onsite
wastewater treatment systems. Control panels are
generally installed with new systems, but may also be
retrofitted to existing systems.
Examples of onsite systems that maybe equipped with
control panels include the following:
• Septic tank effluent pump (STEP) and grinder
pump (GP) systems associated with septic
tanks and/or pressure sewers;
• Low pressure effluent dispersal systems;
• Aerobic treatment units;
• Recirculating sand filters; and
• Drip dispersal systems.
ADVANTAGES AND DISADVANTAGES
Advantages
• Reduces costs for operation and maintenance
(O&M) by preventing failures and reducing
the amount of service time spent gathering
information about the malfunction;
• Lowers energy consumption; and
• Increases manageability and reliability of onsite
systems.
Disadvantages
• Increases initial capital costs;
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• Increased complexity requires higher level of
training to install and operate (may require an
electrician).
DESIGN CRITERIA
Control panels are usually conveniently located where
they will be accessible for operation and maintenance.
They should be within sight of the pump.
Figure 1 shows a typical control panel. The basic
components and features of this control panel include
the following:
Source: Orenco Systems Inc., 2001.
FIGURE 1 TYPICAL CONTROL
PANEL
Programmable Timer - Precisely controls the
pumping doses. The timer is programmed so that the
"on" time (dosing period) is short and effluent is dosed
in small volumes. The "off setting spaces resting
periods uniformly between doses throughout the day.
Programmable timers are particularly beneficial in
systems that require surge control, where a long period
of storage is required between intermittent discharges
(e.g., churches, schools, etc.). Timers are available
with digital or analog features, and provide adjustable
on/off duration settings. A timer can be disabled by a
low level float, thereby maintaining a minimum liquid
level.
Motor Contactor - Switches power to the pump on
command through a signal from the programmable
timer.
Toggle Switch (HOA Switch) - Allows the pumping
operation to be automatically or manually controlled
without interrupting the memory of the programmable
timer.
Current Limiting Circuit Breaker - Provides a
disconnect means and secondary overload protection
for the pump circuit.
Fuse Disconnect - Provides a separate disconnect
means and overload protection for the control circuitry
(alarm system, motor contactor, programmable timers,
relays, etc.). Power to the alarm and control circuitry
is wired separately from the pump circuit, so that the
alarm system remains functional if the internal overload
switch or current-liming circuit breaker is tripped.
Audible Alarm - Provides an audible alarm when a
high or low liquid level requires correction. The alarm
should be loud enough to provide ample warning but
not so loud that it causes irritation. A minimum of 80
decibels sound pressure at 24 inches is recommended.
A push-to-silence feature should also be included to
ensure that the alarm does not become a nuisance.
Visual Alarm - Provides visual indication when a high
or low liquid level requires correction. The alarm light
is usually red and varies in shape and size.
Audio-Alarm Silence Relay - Automatically resets the
audio alarm after the alarm condition has been
corrected.
Redundant-Off/Low Level Alarm Relay -
Automatically overrides the pump control circuit to shut
down the pump and energize the alarm system to signal
a low liquid level condition.
Terminal Blocks - Touchsafe type terminal blocks
provide greater protection against accidental shorting
across terminals and touching of live connections.
Enclosure - Should be constructed of noncorroding
and durable materials rated NEMA 4X to ensure
adequate environmental protection for the enclosed
components.
Lockable Latch - Provides lock-out capability to
ensure security.
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Listing - All controls should be manufactured by a
company listed by an approved accrediting agency
(e.g., UL, CSA, or ETL). At locations where
flammable or explosive materials maybe present, all
controls and relays should be intrinsically safe, meaning
that they operate at low energy to prevent electrical
devices from creating arcs, sparks, or heat (during
normal or fault conditions) that could ignite an
explosive substance.
Warnings and Instructional Stickers - All control
systems must contain the proper electrical warnings
and instructional information to ensure user awareness
and safety.
Wiring Diagram - Provides float and pump wiring
instructions and information regarding the intended
function of each component.
PERFORMANCE
River Rock Landing, Michigan
River Rock Landing is a newly-developed residential
site consisting of 29 homes outside of Lansing,
Michigan. A community cluster treatment system was
constructed to treat an estimated peak flow of 37,900
L/d (10,000 gpd). Wastewater is collected through a
STEP system with small diameter pressure sewers,
then treated with side-by-side duplex recirculating sand
filters followed by side-by-side duplex intermittent sand
filters. The treated effluent is returned to groundwater
through an unlined pond. An NPDES discharge permit
was obtained to manually discharge excess water from
the pond to the nearby Grand River if necessary
(Stephens 2000).
The treatment facility is required by the Michigan
Department of Environmental Quality to be operated
under the supervision of a qualified and certified
operator. As part of the management program for the
facility, a control panel was installed at the treatment
site. A dedicated telephone line is connected to this
control panel, enabling a computer with a modem to
access it directly from any location. The panel at this
site is programmed to record and report on demand
the following information:
• Current high and low water alarm conditions,
and a log of past alarm events;
• Pump run events and run times;
• Water level readings in the tanks and pond; and
• Amperage being drawn by pumps (Stephens
2000).
In addition to these monitoring functions, the program
allows the remote operator to make system adjustments
as follows:
• Adjust programmed pump run cycles (time-off
and time-on settings);
• Adjust alarm characteristics such as audible
delays;
• Set and adjust high-level pump override cycles;
and
• Turn pumps on and off as necessary to correct a
high water condition (Stephens 2000).
These monitoring capabilities do not eliminate the need
for personal visits to the site to evaluate the
performance of system components that are not
accessible over the phone wire. However, the ability to
monitor and manage the system provides the operator
with confidence that common system management
problems will be identified. In addition, system
information logs provide performance records to help
the operator recognize trends and troubleshoot
problems (Stephens 2000).
Island City Academy, Michigan
Island City Academy is a new charter school located
outside of Eaton Rapids, Michigan. An estimated peak
wastewater flow of 18,900 L/d (5,000 gpd) enters a
septic tank, then flows to a pair of side-by-side
recirculating sand filters. Final effluent is discharged to
a series of pressure-dosed soil absorption trenches.
The wastewater treatment facility is fitted with a control
panel that monitors and reports pump run times and
events, as well as alarm conditions. Programmable
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timing features can be adjusted and pumps can be
controlled remotely through the control panel. Daily
flow information is also logged for future reference. At
one point an employee of the Academy reported that
several of the toilets at the Academy would not flush
properly. The system operator was able to check the
treatment system and verify that it was operating
normally. Academy staff were then able to contact a
drain cleaning firm to clear a stoppage in the building
plumbing which caused the toilet malfunction (Stephens
2000).
OPERATION AND MAINTENANCE
When an alarm occurs, the user should contact an
accredited maintenance service. An average of 24
hours of reserve storage is provided above the alarm
level (Bounds 1995), and response within this time
period is adequate.
When servicing any control system, all warnings must
be given strict attention. An operator must not work
on any system without first disconnecting the power at
the circuit breaker and/or disconnect fuse. All control
panels should be provided with a lockable latch to
ensure operator safety when working away from the
control panel.
COSTS
Control panels range in price from approximately
$1,500 to $3,000, depending on options selected
(Jesperson 2000).
REFERENCES
Other Related Fact Sheets
Sewers, Lift Station
EPA 832-F-00-073
September 2000
Recirculating Sand Filters
EPA 832-F-99-079
September 1999
Sewers, Pressure
EPA 832-F-02-006
September 2002
Other EPA Fact Sheets can be found at the following
web address:
http://www.epa.gov/owm/mtb/mtbfact.htm
1. Barret, Michael E. and J. F. Malina, Jr., Sep.
1,1991. Technical Summary of Appropriate
Technologies for Small Community
Wastewater Treatment Systems. The
University of Texas at Austin.
2. Bounds, Terry R., 1995. Pumps, Controls
and Regulations. 1995 Northwest Onsite
Wastewater Treatment Short Course and
Equipment Exhibition.
3. City of Austin, "Septic Tank." Site accessed
May 2000.
http://www.ci.austin.tx.us/wri/treatl.htm
4. Corbitt, Robert A., 1990. Standard
Handbook of Environmental Engineering
McGraw-Hill, Inc., New York, New York.
5. Crites, R. and G. Tchobanoglous, 1998.
Small and Decentralized Wastewater
Management Systems, WCB. McGraw-Hill,
Inc. Boston, Massachusetts.
6. Jesperson, Kathy, 1999. Remote Monitoring
Keeps Watch for Trouble. Small Flows
Quarterly, Spring 1999, Vol. 13, No. 2.
7. Jesperson, Kathy, 2000. Remote Monitoring
Use Is on the Rise. Small Flows Quarterly,
Winter 2000, Vol. l,No. 1.
8. Stephens, Larry D., 2000. Remote
Management: A Valuable Tool for the
Future of Decentralized Wastewater
Treatment. NOWRA 2000 Annual Meeting.
(http://www.scssystemsllc.com/zPapers/Rem
oMang.html).
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9. U.S. Environmental Protection Agency. 1980.
Design Manual: Onsite Wastewater
Treatment & Disposal Systems. EPA Office
of Water. EPA Office of Research &
Development. Cincinnati, Ohio. EPA 625/1-
80/012.
10. U.S. Environmental Protection Agency. Sep.
1992. Design Manual: Wastewater
Treatment and Disposal for Small
Communities. EPA Office of Water. EPA
Office of Research & Development.
Cincinnati, Ohio. EPA 625/R-92/005.
ADDITIONAL INFORMATION
William A. Cagle
Orenco Systems, Inc.
814 Airway Avenue
Sutherlin OR 97479
(541) 459-4449
Mike Mines
On-Site Systems, Inc.
(865) 740-7994
National Small Flows Clearinghouse
at West Virginia University
P. O. Box 6064
Morgantown WV 26506
Larry D. Stephens
Stephens Consulting Services, P. C.
P. O. Box 708
Haslett MI 48840
(517)339-8692
The mention of trade names or commercial products
does not constitute endorsement or recommendation
for use by the U. S. Environmental Protection Agency
(EPA).
Office of Water
EPA 832-F-02-011
September 2002
For more information contact:
Municipal Technology Branch
U.S. EPA
1200 Pennsylvania Avenue, NW
Mail Code 4204M
Washington, D.C. 20460
* 2002 *
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