United States
Environmental Protection
Agency
Water Engineering Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-87/108 Apr. 1 988
&EPA Project Summary
Centralized Management of
Small Treatment Plants Using
Instruments and Remote
Alarms
Irwin J. Kugelman and Michael D. Cummins
Small wastewater treatment plants
comprise the majority of the waste-
water treatment plants in the United
States. They also treat a significant
portion of the total flow. The operation
of these plants is intermittent with the
plant often unattended the majority of
time. Such operation can result in
failure of the plants. Unfortunately,
costs limit the use of increased operator
surveillance.
Continuous monitoring of critical
equipment and parameters, however,
makes it unnecessary for operators to
visit the remote sites on a daily basis.
Except when critical alarms are iden-
tified, trips to each facility can be
reduced to periodic (e.g., weekly)
operations and maintenance visits. This
mode of ' 'circuit rider" operation
reduces unnecessary travel between
facilities and allows for increased
productivity or reduced staffing of
operations and maintenance crews.
The U.S. EPA and the County of
Cuyahoga, Ohio, cooperated on a field
evaluation of this concept. Several low-
cost, field-proven sensors were
installed at the Richmond Park Terrace
Wastewater Treatment plant. These
were wired to a programmable logic
controller (PLC) and, in turn, to a
telemetering system.
The results of the study revealed that
a programmable controller provided a
flexible low-cost alternative to conven-
tional hard-wired relay electrical con-
trol systems and that the automatic
dialer provided a flexible alarm system
to contact operators by telephone
when emergency service is required.
The following basic sensor-controller-
telephone alarm system was recom-
mended for installation in intermit-
tently or unmanned small treatment
plants:
Programmable controller.
Automatic dialer.
Pressure switches.
Wet well level indicators.
Chlorine leak detectors, and
Power demand sensors
The system provided improved oper-
ation at the Richmond Park Terrace
Wastewater Treatment Plant.
This Project Summary was- devel-
oped by EPA's Water Engineering
Research Laboratory, Cincinnati- OH.
to announce key findings of the
research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering
information at back).
Introduction
In the United States, domestic sewage
treatment plants with a rated capacity of
1 million gal/day or less represent 85%
of the number of plants and treat 15%
of the aggregate flow. The operation and
maintenance of these small treatment
plants and associated lift stations pose
a number of unique and difficult prob-
lems to the authority responsible for their
performance. Because of financial and
manpower limitations, these facilities
-------
must operate unattended the majority of
the time. Undetected mechanical, elec-
trical, or process failures can result in
gross pollution (permit violations), equip-
ment and property damage, and public
complaints.
The application of remote monitoring
of critical equipment components and
operational parameters can help alle-
viate many of these problems. Contin-
uous monitoring of critical equipment
and parameters make it unnecessary for
operators to visit the remote sites on a
daily basis. Except when critical alarms
are identified, trips to each facility can
be reduced to periodic (e.g., weekly)
operations and maintenance visits This
mode of operation reduces unnecessary
travel between facilities and allows for
increased productivity or reduced staf-
fing of operations and maintenance
crews. When a failure or malfunction is
recognized, the cause of the alarm can
be diagnosed from the central monitoring
site and appropriate action taken,
whether it be the immediate dispatch of
a repair crew or logging for maintenance
at the next scheduled visit to the plant.
This immediate identification of alarms
significantly reduces the time needed to
respond to plant problems and minimizes
damages to plant equipment. This
reduced response time should improve
reliability of the plant and lead to
improved effluent quality overall.
Wastewater Treatment Plant
A low-cost sensor controller and
telemetering system was installed and
evaluated at the Richmond Park Terrace
WWTP, a 198,000 gal/day design capac-
ity extended aeration package facility.
Located in the city of Richmond Heights,
Ohio, the plant serves an apartment
complex with a total of 720 units and
a convenience shopping center.
The plant consists of sewage commin-
utor and wet well with an adjacent lift
station, three parallel extended aeration
tanks with final settling tanks, a chlorine
contact tank, and a sludge holding tank.
The lift station has a duplex pumping
system consisting of two Gormann-Rupp
Model 14 CZ pumps*, each with a
capacity of 300 gpm at 24 ft of head.
The wastewater, after comminution, is
pumped to a flow splitter box. From there,
it flows by gravity to three rectangular
steel aeration tanks, each with a capacity
Mention of trade names or commercial products
does not constitute endorsement or recommenda-
tion for use.
of 66,000 gal. Aeration is provided by
four Roots-Connersville blowers, each
capable of delivering 300 ftVmin of air.
The aeration tank detention time is 24
hr after aeration; the mixed liquor solids
are settled in the final clarifier at a
minimal overflow rate of 300 gal per ft2/
day. The overall detention time in the
settler is 4 hr.
The clarified effluent then enters a
chlorine contact tank with 30 min contact
time. Chlorine is fed to the tank by a
manually set solution feed chlorinator
with a capacity of 200 Ib/day. After
chlorination the effluent flows through
a 90° V-notch weir, with its float mech-
anism signal transmitted to a totalizer/
recorder, into a manhole discharging to
a creek ultimately flowing into Lake Erie.
Remote Monitoring System
The sensors selected for evaluation
and their alarm functions in the remote
monitoring system are shown in Table
1. The sensors included personnel safety
and security monitors as well as process
and equipment monitors. The sensor
monitoring and the alarm response
system used a Texas Instruments Model
5TI programmable logic controller and a
Butler National Corp ADAS II automatic
dialer to initiate alarm messages by
telephone. The total estimated cost of the
experimental system including sensors
and installation supplies was $18,961
with an estimated 732 labor hr for
installation.
The sensor selection was oriented
toward a basic low-cost monitoring
concept capable of providing an alarm at
a central site that would detect impend-
ing plant upset and/or mechanical
breakdown. An important objective of the
evaluation was to assess which of the
sensor alarms were desirable for mon-
itoring and controlling circuit rider
operation of small extended air package
plants. Remote process control was not
considered for this system. The program-
ming approach for the alarm functions
and the results of the application of the
system are described in the report.
Conclusions
The results of the study produced the
following conclusions:
• Programmable controllers provide a
flexible, low-cost alternative to con-
ventional hard-wired relay electrical
control systems for small package
plants.
• An automatic dialer provides a flexible
alarm system to contact operators by
telephone when emergency service is
required at unmanned remote facil-
ities (package plants or lift stations).
In conjunction with a programmable
logic controller, an automatic dialer
provides the capability to identify
alarm signals according to type of
emergency, priority for service, and/
or location of the problem.
• A priority ranking has to be estab-
lished for sensor signals to distinguish
emergency conditions that justify
immediate operator response from
long-term problems where the
required service can be scheduled
through normal channels. For the
Richmond Park Terrace WWTP dem-
onstration, the following were
selected as high priority alarms:
a. Wet well level high (influent pump
failure),
b. Wet well level low (influent pump
loss of prime),
c. Possible loss of phase in power
supply,
d. Low air pressure at aerator (air leak,
blower failure, or power outage),
e. Low air pressure at manifold (blower
failure or power outage),
f. Not enough blowers on (blower
failure or power outage),
g. Break in,
h. Fire, and
i. Chlorine leak.
The following sensor signals were
specified as lower in priority, indicated
possible need for scheduled mainte-
nance.
a. Bearing temperature too hot
(impending bearing failure on a
pump, blower, or driving motor).
b. Sludge blanket level high in final
clarifier.
c. High air pressure at manifold (pres-
sure buildup, due to sludge deposits
in the diffusers).
d. Comminutor failure.
• Monitoring for air pressure can detec
alarm conditions for low pressure;
due to power outage, or leaks in the
air distribution system. It also detect!
patterns of slowly increasing aii
-------
Table 1. Monitoring Sensors for Small (Package/ Wastewater Treatment Plants
Location Sensor Type Protect Against
Gates and Doors
Buildings
Chlorine Room
Lift Station
Wet We/I
Lift Station Pumps
Blowers
Security
Smoke
Chlorine Leak Detector
Low Level
High Level
High Bearing Temperature
Power Demand
Low Pressure
High Bearing Temperature
Power Demand
Intruders. Vandalism
Fire
Hazardous Atmosphere
Loss of Pump Prime
Flooding
Loss of Lubrication
Power Outage
Leak in Air Headers
Loss of Lubrication
Clarifiers
Return Sludge Pumps
Sludge Scraper Drive
Aeration Tank
Settling Tank
Chlorine Contact
Tank
Sludge Blanket Level
High Bearing Temperature
Power Demand
High Torque
Power Demand
Dissolved Oxygen.
Low DO Alarm
Dissolved Oxygen,
High DO Alarm
Sludge Blanket
Detector,
High Level Alarm
Residual Chlorine
High Level Alarm
Washout of Sludge
Loss of Lubrication
Power Outage
Motor Overload
Power Outage
Shock Load
Oxygen Demand
Excessive Blower
Power
Loss of Activated
Sludge So/ids by
Hydraulic Washout
or Bulking
Excessive Chlorine
Usage
pressure, which indicate a need for
cleaning of diffusers.
Phase sequence monitors provide
low-cost and effective means to detect
conditions of no power to a three-
phase motor for blowers or pumps.
They can also detect phase loss in the
electrical distribution system, and
thereby avoid considerable potential
damage.
Monitoring for the
tures using externi
mocouples dan >|jo
ing failure as a pa
steadily rising tern
bearing tempera-
ly mounted ther-
nmpending bear-
ern of slowly but
leratures relative
to local ambient conditions.
• Ultrasonic sludge blanket detectors,
although free from fouling by biolog-
ical growth, may not be sufficiently
accurate for use in controlling biolog-
ical waste treatment systems.
• Based on the results obtained, the
following basic sensor-controller-
telephone alarm system was recom-
mended for installation in package
plants:
a. Programmable controller,
b. Automatic dialer,
c. Pressure switches,
d. Wet well level indicator,
e. Chlorine leak detector, and
f. Power demand sensors.
The cost of the recommended basic
system including installation supplies
was $10,994 with an estimated 360
labor hr need for installation.
The full report was submitted in
fulfillment of Grant No. R-806333-01 to
Cuyahoga County under the sponsorship
of the U.S. Environmental Protection
Agency.
-------
Irwin J. Kugelman is now with Lehigh University, Bethlehem, PA 18015; and
the EPA author, Michael D. Cummins, is with the Technical Support Division,
Office of Water, Cincinnati, OH 45268.
Walter W. Schuk was the EPA Project Officer (see below for present contact).
The complete report, entitled "Centralized Management of Small Treatment
Plants Using Instruments and Remote Alarms," (Order No. PB 88-147 798/
AS; Cost- $14.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
For further information, Dolloff F. Bishop can be contacted at:
Water Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S2-87/108
0000329 PS
U S ENVIR PROTECTION AGENCY
REGION 5 LIBRARY
230 S DEARBORN STREET
CHICAGO IL 60604
------- |