| Distributed Control System Honored
for Energy Savings
September 1987 - ESCOR was among eight organizations honored
by Wisconsin Governor Tommy Thompson for achievements in developing or
introducing energy innovations. ESCOR received recognition as part of the
1987 Governor's Awards for Energy Innovation. This is an annual statewide
competition with energy conservation and renewable energy projects eligible
for the award.
"The 1987 Energy Award winners provide a challenge to energy consumers
throughout the state to adopt similar programs, and to examine new technologies
that can make them winners in future years." the Gov. Thompson said.
ESCOR was organized in 1984 specifically to provide automatic controls
to small wastewater treatment plants. The award was given to ESCOR "...
for designing and installing a special computerized control system for
the Saukville Wastewater Treatment Plant ... which saves the Village more
than $8,000 annually in energy costs."
There are two treatment plants in Wisconsin that have similar ESCOR
systems: Saukville, the first to be operational, and the Walworth County
Metropolitan Sewerage District (WALCOMET). The controls will pay for themselves
within five years through energy cost reductions alone.
Plant operators Gene Hueppchen and Glenn McCarty were instrumental in
optimizing the system for Saukville. At WALCOMET, Manager Joe Cannestra
and Chief Operator Steve Miller were the keys to a successful design. The
ESCOR systems at both WWTPs were part of ongoing conservation programs.
Although new technology has made computer controls practical for wastewater
treatment, their implementation has not been widespread. This is due to
a history of problems with older technology and the difficulty of providing
economic justification for the systems, especially in small treatment plants.
Consequently, ESCOR designed a system specifically for retro-fitting
small facilities. Because of their background in wastewater treatment,
the engineers were able to develop strategies that adapted energy savings
to process requirements.
Included in the additions made to the Saukville plant were dissolved
oxygen and blower control, HVAC optimization and the scheduling of industrial
waste pumping. The control is performed by a central industrial computer
with operator access through a conventional personal computer. This allows
operators to use spreadsheets and other programs without disturbing process
controls. Remote I/O panels are scattered throughout the plant.
The WALCOMET system is similar, but adds control of trickling filter
pumps and sand filter backwash pumps, including several methane fueled
engines. Anaerobic digesters are tied into the system to optimize use of
the methane generated and for automatic control of supernatant pumping.
The DO control at WALCOMET includes air flow balancing and multiple DO
probes in each basin. ESCOR also designed a special belt drive system to
reduce excess blower capacity.
For additional information contact the Village of Saukville WWTP at
(414) 284-3185 or WALCOMET at (414) 728-4140. If you would like more information
about ESCOR contact Tom Jenkins.
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| Dissolved Oxygen Control Earns
Utility Rebate
May 1989 - The Village of Grafton, Wis. received a check
for $15,750.00 from the electric company on May 11, 1989. A full 50% of
the cost of ESCOR's distributed process control system was paid by the
Wisconsin Electric Power Company rebate.
In addition to the rebate, Grafton will save an estimated $5,600 per
year in energy costs through reduced consumption and demand.
The Grafton facility employs four 100 hp centrifugal blowers for aeration.
Two conventional activated sludge basins perform BOD5 removal and nitrification.
Primary effluent flow and air flow are manually balanced between the two
basins. Following secondary clarification the effluent is chlorinated and
discharged into the Milwaukee River.
The ESCOR system was provided on a turnkey basis, with all engineering,
programming, hardware and installation included. The system incorporates
ESCOR's proprietary DO and blower control system, as well as electric power
demand monitoring and load shedding, HVAC optimization, and continuous
data logging of critical process and energy consumption parameters.
Two computers were provided with the system. The control logic, data
logging and I/O polling are handled by the Central Control Unit (CCU),
an industrial computer located in the plant's existing graphic display
panel. This is a completely solid state unit and no disk drives, keyboards
or monitors are required for operation. Several days of logged data are
stored in the CCU. Battery backed memory can save the program and logged
data for several months without external power.
Operator access to the system is through a conventional PC. Use of the
separate PC enables the operator to access the system for data reporting
and setpoint changes on an occasional basis. The rest of the time the PC
is available for report generation, operations analysis and other applications.
A modem is provided so the system can be remotely accessed by ESCOR.
Two remote I/O panels were provided. One is located adjacent to the
blowers for inlet valve control. The second is near the MCC and the existing
blower surge panel for blower motor control.
Sensors provided by ESCOR include the two DO transmitters, indoor and
outdoor air temperature sensors for HVAC optimization and a power meter
pulse relay connected to the electric company's meter. The four motor operated
inlet valves were also included. Existing instruments were incorporated
into the system for influent flow, final DO and air flow to the secondary
aeration basins and post aeration.
Tom Krueger, manager of the Water and Wastewater Department and Operator
Rich Wesson were closely involved in the design process. The calculations
and liaison with Wisconsin Electric were included in ESCOR's service. The
rebate was part of the utility's "Smart Money" program which encourages
conservation and demand limiting for industrial and commercial customers.
A significant portion of the savings was obtained by eliminating unnecessary
blower starts during summer months.
For additional information contact the Village of Grafton WWTP at (414)
377-1440. If you would like more information about ESCOR contact Tom Jenkins.
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| Aeration Control System Completes
Upgrade
February 1992 - ESCOR has successfully completed a software
upgrade on the aeration control system at the Oconomowoc, Wis. WWTP. ESCOR's
integrated Dissolved Oxygen (DO) and blower control system was installed
in 1989 along with fine bubble diffusers and two 75 hp centrifugal blowers.
Dick Neterval, Wastewater Treatment Plant Superintendent, was "well satisfied"
with the control system.
The Oconomowoc plant uses grit removal and primary clarification prior
to conventional activated sludge. The plant influent is a combination of
domestic and dairy wastes. The dairy waste causes frequent slug loading
of the aeration basins, sometimes in excess of the design organic loading
of the plant. The plant is routinely unmanned at night and only partially
staffed on weekends.
The 1989 system was part of a retrofit designed by consulting engineers
McMahon and Associates as part of a long term energy conservation program
at Oconomowoc. Neterval and his staff had tracked energy use at the plant
for several years and had incorporated load shedding and similar energy
conservation measures. When the plant decided to change from coarse bubble
to ceramic fine bubble diffusers Neterval asked to have automatic DO control
included.
In addition to improved energy performance and faster recovery from
the slug loading, the new equipment solved some other operating problems
for the plant. Neterval likes the electric motor operated valves, since
the pneumatic operators on the old blower control system caused a lot of
problems. The aeration and DO control panel was mounted in the existing
main display enclosure and the operators find it convenient to have all
the controls and indicators in one spot.
According to Neterval the Enterra DO probes and transmitters are "100%
better" than the old brand, which had constant problems with probes and
electronics. Now the staff only checks the DO probes once every four to
five weeks by comparing the readings with a YSI lab unit. If the measurements
differ by more than 1/2 ppm they simply wash the probe in a bucket of water,
wipe off the end, air recalibrate and put it back in the basin. Even with
the heavy dairy waste loading the membranes only require replacement three
times per year.
After the first year of operation Neterval was pleased with the performance
of the system. Even though the plant was closely monitored before the retrofit,
Neterval said the new system "definitely does a lot better job of controlling
DO" He reported that the combined effect of all of the energy conservation
efforts was a 38% drop in total plant energy costs, from $120,000 in 1983
to $74,000 in 1990.
By 1991 the plant loadings increased and Neterval determined that more
air was needed. In order to meet the additional requirements he originally
considered replacing one of the new blowers with a larger unit. ESCOR analyzed
his system and determined that motor replacement on the existing blower
would meet Neterval's objective at a significant savings. The ESCOR control
software was upgraded to accommodate the differences in operating characteristics
between blowers. At the same time, the program was modified to permit future
use of a third blower for standby capacity. The revised software and blowers
have been running without problems since start-up.
For additional information contact the Oconomowoc WWTP at (414) 569-2192.
If you would like more information about ESCOR call Tom Jenkins.
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| Networked Blower Control System
On-Line
November 1991 - A state of the art blower control system
from ESCOR has gone on-line at the Beloit, Wis. WWTP. The unique system
uses a communications network to control discharge pressure and flow for
five centrifugal blowers. Combined discharge flow of the blowers is 40,000
SCFM.
The ESCOR package is a true distributed control system. Six separate
processors exchange data on a dedicated communications network. Each blower
has a local control panel with a processor capable of independent control
if the network fails. These panels control blower discharge flow to ±
5% of setpoint.
The sixth processor is a master panel. Using the MS-DOS operating system,
it monitors the common discharge header pressure and maintains it to less
than 0.1 psi deviation. If the pressure fluctuates, the master panel sends
new flow setpoints to each blower's local control panel. Regardless of
the mix of blowers running, all are operated at the same percentage of
flow range.
The blowers and controls are at the heart of a new wastewater treatment
facility that incorporates diffused air activated sludge. The plant performs
nitrification and denitrification in addition to BOD5 removal. The city's
consulting engineer was Ch2MHill. ESCOR provided customized control technology
to meet their specifications.
Three of the five blowers utilize 4,160 Volt, 600 horsepower motors.
The other two units have 400 horsepower motors at 460 Volts. The ESCOR
system controls a total of 2,600 installed horsepower. The system was built
with provisions for one future blower.
A complete monitoring system is used to provide safety shutdown of the
blowers. Monitored parameters include motor winding and motor bearing temperature,
blower bearing temperature and blower bearing oil level. The local panels
also continuously monitor and display discharge air flow, pressure and
temperature. Blower amperage is also input to the system and used for surge
and overload control.
Blower flow is controlled by inlet butterfly valves. Each blower also
has a blow-off valve for surge control and starting. The blow-offs can
be modulated to maintain air flow when the aeration headers are restricted.
A special differential pressure switch and check valve system are used
to detect loss of flow to the aeration header.
All valves are pneumatically operated, with integral transducers to
convert the 4-20 mA signal from the local control panel to 3-15 psi. Both
valves are capable of continuous modulation. In addition, the blow-offs
have a special "fast open" system to relieve surge within one second of
occurrence. The blow-off is then closed, and the blower is automatically
brought back on line.
The entire Beloit WWTP is monitored by a PLC system with color graphics
computer terminals for operator interface. This system was designed by
CH2MHill and monitors virtually every unit process from remote pump stations
through solids handling. The ESCOR system interfaces to the PLC I/O system
for alarms and data logging.
For additional information contact Scott Varney of the Beloit WWTP at
(608) 364-2888. For more information about ESCOR contact Tom Jenkins.
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| Direct Flow Control System
Minimizes Pressure
August 1993 - ESCOR's proprietary Dissolved Oxygen and
blower control system with direct flow control for basin balancing is proving
itself on a particularly demanding project. The integrated system at Niagara
Paper, Niagara, WI is controlling four 300 horsepower multi-stage centrifugal
blowers which provide air to three aeration basins. The system provides
individual DO and air flow control for each basin to provide optimum process
control and energy savings. Making ESCOR's job more difficult was a difference
of nearly two feet in diffuser submergence between basins!
On smaller systems it is usually not cost effective to control the air
flow and DO independently for each basin. Most plants can achieve at least
a 20% reduction in energy by automatically controlling blowers and manually
controlling the air flow distribution to individual basins. Plants that
have three blowers with motors smaller than 200 horsepower each typically
cannot recover the cost of the additional controls by the improved efficiency.
Using separate automatic basin controls improves the energy savings
achieved with an ESCOR system to at least 25%. For a facility the size
of the Niagara Paper treatment system the additional energy savings pay
for the additional hardware in about a year. The process performance is
also improved because the variations in DO level between basins are eliminated.
The conventional approach to controlling air flow from a common header
to multiple basins uses discharge pressure control. The intent is to minimize
the impact each basin's valve movement has on other air flows. This logic
requires an additional discharge pressure drop of 1 psi or more across
the basin valves to maintain control. The result is a waste of approximately
10% of the blower power.
ESCOR's proprietary flow control logic eliminates the need for discharge
pressure control. Using an air flow signal from each basin, it keeps one
valve completely open to minimize system pressure.
A few conventional systems incorporate a "most open valve" scheme into
discharge pressure control, but they are not as efficient or accurate as
the Niagara Paper strategy. It automatically determines which valve
should be at maximum position. This not only produces minimum back
pressure, but provides consistent air flow and DO control despite process
fluctuations. If the total air supply is limited by blower capacity or
turndown the ESCOR system distribute available flow proportionately, eliminating
the problem of independent control loops forcing all baisn valves to their
limits.
The Niagara plant employs another improvement over conventional controls
- the elimination of 4-20 mA positioners on blower inlet and basin control
valves. ESCOR's direct valve control algorithms eliminate the expense,
wiring, and calibration costs associated with conventional positioners.
The Niagara mill has a Distributed Control System (DCS) and SCADA software,
and originally planned on expanding it to implement DO and blower control.
After learning about ESCOR's technology, however, the plant engineers concluded
that they would get superior control at lower cost with the ESCOR system.
Critical process signals, such as DO level and blower status, are wired
to the DCS for monitoring only.
For additional information contact Ray White of Niagara Paper at (715)
251-3151. For more information about ESCOR's services contact Tom Jenkins.
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| Combining Variable Speed and
Inlet Throttling Blower Controls
April 1995 - ESCOR pioneered the successful implementation
of Dissolved Oxygen [DO] control with variable speed multi-stage centrifugal
blowers. The recently completed upgrade at the Uniontown, PA Wastewater
Treatment Plant has taken this technology another step. The system combines
two 350 horsepower blowers using Variable Frequency Drives (VFDs) with
two 200 horsepower blowers using inlet throttling. Both sets of blowers
discharge into a common header.
The original ESCOR system was installed in 1992. At that time the variable
speed blowers were only used for aeration, and the constant speed blowers
supplied air to a separate header for RAS air lift pumps and channel aeration.
The variable speed blowers utilized air flow transmitters for control
and surge protection. This technique provides extremely accurate control,
improves operating range, and yields more accurate blower protection. Conventional
surge controls use motor amperage to prevent operation in surge conditions.
This is not accurate when used with VFDs because the normal relationship
between air flow and motor amperage is distorted at reduced speeds.
The 1995 modifications were part of a plant upgrade designed by Chester
Engineers. Submerged turbine aerators were replaced with fine pore diffusers.
The discharge headers were joined to permit operating the most economical
combination of blowers to meet total air requirements. Separate flow controls
were provided for the RAS pumping and aeration take-offs from the common
header.
Employing ESCOR's exclusive direct flow control logic, the new system
eliminated previous fluctuations in RAS flow caused by variations in blower
output.
The improvements were economically implemented by using thermal dispersion
air flow transmitters and insertion fittings. Eliminating 4-20 mA positioners
on blower inlet and basin flow control valves further reduced cost and
improved reliability.
The upgraded system automatically starts and stops blowers to achieve
the most efficient combination. Depending on total air demand variable
speed or a combination of variable speed and inlet throttled blowers
discharge into a common header.
On site testing was conducted to verify energy savings. A 350 horsepower
blower was modulated from maximum flow to surge by three separate methods:
discharge throttling, inlet throttling, and variable speed. The test data
clearly demonstrated improved performance with VFDs. The energy consumption
was 15% lower across the entire flow range. The turndown improved from
36% to 57% - a significant advantage for the blowers with VFDs.
For additional information contact Dennis Perry of Uniontown Joint Sewer
Authority at (412) 438-5844. For more information about ESCOR's services
contact Tom Jenkins.
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| Integrated Aeration Control
System Exceeds Expectations
January 1993 - ESCOR's proprietary Dissolved Oxygen and
blower control system will save 20% of the blower power in a typical domestic
wastewater treatment plant. This is enough to provide a quick payback in
all but the smallest facilities. A recent application, however, exceeded
these savings by a significant margin. According to design engineer Jim
Suozzo "I estimate that we have saved 35% on our power costs so far..."
because
of the DO control system.
In mid 1992 the Walton, N.Y. WWTP completed start-up of a plant upgrade
from trickling filters to complete mix activated sludge. Delaware Engineering
provided design, start-up and operating services to the plant during the
upgrade. The plant was designed for 1.17 mgd ADF. In addition to the city's
typical domestic wastewater, a significant portion of the 12,000 lb/day
BOD5 organic loading results from a dairy plant.
The dairy discharges to the WWTP from 7:00 AM to 5:00 PM five days a
week, including significant slug loading. Although equalization and pH
control precede the aeration basins, they are still subjected to wide fluctuations
in hydraulic and organic loading.
Delaware Engineering initially specified a conventional PLC based system
for DO control and multiple constant speed PD blowers for aeration. Additional
analysis, however, convinced them that centrifugal blowers and an integrated
DO and blower control system would provide increased savings and better
process performance for the owner.
The system installed at the Walton WWTP was designed, built, and serviced
by ESCOR. It was provided by representative Dan Reed as part of the blower
package. The integrated system controls four 100 hp blowers. Surge and
overload prevention, inlet throttling and safety shutdown were included
in the central control unit along with full manual overrides. Hybrid analog/digital
indicators for blower amps and CFM are mounted on the front panel.
Automatic throttling of the inlet valve is controlled by powering a
simple motor operator directly from the ESCOR panel. Adjustments are based
on motor amperage readings. Positioners, feedback pots and troublesome
transducers are eliminated.
The DO control employs ESCOR's proprietary floating control algorithm.
This technique provides an unmatched combination of control stability and
response to slug loading. The two aeration basins are operated in parallel,
and air flow and hydraulics are manually balanced.
A single DO transmitter is used for both basins. If throttling running
blowers within the safe operating range is not adequate to achieve the
target DO, additional units are automatically started or stopped as required.
Field adjustable time delays prevent excessive starting and stopping.
The scrolling display on the keypad provides critical process and alarm
data on a continuous basis. Tuning is as simple as setting a microwave
oven, with "real world" units and English prompts. A printer permanently
records alarms and tuning parameters. A message is also printed when bearing
lubrication intervals elapse.
For additional information contact Jim Suozzo of Delaware Engineering
at (607) 432-8073. For more information about ESCOR's services contact
Tom Jenkins.
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| Pressure Controls Bring Good
Things to GE
August 1996 - The Euclid Lamp Plant in Cleveland Ohio
is one of General Electric Company's original light bulb manufacturing
facilities. Part of the building dates back to the days of Thomas Edison,
whose portrait hangs in the main entrance.
A variety of manufacturing processes require low pressure air, provided
by three 100 hp multi-stage centrifugal blowers discharging into a common
header. In order to insure production quality it is critical to have the
air system maintain constant pressure. Because of fluctuations in production,
shift changes, etc. the air demand is constantly changing, making manual
control impractical.
GE Supply Co. knew that applying Variable Frequency Drives (VFDs) to
the existing blowers should provide better control and significant energy
savings. Based on projected savings the Euclid Lamp Plant installed three
GE AF-300C drives in 1995.
Unfortunately, the control system for the blowers and drive was not
able to meet the system needs or take advantage of the VFD capabilities.
Supplied by a local systems integrator, it incorporated conventional strategies:
P-I-D control for discharge pressure, pneumatically operated inlet valves,
and speed control for the VFDs. This system was unable to accurately maintain
discharge pressure. Automatic operation of multiple blowers was not possible.
Changes in system demand caused frequent blower surge and required manual
intervention to prevent blower damage and restore air flow.
Eventually GE called on their blower representative, BissNuss, for assistance.
BissNuss recommended that the system be replaced with an integrated control
package engineered and provided by ESCOR.
ESCOR eliminated the inlet butterfly valves and added discharge check
valves on each blower. Thermal dispersion air flow transmitters were installed
on each blower to provide accurate control and surge protection. The existing
pressure transmitter was reused, and three existing pressure controllers
were utilized to offset differences in demand between branches. The VFDs
were re-tuned by GE Supply with ESCOR's assistance. Finally, a motor operated
blow-off valve was added to allow safe blower operation during periods
of low air demand.
The new control panel employs ESCOR's unique floating control algorithm
for pressure, speed, and flow control. All the required logic for the three
blowers is programmed into a single GE Fanuc 90-30 PLC. An LCD touch screen
provides a graphic display of operating data and system tuning. Full manual
overrides are provided, and surge shutdown is provided in manual and automatic
operation.
A tight schedule was required to implement the new system during normal
plant shutdown. ESCOR had less than a week for testing and system start-up.
The new system is a complete success. The controls hold system pressure
to within ±0.1 psi and provide automatic operation of multiple blowers.
The energy savings potential of the AF-300C VFDs are fully utilized. The
plant's electrician, observing the motor amperage, initially thought the
display was inaccurate because he "never saw it that low before". Because
of the tight control the pressure setpoint was reduced by 10% for even
greater savings.
For additional information contact Bill Grabo of GE Supply Co. at
(216) 778-6449. For more information about ESCOR's services contact
Tom Jenkins.
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| Radio Telemetry & SCADA
System Combines Technologies
January 2000 - A new Supervisory Control and Data Acquisition
(SCADA) system provided by ESCOR for the City of Jacksonville, North Carolina
exhibits ESCOR's engineering expertise by combining a variety of control,
communications, and operator interface technologies.
The City of Jacksonville, located on the North Carolina coast, is the
gateway to the Camp LeJeune U.S. Marine Base. When the City decided to
update their wastewater telemetry and combine it with the water system's
SCADA they presented a variety of challenges to potential suppliers. The
requirements included a variety of telemetry devices, combining new and
existing Input/Output (I/O) equipment, and real time operating data displayed
on a dual PC graphic interface. Reliable communications during the area's
frequent hurricanes is essential.
The wastewater treatment system includes twenty-eight pumping stations
connected to the wastewater administration site by a leased-line telephone
telemetry system. Originally connected to an annunciator system, the pump
and alarm monitoring points were re-terminated to a new PLC. This PLC also
serves as the communications master for a variety of additional devices.
Four new wastewater sites are connected to the administration site PLC
by Pacific Crest digital radios. Using a newly licensed UHF frequency,
the sites are polled by the master at 4800 bps. Using Modbus RTU protocol
each location is updated several times each second. Each of the sites uses
a Control Microsystems Remote Telemetry Unit (RTU) for discrete and analog
I/O. One site, a land application treatment facility, has 36 discrete inputs.
In addition to superior communications capabilities and expandable I/O,
these RTUs include ladder logic capabilities. Alarm, data logging, and
local logic interlocks are incorporated into the RTU's logic to provide
data integrity and reliable control even if communications failures occur.
Twenty-four water locations were consolidated into the ESCOR system.
These include wells, pump stations, and elevated tanks. The original RTUs,
most installed in 1990, used a proprietary communications protocol and
analog radios operating at 300 bps over a VHF licensed frequency.
The original RTUs were replaced with new Control Microsystems units.
The original analog radio link and frequency was maintained. New Bell 202
compatible modems were used to connect the RTU's Modbus serial communications
to these radios, increasing the communications to 1200 bps. One of the
elevated tank sites is configured as a repeater station, connecting the
original analog radios with the new digital radio systems.
The old water SCADA system used proprietary operator interface software.
Running on a 386 PC with a Concurrent DOS operating system, the interface
was slow, was not easily expandable, and was not Y2K compatible.
The screens, trends, and reports from the water system were expanded
and incorporated into a new WonderWare graphical interface. State of the
art PCs and a Windows NT operating system insure expansion capability.
Two fully independent PCs are used. Both PCs display all screens for both
the water and wastewater systems. Each PC is connected to a separate communications
port on the master PLC. To insure data integrity and consistency critical
alarm and data logging functions are programmed into the PLC.
One of the advantages of the ESCOR system was the use of Modbus communications
for the entire system. This allows future expansion using RTUs, PLCs, and
other control system components from a variety of manufacturers.
For additional information contact Ray Holder of the City of Jacksonville
at
(910) 938-5266. For more information about ESCOR's services contact
Tom Jenkins.
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