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Scada
Introduction
Supervisory
Control
And
Data
Acquisition
(SCADA) systems are becoming more common in wastewater treatment plants because
of a variety of functions they can perform. SCADA systems can consist of a
variety of equipment, such as autodialers, system monitors, gauges and
alarms. These units are then connected to a central control unit such as a
computer, allowing plant operators to control the equipment directly from the
central control unit. The SCADA equipment can perform functions such as
flow monitoring, alarm notification, data logging, and flexible system
communication. Remote areas such as WWMA'a CSO overflow regulators and
Ardara Pump Station could be monitored and checked at any time right from the
Plant. SCADA systems can be configured to send faxes or place telephone
calls in situations such as plant malfunctions or abnormal conditions. A
system adapter can even be added to allow plant workers to use the telephone to
control equipment. As the plant continues to upgrade and expand,
computerized systems using SCADA will be invaluable at maintaining system
controls and allowing plant operators the flexibility of system operation from a
computer or, if necessary, a telephone.
Existing System Requirements
Although WWMA currently
has some computerized system controls for items such as the wetwell pumps and
various other pumps and valves, the system's use is limited and not centralized.
The Panalarm panel in the control building operates in a run/off mode and is
only capable of monitoring whether or not equipment is operating properly.
Control of the equipment cannot be performed from the Panalarm and must be
performed at the location of the equipment or at one of the motor control
centers or local control stations. A centralized control system such as
SCADA would link plant-wide operations and allow the control and operation of
various processes from one location, eliminating the need for the Panalarm.
Reasons for Exploring Alternatives
Plant
costs and ease of control and maintenance are the main reasons for exploring the
implementation of a SCADA system. While the Panalarm displays the status
of different pieces of equipment, an alarm system that could be provided by a
SCADA setup would alert plant workers of a problem immediately, thus allowing
quicker response time and avoiding possible equipment damage and breakdown.
Another reason to
consider SCADA is ease of data acquisition. WWMA operates three overflow
regulators in remote locations from the plant, as well as a remote pump station.
A SCADA system would allow a dial-in procedure by which plant workers can easily
check the status of remote equipment from the plant at any time. This
would reduce the need for off-site trips and allow for a more frequent
monitoring process.
An added benefit of the
SCADA system is centralization of control. As was previously discussed,
the Panalarm monitors the operation of various pieces of equipment but does not
operate the equipment from the Panalarm itself. Any changes to equipment
operation have to be performed by plant workers. A SCADA system could
computerize as many pieces of equipment as WWMA wants and process the data for
collection at one central location, such as the manager's office. This
would eliminate the need for manual equipment control at the equipment location
or control centers/stations.
The majority of new
equipment has built-in provisions for automated control or remote monitoring.
The Authority recently purchased new plant operating software to monitor
operation and maintenance functions.
Recommendations and Summary of Equipment
HDR Engineering, Inc.
recommends that the Authority consider the installation of a SCADA system to
improve plant operation and maintenance capabilities. While this is not a
priority item, implementation should be considered within the next five years.
The following list summarizes the list of items necessary for a relatively
simple SCADA system for the Plant:
- Remote Terminal
Units (RTU's)
- Hard-Wired Power
Supply
- Battery and Mounting
Kit
- Software Package to
Run System
- Modem Module for
RTU's
- Personal Computer
- Electrical
Considerations
The complexity of a
SCADA system is dependent on how detailed the system would be and costs needed
to centrally computerize many of its operations. Basic systems with
minimum controls are fairly inexpensive, while larger systems, by default, costs
more but have greater capabilities. A simple system may consist of
providing data acquisition for areas such as the CSO overflow control points as
well as monitoring points for different pumps, valves, and other equipment.
Costs rise as additional control points are added; however, WWMA's applications
will probably require a relatively small number of control points.
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