Remote Real-Time Monitoring of a Distribution System A Case Study in Washington D.C.
Srinivas Panguluri (Shaw Environmental, Inc.), Robert M. Clark (Consultant), and Roy C. Haught (U.S. EPA - Water Supply and Water Resources Division) Presented by Srinivas Panguluri, P.E.
Presentation Outline
o o o o o
Overview of the Case Study System Selection and Implementation Lessons Learned Te chnology Tre Re w nds vie Q&A - Discussion
Overview of the Case Study
In 1996, following a number of Colifom violations EPA Region-3 directed DC Water and Sewer Authority (WASA) to implement several corrective actions One of the corrective actions proposed was remote monitoring of water quality. In 1997, EPA initiated a study to install a remote monitoring network
Overview of the Case Study
Fort Reno Tank was selected as the first location for remote monitoring system implementation Four water quality parameters were selected for monitoring in this Case Study - Temperature, Chlorine, Turbidity, pH The study was later on expanded to two other locations Bryant Street and Blue Plains The existing WASA's SCADA system was adapted for data collection
Overview - System Layout
Overview Publishing Data
Overview Web Access
Overview Data Browsing
Overview Sampling System
Overview Sample Data
35.000 30.000
25.000
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15.000
10.000
5.000
-5.000
01-Aug-97
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Date - Time Resi. CL2 (ppm) pH Temperature (oC) Turbidity (NTU)
System Selection and Implementation
Off-the-shelf online monitoring instrumentation for Temperature, Chlorine, Turbidity and pH with 420 mA external outputs were used A custom water sampling system was built for each site A Preliminary Assessment for selecting and implementing the appropriate Data Acquisition System was performed. Key factors are outlined as follows: Initial and ongoing $ - EPA/WASA
System Selection and Implementation
Ease of use and programmability - Proprietary Hardware Networkable - Yes System Scalable - Yes Data/System Redundancy - Yes System Security One Way Data Transfer Remote Access Capability - Not Available System Response Time - More than adequate Historical Trend Data Storage/Transfer Capability - Limited Storage Availability of Local Support - WASA
System Selection and Implementation
Software Features Graphics, Trending and Reports Remote Access - Added a Windows-based PC workstation to dial into using pcAnywhere/ Reachout Software (added security, prevents remote access to the WASA SCADA system) Trending - Export Program in Access97 Reporting - Queries to chart in Excel97 Power Availability - Yes
System Selection and Implementation
Summary Existing Scalable SCADA System and onsite support Programs were developed to work around some of the existing system limitations Phased Implementation
Lessons Learned
Train and retrain "hands-on" as much as possible both for operation and troubleshooting activities Teach operational awareness Need to customize the user's manual, provide phone support
Lessons Learned
Frequent changes in WASA support personnel affected some troubleshooting activities Dead pigeons were found floating in the Fort Reno tank by WASA personnel. cleaning The procedure damaged some of the sensor equipment. The initial data could not be validated due to the lack of calibration records
Lessons Learned
The network link between the water and sewer side has limited bandwidth. The errors generated in the network traffic using this link frequently cause a bottleneck in the system and eventually led to a few system crashes Lack of communication between WASA personnel and the contractors working at the Fort Reno site caused the tank to overflow and the sampling system was submerged
Technology Trends Review
Instrumentation Conventional Ion selective electrodes, GC, LC, optical, etc. Bio-sentinels based on observing and evaluating the behavior of living organisms - Daphina, Fish, Clam, Bacteria, Algae, etc. Bio-sensors - DNA based, flow cytometry, etc.
Technology Trends Review
Instrumentation (Contd.) Solid State Microchips Other (ZAPS) Remote Data Acquisition Technologies Wireless Cellular, CDPD, Cellmetry/Aeris, Radio's ISM/VHF/UHF, PCS, Satellite Encryption - Key Based DES/AES symmetric (or secret-key), RSA asymmetric (or public-key) algorithms
Technology Trends Review
Remote Data Acquisition Technologies (Contd.) The Polled System: Pros: Data gathering is simple, no collisions, link failure can easily be detected Cons: Interrupt type request cannot be handled immediately, wait time increases with the number of locations, all communications must pass through the master.
Technology Trends Review
Remote Data Acquisition Technologies (Contd.) The Interrupt System: Pros: Reduces unnecessary transfer of data, quick detection of urgent status information, allows peer-to-peer communication Cons: Link failure may be detected after a long period of time, operator action is needed to have the latest value, collision of data may occur and cause delays
Technology Trends Review
Power Requirements Solar and other power options ...