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Upgrade of U.S. EPA's Experimental Stream Facility Supervisory Control and Data Acquisition System
Citation:
Weaver, P., C. Wierenga, G. Lubbers, S. Panguluri, D. Brown, AND C. Nietch. Upgrade of U.S. EPA's Experimental Stream Facility Supervisory Control and Data Acquisition System. To be Presented at Society of Environmental Toxicology and Chemistry 36th annual meeting North America, Salt Lake City, UT, November 01 - 05, 2015.
Impact/Purpose:
US EPA's Experimental Stream Facility (ESF) conducts chronic (>28 day) dose-response tests at the community scale using 16 stream mesocosms. The design objective is to balance the benefits of a bench-top setting in terms of flow rates, irradiance and dose concentration, and a field study, where biota and water quality are continuously changing. Meeting this objective requires sophisticated Supervisory Control and Data Acquisition (SCADA). This presentations how a SCADA upgrade was designed for ESF.
Description:
The Supervisory control and data acquisition (SCADA) system for the U.S. EPA’s Experimental Stream Facility (ESF) was upgraded in 2015. The upgrade added additional hardwired connections, new wireless capabilities, and included a complete rewrite of the software interface. Unique demands of the mesocosm dosing experiments at ESF require rather sophisticated SCADA not typical for model stream facilities. First, in order to implement continuous dose-response designs at the whole mesocosm scale and over periods considered chronic (i.e. > 28 d) while minimizing the potentials for divergence among replicate mesocosms inflow and recirculation rates and metering of chemical stocks require precise control and constant monitoring in a fail-safe mode. Second, to achieve flexibility in simulations so that pollutant loads can be delivered to mimic both point source and non-point source conditions, and pulsed or intermittent dilution effects, the SCADA had to be configured to handle logic control in response to automatically sensed events, such as simulated or actual rainfall or turbidity excursions in the parent water source. Additional water delivery sources from a reverse osmosis or a waste water treatment plant had to be incorporated, as well as monitoring of recirculation flow rates. Because the ESF is an indoor facility, a grow light system mimics actual outside photoperiods which is another automated component of the SCADA. Finally, data continuous water quality sensors on the main source inflows and positioned at the mesocosm outflows are acquired in lossless fashion for both unit-scale alarm notifications and as key components of experimental results and interpretation. The new ESF SCADA allows for remote monitoring and process control for sixteen 0.5m x 8.5m mesocosms and associated river water, RO water, waste water, and chemical stock tanks. The SCADA along with the hardware that it controls and monitors can reproduce inflow rates across all replicate units within 0.006 L.s-1 over a range of .03 to 3.0 L s-1. While monitoring the consistency of chemical feed pump rates to ensure desired dosing gradient targets in-stream are met. Simultaneously it is continuously logging background water quality data for sending alarm notifications, trends analysis and making whole mesocosm metabolism estimates.
