Temporary Configurations of Online Analyzers to Optimize BNR
Authors:
- Chris White, Daniel Edwards, and Joe Rohrbacher - Hazen and Sawyer
Online analyzers have become more reliable, especially in hostile environments such as high solids and aerated areas, and the controllers for the analyzers often include built-in data logging capabilities. These attributes can be leveraged during pilot studies and plant start-ups. Pilot studies often require labor intensive data collection efforts to capture process information normally not available in most plant supervisory control and data acquisition (SCADA) systems. Process control during plant start-ups often requires a conservative approach while process instrumentation is not fully integrated into the SCADA system. By taking advantage of the on-board data logging capabilities of today’s online analyzers, plant operations may be optimized while in a temporary instrumentation configuration.
Economical solutions may be realized through the effective calibration of process models coupled with correct placement of online instrumentation. Current probe technologies have yielded systems of collecting data within biological nutrient removal (BNR) basins that are not significantly affected by air bubbles or high solids concentrations. Furthermore, probe controllers may easily be configured to capture data and download directly to a laptop computer for pilot applications, without the need for probe installation and configuration into the plant SCADA system.
During a phosphorous removal pilot study, online nutrient analyzers were temporarily mounted to monitor nutrient levels as chemical dosing was reduced and process adjustments were made. The online analyzers provided an early warning system to allow a more aggressive chemical feed reduction schedule without placing the plant at unnecessary risk for permit violation. Incorporation of online nutrient probes during denitrification pilot operations also yielded significant data. No modifications were required to plant systems and the probes were not affected by process conditions during either pilot study.
During start-ups of two plant upgrades, data collected from DO probes allowed the adjustment of blower operation to effectively provide proper aeration to basins before the instrumentation was integrated into the controls system. This capability allowed plant operators to identify potential issues with the aeration system and reduce the number of periodic manual measurements of the basins.
Online nutrient analyzers, regardless of being fully integrated into SCADA, allow the possibility for plant operators to closely monitor nutrients, meet permit limits more economically, and maintain and troubleshoot process control during system start-up.
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