OVERLAND PARK, KANSAS
The Challenge Inconsistent secondary clarifier performance limited the quality of effluent that the Douglas L. Smith Middle Basin advanced wastewater treatment facility in Overland Park, Kansas, could produce. The Operations Engineer sought to achieve the lowest total suspended solids (TSS) and most consistent effluent by controlling the solids retention time (SRT). In order to implement this solution, a new monitoring system was required for continuous online measurement of TSS in the mixed liquor suspended solids (MLSS) and return activated sludge (RAS). The desired characteristics of the new monitoring system were long-term accuracy and simple maintenance. Furthermore, it had to be applicable at the other treatment facilities owned by Johnson County. The Solution Based on project specifications, three monitoring system suppliers were selected for an on-site demonstration. The competing TSS sensors were placed side-by-side in an aeration basin and performance was compared over a 2-month trial period. Accuracy was verified with gravimetric analysis of grab samples collected near the sensors and maintenance activities were logged. The IQ SensorNet (IQSN) system from YSI, had the highest accuracy and the least maintenance due to its unique, integrated self-cleaning system and was selected for permanent installation. IQSN ViSolid TSS sensors were installed at the oxic end of each of the four treatment trains to monitor MLSS. Additionally, insertion mounted ViSolid sensors were installed into RAS pipelines. According to Doug Nolkemper, the Operations Engineer, “If it works in MLSS it will work in RAS”, because RAS is just concentrated mixed liquor. Measurements from the sensors are output to the SCADA system through 4-20 mA signals. The target SRT is maintained by automatic adjustment of the sludge wasting rate using a formula programmed into the Allen Bradley PLC and calculated using the online monitoring data.
Objective: Total Suspended Solids Monitoring for Process Stability
Inside the Douglas L. Smith Middle Basin Plant
Acknowledgements: Many thanks to Doug Nolkemper, Operations Engineer at the Douglas L. Smith Middle Basin treatment plant, for providing his experience with the IQ SensorNet system and sensors.
Screen shot from SCADA system showing MLSS monitoring data and automated waste activated sludge control
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