Application Note

WWTP Utilizes Online Instrumentation And SCADA To Keep Operating Costs Low And Effluent Quality High

Source: YSI, a Xylem brand

Providing the best value to wastewater customers requires a team of operators that have a deep sense of ownership and are committed to continuous improvement. Such is the case for the operating staff at one wastewater treatment plant whose progressive attitude and a philosophy of “do it right” led them to an investment in online instrumentation and SCADA for compliance, monitoring, and control.

An advanced level of wastewater treatment is provided for an average daily flow of 2 mgd. The flow sheet consists of equalization, preliminary treatment, primary settling, trickling filters, a 2-stage activated sludge system, and tertiary filters. The National Pollutant Discharge Elimination System (NPDES) discharge permit requires monitoring of pH, total suspended solids (TSS), and 5-day carbonaceous biochemical oxygen demand (CBOD5) in the influent and limits the pH and the concentration of TSS, CBOD5, ammonia-nitrogen (NH3-N), and dissolved oxygen (DO) in the treated effluent.

The wastewater plant invested in SCADA and the YSI IQ SensorNet online process monitoring system several years ago. Selection of the SCADA component was easy on account of the previous experience of the Utilities Director in the power generation industry. Selection of the IQ SensorNet came about after a trusted associate brought it to the attention of the wastewater superintendent. The superintendent liked the IQ SensorNet system overall, especially the ability to measure up to 20 parameters on a single network. The original system installed consisted of a universal controller (2020 XT); seven sensors including two pH (SensoLyt®), three DO (TriOxmatic®), and two TSS (ViSolid®); a Modbus module for communication with the PLC; and a spare sensor connection cable for calibrating sensors in the lab.