NORTHEAST OHIO
Northeast Ohio - 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 team at one mid-sized 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. The Challenge 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 Solution The wastewater plant invested in SCADA and the YSI IQ SensorNet (IQSN) online process monitoring system several years ago. The superintendent liked the IQSN 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. The most critical objective for any wastewater treatment plant is compliance with the discharge permit. Continuous measurements from a pH sensor in the influent, and pH and DO sensors in the effluent, directly satisfy discharge permit reporting requirements and verify compliance with discharge permit limitations. Additional sensors deployed in the treatment system enable operators to automatically control operating parameters to ensure cost-effective compliance. The activated sludge aeration system represents the bulk of treatment and the largest portion of operating costs. Therefore, as the superintendent puts it, “It seems unwise to not fine-tune the aeration system to the greatest extent possible.” Mixed liquor suspended solids (MLSS) concentration and DO concentration are critical operating parameters for the activated sludge system. If the concentration of either is inadequate, treatment performance degrades and discharge permit violations occur. On the other hand, excessive levels result in wasted energy and higher operating costs that must be passed on to ratepayers.
Objective: Keeping Operating Costs Low and Effluent Quality High
IQ SensorNet ultrasonic cleaning, UltraClean, is capable of preventing biofouling of the sensors in very harsh conditions saving time and money on sensor maintenance.
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