Biological Nutrient Removal Applications for Monitoring Oxidation Reduction Potential

What this presentation covers

Key Takeaways

• ORP fundamentals: measures electron donating/accepting ability, quantifies oxidizing/reducing potential of the mixed liquor
• Process zone identification by ORP: Oxic (≥ +100 mV), Anoxic (-100 to +100 mV), Anaerobic (≤ -100 mV)
• Intermittent aeration control strategy: ORP high setpoint +250 mV turns off aeration; low setpoint 0 mV triggers 40-minute anaerobic timer for phosphorus release
• Demonstrated results: effluent TP consistently < 1 mg/L, TMDL requirements met, zero chemical addition required
• Continuous-flow applications: effluent ammonia control upstream of chloramination, aeration optimization, simultaneous nitrification/denitrification at low DO
• Extended aeration case study: ORP maintained -270 to -200 mV, ammonia 1-3.5 mg/L, nitrate < 1 mg/L, minimal aeration and chlorine usage
• Sensor care: one-point offset calibration with Zobel solution (231 mV at 25°C), pH-style cleaning, 6-month online / 1-year handheld electrode warranty

About the Author

Medhat Gad — P.Eng., PMP — Principal Engineer at BioTerraVa with 36+ years of water and wastewater infrastructure delivery across North America, the Middle East, and North Africa.

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