Beyond Compliance: Using Continuous N₂O Sensing in BNR Processes to Drive Load Balancing, COD Dosing, and Process Resilience
Tuesday, September 29, 2026 3:00 PM to 4:30 PM · 1 hr. 30 min. (US/Central)
New Orleans Convention Center
Technology Spotlight
Hall H Booth 7249
Information
Nitrous oxide (N₂O) carries a global warming potential 273 times greater than CO₂ and can account for more than 70% of direct greenhouse gas emissions at a wastewater treatment plant. As utilities decarbonize and reduce fossil fuel consumption, N₂O will become the dominant GHG source for many facilities. Yet N₂O is not a fixed property of a plant – it is produced dynamically in BNR processes whenever low dissolved oxygen, nitrite accumulation, incomplete denitrification due to carbon limitation, or simultaneous nitrification and denitrification (SND) create the conditions for its formation. These drivers interact in ways that conventional DO, ammonia, or nitrate sensors cannot fully diagnose. A sensor that sees N₂O directly – at the point of formation in the water column – is the missing piece.
The N₂O Wastewater System
The N₂O Wastewater System uses an amperometric electrochemical sensor to measure dissolved N₂O continuously and directly in the activated sludge, with real-time temperature compensation for accuracy across all process conditions. Unlike off-gas approaches, the liquid-phase sensor captures N₂O in both aerated nitrification zones and non-aerated denitrification zones simultaneously – field data show that denitrification phases contribute 12–16% of total plant N₂O emission, a fraction invisible to surface measurements. Installation is straightforward: the sensor mounts on the tank railing, connects to SCADA, PLC, or process control platforms, and requires calibration only at installation and every two months. Up to 16 sensors run from a single operator console.
Three Operational Insights the N₂O Signal Delivers
Field campaigns at two full-scale Danish WWTPs – Aalborg Vest (265,000 PE, low-emission, 0.28% N₂O-N/TNinlet) and Lynetten (1,000,000 PE, high-emission, 6.3% N₂O-N/TNinlet) – revealed that continuous N₂O monitoring delivers three categories of actionable insight that no other BNR sensor provides:
• Load balancing across treatment trains N₂O levels varied by up to ±41% between individual tanks at Lynetten under nominally equal hydraulic loading. Persistently elevated N₂O in a specific train flags uneven nitrogen load distribution, reject water routing issues, or flow imbalances – giving operators a sensitive leading indicator to correct problems before they appear in effluent quality.
• COD dosing and carbon availability N₂O accumulates when carbon is insufficient to complete denitrification – the same condition that drives effluent nitrate violations. The liquid-phase sensor detects this limitation faster and more specifically than nitrate or nitrite sensors alone, enabling tighter, demand-driven COD dosing: adding external carbon only when and where it is needed, cutting chemical costs while simultaneously suppressing N₂O emissions.
• Process resilience through early warning Early detection of nitrite spikes, low-DO excursions, and SND activity – all high-risk conditions for N₂O production – allows operators to intervene before emissions escalate. Combined with N₂O-based aeration control, the signal becomes an active tool for suppressing peak emissions, reducing energy use, and building a lower-carbon, more resilient BNR process.
The N₂O Wastewater System
The N₂O Wastewater System uses an amperometric electrochemical sensor to measure dissolved N₂O continuously and directly in the activated sludge, with real-time temperature compensation for accuracy across all process conditions. Unlike off-gas approaches, the liquid-phase sensor captures N₂O in both aerated nitrification zones and non-aerated denitrification zones simultaneously – field data show that denitrification phases contribute 12–16% of total plant N₂O emission, a fraction invisible to surface measurements. Installation is straightforward: the sensor mounts on the tank railing, connects to SCADA, PLC, or process control platforms, and requires calibration only at installation and every two months. Up to 16 sensors run from a single operator console.
Three Operational Insights the N₂O Signal Delivers
Field campaigns at two full-scale Danish WWTPs – Aalborg Vest (265,000 PE, low-emission, 0.28% N₂O-N/TNinlet) and Lynetten (1,000,000 PE, high-emission, 6.3% N₂O-N/TNinlet) – revealed that continuous N₂O monitoring delivers three categories of actionable insight that no other BNR sensor provides:
• Load balancing across treatment trains N₂O levels varied by up to ±41% between individual tanks at Lynetten under nominally equal hydraulic loading. Persistently elevated N₂O in a specific train flags uneven nitrogen load distribution, reject water routing issues, or flow imbalances – giving operators a sensitive leading indicator to correct problems before they appear in effluent quality.
• COD dosing and carbon availability N₂O accumulates when carbon is insufficient to complete denitrification – the same condition that drives effluent nitrate violations. The liquid-phase sensor detects this limitation faster and more specifically than nitrate or nitrite sensors alone, enabling tighter, demand-driven COD dosing: adding external carbon only when and where it is needed, cutting chemical costs while simultaneously suppressing N₂O emissions.
• Process resilience through early warning Early detection of nitrite spikes, low-DO excursions, and SND activity – all high-risk conditions for N₂O production – allows operators to intervene before emissions escalate. Combined with N₂O-based aeration control, the signal becomes an active tool for suppressing peak emissions, reducing energy use, and building a lower-carbon, more resilient BNR process.