Engineering Resilience in Water Supply: How Ozone-Based Oxidation Supports DC Water’s Pure Water DC Vision

In November 2025, DC Water announced a major new initiative: Pure Water DC, a comprehensive strategy to secure Washington D.C.’s long-term water future. Central to the plan is the exploration of advanced water reuse, treating reclaimed water to a level suitable for potable use, and integrating it as a second source alongside the Potomac River.

This shift reflects a national trend: utilities are preparing for a future where drought, contamination events, population growth, and aging infrastructure place unprecedented strain on water systems. Pure Water DC is more than a local plan; it’s a blueprint for a resilient, decentralized water supply.

And at the core of that blueprint is advanced oxidation, led by technologies like ozone (O₃) and ozone-based advanced oxidation processes (AOPs).

At Pinnacle Ozone Solutions, we design ozone systems that are modular, precise, and engineered for reuse, making us a critical partner in the transformation of American water systems toward resilience.

Why DC Water Is Pursuing Advanced Reuse

DC’s current drinking water comes entirely from the Potomac River, treated at the Washington Aqueduct, then distributed city-wide. But this system, while high quality, is vulnerable to:

• Single-source risk: No alternative if the Potomac is compromised (drought, spill, turbidity, or contamination)
• Climate variability: Extreme weather alters raw water chemistry, volume, and reliability
• Population growth: Increased demand in the capital region
• Regulatory evolution: The need to anticipate stricter treatment requirements, including for emerging contaminants

Pure Water DC envisions an advanced water treatment facility at Blue Plains capable of producing purified water from highly treated wastewater. This would not only support indirect potable reuse but also enable source diversity, storage flexibility, and emergency preparedness.

The Role of Ozone in Advanced Reuse

Multi-Barrier Micropollutant Removal

Water reuse demands more than disinfection, it requires removal of pharmaceuticals, endocrine-disrupting compounds, and trace organics not captured by conventional treatment.

Ozone provides:

• Direct oxidation of electron-rich molecules like carbamazepine, sulfamethoxazole, ibuprofen, and EE2
• AOP capability when paired with hydrogen peroxide (O₃ + H₂O₂) or UV (O₃ + UV), generating hydroxyl radicals (·OH) with oxidation potentials up to 2.8 V
• Destruction of many DBP precursors, improving downstream membrane and BAC/GAC performance

Pathogen Inactivation with Residual-Free Disinfection

Ozone is highly effective against a broad spectrum of pathogens:

Unlike chlorine, ozone leaves no residual disinfectants or halogenated by-products. This is ideal in reuse systems where downstream polishing (BAC, membranes, UV) benefits from a cleaner oxidant profile.

Improved UVT and GAC Performance

Ozone pre-oxidation reduces organic fouling, increases UV transmission, and decreases GAC loading by:

• Breaking high-molecular-weight NOM into biodegradable compounds
• Enhancing DOC removal ahead of final disinfection
• Reducing color and improving aesthetic quality

Engineering Considerations for Ozone in Reuse Trains

• Dose and Contact Time
  • Ozone Dose Range: 2–5 mg/L (adjusted based on TOC, UVT, bromide, temperature)
  • Contact Time (CT): Designed per pathogen inactivation + micropollutant oxidation targets
  • ORP Monitoring: Maintains process control (typical reuse setpoints: 300–500 mV)
• Contactor Design
  • Pinnacle systems utilize pressurized injection contactors, achieving >95% mass transfer efficiency
  • Hydraulic residence time is optimized to complete oxidation before downstream processes
  • Off-gas destruct units prevent atmospheric ozone release
• AOP Integration
  • O₃ + H₂O₂ systems generate ·OH radicals in a controlled pH/alkalinity environment
  • H₂O₂ dosing is based on [H₂O₂]/[O₃] ratios (typically 0.5–1.0 molar)
  • Requires monitoring of ozone residual, peroxide residual, and scavenging species
• Materials and Safety
  • Ozone-resistant materials (316L SS, PTFE, PVDF, Viton seals)
  • Redundant leak detection and interlocks
  • Automated shutdowns tied to gas sensors and ORP spikes

Example Reuse Train Incorporating Ozone

Potential Advanced Treatment Train – Pure Water DC Style:

1. Tertiary filtration (cloth filter / membrane)
2. Ozone contactor (TOC, T&O, micro-C, pathogen reduction)
3. AOP reactor (O₃ + H₂O₂ or O₃ + UV)
4. BAC filter (assimilable organic carbon removal)
5. UV disinfection (final log inactivation)
6. Stabilization / pH adjustment
7. Distribution / reservoir recharge / potable blending

Conclusion: For Resilient Reuse, Oxidation Must Be Smart, and Ozone Delivers

DC Water’s Pure Water DC initiative is a landmark moment in the evolution of U.S. water supply planning. It recognizes that treatment performance is now a public health asset and a security strategy.

Ozone, as both an oxidant and an AOP enabler, is uniquely positioned to meet the needs of modern reuse systems:

• Disinfection without residual risks
• Micropollutant destruction with chemical minimalism
• Improved filterability, UVT, and system resilience
• Scalable, controllable oxidation ready for diverse feedwaters

At Pinnacle Ozone Solutions, we engineer systems that meet and exceed the technical demands of water reuse, with the precision and safety required for projects like Pure Water DC and beyond.

References

• DC Water (2025). “Pure Water DC” Program Announcement. dcwater.com
• von Gunten, U. (2003). Oxidation Chemistry of Ozone in Water Treatment. Water Research.
• Langlais, Reckhow, Brink (1991). Ozone in Water Treatment: Application and Engineering
• WRF Project #4767. Ozone + AOP Performance in Potable Reuse Pilots
• Pinnacle Project Data (2020–2024)