Phoenix, AZ, Adopts Real-Time Sewer-monitoring Technology to Optimize Operations and Balance Current and Future Expectations

Phoenix, AZ, is a leader in wastewater reuse and water conservation practices. Approximately 97% of the city's wastewater is recycled for uses, such as irrigation and for cooling water for the Palo Verde Nuclear Plant. As the 5th largest city in the United States, Phoenix celebrates its growth as it explores innovative ways to meet current needs and keep pace with the impacts on its aged sewer system brought on by increasing population, development and climate change.

The city's Water Services Department's Wastewater Division (the Division) aims to protect public health and the environment by ensuring compliance with regulations and utilizing advanced technologies to optimize its sewer operations. The Wastewater Division manages the city's separate sewer system and wastewater collection and treatment operations, serving more than 2.5 million residents. The system consists of 5,017 miles of gravity and force main sewer lines, 28 lift stations, 94,000 manholes, 8,290 cleanouts, and three wastewater treatment plants.

Phoenix faced challenges managing its sewer and stormwater infrastructures. Sanitary sewer overflows (SSO) posed environmental risks and regulatory concerns. Elevated levels of H2S emitting from the lift stations and treatment plants provoked complaints from residents about the odor and created health safety hazards for workers and the community.

To better understand the changes and challenges within Phoenix's wastewater collection system and to manage its capacity, the Division turned to technology to remotely monitor its infrastructure in real-time and gain valuable insights to ensure operational resilience. Of particular concern was monitoring high-frequency cleaning areas to be more efficient in cleaning rotations. The decision to incorporate real-time remote technology was part of the Water Services Department's $3.05 billion, five-year capital improvement plan (2003-2008) to rehabilitate and sustain its water and wastewater systems.

Phoenix deployed remote satellite-based ultra-sonic monitors across critical points in the sewer and stormwater systems to proactively identify, manage, and mitigate risks with level, flow and Hydrogen Sulfide (H2S). The monitors are mounted underneath manhole covers and do not require confined space entry. The monitors' satellite integration provides comprehensive observation and data collection, enabling proactive maintenance and timely intervention when issues arise. The monitors also are mobile and can be easily moved around to assess various locations as needed. The uninterrupted real-time data is transmitted to a dashboard on a secure website and sounds alarms and alerts to operations staff through cell phones and other mobile communications devices. Alarms occur even during sewer surcharges.

The integration of sewer-monitoring technology in Phoenix has shown significant improvements in system reliability and operations efficiency, including early identification to reduce sanitary sewer overflows (SSOs), blockages and service interruptions, improved cleaning schedules, and identification of areas and frequencies of H2S gas spikes that result in odors and system corrosion.

The added ability to collect data and metrics for such things as trend analysis and modeling has improved day-to-day operations and has been useful in updating annual infrastructure master plans that reflect the utility's priorities and align operating and capital budgets to support those priorities.

The data and metrics have helped refine maintenance schedules and response times and identify areas of H2S so staff can evaluate chemical dosing for cost savings. The data and metrics also have been useful with regulatory compliance and for updating annual infrastructure master plans that reflect the utility's highest priorities and align operating and capital budgets to support those priorities and protect the environment, the public and workers.

For nine months in 2024, Phoenix monitored 10 frequently visited areas (FVA) and realized a 94% reduction in unnecessary cleaning. That saved the city more than $41,000 in manpower during that nine-month period and the District was able to redirect staff to other sites that needed attention.

Also in 2024, Phoenix installed 19 monitors to detect water intrusion in utility vaults to avoid infrastructure degradation, failures, and regulatory action. The vault monitors also eliminate the need for frequent time-consuming and often labor-intensive visual vault inspections. Of 19 vaults, the monitors identified eight with leaky valves and wastewater that had potential to overflow. Staff immediately addressed those issues.