Remote Smart Monitors Bolster Sewer Odor Mitigation Program for District of Columbia Water and Sewer Authority

INTRODUCTION: MAKING WATER & AIR A PRIORITY WITH SMART TECHNOLOGY DC Water distributes drinking water and collects and treats wastewater for more than 700,000 residents and 21.3 million annual visitors in the District of Columbia. DC Water also provides wholesale wastewater treatment services for 1.6 million people in Montgomery and Prince George's counties in Maryland, and Fairfax and Loudoun counties in Virginia. To collect wastewater, DC Water operates 1,900 miles of sanitary and combined sewers, 16 stormwater stations, 22 flow-metering stations, nine (9) wastewater pumping stations, and 75,000 catch basins and manholes. To treat wastewater, DC Water operates the Blue Plains Advanced Wastewater Treatment Plant, which is considered the largest advanced wastewater treatment facility in the world. On average, nearly 300 million gallons of raw sewage flows into the plant daily. THE CHALLENGE: A 'CATCH 22' LEADS TO A SMART DECISION The Potomac Interceptor (PI) is a 50-mile-long linear gravity sewer system that flows parallel to the Potomac River from Montgomery County, Loudoun County and Fairfax County to the District of Columbia (DC). Due to many drops in the system, high turbulence is created, causing massive corrosion. To prevent corrosion at high rates, forced ventilation of the headspace is needed, but that releases odorous sewer gas into the atmosphere. Six (6) odor control facilities (OCF) were constructed to provide long-term control of odors and to reduce Hydrogen Sulfide and Dimethyl Sulfide gasses that cause corrosion and odors. After construction of the OCF's, DC Water continued to focus on controlling the odor and corrosion in the system by implementing a multi-phase OCF Optimization Plan. Phase 1 of the Optimization successfully reduced odor complaints, however, DC Water still looked for a way to measure the gas release in smaller concentrations to help control odor across the 50 mile; preserve utility resources; and better manage utility personnel time. THE SOLUTION: H2S GAS MONITORING WITH SMART TECHNOLOGY Taking a more proactive approach, DC Water started a pilot odor control optimization program in 2022, which included smart technology to measure real-time H2S gas levels. The sensors gave DC Water constant visibility of the odorous gasses in the system and alerted them of a potential H2S spike near the OCFs. The sensors seamlessly operate with the hardware system, enabling reliable, real-time measurements of H2S levels in remote locations over extended periods of time by utilizing the iridium satellite network. A total of six (6) sensors were installed along the linear Potomac Interceptor at critical points. THE RESULT: MEASURABLE RETURN ON SMART INVESTMENT In addition to a better overall understanding of the PI, DC Water has been able to quickly identify and address problematic areas and be notified in real-time of a potential H2S spike. By setting high-level alarms, DC Water is notified of a potential change in operation at the OCF. The real-time data has allowed the utility to better allocate resources (staff and vehicle travel costs). The real-time data recorded from the sensors showed odor complaints decreased to 0. Along with eliminating odor complaints, DC Water increased efficiency of its operation. The utility was able to reduce inspection and travel time for crews, and it reduced overtime and fuel costs by having increased awareness of the sewer system to pinpoint issues across the 50-mile-long Potomac Interceptor before they occur. Additionally, DC Water has been able to prolong the use of its infrastructure by decreasing corrosion. DC Water continues to demonstrate how technology is preserving money, staff time and assets. The utility has garnered a positive return on its investment.