BOSTON – An innovative sensor technology to provide real-time information on the amount of nitrogen in wastewater has been developed as part of a U.S. Environmental Protection Agency (EPA) research challenge. The sensor has completed rigorous field testing on Cape Cod. The new technology shows strong potential for use in coastal areas where excess nutrients from septic systems adversely affect water quality in nearby surface and groundwater.
The nitrogen sensor designed for use in advanced treatment septic systems was developed by Dr. Qingzhi Zhu at the School of Marine and Atmospheric Sciences, New York State Center for Clean Water Technology at Stony Brook University in Stony Brook, N.Y. This project won EPA's "Advanced Septic System Nitrogen Sensor Challenge" in 2020 after an international competition to advance the development of low-cost sensors to measure nitrogen levels discharged from advanced septic systems.
The sensor has now completed extensive independent third-party testing performed at the Massachusetts Alternative Septic System Test Center in Sandwich, Mass. The prototype sensor was exposed to wastewater effluent from standard, as well as advanced, nitrogen-reducing septic systems for six months. The sensor was tested with effluent receiving various levels of treatment, a simulated septic system failure, and a septic system during a simulated power outage. The testing successfully verified the long-term performance of the new technology in the field and promises to aid efforts to address significant estuarine water quality and ecological problems caused by excess nitrogen.
"The ability to measure nitrogen concentrations in the effluent exiting advanced septic systems will provide real-time data on the performance of these systems and help safeguard water quality in coastal communities," said EPA New England Acting Regional Administrator Deb Szaro. "I applaud the determination and creativity shown by Dr. Zhu and his team, and by EPA scientists in pursing the goal over many years to develop technology for these measurements. EPA is hopeful that this new technology will increase the viability and use of innovative/ alternative septic systems, which are an integral part of our region's future wastewater treatment infrastructure as we move to address the ecological issues caused by high levels of nitrogen."
The groundbreaking sensor is designed to be used in innovative/alternative nitrogen-reducing septic systems (I/A systems). The Stony Brook University team and the New York State Center for Clean Water Technology believe that the commercial adoption of the sensor can help increase consumer and regulator confidence in the performance of I/A systems, leading to more widespread use by homeowners, municipalities and other organizations seeking to reduce nitrogen pollution and restore coastal water quality.
Conventional septic systems are not designed to remove nitrogen from wastewater. Nitrogen from conventional residential septic systems, along with excess nitrogen from lawn fertilizer and other sources, enters groundwater and eventually surface water where it can cause harmful algal blooms, low dissolved oxygen, and fish and shellfish kills. In contrast, I/A systems are specifically engineered to turn the nitrogen in wastewater into harmless nitrogen gas. The nitrogen removal performance of these systems has traditionally been determined by sampling and lab analysis, which are costly and labor intensive. With the new sensor technology, nitrogen concentrations in the effluent leaving an I/A system are measured directly and transmitted electronically to remote locations in near-real time. Stony Brook University has already begun to deploy prototype sensor units in I/A systems that are being installed on Cape Cod and Long Island, with plans to deploy more in the future.
Development and initial testing of the Stony Brook I/A system nitrogen sensor occurred as part of the EPA's Advanced Septic System Nitrogen Sensor Challenge initiated in January 2017 and concluded in November 2019. Completion of the performance verification is the culmination of over five years of EPA national and regional support to develop and implement an EPA Test and Quality Assurance Plan (T/QAP) (pdf) and protocol consistent with the International Standardization Organization (ISO) 14034 ETV standard. The verification statement (pdf) for the sensor's rigorous field testing is available.
Funding and support came from EPA's Office of Research and Development (ORD), Office of Water (OW), Office of Wastewater Management (OWM), Regions 1 and 2, and the Southeast New England Program (SNEP).