NSF-BSF: Collaborative Research: Solids and reactive transport processes in sewer systems of the future: modeling and experimental investigation

In the United States, there are approximately 16,000 sanitary sewer systems serving more than 190 million people through over 740,000 miles of public sewers. Sanitary sewers are underground pipes designed to deliver sewage water from residential, commercial, and industrial buildings to the city sewage treatment plants. This wastewater contains solid waste such as human excreta, soiled water from sinks, showers, and toilets, and other waste.

Sanitary sewers are critical to the communities that they serve for managing and disposing of wastewater in a safe manner. Two major problems affecting these sanitary sewer systems are blockages and the formation of hydrogen sulfide, a highly toxic and corrosive gas. Sewer blockages can result in overflow of untreated contaminated wastewater into individual properties, local communities, and the environment.

Sewer blockages can also lead to bad smells and the release of harmful gases, such as hydrogen sulfide, which is dangerous to human health. The goal of this NSF-BSF project is to investigate the characteristics of the solid waste that enters sewers, the factors that affect how it moves and accumulates, and the formation of hydrogen sulfide and other harmful substances in sewer systems.

To advance this goal, the Principal Investigators (PIs) will use a combination of laboratory and field experiments, as well as computer modeling, to predict how solid waste and harmful substances travel in sewers. The PIs also propose to develop software tools to help track and model these processes, considering different sources of uncertainty. The successful completion of this project will benefit society through the generation of new data and models to improve the fundamental understanding of how solids move in sewers and identify vulnerabilities and potential problems that may arise from future changes in wastewater characteristics.

Additional benefits to society will be achieved through student education and training including the mentoring of one undergraduate and one graduate student at the university of Texas, Austin and one graduate student at the University of Illinois at Chicago.

Sewer blockages and the formation of hydrogen sulfide, a highly toxic and corrosive gas, are two critical issues that compromise the integrity of sanitary sewers and have severe economic, environmental, and public health impacts. The increased adoption of sustainable water technologies is forecasted to significantly alter the quantity and quality of the wastewater discharged into sewer systems, leading to unintended negative implications.

Water demand reductions are expected to increase the deposition of solids and alter the solid-liquid biochemical processes within the sewer system, exacerbating sewer blockages and hydrogen sulfide formation. The overarching goal of this NSF-BSF project is to investigate the dynamic characteristics of domestic solids discharged to sewers, the factors that affect the transport, deposition, and accumulation of these solids, and the formation and transformation of hydrogen sulfide and other key biochemical species in sewer systems.

The specific objectives of the research are to 1) conduct lab and field experiments to characterize the physical aspects of gross solids transport, deposition, and transformation in sewers; 2) develop open-source software tools to model solid-liquid biochemical interactions, enable tracking the fate and transport of key biochemical species in sewer systems, and quantify and propagate different sources of uncertainty; and 3) create a computational framework for identifying potential breakpoints due to future changes in the characteristics of wastewater discharges under various decentralized water technologies, population shifts, and changes in infiltration/inflow patterns due to climate change. The successful completion of this project will bridge the fundamental knowledge gaps in solids transport and solid-liquid biochemical processes in sewer systems and will enable identifying vulnerabilities under future uncertain long- and short-term shifts in wastewater characteristics.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.