For decades, municipal wastewater treatment operations focused solely on cleaning the incoming wastewater so that it could be discharged and later reused without posing a risk to human health or the environment. During the treatment process, not much attention was paid to the extraction and recovery of other valuable resources contained in the waste stream, such as energy and nutrients. This dismissal was in line with broader societal attitudes of distaste for anything having to do with wastewater. As a Wisconsin court put it, even the post-treatment cleaned water prompted “revulsion.”[1]

Today, it has become increasingly clear that wastewater is part of a broad nexus of resource inputs and outputs including water, energy, food, and carbon. The failure to harvest the secondary resources from wastewater has been a missed opportunity, because those resources can play a critical role in efforts to develop a sustainable circular economy and reduce waste generation. That realization has prompted some municipalities to pursue projects aimed at more complete utilization of the resources in the wastewater.

In two recent grant-funded projects,[2] the Law School’s Water Law and Policy Initiative examined pathways to overcoming legal and regulatory barriers to these efforts.

Energy

The wastewater treatment process involves significant energy consumption, but today’s water resource recovery facilities (WRRFs) could become net energy generators by extracting energy from the wastewater they clean. Energy costs account for a quarter or more of a typical WRRF’s operating budget. The total annual energy usage for water and wastewater treatment in the United States is approximately 56 billion kilowatt-hours, costing about $4 billion each year, according to the United States Environmental Protection Agency. In some places, the electrical grid is under significant strain, and heavy energy demand for wastewater treatment could further degrade its functionality.

While estimates vary as to the amount of energy contained in wastewater, there is general agreement that it is significant. By some estimates, assuming complete capture and efficiency, a large WRRF could theoretically power thousands of residential customers with electricity produced from anaerobic digestion; however, this “back of the envelope” calculation neglects losses during the energy production and transmission processes, which can be substantial.

When it comes to harnessing this energy, true success stories are still somewhat rare, in part due to an array of barriers. These include financial barriers such as capital and operational costs, regulatory barriers such as uneven implementation of the Public Utility Regulatory Policies Act, a federal law designed to expand opportunities for renewable energy generation by small power producers like WRRFs, market entry barriers, and state-specific issues such as designation (and regulation) as a public utility. Removing these barriers and extracting this untapped source of energy could be a “game changer.” As described in more detail in a forthcoming publication in the LSU Journal of Energy Law and Resources, policymakers should consider streamlining regulatory policies and energy markets to incentivize those developments.

Nutrients

As compared to energy generation, it has been more common for WRRFs to recycle or even sell the solid component generated by the wastewater treatment process, known as “biosolids,” because biosolids are valuable fertilizer due to the nutrients they contain. But a different problem has arisen in this context.

WRRFs and the municipalities that operate them have struggled to quantify and manage the potential for legal liability resulting from emerging contaminants such as per- and polyfluoroalkyl substances (PFAS) that pass through treatment facilities but are not removed by standard treatment practices. PFAS are hazardous to human health, persistent in the environment, and difficult to remove from wastewater, making for an intractable problem, especially when intertwined with potentially valuable byproducts of the wastewater treatment process such as biosolids.

Our interdisciplinary research effort examined the potential liability concerns associated with PFAS residue in biosolids and then identified preliminary strategies for utilities to control the sources of PFAS discharges to wastewater collection systems. The concerns include responsibility for environmental remediation costs under federal and state laws, toxic tort lawsuits brought by plaintiffs alleging injury caused when they came into contact with PFAS contained in biosolids applied to the land, and enforcement actions resulting from noncompliance with state or federal laws and regulations governing biosolids.

Prohibiting the application of biosolids to the land due to trace PFAS contamination may transfer the risk to groundwater (if the biosolids are impounded in a landfill), strain the assimilative capacity of the environment, and impose financial burdens on municipalities and other operators of public wastewater treatment systems. The only solutions are development of affordable and effective PFAS removal techniques, or source control to keep PFAS out of the waste stream. Wastewater utilities should be very diligent about understanding the sources of wastewater to their operations, the potential risks to human health and the environment, and the legal risks involved. The resulting paper will appear in the Natural Resources Journal published by the University of New Mexico School of Law.

I presented these research results at a recent Law School event held in conjunction with Chicago Water Week presented by Current. A recording of that program is available here.

[1] Stearns v. State Committee on Water Pollution, 274 Wis. 101, 109-10 (1956).

[2] Both projects were funded by the National Science Foundation I/UCRC for Water Equipment and Policy.