STATEMENT OF ISSUES

Over 292 million tons of municipal solid waste are generated in the U.S., with approximately 1/3 utilized for recycling and composting (both of which include land application; US EPA, 2023). According to the US EPA (2018), approximately 48% of these materials are either composted, combusted for energy recovery or recycled, respectively, while the remaining 52% are landfilled. Specifically in terms of material disposal, ~50% of biosolids, 98% of food scraps and 45% of yard trimmings are currently landfilled or incinerated at a substantial cost to the industry and public (King et al., 2011). Thus, increasing reuse of various residual materials such as valuable soil amendments offers the potential to replace disposal costs with beneficial agronomic and environmental uses. It is predicted that 52% of the world’s population will live in regions under water stress by 2050 (Schlosser et al., 2014), resulting in high demand for wastewater recycling and reuse for agricultural production. In addition, treated liquid wastes, such as wastewater effluent, recycled water and other non-potable waters, present opportunities for beneficial reuse in lieu of surface water discharge or expensive treatment. However, there are consistently numerous obstacles that prevent the full beneficial utilization of the above materials.

Obstacles that limit the beneficial use of residual products include conflicting regulations or the absence of regulations on residuals use, lack of public outreach and communication, and limited research on optimizing residuals-based product development. Fortunately, current and increasing evidence exits exemplifying that land application of a variety of residuals do provide agronomic and environmental benefits, which were either not previously well understood or are critical to addressing emerging environmental issues (e.g., system resiliency in the face of changing environmental factors highlighted in Brown et al., 2011a,b). The W4170 workgroup, who consists of some of the best minds and resources within and outside the State Agricultural Experiment Station System (e.g., US EPA, municipality personnel, private entities), proposes to continue to conduct research towards sustainable use of residual products. The W4170 proposes to continue investigating the biogeochemical cycling of plant nutrients, movement and potential adverse impacts of trace element and emerging contaminants within ecosystems and the food chain, their long-term bioavailability in residual-amended soils, and soil health effects from application of residuals. These investigations will generate knowledge needed to develop and promote residuals recycling practices that are protective of human health and the environment. Outcomes will provide data for continuing one-health based risk assessment required by the US EPA Part 503 Rule for biosolids land-application as well as for developing regulations for land-based recycling of residuals and reclaimed water. Research will also focus on reuse benefits including field and watershed scale effects on soil quality/health, plant drought response, soil carbon sequestration, water quality, greenhouse gas emissions and climate change impacts associated with soil-based residuals and reclaimed water reuse. We will also explore the potential for residual based product usage in urban and agriculture systems, and green stormwater infrastructures as well in restoration of degraded lands. W4170 members are currently conducting and synthesizing both short- and long-term research that will enable the development of guidelines for the sustainable use of a wide variety of residuals and residual by-products: maximizing benefits while minimizing the potential for unintended negative consequences.

JUSTIFICATION:

The beneficial use of residuals requires an understanding of both potential hazards and the value of constituents in the by-products. Investigation of the fate and behavior of contaminants and nutrients in biosolids-amended soils has been the historic research focus of the W4170 multistate workgroup. Research conducted previously by the workgroup formed the basis for the U.S. EPA Part 503 biosolids rule, which is one of the few rules to include bioavailability assessments in the development of limits for critical contaminants (National Research Council, 2009). Two subsequent NAS reviews, focused on the 503 rule, confirmed that the scientific basis for this rule and risk assessment were valid. Members of the W4170 group have contributed research and technical expertise that has led to guidance that permit beneficial reuse of many industrial and municipal byproduct for land application or as feedstocks in manufactured soil blends, including spent foundry sands (U.S. EPA, 2014), water treatment waste residuals, and many other residuals. Research conducted by W4170 members included evaluating the occurrence of per- and polyfluoroalkyl substances (PFAS), a large family of chemicals of high concern in biosolids including comparing with non-biosolids-based compost (Lazcano-Kim et al., 2020; Schaefer et al, 2022; Bolan et al., 2021) as well as the effect of treatment on PFAS presence in biosolids (Lazcano-Kim et al., 2019; Li and Koosaletse-Mswela, 2023). PFAS analysis in municipal solid waste composts from across the country (Choi et al., 2019) contributed to the successful passage in 2018 of the State of Washington’s Healthy Food Packaging Act which bans the use of the entire class of PFAS in paper food packaging after January 1, 2022 assuming suitable alternatives are identified (HB2658-2017-18). This type of law will help prevent the use of products from other countries where PFAS-related bans may not exist and will prevent unwanted contaminants in our food, reduce their input into wastewater treatment plants, thus biosolids, and will minimize their entry into compostable materials where their presence has been pervasive. Research by members included PFAS presence and release from drinking water treatment residuals and their subsequent potential to be applied with biosolids to reduce PFAS leaching and crop uptake (Graveson et al., 2023; Broadbent et al, 2023). Additional work included synthesizing data on plant uptake of PFAS and uptake mechanisms, which guided current research underway (Costello et al., 2023; Wang et al., 2020). More recently, W4170 members also performed laboratory and field studies to quantify the occurrence, persistence, fate and plant uptake of PFAS. Studies to date highlight the importance and magnitude of perfluoroalkyl acid (PFAA) precursors such as the polyfluoroalkyl phosphate esters (diPAPs) present in biosolids when land-applied serve as a long-term source of more mobile PFAA after land-applied. Also, field data consistently show low to negligible precursors in the soil profile within one year after biosolids have been applied, an accumulation of the longer-chain PFAS in the upper 1-2 feet of soil, although some are leached, and migration of shorter-chain PFAS through the soil profile (manuscripts in preparation). Data gaps include what level of PFAS in soils will lead to levels below concern in plants and mitigate strategies from crop selection and management to sorbent additions, particularly in heavily PFAS-contaminated agricultural fields. 

Recently, the U.S. EPA Office of Inspector General released their report “EPA unable to assess the impact of hundreds of unregulated pollutants in land-applied biosolids on human health and the environment” (U.S. EPA, 2018). The U.S. EPA “identified 352 pollutants in biosolids but cannot yet consider these pollutants for further regulation due to either a lack of data or risk assessment tools. Pollutants found in biosolids can include pharmaceuticals, steroids, and flame retardants.” The W4170 committee is “the” USDA NIFA Multistate Committee that can continue to provide data and technical expertise to U.S. EPA for addressing the regulatory needs they identified in the U.S. EPA OIG report. U.S. EPA Office of Water and Office of Research and Development personnel continue to be active members of W4170. Our university members are recognized internationally as leaders in research on the environmental fate of emerging contaminants, e.g, pharmaceuticals, steroids, chemicals from personal care products, flame retardants, microplastics, and PFAS, that can enter the environment with land-applied biosolids. In 2020, the W4170 group wrote a comprehensive review to respond to the request of biosolids stakeholders for W4170 to provide a scientific review of the OIG Report. The review (available at: https://www.nimss.org/system/ProjectAttachment/files/000/000/502/original/W4170%20Response%20to%20OIG%20Report%20July%2023%202020%20final.pdf) addressed chemical, antibiotic, and pathogen issues raised in the OIG report. The W4170 team concluded that OIG report was flawed and that the science of beneficial use of biosolids was lacking. Addressing U.S.EPA OIG data and research gaps will be a priority in the proposed W4170 renewed project.

Human and ecological risk assessment (HERA) science continues to mature with biogeochemical availability-based risk assessment frameworks being developed and/or considered for implementation in the U.S., Canada, the European Union, Australia and other countries. Continued research is needed to provide the scientific basis for risk-based methods and to evaluate residuals and residual-treated soils for adoption by HERA frameworks. Research needed to evaluate contaminants in residuals includes the following: (i) trace element speciation by advanced spectroscopic methods and wet chemical speciation methods; (ii) chemical lability and plant uptake potential of frequently detected trace elements and emerging contaminants in residuals-amended soils in the field; (iii) use of bioavailability to adjust human and ecological exposure in risk assessment frameworks by using inexpensive novel bioaccessibility methods and in vivo methods; and (iv) total combined effects of residuals on soil physical, chemical, nutrient and biological components in order to ascertain alterations in soil quality/health following residuals land application.

Several members of the W4170 were extensively involved in the development of the Part 503 regulation and continue to be involved in the development of risk assessment for other residuals (e.g., the EPA risk assessment for land application of cement kiln dust and foundry sand) and for other pollutants not initially regulated or considered in Part 503 (e.g., barium, PFAS, microplastics, and other emerging contaminants). The scientific approach used in the development of Part 503 has been applied by this group to an expanded variety of residuals, contaminants and receptors. As the understanding of bioavailability is expanding, the group is broadening its focus to develop linkages between quantitative understanding of the contaminant forms and their bioavailability to a range of receptors.

In the past, our group has conducted cooperative projects involving laboratory incubation, greenhouse studies and X-ray absorption spectroscopy to elucidate the role of organic and inorganic components of biosolids and other residuals in binding metals (Brown et al., 2003a; Hettiarachchi et al., 2003a, b, 2006; Ippolito et al., 2009, 2013; Obrycki et al., 2016; Ryan et al., 2003, 2004a; Scheckel et al., 2004). We have demonstrated that biosolids and other soil amendments can reduce the bioavailability of metals in contaminated systems (e.g., Attanayake et al., 2014; 2015; 2017; Barbarick et al., 2015, 2016, 2017; Basta et al., 2001; Brown et al 2003b, 2007; DeVolder et al., 2003; Hettiarachchi and Pierzynski, 2002; Ippolito et al., 2010, 2014; Meiman et al., 2012), while developing various extractants to assess bioavailability of mineral and bioavailable fractions of inorganic contaminants (e.g., Basta and Juhasz, 2014; Basta et al., 2003; Brown et al., 2004; Rodriguez et al., 2003; Ryan et al., 2004; Schroder et al., 2003; Whitacre et al., 2017).

Our W4170 group members have conducted research on occurrence, sorption, transformation, plant uptake, and remediation of PFAS and pharmaceuticals in the environment (Chen et al., 2010; Choi et al., 2023; Ding et al., 2011; Dodgen et al., 2015; Fu et al., 2019; Fu et al., 2016; Gravesen et al., 2023; Kim et al., 2022; Lazcano et al., 2020; Lazcano et al., 2019; Li et al., 2022a; Li et al., 2022b; Song et al., 2010; Wang et al., 2009; Wang et al., 2021; Wang et al., 2022; Wu et al., 2014; Wu et al., 2013).  The trace-levels of antibiotics (e.g. tetracyclines) could exert selective pressure on E. coli to express antibiotic resistant genes, and the magnitude of selective pressure is determined not only by the concentration but also by the surrounding environmental chemistry and speciation tetracycline in environmental matrices (Chen et al., 2015; Zhang et al., 2014a, b). Soil-sorbed tetracyclines are still bioavailable to bacteria to evoke the expression of antibiotic resistance as long as the bacteria are closely attached to soil surfaces (Chen et al., 2017; Zhang et al., 2018). Smaller-sized pharmaceuticals demonstrate a higher translocation potential to plant leaves (Chuang et al., 2019). Pharmaceuticals in soil pore water are the major fraction in soils bioavailable to plants for uptake (Li et al., 2020; Li et al., 2019; Li et al., 2022c).

              Our group’s research has broadened to encompass a range of measurement endpoints as we realize and understand the potential for metals to affect a range of receptors. The goal of this research is to evaluate functions of restored ecosystems utilizing tools such as in vivo and in vitro assays, toxicity assays and measures of microbial community dynamics (Alasmary et al., 2020; 2021; Alexander et al., 2003; Basta and Juhasz, 2014; Bastaand Wragg, 2013; Brown et al., 2004; Hettiarachchi et al., 2003a; Schroder et al., 2003; Sullivan et al., 2005). As a result of cooperative research conducted by members of W4170, in situ remediation options, including biosolids and other residuals, have been utilized at several EPA Superfund NPL (National Priority List) sites, contaminated urban soils, mine lands, forest fire burned areas and overgrazed and degraded ecosystem sites. The tools developed for this research have broadened our understanding on the functioning of soils amended with biosolids or residuals.

The sustainability of biosolids application to agricultural lands has also been demonstrated by evaluating the effects of biosolids application on various aspects of soil functionality, recently termed “soil health.” While the implications of this research are being recognized in agroecosystems and remediation of contaminated sites, such research is also needed for rehabilitation of urban landscapes. Among the greatly expanding potential markets for exceptional quality (EQ) biosolids are used for urban agriculture, turfgrass and other vegetated urban landscapes on anthropogenic soils.

Among the challenges in urban agriculture and other anthropogenic soil landscapes are their commonly degraded nature and potential presence of contaminants in such soils. In contrast to natural soils, human activities strongly influence urban soils through the removal of topsoil, physical disturbances, heavy vehicle traffic and addition of foreign materials (e.g., asphalt, bricks, glass, plastic, etc.), which ultimately result in a highly impaired soil (Craul, 1985; Gregory et al., 2006; Beniston and Lal, 2012; Chaganti and Crohn, 2014). These disturbed soils are characterized by soil compaction, increased bulk density, reduced water infiltration rates and aeration, low water holding capacity, low organic matter content and low fertility, which ultimately limit crop growth and yields and create major constraints for productive urban agriculture (Gregory et al., 2006; Beniston and Lal, 2012; De Sousa et al., 2023).

EQ biosolids can provide organic matter and nutrients necessary to improve anthropogenic soils and promote vegetative establishment and growth. EQ biosolids are by-products of wastewater treatment generated by Processes to Further Reduce Pathogens (PFRPs) and possess low vector attraction and pollutant concentrations. Such products are suitable amendments for landscapes having high public access. Research needs for these newly developed products include quantifying N and P availability and C sequestration potential in anthropogenic soils. Initial work on these questions has been performed (Alvarez-Campos et al., 2018; Alvarez-Campos and Evanylo, 2019a; Brown et al., 2016c), but additional research is needed to ensure appropriate EQ biosolids management for urban landscapes. Biosolids blended with compost and/or other residuals have been shown useful in reducing exposure to Pb contaminated soil, improve soil health and protect public health (Obrycki et al., 2017b). The multistate research group will continue research to improve our understanding of this in field studies, focusing on changes in soil attributes that may have implications for altering soil quality/health (e.g., soil physical, chemical, nutrient, and biological characteristics).

In particular, some of the greatest challenges for expanding the beneficial use of treated wastewater effluent and residuals (such as biosolids) are concerns associated with PFAS compounds. Based on their extensive use in a myriad of products, their existence in the environment is ubiquitous. Land application of biosolids has been shown to disseminate PFAS in soils and subsequently be assimilated by crops and leached to groundwater (Bizkarguenaga et al., 2016; Blaine et al., 2014a, b; Lee et al., 2014; Lindstrom et al., 2011; Sepulvado, et al., 2011; Navarro et al., 2017; Wang et al., 2020). Biological degradation processes that often time reduce trace organic chemicals loads in wastewater treatment and in land-applied biosolids do not alleviate PFAS load since any microbially degradation that occurs leads to persistent perfluoroalkyl acids (PFAAs) (Liu et al., 2017). Even small contributions of PFAAs to water sources can be problematic from a management standpoint given the very low thresholds (at ppt levels) being proposed (4 ppt, USEPA) or already being implemented as screening levels or actual health advisory levels by some states (e.g., 14 ppt in NY).  On March 22, 2019, Maine’s Department of Environmental Protection (DEP) released a memorandum requiring sludge/biosolids program licensees and sludge/biosolids composting facilities to test their materials for PFAS. Any material exceeding the screening standards set for three PFAAs (2.5 mg/kg PFOA, 5.2 mg/kg PFOS or 1,900 mg/kg PFBS) may not be land-applied until DEP approves otherwise.

Another area of concern for the W4170 workgroup is irrigation with water resource recovered from and/or reuse of wastewaters. This particularly holds true due to the fact that fresh water sources for irrigation are limited, and impending water shortages are motivating the intentional reuse of degraded waters (Blaine et al., 2014b). While the application of treated or partially treated wastewater effluents to cropped and forested lands has long been practiced, other sources of degraded water (stormwater, irrigation return flow, gray water, and CAFO effluents) are available to meet anticipated shortfalls. In conjunction with degraded water use, soil application of residual products may, in fact, have positive effects on drought-stressed crops. Several researchers have noted improvements in crop performance with the biosolids land application (e.g., Cogger et al., 2013; Heckman et al., 1987; Lu et al., 2020), with speculation geared towards improvements in soil water relations (Brown et al., 2011a,b). Since many of the major reuse opportunities involve water applications to soil systems (e.g., irrigation), with or without residuals application, addressing the benefits, risks, and sustainability of degraded water reuse logically fits within the scope of the proposed research project. As resource limitations spur development of reuse technologies and renewable commodities, wastewater should be viewed as a renewable resource that contains valuable raw materials. Indeed, many resource-stressed communities have begun to adopt resource recovery systems (RRS), particularly for water. Adoption of resource recovery from, and reuse of, wastewater depends on technological innovations that increase technology efficiencies and lower capital and operational costs. Members of our team are working with academics and professional engineers on valorization of carbon, nutrients (N&P), and water from agricultural, municipal, and industrial wastewaters and their beneficial reuse potential in agricultural systems (Heronemus et al., 2021; Awasthi et al., 2023; Kannan et al., 2023).

In summary, there is a continued need for research on contaminant mobility and bioavailability in both residual-amended soils and in contaminated soils restored with residuals. New ecological endpoints must be investigated to improve risk assessment to ensure human health and environmental safety. Research is also needed to maximize yields via the use of residuals and reclaimed wastewater. Both offer potential alternatives to current, sometimes environmentally detrimental, agricultural and land restoration practices. The experience and expertise of W4170 in addressing these issues are widely recognized and W4170 is well positioned for continued success. The W4170 membership offers the advantage of including institutions and entities (universities, USDA-ARS, US EPA, municipal government utilities) from across the entire US. Such collaboration enables discoveries to account for widespread differences in climate, soils and residual types and sources, whose fate, transport and impact will vary due to across these factors.