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Urine diversion systems, which include waterless urinals and urine-diverting flush toilets, offer opportunities to conserve water, recover nutrients, promote circular economies, and improve sustainability. While technical development of these systems is critical, understanding stakeholder perceptions is equally important for their successful innovation, implementation, and adoption. This study conducts an exploratory analysis of stakeholder perceptions at U.S. academic institutions regarding how urine diversion technologies fit within the broader array of water conservation technologies and factors that influence decision-making related to urine diversion in buildings. We surveyed 65 stakeholders, including executive leaders, administrators, facilities managers, building managers, and sustainability professionals—key groups responsible for the adoption and maintenance of such systems but underrepresented in prior research. Participants reported a high level of awareness of water conservation technologies and varying degrees of implementation. Across all technologies, low-flush fixtures had the highest rate of implementation and waterless urinals had the highest rate of implementation and subsequent removal due to maintenance and infrastructure challenges. Participants also indicated that compliance with plumbing codes was the most critical factor when considering the implementation of urine diversion systems, followed by efficacy and cost-savings, and water conservation and nutrient recovery were among the least important factors. Future studies should focus on aligning urine diversion systems with building codes and regulations, mitigating clogging and odors to improve acceptance and adoption, and estimating costs and benefits when deciding on their implementation. 

Abstract Urine diversion (UD) is a system-of-systems that involves source separation of waste to maximize recovery of valuable nutrients, including phosphorus. Recent research shows how UD systems offer valuable ecological benefits and can aid in water conservation efforts, and public perception studies suggest that UD systems are generally viewed positively by end-users and the general public. Nevertheless, adoption and implementation of this promising sustainability solution remains limited in many countries, including the United States (U.S.). In this perspective, we argue that in order to scale up adoption in the U.S., UD researchers and innovators must do more to address regulatory barriers. We draw on insights from political science research on ‘regulatory regimes’ to introduce the array of regulations that apply to UD systems, with a focus on commercial and institutional buildings. We examine regulatory regimes all along the UD system-of-systems, beginning at the point of collection and ending at the point of beneficial reuse. We then propose next steps to address current regulatory challenges that impact adoption, with an emphasis on the importance of stakeholder coordination. Throughout, we argue that law and regulation plays a critical role in shaping adoption of UD technologies because: (1) different regulatory regimes will be important at different points in the system-of-systems, (2) there may be multiple regulatory regimes that apply to a single subsystem, and (3) it is important to consider that legal and regulatory definitions of a technology may not match scientific understanding. 

Phosphorus (P) is a finite resource and necessary nutrient for agriculture. Urine contains a higher concentration of P than domestic wastewater, which can be recovered by source separation and treatment (hereafter urine diversion). Commercial and institutional (CI) buildings are a logical location for urine diversion since restrooms account for a substantial fraction of water use and wastewater generation. This study estimated the potential for P recovery from human urine and water savings from reduced flushing in CI buildings, and proposed an approach to identify building types and community layouts that are amenable to implementing urine diversion. The results showed that urine diversion is most advantageous in CI buildings with either high daily occupancy counts or times, such as hospitals, schools, office buildings, and airports. Per occupant P recovery benchmarks were estimated to be between 0.04–0.68 g/cap·d. Per building P recovery rates were estimated to be between 0.002–5.1 kg/d, and per building water savings were estimated to be between 3 and 23 % by volume. Recovered P in the form of phosphate fertilizer and potable water savings could accrue profits and cost reductions that could offset the capital costs of new urine diversion systems within 5 y of operation. Finally, urine diversion systems can be implemented at different levels of decentralization based on community layout and organizational structure, which will require socioeconomic and policy acceptance for wider adoption. 

Research and practice suggest markers of drinking water quality such as trihalomethanes (THMs), can change during treatment and distribution, potentially elevating health risk of end users. Models have been developed to predict THM formation at drinking water treatment plants (DWTP), in drinking water distribution systems (DWDS), and to a lesser extent, building premise plumbing (PP). The goal of this research was to evaluate the performance of published THM models and their development methodology, with the purpose of improving future THM model development. Water quality variable data were collected from literature and used as inputs for collected models. Mean and variance of model prediction values were used to measure THM model performance compared to THM data trends from literature. The research found differences in model formulation, water quality variable selection, and model development practices, despite evaluated models being statistical in nature. These differences lead to substantial inconsistencies in model output behavior. Diversity of data used for model development was found to be the most important factor for generalizable model prediction capabilities. Following these findings, a new framework was proposed to encourage novel strategies, data sharing, and collaboration among researchers and practitioners to improve THM model development, application, and performance. Potential use of machine learning techniques for future model development was also discussed based on findings. 

Abstract Human urine is a readily available nutrient source that can complement commercial fertilizer production, which relies on finite mineral resources and global supply chains. This study evaluated the effectiveness of a simplified solar distillation process for urine to recover phosphorus (P) and nitrogen for agricultural use and water for non-potable purposes. Synthetic fresh, synthetic hydrolyzed, real fresh, and real hydrolyzed urine were exposed to direct sunlight for 6 h in a simple distillation apparatus, which produced distillation bottoms and distillate. Metal phosphate precipitation in the distillation bottoms was evaluated to recover P. The non-potable water was recovered as distillate. Hydrolyzed urine recovered more metal phosphate solid in the distillation bottoms and had a higher conductivity in the distillate than fresh urine. Hydrolyzed urine also achieved greater distillate volume recovery than fresh urine. Hydrolyzed urine had a greater presence of UV-absorbing organics in the distillate than fresh urine and therefore produced a lower-quality product water. There was no significant correlation between the daily high air temperature and the volume of distillate recovered. This study provides a comprehensive data set on simplified solar distillation of human urine considering the fate of nutrients and water for different types of urine.