Nonwater urinals are critical in urine diversion and nutrient recovery systems because of their ability to collect undiluted urine. However, because of their propensity to clog, nonwater urinals have garnered a negative reputation that could put future implementation of building-scale urine diversion systems at jeopardy. The goal of this project was to create a nonwater urinal testbed to test a chemical addition technique that has proven to decrease precipitation-induced clogging of nonwater urinals. Specifically, (1) a cyber-physical system (CPS) with sensors and actuators was created to monitor urine chemistry in real-time, (2) three actuator–controlled experiments were conducted to compare (i) chemical addition after every urination, (ii) a rule-based chemical addition technique, and (iii) an artificial neural network, predictive model chemical addition technique, and (3) NH4+, PO4, Ca2+, and Mg2+ concentrations were tracked throughout the collection system to monitor urea hydrolysis and calculate nutrient losses within the urinal testbed. Research has shown that acetic acid addition at the urinal decreases urine pH, creating unfavorable conditions for the urea hydrolysis. The CPS monitored pH and conductivity data in real-time that was measured in three locations for each urinal, from the urinal through the drain line to the storage tanks. Using that data, the CPS controlled the pumps that delivered urine and acetic acid to the urinals. Data were transferred and stored in the cloud for data analysis. The first experiment showed that a constant volume of acid addition was able to inhibit urea hydrolysis, i.e. keeping nitrogen in the urea form, and decreases losses of phosphorus within the system, even when urination volume and frequency was randomized. The second and third experiments showed that a rule-based actuator control acted as a reactive control, while the predictive model actuator control was a proactive control on precipitation. The rule-based and predictive model experiments reduced the use of acetic acid, making it a more economical and sustainable option for building operators. These techniques of employing a CPS can be used in real world systems as a way of stabilizing urea in preparation for nutrient recovery technologies. This presentation will detail the benefits of real-time monitoring of nonwater urinal system using a CPS guided by urine chemistry, and discuss implications of the work to subsequent nutrient recovery operations.

“Smart” nonwater urinals for urea stabilization, phosphorus recovery, and water conservation

256th National Meeting (2018)

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