Human urine contributes 50-90% phosphorus (P), nitrogen (N), and potassium (K) to municipal wastewater yet accounts for approximately 1% of total volumetric flow. Thus source separation and treatment of urine has been proposed to create high concentrations of nutrients in a small volume for effective recovery and reuse. The goal was to treat urine through an integrated system of physicochemical processes--struvite precipitation for P recovery, air stripping for N recovery, and evaporation for K recovery--and document the quality and quantity of nutrients recovered—in liquid and solid form-- as useable fertilizer. Struvite precipitation experiments were stimulated using Imhoff cones, jar tester, and three Mg sources—MgCl2, MgO, and MgCO3. In theory, the effluent remaining after struvite precipitation would contain low to no P, but high concentrations of N and K. For ammonia air stripping/absorption, the percentage of dissolved gas was dependent on temperature and pH. Four conditions—(1) high pH/room temp, (2) high pH/high temp, (3) no pH change/high temp, and (4) no pH change/room temp—were carried out for each sample with constant airflow. Ammonia gas was then absorbed by sulfuric acid, resulting in a concentrated nitrogen fertilizer, (NH4)2SO4. The remaining effluent was evaporated via the sun and evaluated as a potassium fertilizer. For struvite precipitation, MgCl2 recovered approximately 95% of P as struvite while MgO and MgCO3 recovered 60-70%. Increasing the pH and temperature of air stripping/absorption recovered 90% of ammonia as ammonium sulfate while the other conditions recovered 70-75%. Evaporation resulted in a KCl and NaCl2 dominated product. This research has the potential to decrease the energy and materials required for nutrient removal at wastewater facilities, decrease nutrient discharge to receiving waters and provide a sustainable source for fertilizer production.

Solution to pollution is not dilution: An integrated system for total nutrient recovery from source separated urine

253rd National Meeting (2017)

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