914
Electrochemical Stripping to Recover Nitrogen from Wastewater

Wednesday, 3 October 2018: 15:00
Universal 3 (Expo Center)
W. A. Tarpeh (Stanford University)
Electrochemical water treatment replaces chemical inputs with electricity, allowing for fine-tuning of unit processes through control of applied current and potential. These modular systems are flexible to varying degrees of centralization and robust to handle intermittent flows and shock loadings. Recovering nitrogen from separately collected urine can potentially reduce costs and energy of wastewater nitrogen removal and fertilizer production. Through benchtop experiments, we demonstrate the recovery of nitrogen from urine as ammonium sulfate using electrochemical stripping, a combination of electrodialysis and membrane stripping. Nitrogen was selectively recovered with 93% efficiency in batch experiments with real urine and required 30.6 MJ kg N–1 in continuous-flow experiments (slightly less than conventional ammonia stripping). The effects of solution chemistry on nitrogen flux, electrolytic reactions, and reactions with electro-generated oxidants were evaluated using synthetic urine solutions. Fates of urine-relevant trace organic contaminants, including electrochemical oxidation and reaction with electro-generated chlorine, were investigated with a suite of common pharmaceuticals. Trace organics (<0.1 mg L–1) and elements (<30 mg L–1) were not detected at appreciable levels in the ammonium sulfate fertilizer product. This novel approach holds promise for selective recovery of nitrogen from concentrated liquid waste streams such as source-separated urine, anaerobic digester effluent, and nitrogen-rich food waste.