Recovery nitrogen and phosphorus from source-separated urine by polytetrafluoroethylene-polypropylene membrane distillation

Urine consists of approximately 95 % water, 3.5 % organic matter, and 1.5 % inorganic salts. Membrane distillation (MD) offers a potential approach for urine resource utilization. To some extent, it reduces the loss of nitrogen and phosphorus resources. However, MD is also accompanied by problems such as high membrane cost, membrane fouling and membrane wetting. In light of these issues, this study employs polytetrafluoroethylene (PTFE) as the separation layer and polypropylene (PP) as the support layer to make a distillation membrane. The feasibility and efficiency of the PTFE-PP membrane in intercepting and recovering nitrogen and phosphorus from source-separated urine were investigated. Results obtained through 14 days of continuous operation demonstrated that the recovery rates of nitrogen and phosphorus were 95 % and 99 %, respectively. The dissolved organic carbon recovery rate was 95 %, and urea as well as the macromolecular organic matter in dissolved organic matter were significantly intercepted. The phosphorus content in the permeate was 0.022 mg/L, which met the Ⅱ class standard of China's surface water and the basic water use standard of the United States Environmental Protection Agency. This finding reduces the pressure on sewage treatment plants. PTFE-PP distillation membrane has important potential in recovering nitrogen and phosphorus from urine and alleviating global water shortage.