Recovery of Urea from Human Urine Using Nanofiltration and Reverse Osmosis

Urea is a high-production chemical with critical uses in agriculture, transportation, and air pollution control. Urine is a waste product that could supplement synthetic urea production. This study utilized reverse osmosis and nanofiltration (NF) separation to selectively recover urea from fresh human urine. Urea permeation experiments were conducted to determine the effects of urea stabilization via pH adjustment and membrane type on urea permeation and ion rejection. Fouling mitigation experiments were conducted to determine the efficacy of microfiltration pretreatment on reducing membrane fouling. Results showed that NF90 produced a purer urea product than did BW30, permeating 76% of the urea while rejecting 68% of the conductivity. NF270 permeated >95% of urea while rejecting up to 82% of the phosphorus, allowing for the separation of nitrogen and phosphorus in liquid streams. Urea stabilization did not reduce urea permeation or conductivity rejection, signifying the use of pH 5 as a suitable condition due to its ease of application. Microfiltration pretreatment of urine reduced foulant thickness and permeate flux loss.