Abstract: To achieve nutrients recovery from source-separated urine, the study investigated the impact of key factors in a vacuum membrane distillation system on the concentration effect and energy consumption of alkalized urine. Real fresh urine, alkalized and diluted fivefold with calcium hydroxide, was used as the treatment object. The influence of feed temperature (40-70 ℃), condensation temperature (0-20 ℃), and feed pump speed (1 000-1 600 r/min) was investigated, and the significance of each factor was analyzed through multiple linear regression. The results showed that feed temperature was the core factor affecting membrane flux and energy consumption. When the temperature increased from 40 ℃ to 70 ℃, membrane flux increased from 0.82 L/(m2·h)to 3.02 L/(m2·h). When the feed temperature was 70 ℃, the water recovery efficiency reached 72.36%, the urine concentration index reached 3.62, and the specific energy consumption decreased by 29.3%. At a condensation temperature of 20 ℃, membrane flux, water recovery efficiency, and energy consumption efficiency were all superior to those at 0 ℃, with a specific energy consumption reduction of 13.0%. The feed pump speed had no significant impact on treatment efficiency and energy consumption, with membrane flux stabilizing at 1.99-2.06 L/(m2·h)and specific energy consumption maintaining at 1.429-1.442 kWh/L. The total energy consumption of the system mainly came from the heating of the feed, with a total salt rejection efficiency exceeding 98.5% and a total nitrogen recovery efficiency of over 80%. The multiple linear regression model exhibited good fit with the experimental results. This study indicates that vacuum membrane distillation is suitable for the concentration of alkalized urine, providing theoretical support for process optimization.

Key words: vacuum membrane distillation, source-separation, urine, alkaline dehydration, energy consumption