The influence of pH to the P-recovery from human urine via struvite formation

摘要

The urine from flushing toilet contains different nutrients, such as nitrogen, phosphorus, etc., and pathogens are few, so it has a very good value as fertilizer. This experiment uses struvite formation process to recycle phosphorus of urine and has studied the influence of the pH value to the effect of phosphorus recycling with emphasis. The test result indicated that the influence of different magnesium/phosphorus to the pH value of urine has little difference. The effect of the phosphorus recycling from urine via struvite is different under the condition of different urine initial pH value. When initial pH value of the urine climbs to 8 from 7, the phosphorus return-ratio increases quite big. When the urine's initial pH value elevates between 8 and 10, the phosphorus return-ratio has a tendency to increase, but is quite gentle. Along with the urine's initial pH value elevates continuously, and the phosphorus return-ratio has a downtrend. In addition, under different urine's initial pH value conditions, the ingredient of struvite precipitation is different. When the urine's initial pH value is 7, it nearly has no precipitation. When the urine's initial pH value changes in 8～10 scopes, the production precipitation is mainly the struvite crystal. When the urine's initial pH value elevates to 11 above, the production precipitation is mainly the amorphous state material. The pH value of urine will drop after it becomes struvite.