| 초록 |
Phosphorus (P) is an essential fertilizer for the production of agricultural crop. Wastewater sludge is a significant sink for P and the sludge ash has high content of P (about 10%). Wet chemical elution of P from sludge ash using acid or alkali is the most commonly used method for P recovery. In this study, we used acidic pre-treatment and alkali leaching to recover P and Al which can be reused as a precipitant in wastewater treatment plants. The effects of liquid/solid ratio, doses of acid and alkali, and Ca/P ratio for P precipitation were investigated to find the optimal condition of P recovery and minimization of heavy metal contents in the recovered solids. Hydrochloric acid and sulfuric acid were compared for the pre-treatment. P contents in the leachate increased when the pH is less than 3 at the L/S ratio of 10. The P seems to be released from Ca-P when the pH was higher than 3, and Al-P is the main source of P release when the pH is less than 3. Other metal components in the leachates were also measured to investigate the dissolution dynamics of P and Al from the ash. |
