Incinerated sewage sludge ash contains signifcant amounts of phosphorus. This research optimized the phosphorus extrac- tion process using ultrasonic and leaching processes and determined the most suitable process conditions by the Response Surface Methodology (RSM). This was done by evaluating the efect of diferent parameters such as the lemon juice (10 to 70% v/v), sewage sludge density (0.2 to 4% w/v), ultrasonic power (50 to 200 W), and time (0 to 120 min). Central Com- posite Design (CCD) defned a reduced cubic model with R2 and Adjusted R2 , 0.947 and 0.904, respectively. In the optimal conditions including sewage sludge density of 1.17% w/v, lemon juice of 55% v/v, ultrasonic power was 87 W, and 34 min the highest phosphorus extraction was received to 94%. In addition, these studies show that leaching process signifcantly contributes to detoxifcation, and reuse of sewage sludge.
