The invention is a process which involves immersing the sludge in a liquid medium, such as water, and then adding acid to lower the pH (the measure of the acidity of a solution) to a range from 0 to 3.5. The acid causes the solid rubber to clump together, which can then be easily collected and separated from the liquid medium. The recovered rubber is washed and dried, after which it is suitable for sale. The remaining liquid is then adjusted to a pH level between 6 and 14, which causes the inorganic substances to precipitate out. One of these substances is magnesium ammonium phosphate, which is extremely valuable as a fertilizer as well as for use in ceramics manufacturing.