Fig. 7. Typical X-ray spectra (energy-dispersive X-ray elemental spectrometry, EDXS) of particles of alum-stabilized sludge (Al to P ratio = 1.04). The element content is given in g kg^–1 as calculated by the ZAF method: (A) P = 91.4, Ca = 125.7, Al = 17.1, and S = 24.1 for the Ca-P particle; (B) P = 8.2, Ca = 136.7, Al = 11.5, and S = 116.2 for the Ca-S particle.