Table 1.

Elemental analysis, ash content, pH at the point of zero charge (pHpzc) and textural parameters of the selected drinking water treatment sludges (WTSs). The values presented for the ash content correspond to the mean of duplicates ($\overline{X}\pm \sigma$, n = 2).

Parameter	WTS1	WTS2
C (w/w%)	24.31	34.09
N (w/w%)	0.24	0.46
H (w/w%)	2.64	2.92
S (w/w%)	0.16	0.18
O (w/w%) *	29.78	31.49
Ash (w/w%)	42.9 ± 0.2	30.8 ± 0.8
Surface area (m2/g)	127	318
Vtotal (cm3/g)	0.065	0.161
pHpzc	11.29	7.46

* Obtained by difference (%O = 100 − %C − %H − %N − %S − %Ashes).