Table 2.

The characteristics of the municipal sludge used in this research *.

Description	Thickened Waste-Activated Sludge	Dewatered Sludge Cake
pH	6.5 ± 0.1	5.8 ± 0.2
TS (% w/w)	3.5 ± 0.2	19.2 ± 0.34
VS (% w/w)	2.7 ± 0.2	16.8 ± 0.35
VS/TS (%)	77.4	87.6 ± 0.24
Total COD ($\mathrm{mg}/\mathrm{L}$)	37,420 ± 574	265,702 ± 9422
Soluble COD ($\mathrm{mg}/\mathrm{L}$)	1740 ± 350	11,991 ± 591
Total VFAs	309 ± 23	1857 ± 36
Ammonia ($\mathrm{mg}/\mathrm{L}$)	201± 17	678 ± 82
Alkalinity ($\mathrm{mg}/\mathrm{L}$ as CaCO3)	632 ± 128	2145 ± 327

* TS: Total solids; VS: Volatile solids; COD: Chemical oxygen demand; VFAs: Volatile fatty acids as summation of acetic, propionic, and butyric acids.