Recovery of Bacillus licheniformis Alkaline Protease from Supernatant of Fermented Wastewater Sludge Using Ultrafiltration and Its Characterization

Table 1

Physical and chemical characteristics of secondary sludge.

Characteristics	Concentration
Physical characteristics:
Total solids (g/L)	29 ± 1.2
Volatile solids (g/L)	18 ± 0.6
Suspended solids (g/L)	22 ± 0.9
Volatile suspended solids (g/L)	17 ± 0.7
pH	5.7 ± 0.3
Chemical characteristics:
Total carbon (%, dry total solids)	38.12 ± 1.5
Total nitrogen (%, dry total solids)	5.5 ± 0.3
Ammonical nitrogen (mg N/kg)	680 ± 22.1
Total phosphorus (mg P/kg)	12 422 ± 42
Orthophosphates (mg P/kg)	7 780 ± 24
Metals (in mg/kg) (dry basis):
Al^3+	13 305 ± 41
Ca^2+	16 160 ± 45
Cd^2+	3.5 ± 0.16
Cr^3+	66.5 ± 2
Cu^2+	270 ± 9
Fe^2+	10 365 ± 30
Mg^2+	1874 ± 62
Mn^2+	198 ± 6.9
K^+	1720 ± 53
Pb^2+	61 ± 2
Zn^2+	477 ± 15